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902004c1ee4e6234e229d7eb890a75b5fac2eaa1
MaxScale/server/modules/routing/readwritesplit/readwritesplit.c
VilhoRaatikka 902004c1ee Fix to bug #463, http://bugs.skysql.com/show_bug.cgi?id=463 
mysql_common.c:gw_MySQL_get_next_packet didn't handle case where an insert command followed by alter table in the same read buffer. It shouldn't been possible without multi-statement being set.
2014-08-14 22:33:57 +03:00

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/*
* This file is distributed as part of the SkySQL Gateway. It is free
* software: you can redistribute it and/or modify it under the terms of the
* GNU General Public License as published by the Free Software Foundation,
* version 2.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 51
* Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Copyright SkySQL Ab 2013
*/
#include <stdio.h>
#include <strings.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <router.h>
#include <readwritesplit.h>
#include <mysql.h>
#include <skygw_utils.h>
#include <log_manager.h>
#include <query_classifier.h>
#include <dcb.h>
#include <spinlock.h>
#include <modinfo.h>
#include <mysql_client_server_protocol.h>
MODULE_INFO info = {
MODULE_API_ROUTER,
MODULE_BETA_RELEASE,
ROUTER_VERSION,
"A Read/Write splitting router for enhancement read scalability"
};
#if defined(SS_DEBUG)
# include <mysql_client_server_protocol.h>
#endif
extern int lm_enabled_logfiles_bitmask;
/**
* @file readwritesplit.c The entry points for the read/write query splitting
* router module.
*
* This file contains the entry points that comprise the API to the read write
* query splitting router.
* @verbatim
* Revision History
*
* Date Who Description
* 01/07/2013 Vilho Raatikka Initial implementation
* 15/07/2013 Massimiliano Pinto Added clientReply
* from master only in case of session change
* 17/07/2013 Massimiliano Pinto clientReply is now used by mysql_backend
* for all reply situations
* 18/07/2013 Massimiliano Pinto routeQuery now handles COM_QUIT
* as QUERY_TYPE_SESSION_WRITE
* 17/07/2014 Massimiliano Pinto Server connection counter is updated in closeSession
*
* @endverbatim
*/
static char *version_str = "V1.0.2";
static ROUTER* createInstance(SERVICE *service, char **options);
static void* newSession(ROUTER *instance, SESSION *session);
static void closeSession(ROUTER *instance, void *session);
static void freeSession(ROUTER *instance, void *session);
static int routeQuery(ROUTER *instance, void *session, GWBUF *queue);
static void diagnostic(ROUTER *instance, DCB *dcb);
static void clientReply(
ROUTER* instance,
void* router_session,
GWBUF* queue,
DCB* backend_dcb);
static void handleError(
ROUTER* instance,
void* router_session,
GWBUF* errmsgbuf,
DCB* backend_dcb,
error_action_t action,
bool* succp);
static void print_error_packet(ROUTER_CLIENT_SES* rses, GWBUF* buf, DCB* dcb);
static int router_get_servercount(ROUTER_INSTANCE* router);
static int rses_get_max_slavecount(ROUTER_CLIENT_SES* rses, int router_nservers);
static int rses_get_max_replication_lag(ROUTER_CLIENT_SES* rses);
static backend_ref_t* get_bref_from_dcb(ROUTER_CLIENT_SES* rses, DCB* dcb);
static uint8_t getCapabilities (ROUTER* inst, void* router_session);
#if defined(NOT_USED)
static bool router_option_configured(
ROUTER_INSTANCE* router,
const char* optionstr,
void* data);
#endif
#if defined(PREP_STMT_CACHING)
static prep_stmt_t* prep_stmt_init(prep_stmt_type_t type, void* id);
static void prep_stmt_done(prep_stmt_t* pstmt);
#endif /*< PREP_STMT_CACHING */
int bref_cmp_global_conn(
const void* bref1,
const void* bref2);
int bref_cmp_router_conn(
const void* bref1,
const void* bref2);
int bref_cmp_behind_master(
const void* bref1,
const void* bref2);
int bref_cmp_current_load(
const void* bref1,
const void* bref2);
/**
* The order of functions _must_ match with the order the select criteria are
* listed in select_criteria_t definition in readwritesplit.h
*/
int (*criteria_cmpfun[LAST_CRITERIA])(const void*, const void*)=
{
NULL,
bref_cmp_global_conn,
bref_cmp_router_conn,
bref_cmp_behind_master,
bref_cmp_current_load
};
static bool select_connect_backend_servers(
backend_ref_t** p_master_ref,
backend_ref_t* backend_ref,
int router_nservers,
int max_nslaves,
int max_rlag,
select_criteria_t select_criteria,
SESSION* session,
ROUTER_INSTANCE* router);
static bool get_dcb(
DCB** dcb,
ROUTER_CLIENT_SES* rses,
backend_type_t btype);
static void rwsplit_process_router_options(
ROUTER_INSTANCE* router,
char** options);
static ROUTER_OBJECT MyObject = {
createInstance,
newSession,
closeSession,
freeSession,
routeQuery,
diagnostic,
clientReply,
handleError,
getCapabilities
};
static bool rses_begin_locked_router_action(
ROUTER_CLIENT_SES* rses);
static void rses_end_locked_router_action(
ROUTER_CLIENT_SES* rses);
static void mysql_sescmd_done(
mysql_sescmd_t* sescmd);
static mysql_sescmd_t* mysql_sescmd_init (
rses_property_t* rses_prop,
GWBUF* sescmd_buf,
unsigned char packet_type,
ROUTER_CLIENT_SES* rses);
static rses_property_t* mysql_sescmd_get_property(
mysql_sescmd_t* scmd);
static rses_property_t* rses_property_init(
rses_property_type_t prop_type);
static void rses_property_add(
ROUTER_CLIENT_SES* rses,
rses_property_t* prop);
static void rses_property_done(
rses_property_t* prop);
static mysql_sescmd_t* rses_property_get_sescmd(
rses_property_t* prop);
static bool execute_sescmd_history(backend_ref_t* bref);
static bool execute_sescmd_in_backend(
backend_ref_t* backend_ref);
static void sescmd_cursor_reset(sescmd_cursor_t* scur);
static bool sescmd_cursor_history_empty(sescmd_cursor_t* scur);
static void sescmd_cursor_set_active(
sescmd_cursor_t* sescmd_cursor,
bool value);
static bool sescmd_cursor_is_active(
sescmd_cursor_t* sescmd_cursor);
static GWBUF* sescmd_cursor_clone_querybuf(
sescmd_cursor_t* scur);
static mysql_sescmd_t* sescmd_cursor_get_command(
sescmd_cursor_t* scur);
static bool sescmd_cursor_next(
sescmd_cursor_t* scur);
static GWBUF* sescmd_cursor_process_replies(GWBUF* replybuf, backend_ref_t* bref);
static void tracelog_routed_query(
ROUTER_CLIENT_SES* rses,
char* funcname,
backend_ref_t* bref,
GWBUF* buf);
static bool route_session_write(
ROUTER_CLIENT_SES* router_client_ses,
GWBUF* querybuf,
ROUTER_INSTANCE* inst,
unsigned char packet_type,
skygw_query_type_t qtype);
static void refreshInstance(
ROUTER_INSTANCE* router,
CONFIG_PARAMETER* param);
static void bref_clear_state(backend_ref_t* bref, bref_state_t state);
static void bref_set_state(backend_ref_t* bref, bref_state_t state);
static sescmd_cursor_t* backend_ref_get_sescmd_cursor (backend_ref_t* bref);
static int router_handle_state_switch(DCB* dcb, DCB_REASON reason, void* data);
static bool handle_error_new_connection(
ROUTER_INSTANCE* inst,
ROUTER_CLIENT_SES* rses,
DCB* backend_dcb,
GWBUF* errmsg);
static bool handle_error_reply_client(SESSION* ses, GWBUF* errmsg);
static BACKEND* get_root_master(
backend_ref_t* servers,
int router_nservers);
static bool have_enough_servers(
ROUTER_CLIENT_SES** rses,
const int nsrv,
int router_nsrv,
ROUTER_INSTANCE* router);
static SPINLOCK instlock;
static ROUTER_INSTANCE* instances;
/**
* Implementation of the mandatory version entry point
*
* @return version string of the module
*/
char *
version()
{
return version_str;
}
/**
* The module initialisation routine, called when the module
* is first loaded.
*/
void
ModuleInit()
{
LOGIF(LM, (skygw_log_write_flush(
LOGFILE_MESSAGE,
"Initializing statemend-based read/write split router module.")));
spinlock_init(&instlock);
instances = NULL;
}
/**
* The module entry point routine. It is this routine that
* must populate the structure that is referred to as the
* "module object", this is a structure with the set of
* external entry points for this module.
*
* @return The module object
*/
ROUTER_OBJECT* GetModuleObject()
{
return &MyObject;
}
static void refreshInstance(
ROUTER_INSTANCE* router,
CONFIG_PARAMETER* singleparam)
{
CONFIG_PARAMETER* param;
bool refresh_single;
if (singleparam != NULL)
{
param = singleparam;
refresh_single = true;
}
else
{
param = router->service->svc_config_param;
refresh_single = false;
}
while (param != NULL)
{
config_param_type_t paramtype;
paramtype = config_get_paramtype(param);
if (paramtype == COUNT_TYPE)
{
if (strncmp(param->name, "max_slave_connections", MAX_PARAM_LEN) == 0)
{
router->rwsplit_config.rw_max_slave_conn_percent = 0;
router->rwsplit_config.rw_max_slave_conn_count =
config_get_valint(param, NULL, paramtype);
}
else if (strncmp(param->name,
"max_slave_replication_lag",
MAX_PARAM_LEN) == 0)
{
router->rwsplit_config.rw_max_slave_replication_lag =
config_get_valint(param, NULL, paramtype);
}
}
else if (paramtype == PERCENT_TYPE)
{
if (strncmp(param->name, "max_slave_connections", MAX_PARAM_LEN) == 0)
{
router->rwsplit_config.rw_max_slave_conn_count = 0;
router->rwsplit_config.rw_max_slave_conn_percent =
config_get_valint(param, NULL, paramtype);
}
}
if (refresh_single)
{
break;
}
param = param->next;
}
#if defined(NOT_USED) /*< can't read monitor config parameters */
if ((*router->servers)->backend_server->rlag == -2)
{
rlag_enabled = false;
}
else
{
rlag_enabled = true;
}
/**
* If replication lag detection is not enabled the measure can't be
* used in slave selection.
*/
if (!rlag_enabled)
{
if (rlag_limited)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Warning : Configuration Failed, max_slave_replication_lag "
"is set to %d,\n\t\t but detect_replication_lag "
"is not enabled. Replication lag will not be checked.",
router->rwsplit_config.rw_max_slave_replication_lag)));
}
if (router->rwsplit_config.rw_slave_select_criteria ==
LEAST_BEHIND_MASTER)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Warning : Configuration Failed, router option "
"\n\t\t slave_selection_criteria=LEAST_BEHIND_MASTER "
"is specified, but detect_replication_lag "
"is not enabled.\n\t\t "
"slave_selection_criteria=%s will be used instead.",
STRCRITERIA(DEFAULT_CRITERIA))));
router->rwsplit_config.rw_slave_select_criteria =
DEFAULT_CRITERIA;
}
}
#endif /*< NOT_USED */
}
/**
* Create an instance of read/write statement router within the MaxScale.
*
*
* @param service The service this router is being create for
* @param options The options for this query router
*
* @return NULL in failure, pointer to router in success.
*/
static ROUTER *
createInstance(SERVICE *service, char **options)
{
ROUTER_INSTANCE* router;
SERVER* server;
int nservers;
int i;
CONFIG_PARAMETER* param;
char *weightby;
if ((router = calloc(1, sizeof(ROUTER_INSTANCE))) == NULL) {
return NULL;
}
router->service = service;
spinlock_init(&router->lock);
/** Calculate number of servers */
server = service->databases;
nservers = 0;
while (server != NULL)
{
nservers++;
server=server->nextdb;
}
router->servers = (BACKEND **)calloc(nservers + 1, sizeof(BACKEND *));
if (router->servers == NULL)
{
free(router);
return NULL;
}
/**
* Create an array of the backend servers in the router structure to
* maintain a count of the number of connections to each
* backend server.
*/
server = service->databases;
nservers= 0;
while (server != NULL) {
if ((router->servers[nservers] = malloc(sizeof(BACKEND))) == NULL)
{
/** clean up */
for (i = 0; i < nservers; i++) {
free(router->servers[i]);
}
free(router->servers);
free(router);
return NULL;
}
router->servers[nservers]->backend_server = server;
router->servers[nservers]->backend_conn_count = 0;
router->servers[nservers]->be_valid = false;
router->servers[nservers]->weight = 1000;
#if defined(SS_DEBUG)
router->servers[nservers]->be_chk_top = CHK_NUM_BACKEND;
router->servers[nservers]->be_chk_tail = CHK_NUM_BACKEND;
#endif
nservers += 1;
server = server->nextdb;
}
router->servers[nservers] = NULL;
/*
* If server weighting has been defined calculate the percentage
* of load that will be sent to each server. This is only used for
* calculating the least connections, either globally or within a
* service, or the numebr of current operations on a server.
*/
if ((weightby = serviceGetWeightingParameter(service)) != NULL)
{
int n, total = 0;
BACKEND *backend;
for (n = 0; router->servers[n]; n++)
{
backend = router->servers[n];
total += atoi(serverGetParameter(
backend->backend_server, weightby));
}
if (total == 0)
{
LOGIF(LE, (skygw_log_write(LOGFILE_ERROR,
"WARNING: Weighting Parameter for service '%s' "
"will be ignored as no servers have values "
"for the parameter '%s'.\n",
service->name, weightby)));
}
else
{
for (n = 0; router->servers[n]; n++)
{
int perc;
backend = router->servers[n];
perc = (atoi(serverGetParameter(
backend->backend_server,
weightby)) * 1000) / total;
if (perc == 0)
perc = 1;
backend->weight = perc;
if (perc == 0)
{
LOGIF(LE, (skygw_log_write(
LOGFILE_ERROR,
"Server '%s' has no value "
"for weighting parameter '%s', "
"no queries will be routed to "
"this server.\n",
server->unique_name,
weightby)));
}
}
}
}
/**
* vraa : is this necessary for readwritesplit ?
* Option : where can a read go?
* - master (only)
* - slave (only)
* - joined (to both)
*
* Process the options
*/
router->bitmask = 0;
router->bitvalue = 0;
/** Call this before refreshInstance */
if (options)
{
rwsplit_process_router_options(router, options);
}
/**
* Set default value for max_slave_connections and for slave selection
* criteria. If parameter is set in config file max_slave_connections
* will be overwritten.
*/
router->rwsplit_config.rw_max_slave_conn_count = CONFIG_MAX_SLAVE_CONN;
if (router->rwsplit_config.rw_slave_select_criteria == UNDEFINED_CRITERIA)
{
router->rwsplit_config.rw_slave_select_criteria = DEFAULT_CRITERIA;
}
/**
* Copy all config parameters from service to router instance.
* Finally, copy version number to indicate that configs match.
*/
param = config_get_param(service->svc_config_param, "max_slave_connections");
if (param != NULL)
{
refreshInstance(router, param);
}
/**
* Read default value for slave replication lag upper limit and then
* configured value if it exists.
*/
router->rwsplit_config.rw_max_slave_replication_lag = CONFIG_MAX_SLAVE_RLAG;
param = config_get_param(service->svc_config_param, "max_slave_replication_lag");
if (param != NULL)
{
refreshInstance(router, param);
}
router->rwsplit_version = service->svc_config_version;
/**
* We have completed the creation of the router data, so now
* insert this router into the linked list of routers
* that have been created with this module.
*/
spinlock_acquire(&instlock);
router->next = instances;
instances = router;
spinlock_release(&instlock);
return (ROUTER *)router;
}
/**
* Associate a new session with this instance of the router.
*
* The session is used to store all the data required for a particular
* client connection.
*
* @param instance The router instance data
* @param session The session itself
* @return Session specific data for this session
*/
static void* newSession(
ROUTER* router_inst,
SESSION* session)
{
backend_ref_t* backend_ref; /*< array of backend references (DCB,BACKEND,cursor) */
backend_ref_t* master_ref = NULL; /*< pointer to selected master */
ROUTER_CLIENT_SES* client_rses = NULL;
ROUTER_INSTANCE* router = (ROUTER_INSTANCE *)router_inst;
bool succp;
int router_nservers = 0; /*< # of servers in total */
int max_nslaves; /*< max # of slaves used in this session */
int max_slave_rlag; /*< max allowed replication lag for any slave */
int i;
const int min_nservers = 1; /*< hard-coded for now */
client_rses = (ROUTER_CLIENT_SES *)calloc(1, sizeof(ROUTER_CLIENT_SES));
if (client_rses == NULL)
{
ss_dassert(false);
goto return_rses;
}
#if defined(SS_DEBUG)
client_rses->rses_chk_top = CHK_NUM_ROUTER_SES;
client_rses->rses_chk_tail = CHK_NUM_ROUTER_SES;
#endif
/**
* If service config has been changed, reload config from service to
* router instance first.
*/
spinlock_acquire(&router->lock);
if (router->service->svc_config_version > router->rwsplit_version)
{
/** re-read all parameters to rwsplit config structure */
refreshInstance(router, NULL); /*< scan through all parameters */
/** increment rwsplit router's config version number */
router->rwsplit_version = router->service->svc_config_version;
/** Read options */
rwsplit_process_router_options(router, router->service->routerOptions);
}
/** Copy config struct from router instance */
client_rses->rses_config = router->rwsplit_config;
spinlock_release(&router->lock);
/**
* Set defaults to session variables.
*/
client_rses->rses_autocommit_enabled = true;
client_rses->rses_transaction_active = false;
router_nservers = router_get_servercount(router);
if (!have_enough_servers(&client_rses,
min_nservers,
router_nservers,
router))
{
goto return_rses;
}
/**
* Create backend reference objects for this session.
*/
backend_ref = (backend_ref_t *)calloc(1, router_nservers*sizeof(backend_ref_t));
if (backend_ref == NULL)
{
/** log this */
free(client_rses);
free(backend_ref);
client_rses = NULL;
goto return_rses;
}
/**
* Initialize backend references with BACKEND ptr.
* Initialize session command cursors for each backend reference.
*/
for (i=0; i< router_nservers; i++)
{
#if defined(SS_DEBUG)
backend_ref[i].bref_chk_top = CHK_NUM_BACKEND_REF;
backend_ref[i].bref_chk_tail = CHK_NUM_BACKEND_REF;
backend_ref[i].bref_sescmd_cur.scmd_cur_chk_top = CHK_NUM_SESCMD_CUR;
backend_ref[i].bref_sescmd_cur.scmd_cur_chk_tail = CHK_NUM_SESCMD_CUR;
#endif
backend_ref[i].bref_state = 0;
backend_ref[i].bref_backend = router->servers[i];
/** store pointers to sescmd list to both cursors */
backend_ref[i].bref_sescmd_cur.scmd_cur_rses = client_rses;
backend_ref[i].bref_sescmd_cur.scmd_cur_active = false;
backend_ref[i].bref_sescmd_cur.scmd_cur_ptr_property =
&client_rses->rses_properties[RSES_PROP_TYPE_SESCMD];
backend_ref[i].bref_sescmd_cur.scmd_cur_cmd = NULL;
}
max_nslaves = rses_get_max_slavecount(client_rses, router_nservers);
max_slave_rlag = rses_get_max_replication_lag(client_rses);
spinlock_init(&client_rses->rses_lock);
client_rses->rses_backend_ref = backend_ref;
/**
* Find a backend servers to connect to.
* This command requires that rsession's lock is held.
*/
rses_begin_locked_router_action(client_rses);
succp = select_connect_backend_servers(&master_ref,
backend_ref,
router_nservers,
max_nslaves,
max_slave_rlag,
client_rses->rses_config.rw_slave_select_criteria,
session,
router);
rses_end_locked_router_action(client_rses);
/** Both Master and at least 1 slave must be found */
if (!succp) {
free(client_rses->rses_backend_ref);
free(client_rses);
client_rses = NULL;
goto return_rses;
}
/** Copy backend pointers to router session. */
client_rses->rses_master_ref = master_ref;
/* assert with master_host */
ss_dassert(master_ref && (master_ref->bref_backend->backend_server && SERVER_MASTER));
client_rses->rses_capabilities = RCAP_TYPE_STMT_INPUT;
client_rses->rses_backend_ref = backend_ref;
client_rses->rses_nbackends = router_nservers; /*< # of backend servers */
router->stats.n_sessions += 1;
/**
* Version is bigger than zero once initialized.
*/
atomic_add(&client_rses->rses_versno, 2);
ss_dassert(client_rses->rses_versno == 2);
/**
* Add this session to end of the list of active sessions in router.
*/
spinlock_acquire(&router->lock);
client_rses->next = router->connections;
router->connections = client_rses;
spinlock_release(&router->lock);
return_rses:
#if defined(SS_DEBUG)
if (client_rses != NULL)
{
CHK_CLIENT_RSES(client_rses);
}
#endif
return (void *)client_rses;
}
/**
* Close a session with the router, this is the mechanism
* by which a router may cleanup data structure etc.
*
* @param instance The router instance data
* @param session The session being closed
*/
static void closeSession(
ROUTER* instance,
void* router_session)
{
ROUTER_CLIENT_SES* router_cli_ses;
backend_ref_t* backend_ref;
/**
* router session can be NULL if newSession failed and it is discarding
* its connections and DCB's.
*/
if (router_session == NULL)
{
return;
}
router_cli_ses = (ROUTER_CLIENT_SES *)router_session;
CHK_CLIENT_RSES(router_cli_ses);
backend_ref = router_cli_ses->rses_backend_ref;
/**
* Lock router client session for secure read and update.
*/
if (!router_cli_ses->rses_closed &&
rses_begin_locked_router_action(router_cli_ses))
{
int i = 0;
/**
* session must be moved to SESSION_STATE_STOPPING state before
* router session is closed.
*/
#if defined(SS_DEBUG)
SESSION* ses = get_session_by_router_ses((void*)router_cli_ses);
ss_dassert(ses != NULL);
ss_dassert(ses->state == SESSION_STATE_STOPPING);
#endif
/**
* This sets router closed. Nobody is allowed to use router
* whithout checking this first.
*/
router_cli_ses->rses_closed = true;
for (i=0; i<router_cli_ses->rses_nbackends; i++)
{
backend_ref_t* bref = &backend_ref[i];
DCB* dcb = bref->bref_dcb;
/** Close those which had been connected */
if (BREF_IS_IN_USE(bref))
{
CHK_DCB(dcb);
/** Clean operation counter in bref and in SERVER */
while (BREF_IS_WAITING_RESULT(bref))
{
bref_clear_state(bref, BREF_WAITING_RESULT);
}
bref_clear_state(bref, BREF_IN_USE);
bref_set_state(bref, BREF_CLOSED);
/**
* closes protocol and dcb
*/
dcb_close(dcb);
/** decrease server current connection counters */
atomic_add(&bref->bref_backend->backend_server->stats.n_current, -1);
atomic_add(&bref->bref_backend->backend_conn_count, -1);
}
}
/** Unlock */
rses_end_locked_router_action(router_cli_ses);
}
}
static void freeSession(
ROUTER* router_instance,
void* router_client_session)
{
ROUTER_CLIENT_SES* router_cli_ses;
ROUTER_INSTANCE* router;
int i;
backend_ref_t* backend_ref;
router_cli_ses = (ROUTER_CLIENT_SES *)router_client_session;
router = (ROUTER_INSTANCE *)router_instance;
backend_ref = router_cli_ses->rses_backend_ref;
for (i=0; i<router_cli_ses->rses_nbackends; i++)
{
if (!BREF_IS_IN_USE((&backend_ref[i])))
{
continue;
}
}
spinlock_acquire(&router->lock);
if (router->connections == router_cli_ses) {
router->connections = router_cli_ses->next;
} else {
ROUTER_CLIENT_SES* ptr = router->connections;
while (ptr && ptr->next != router_cli_ses) {
ptr = ptr->next;
}
if (ptr) {
ptr->next = router_cli_ses->next;
}
}
spinlock_release(&router->lock);
/**
* For each property type, walk through the list, finalize properties
* and free the allocated memory.
*/
for (i=RSES_PROP_TYPE_FIRST; i<RSES_PROP_TYPE_COUNT; i++)
{
rses_property_t* p = router_cli_ses->rses_properties[i];
rses_property_t* q = p;
while (p != NULL)
{
q = p->rses_prop_next;
rses_property_done(p);
p = q;
}
}
/*
* We are no longer in the linked list, free
* all the memory and other resources associated
* to the client session.
*/
free(router_cli_ses->rses_backend_ref);
free(router_cli_ses);
return;
}
/**
* Provide a pointer to a suitable backend dcb.
* Detect failures in server statuses and reselect backends if necessary.
*/
static bool get_dcb(
DCB** p_dcb,
ROUTER_CLIENT_SES* rses,
backend_type_t btype)
{
backend_ref_t* backend_ref;
int smallest_nconn = -1;
int i;
bool succp = false;
BACKEND *master_host = NULL;
CHK_CLIENT_RSES(rses);
ss_dassert(p_dcb != NULL && *(p_dcb) == NULL);
if (p_dcb == NULL)
{
goto return_succp;
}
backend_ref = rses->rses_backend_ref;
/* get root master from availbal servers */
master_host = get_root_master(backend_ref, rses->rses_nbackends);
if (btype == BE_SLAVE)
{
for (i=0; i<rses->rses_nbackends; i++)
{
BACKEND* b = backend_ref[i].bref_backend;
/* check slave bit, also for relay servers (Master & Servers) */
if (BREF_IS_IN_USE((&backend_ref[i])) &&
(SERVER_IS_SLAVE(b->backend_server) || SERVER_IS_RELAY_SERVER(b->backend_server)) &&
(master_host != NULL && b->backend_server != master_host->backend_server) &&
(smallest_nconn == -1 ||
b->backend_conn_count < smallest_nconn))
{
*p_dcb = backend_ref[i].bref_dcb;
smallest_nconn = b->backend_conn_count;
succp = true;
ss_dassert(backend_ref[i].bref_dcb->state != DCB_STATE_ZOMBIE);
}
}
if (!succp)
{
backend_ref = rses->rses_master_ref;
if (BREF_IS_IN_USE(backend_ref))
{
*p_dcb = backend_ref->bref_dcb;
succp = true;
ss_dassert(backend_ref->bref_dcb->state != DCB_STATE_ZOMBIE);
ss_dassert(
(master_host && (backend_ref->bref_backend->backend_server == master_host->backend_server)) &&
smallest_nconn == -1);
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Warning : No slaves connected nor "
"available. Choosing master %s:%d "
"instead.",
backend_ref->bref_backend->backend_server->name,
backend_ref->bref_backend->backend_server->port)));
}
}
ss_dassert(succp);
}
else if (btype == BE_MASTER)
{
for (i=0; i<rses->rses_nbackends; i++)
{
BACKEND* b = backend_ref[i].bref_backend;
if (BREF_IS_IN_USE((&backend_ref[i])) &&
(master_host && (b->backend_server == master_host->backend_server)))
{
*p_dcb = backend_ref[i].bref_dcb;
succp = true;
goto return_succp;
}
}
}
return_succp:
return succp;
}
/**
* The main routing entry, this is called with every packet that is
* received and has to be forwarded to the backend database.
*
* The routeQuery will make the routing decision based on the contents
* of the instance, session and the query itself in the queue. The
* data in the queue may not represent a complete query, it represents
* the data that has been received. The query router itself is responsible
* for buffering the partial query, a later call to the query router will
* contain the remainder, or part thereof of the query.
*
* @param instance The query router instance
* @param session The session associated with the client
* @param queue Gateway buffer queue with the packets received
*
* @return if succeed 1, otherwise 0
* If routeQuery fails, it means that router session has failed.
* In any tolerated failure, handleError is called and if necessary,
* an error message is sent to the client.
*
* For now, routeQuery don't tolerate errors, so any error will close
* the session. vraa 14.6.14
*/
static int routeQuery(
ROUTER* instance,
void* router_session,
GWBUF* querybuf)
{
skygw_query_type_t qtype = QUERY_TYPE_UNKNOWN;
GWBUF* plainsqlbuf = NULL;
char* querystr = NULL;
char* startpos;
mysql_server_cmd_t packet_type;
uint8_t* packet;
int ret = 0;
DCB* master_dcb = NULL;
DCB* slave_dcb = NULL;
ROUTER_INSTANCE* inst = (ROUTER_INSTANCE *)instance;
ROUTER_CLIENT_SES* router_cli_ses = (ROUTER_CLIENT_SES *)router_session;
bool rses_is_closed = false;
size_t len;
MYSQL* mysql = NULL;
CHK_CLIENT_RSES(router_cli_ses);
/** Dirty read for quick check if router is closed. */
if (router_cli_ses->rses_closed)
{
rses_is_closed = true;
}
ss_dassert(!GWBUF_IS_TYPE_UNDEFINED(querybuf));
packet = GWBUF_DATA(querybuf);
packet_type = packet[4];
if (rses_is_closed)
{
/**
* MYSQL_COM_QUIT may have sent by client and as a part of backend
* closing procedure.
*/
if (packet_type != MYSQL_COM_QUIT)
{
LOGIF(LE,
(skygw_log_write_flush(
LOGFILE_ERROR,
"Error: Failed to route %s:%s:\"%s\" to "
"backend server. %s.",
STRPACKETTYPE(packet_type),
STRQTYPE(qtype),
(querystr == NULL ? "(empty)" : querystr),
(rses_is_closed ? "Router was closed" :
"Router has no backend servers where to "
"route to"))));
}
goto return_ret;
}
inst->stats.n_queries++;
startpos = (char *)&packet[5];
master_dcb = router_cli_ses->rses_master_ref->bref_dcb;
CHK_DCB(master_dcb);
switch(packet_type) {
case MYSQL_COM_QUIT: /*< 1 QUIT will close all sessions */
case MYSQL_COM_INIT_DB: /*< 2 DDL must go to the master */
case MYSQL_COM_REFRESH: /*< 7 - I guess this is session but not sure */
case MYSQL_COM_DEBUG: /*< 0d all servers dump debug info to stdout */
case MYSQL_COM_PING: /*< 0e all servers are pinged */
case MYSQL_COM_CHANGE_USER: /*< 11 all servers change it accordingly */
case MYSQL_COM_STMT_CLOSE: /*< free prepared statement */
case MYSQL_COM_STMT_SEND_LONG_DATA: /*< send data to column */
case MYSQL_COM_STMT_RESET: /*< resets the data of a prepared statement */
qtype = QUERY_TYPE_SESSION_WRITE;
break;
case MYSQL_COM_CREATE_DB: /**< 5 DDL must go to the master */
case MYSQL_COM_DROP_DB: /**< 6 DDL must go to the master */
qtype = QUERY_TYPE_WRITE;
break;
case MYSQL_COM_QUERY:
plainsqlbuf = gwbuf_clone_transform(querybuf,
GWBUF_TYPE_PLAINSQL);
len = GWBUF_LENGTH(plainsqlbuf);
/** unnecessary if buffer includes additional terminating null */
querystr = (char *)malloc(len+1);
memcpy(querystr, startpos, len);
memset(&querystr[len], 0, 1);
/**
* Use mysql handle to query information from parse tree.
* call skygw_query_classifier_free before exit!
*/
qtype = skygw_query_classifier_get_type(querystr, 0, &mysql);
break;
case MYSQL_COM_STMT_PREPARE:
plainsqlbuf = gwbuf_clone_transform(querybuf,
GWBUF_TYPE_PLAINSQL);
len = GWBUF_LENGTH(plainsqlbuf);
/** unnecessary if buffer includes additional terminating null */
querystr = (char *)malloc(len+1);
memcpy(querystr, startpos, len);
memset(&querystr[len], 0, 1);
qtype = skygw_query_classifier_get_type(querystr, 0, &mysql);
qtype |= QUERY_TYPE_PREPARE_STMT;
break;
case MYSQL_COM_STMT_EXECUTE:
/** Parsing is not needed for this type of packet */
#if defined(NOT_USED)
plainsqlbuf = gwbuf_clone_transform(querybuf,
GWBUF_TYPE_PLAINSQL);
len = GWBUF_LENGTH(plainsqlbuf);
/** unnecessary if buffer includes additional terminating null */
querystr = (char *)malloc(len+1);
memcpy(querystr, startpos, len);
memset(&querystr[len], 0, 1);
qtype = skygw_query_classifier_get_type(querystr, 0, &mysql);
#endif
qtype = QUERY_TYPE_EXEC_STMT;
break;
case MYSQL_COM_SHUTDOWN: /**< 8 where should shutdown be routed ? */
case MYSQL_COM_STATISTICS: /**< 9 ? */
case MYSQL_COM_PROCESS_INFO: /**< 0a ? */
case MYSQL_COM_CONNECT: /**< 0b ? */
case MYSQL_COM_PROCESS_KILL: /**< 0c ? */
case MYSQL_COM_TIME: /**< 0f should this be run in gateway ? */
case MYSQL_COM_DELAYED_INSERT: /**< 10 ? */
case MYSQL_COM_DAEMON: /**< 1d ? */
default:
break;
} /**< switch by packet type */
/**
* If autocommit is disabled or transaction is explicitly started
* transaction becomes active and master gets all statements until
* transaction is committed and autocommit is enabled again.
*/
if (router_cli_ses->rses_autocommit_enabled &&
QUERY_IS_TYPE(qtype, QUERY_TYPE_DISABLE_AUTOCOMMIT))
{
router_cli_ses->rses_autocommit_enabled = false;
if (!router_cli_ses->rses_transaction_active)
{
router_cli_ses->rses_transaction_active = true;
}
}
else if (!router_cli_ses->rses_transaction_active &&
QUERY_IS_TYPE(qtype, QUERY_TYPE_BEGIN_TRX))
{
router_cli_ses->rses_transaction_active = true;
}
/**
* Explicit COMMIT and ROLLBACK, implicit COMMIT.
*/
if (router_cli_ses->rses_autocommit_enabled &&
router_cli_ses->rses_transaction_active &&
(QUERY_IS_TYPE(qtype,QUERY_TYPE_COMMIT) ||
QUERY_IS_TYPE(qtype,QUERY_TYPE_ROLLBACK)))
{
router_cli_ses->rses_transaction_active = false;
}
else if (!router_cli_ses->rses_autocommit_enabled &&
QUERY_IS_TYPE(qtype, QUERY_TYPE_ENABLE_AUTOCOMMIT))
{
router_cli_ses->rses_autocommit_enabled = true;
router_cli_ses->rses_transaction_active = false;
}
/**
* Session update is always routed in the same way.
*/
if (QUERY_IS_TYPE(qtype, QUERY_TYPE_SESSION_WRITE) ||
QUERY_IS_TYPE(qtype, QUERY_TYPE_PREPARE_STMT) ||
QUERY_IS_TYPE(qtype, QUERY_TYPE_PREPARE_NAMED_STMT))
{
/**
* It is not sure if the session command in question requires
* response. Statement is examined in route_session_write.
*/
bool succp = route_session_write(
router_cli_ses,
querybuf,
inst,
packet_type,
qtype);
if (succp)
{
ret = 1;
}
goto return_ret;
}
else if (QUERY_IS_TYPE(qtype, QUERY_TYPE_READ) &&
!router_cli_ses->rses_transaction_active)
{
bool succp;
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"[%s]\tRead-only query, routing to Slave.",
inst->service->name)));
ss_dassert(QUERY_IS_TYPE(qtype, QUERY_TYPE_READ));
/** Lock router session */
if (!rses_begin_locked_router_action(router_cli_ses))
{
goto return_ret;
}
succp = get_dcb(&slave_dcb, router_cli_ses, BE_SLAVE);
if (succp)
{
if ((ret = slave_dcb->func.write(slave_dcb, querybuf)) == 1)
{
backend_ref_t* bref;
atomic_add(&inst->stats.n_slave, 1);
/**
* Add one query response waiter to backend reference
*/
bref = get_bref_from_dcb(router_cli_ses, slave_dcb);
bref_set_state(bref, BREF_QUERY_ACTIVE);
bref_set_state(bref, BREF_WAITING_RESULT);
}
else
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Routing query \"%s\" failed.",
querystr)));
}
}
rses_end_locked_router_action(router_cli_ses);
ss_dassert(succp);
goto return_ret;
}
else
{
bool succp = true;
if (LOG_IS_ENABLED(LOGFILE_TRACE))
{
if (router_cli_ses->rses_transaction_active) /*< all to master */
{
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Transaction is active, routing to Master.")));
}
else
{
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Begin transaction, write or unspecified type, "
"routing to Master.")));
}
}
/** Lock router session */
if (!rses_begin_locked_router_action(router_cli_ses))
{
goto return_ret;
}
if (master_dcb == NULL)
{
succp = get_dcb(&master_dcb, router_cli_ses, BE_MASTER);
}
if (succp)
{
if ((ret = master_dcb->func.write(master_dcb, querybuf)) == 1)
{
backend_ref_t* bref;
atomic_add(&inst->stats.n_master, 1);
/**
* Add one write response waiter to backend reference
*/
bref = get_bref_from_dcb(router_cli_ses, master_dcb);
bref_set_state(bref, BREF_QUERY_ACTIVE);
bref_set_state(bref, BREF_WAITING_RESULT);
}
}
rses_end_locked_router_action(router_cli_ses);
ss_dassert(succp);
if (ret == 0)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Routing to master failed.")));
}
}
return_ret:
if (plainsqlbuf != NULL)
{
gwbuf_free(plainsqlbuf);
}
if (querystr != NULL)
{
free(querystr);
}
if (mysql != NULL)
{
skygw_query_classifier_free(mysql);
}
return ret;
}
/** to be inline'd */
/**
* @node Acquires lock to router client session if it is not closed.
*
* Parameters:
* @param rses - in, use
*
*
* @return true if router session was not closed. If return value is true
* it means that router is locked, and must be unlocked later. False, if
* router was closed before lock was acquired.
*
*
* @details (write detailed description here)
*
*/
static bool rses_begin_locked_router_action(
ROUTER_CLIENT_SES* rses)
{
bool succp = false;
CHK_CLIENT_RSES(rses);
if (rses->rses_closed) {
goto return_succp;
}
spinlock_acquire(&rses->rses_lock);
if (rses->rses_closed) {
spinlock_release(&rses->rses_lock);
goto return_succp;
}
succp = true;
return_succp:
return succp;
}
/** to be inline'd */
/**
* @node Releases router client session lock.
*
* Parameters:
* @param rses - <usage>
* <description>
*
* @return void
*
*
* @details (write detailed description here)
*
*/
static void rses_end_locked_router_action(
ROUTER_CLIENT_SES* rses)
{
CHK_CLIENT_RSES(rses);
spinlock_release(&rses->rses_lock);
}
/**
* Diagnostics routine
*
* Print query router statistics to the DCB passed in
*
* @param instance The router instance
* @param dcb The DCB for diagnostic output
*/
static void
diagnostic(ROUTER *instance, DCB *dcb)
{
ROUTER_CLIENT_SES *router_cli_ses;
ROUTER_INSTANCE *router = (ROUTER_INSTANCE *)instance;
int i = 0;
BACKEND *backend;
char *weightby;
spinlock_acquire(&router->lock);
router_cli_ses = router->connections;
while (router_cli_ses)
{
i++;
router_cli_ses = router_cli_ses->next;
}
spinlock_release(&router->lock);
dcb_printf(dcb,
"\tNumber of router sessions: %d\n",
router->stats.n_sessions);
dcb_printf(dcb,
"\tCurrent no. of router sessions: %d\n",
i);
dcb_printf(dcb,
"\tNumber of queries forwarded: %d\n",
router->stats.n_queries);
dcb_printf(dcb,
"\tNumber of queries forwarded to master: %d\n",
router->stats.n_master);
dcb_printf(dcb,
"\tNumber of queries forwarded to slave: %d\n",
router->stats.n_slave);
dcb_printf(dcb,
"\tNumber of queries forwarded to all: %d\n",
router->stats.n_all);
if ((weightby = serviceGetWeightingParameter(router->service)) != NULL)
{
dcb_printf(dcb,
"\tConnection distribution based on %s "
"server parameter.\n", weightby);
dcb_printf(dcb,
"\t\tServer Target %% Connections "
"Operations\n");
dcb_printf(dcb,
"\t\t Global Router\n");
for (i = 0; router->servers[i]; i++)
{
backend = router->servers[i];
dcb_printf(dcb,
"\t\t%-20s %3.1f%% %-6d %-6d %d\n",
backend->backend_server->unique_name,
(float)backend->weight / 10,
backend->backend_server->stats.n_current,
backend->backend_conn_count,
backend->backend_server->stats.n_current_ops);
}
}
}
/**
* Client Reply routine
*
* The routine will reply to client for session change with master server data
*
* @param instance The router instance
* @param router_session The router session
* @param backend_dcb The backend DCB
* @param queue The GWBUF with reply data
*/
static void clientReply (
ROUTER* instance,
void* router_session,
GWBUF* writebuf,
DCB* backend_dcb)
{
DCB* client_dcb;
ROUTER_CLIENT_SES* router_cli_ses;
sescmd_cursor_t* scur = NULL;
backend_ref_t* bref;
router_cli_ses = (ROUTER_CLIENT_SES *)router_session;
CHK_CLIENT_RSES(router_cli_ses);
/**
* Lock router client session for secure read of router session members.
* Note that this could be done without lock by using version #
*/
if (!rses_begin_locked_router_action(router_cli_ses))
{
print_error_packet(router_cli_ses, writebuf, backend_dcb);
goto lock_failed;
}
/** Holding lock ensures that router session remains open */
ss_dassert(backend_dcb->session != NULL);
client_dcb = backend_dcb->session->client;
/** Unlock */
rses_end_locked_router_action(router_cli_ses);
/**
* 1. Check if backend received reply to sescmd.
* 2. Check sescmd's state whether OK_PACKET has been
* sent to client already and if not, lock property cursor,
* reply to client, and move property cursor forward. Finally
* release the lock.
* 3. If reply for this sescmd is sent, lock property cursor
* and
*/
if (client_dcb == NULL)
{
while ((writebuf = gwbuf_consume(
writebuf,
GWBUF_LENGTH(writebuf))) != NULL);
/** Log that client was closed before reply */
goto lock_failed;
}
/** Lock router session */
if (!rses_begin_locked_router_action(router_cli_ses))
{
/** Log to debug that router was closed */
goto lock_failed;
}
bref = get_bref_from_dcb(router_cli_ses, backend_dcb);
CHK_BACKEND_REF(bref);
scur = &bref->bref_sescmd_cur;
/**
* Active cursor means that reply is from session command
* execution.
*/
if (sescmd_cursor_is_active(scur))
{
if (LOG_IS_ENABLED(LOGFILE_ERROR) &&
MYSQL_IS_ERROR_PACKET(((uint8_t *)GWBUF_DATA(writebuf))))
{
SESSION* ses = backend_dcb->session;
uint8_t* buf =
(uint8_t *)GWBUF_DATA((scur->scmd_cur_cmd->my_sescmd_buf));
size_t len = MYSQL_GET_PACKET_LEN(buf);
char* cmdstr = (char *)malloc(len+1);
/** data+termination character == len */
snprintf(cmdstr, len, "%s", &buf[5]);
ss_dassert(len+4 == GWBUF_LENGTH(scur->scmd_cur_cmd->my_sescmd_buf));
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Failed to execute %s in %s:%d.",
cmdstr,
bref->bref_backend->backend_server->name,
bref->bref_backend->backend_server->port)));
free(cmdstr);
}
if (GWBUF_IS_TYPE_SESCMD_RESPONSE(writebuf))
{
/**
* Discard all those responses that have already been sent to
* the client. Return with buffer including response that
* needs to be sent to client or NULL.
*/
writebuf = sescmd_cursor_process_replies(writebuf, bref);
}
/**
* If response will be sent to client, decrease waiter count.
* This applies to session commands only. Counter decrement
* for other type of queries is done outside this block.
*/
if (writebuf != NULL && client_dcb != NULL)
{
/** Set response status as replied */
bref_clear_state(bref, BREF_WAITING_RESULT);
}
}
/**
* Clear BREF_QUERY_ACTIVE flag and decrease waiter counter.
* This applies for queries other than session commands.
*/
else if (BREF_IS_QUERY_ACTIVE(bref))
{
bref_clear_state(bref, BREF_QUERY_ACTIVE);
/** Set response status as replied */
bref_clear_state(bref, BREF_WAITING_RESULT);
}
if (writebuf != NULL && client_dcb != NULL)
{
/** Write reply to client DCB */
SESSION_ROUTE_REPLY(backend_dcb->session, writebuf);
}
/** Unlock router session */
rses_end_locked_router_action(router_cli_ses);
/** Lock router session */
if (!rses_begin_locked_router_action(router_cli_ses))
{
/** Log to debug that router was closed */
goto lock_failed;
}
/** There is one pending session command to be executed. */
if (sescmd_cursor_is_active(scur))
{
bool succp;
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Backend %s:%d processed reply and starts to execute "
"active cursor.",
bref->bref_backend->backend_server->name,
bref->bref_backend->backend_server->port)));
succp = execute_sescmd_in_backend(bref);
ss_dassert(succp);
}
/** Unlock router session */
rses_end_locked_router_action(router_cli_ses);
lock_failed:
return;
}
/** Compare nunmber of connections from this router in backend servers */
int bref_cmp_router_conn(
const void* bref1,
const void* bref2)
{
BACKEND* b1 = ((backend_ref_t *)bref1)->bref_backend;
BACKEND* b2 = ((backend_ref_t *)bref2)->bref_backend;
return ((1000 * b1->backend_conn_count) / b1->weight)
- ((1000 * b2->backend_conn_count) / b2->weight);
}
/** Compare nunmber of global connections in backend servers */
int bref_cmp_global_conn(
const void* bref1,
const void* bref2)
{
BACKEND* b1 = ((backend_ref_t *)bref1)->bref_backend;
BACKEND* b2 = ((backend_ref_t *)bref2)->bref_backend;
return ((1000 * b1->backend_server->stats.n_current) / b1->weight)
- ((1000 * b2->backend_server->stats.n_current) / b2->weight);
}
/** Compare relication lag between backend servers */
int bref_cmp_behind_master(
const void* bref1,
const void* bref2)
{
BACKEND* b1 = ((backend_ref_t *)bref1)->bref_backend;
BACKEND* b2 = ((backend_ref_t *)bref2)->bref_backend;
return ((b1->backend_server->rlag < b2->backend_server->rlag) ? -1 :
((b1->backend_server->rlag > b2->backend_server->rlag) ? 1 : 0));
}
/** Compare nunmber of current operations in backend servers */
int bref_cmp_current_load(
const void* bref1,
const void* bref2)
{
SERVER* s1 = ((backend_ref_t *)bref1)->bref_backend->backend_server;
SERVER* s2 = ((backend_ref_t *)bref2)->bref_backend->backend_server;
BACKEND* b1 = ((backend_ref_t *)bref1)->bref_backend;
BACKEND* b2 = ((backend_ref_t *)bref2)->bref_backend;
return ((1000 * s1->stats.n_current_ops) - b1->weight)
- ((1000 * s2->stats.n_current_ops) - b2->weight);
}
static void bref_clear_state(
backend_ref_t* bref,
bref_state_t state)
{
if (state != BREF_WAITING_RESULT)
{
bref->bref_state &= ~state;
}
else
{
int prev1;
int prev2;
/** Decrease waiter count */
prev1 = atomic_add(&bref->bref_num_result_wait, -1);
if (prev1 <= 0) {
atomic_add(&bref->bref_num_result_wait, 1);
}
else
{
/** Decrease global operation count */
prev2 = atomic_add(
&bref->bref_backend->backend_server->stats.n_current_ops, -1);
ss_dassert(prev2 > 0);
}
}
}
static void bref_set_state(
backend_ref_t* bref,
bref_state_t state)
{
if (state != BREF_WAITING_RESULT)
{
bref->bref_state |= state;
}
else
{
int prev1;
int prev2;
/** Increase waiter count */
prev1 = atomic_add(&bref->bref_num_result_wait, 1);
ss_dassert(prev1 >= 0);
/** Increase global operation count */
prev2 = atomic_add(
&bref->bref_backend->backend_server->stats.n_current_ops, 1);
ss_dassert(prev2 >= 0);
}
}
/**
* @node Search suitable backend servers from those of router instance.
*
* Parameters:
* @param p_master_ref - in, use, out
* Pointer to location where master's backend reference is to be stored.
* NULL is not allowed.
*
* @param backend_ref - in, use, out
* Pointer to backend server reference object array.
* NULL is not allowed.
*
* @param router_nservers - in, use
* Number of backend server pointers pointed to by b.
*
* @param max_nslaves - in, use
* Upper limit for the number of slaves. Configuration parameter or default.
*
* @param max_slave_rlag - in, use
* Maximum allowed replication lag for any slave. Configuration parameter or default.
*
* @param session - in, use
* MaxScale session pointer used when connection to backend is established.
*
* @param router - in, use
* Pointer to router instance. Used when server states are qualified.
*
* @return true, if at least one master and one slave was found.
*
*
* @details It is assumed that there is only one master among servers of
* a router instance. As a result, the first master found is chosen.
* There will possibly be more backend references than connected backends
* because only those in correct state are connected to.
*/
static bool select_connect_backend_servers(
backend_ref_t** p_master_ref,
backend_ref_t* backend_ref,
int router_nservers,
int max_nslaves,
int max_slave_rlag,
select_criteria_t select_criteria,
SESSION* session,
ROUTER_INSTANCE* router)
{
bool succp = true;
bool master_found;
bool master_connected;
int slaves_found = 0;
int slaves_connected = 0;
int i;
const int min_nslaves = 0; /*< not configurable at the time */
bool is_synced_master;
int (*p)(const void *, const void *);
BACKEND *master_host = NULL;
if (p_master_ref == NULL || backend_ref == NULL)
{
ss_dassert(FALSE);
succp = false;
goto return_succp;
}
/* get the root Master */
master_host = get_root_master(backend_ref, router_nservers);
/** Master is already chosen and connected. This is slave failure case */
if (*p_master_ref != NULL &&
BREF_IS_IN_USE((*p_master_ref)))
{
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [select_connect_backend_servers] Master %p fd %d found.",
pthread_self(),
(*p_master_ref)->bref_dcb,
(*p_master_ref)->bref_dcb->fd)));
master_found = true;
master_connected = true;
/* assert with master_host */
ss_dassert(master_host && ((*p_master_ref)->bref_backend->backend_server == master_host->backend_server) && SERVER_MASTER);
}
/** New session or master failure case */
else
{
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [select_connect_backend_servers] Session %p doesn't "
"currently have a master chosen. Proceeding to master "
"selection.",
pthread_self(),
session)));
master_found = false;
master_connected = false;
}
/** Check slave selection criteria and set compare function */
p = criteria_cmpfun[select_criteria];
if (p == NULL)
{
succp = false;
goto return_succp;
}
if (router->bitvalue != 0) /*< 'synced' is the only bitvalue in rwsplit */
{
is_synced_master = true;
}
else
{
is_synced_master = false;
}
#if defined(EXTRA_SS_DEBUG)
LOGIF(LT, (skygw_log_write(LOGFILE_TRACE, "Servers and conns before ordering:")));
for (i=0; i<router_nservers; i++)
{
BACKEND* b = backend_ref[i].bref_backend;
LOGIF(LT, (skygw_log_write(LOGFILE_TRACE,
"master bref %p bref %p %d %s %d:%d",
*p_master_ref,
&backend_ref[i],
backend_ref[i].bref_state,
b->backend_server->name,
b->backend_server->port,
b->backend_conn_count)));
}
#endif
/* assert with master_host */
ss_dassert(!master_connected ||
(master_host && ((*p_master_ref)->bref_backend->backend_server == master_host->backend_server) && SERVER_MASTER));
/**
* Sort the pointer list to servers according to connection counts. As
* a consequence those backends having least connections are in the
* beginning of the list.
*/
qsort(backend_ref, (size_t)router_nservers, sizeof(backend_ref_t), p);
if (LOG_IS_ENABLED(LOGFILE_TRACE))
{
if (select_criteria == LEAST_GLOBAL_CONNECTIONS ||
select_criteria == LEAST_ROUTER_CONNECTIONS ||
select_criteria == LEAST_BEHIND_MASTER ||
select_criteria == LEAST_CURRENT_OPERATIONS)
{
LOGIF(LT, (skygw_log_write(LOGFILE_TRACE,
"Servers and %s connection counts:",
select_criteria == LEAST_GLOBAL_CONNECTIONS ?
"all MaxScale" : "router")));
for (i=0; i<router_nservers; i++)
{
BACKEND* b = backend_ref[i].bref_backend;
switch(select_criteria) {
case LEAST_GLOBAL_CONNECTIONS:
LOGIF(LT, (skygw_log_write_flush(LOGFILE_TRACE,
"%s:%d MaxScale connections : %d",
b->backend_server->name,
b->backend_server->port,
b->backend_server->stats.n_current)));
break;
case LEAST_ROUTER_CONNECTIONS:
LOGIF(LT, (skygw_log_write_flush(LOGFILE_TRACE,
"%s:%d RWSplit connections : %d",
b->backend_server->name,
b->backend_server->port,
b->backend_conn_count)));
break;
case LEAST_CURRENT_OPERATIONS:
LOGIF(LT, (skygw_log_write_flush(LOGFILE_TRACE,
"%s:%d current operations : %d",
b->backend_server->name,
b->backend_server->port,
b->backend_server->stats.n_current_ops)));
break;
case LEAST_BEHIND_MASTER:
LOGIF(LT, (skygw_log_write_flush(LOGFILE_TRACE,
"%s:%d replication lag : %d",
b->backend_server->name,
b->backend_server->port,
b->backend_server->rlag)));
default:
break;
}
}
}
} /*< log only */
/**
* Choose at least 1+min_nslaves (master and slave) and at most 1+max_nslaves
* servers from the sorted list. First master found is selected.
*/
for (i=0;
i<router_nservers && (slaves_connected < max_nslaves || !master_connected);
i++)
{
BACKEND* b = backend_ref[i].bref_backend;
if (SERVER_IS_RUNNING(b->backend_server) &&
((b->backend_server->status & router->bitmask) ==
router->bitvalue))
{
/* check also for relay servers and don't take the master_host */
if (slaves_found < max_nslaves &&
(max_slave_rlag == -2 ||
(b->backend_server->rlag != -1 && /*< information currently not available */
b->backend_server->rlag <= max_slave_rlag)) &&
(SERVER_IS_SLAVE(b->backend_server) || SERVER_IS_RELAY_SERVER(b->backend_server)) &&
(master_host != NULL && (b->backend_server != master_host->backend_server)))
{
slaves_found += 1;
/** Slave is already connected */
if (BREF_IS_IN_USE((&backend_ref[i])))
{
slaves_connected += 1;
}
/** New slave connection is taking place */
else
{
backend_ref[i].bref_dcb = dcb_connect(
b->backend_server,
session,
b->backend_server->protocol);
if (backend_ref[i].bref_dcb != NULL)
{
slaves_connected += 1;
/**
* Start executing session command
* history.
*/
execute_sescmd_history(&backend_ref[i]);
/**
* When server fails, this callback
* is called.
*/
dcb_add_callback(
backend_ref[i].bref_dcb,
DCB_REASON_NOT_RESPONDING,
&router_handle_state_switch,
(void *)&backend_ref[i]);
backend_ref[i].bref_state = 0;
bref_set_state(&backend_ref[i],
BREF_IN_USE);
/**
* Increase backend connection counter.
* Server's stats are _increased_ in
* dcb.c:dcb_alloc !
* But decreased in the calling function
* of dcb_close.
*/
atomic_add(&b->backend_conn_count, 1);
}
else
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Unable to establish "
"connection with slave %s:%d",
b->backend_server->name,
b->backend_server->port)));
/* handle connect error */
}
}
}
/* take the master_host for master */
else if (master_host &&
(b->backend_server == master_host->backend_server))
{
*p_master_ref = &backend_ref[i];
if (master_connected)
{
continue;
}
master_found = true;
backend_ref[i].bref_dcb = dcb_connect(
b->backend_server,
session,
b->backend_server->protocol);
if (backend_ref[i].bref_dcb != NULL)
{
master_connected = true;
/**
* When server fails, this callback
* is called.
*/
dcb_add_callback(
backend_ref[i].bref_dcb,
DCB_REASON_NOT_RESPONDING,
&router_handle_state_switch,
(void *)&backend_ref[i]);
backend_ref[i].bref_state = 0;
bref_set_state(&backend_ref[i],
BREF_IN_USE);
/** Increase backend connection counters */
atomic_add(&b->backend_conn_count, 1);
}
else
{
succp = false;
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Unable to establish "
"connection with master %s:%d",
b->backend_server->name,
b->backend_server->port)));
/** handle connect error */
}
}
}
} /*< for */
#if defined(EXTRA_SS_DEBUG)
LOGIF(LT, (skygw_log_write(LOGFILE_TRACE, "Servers and conns after ordering:")));
for (i=0; i<router_nservers; i++)
{
BACKEND* b = backend_ref[i].bref_backend;
LOGIF(LT, (skygw_log_write_flush(LOGFILE_TRACE,
"master bref %p bref %p %d %s %d:%d",
*p_master_ref,
&backend_ref[i],
backend_ref[i].bref_state,
b->backend_server->name,
b->backend_server->port,
b->backend_conn_count)));
}
/* assert with master_host */
ss_dassert(!master_connected ||
(master_host && ((*p_master_ref)->bref_backend->backend_server == master_host->backend_server) && SERVER_MASTER));
#endif
/**
* Successful cases
*/
if (master_connected &&
slaves_connected >= min_nslaves &&
slaves_connected <= max_nslaves)
{
succp = true;
if (slaves_connected == 0 && slaves_found > 0)
{
LOGIF(LE, (skygw_log_write(
LOGFILE_ERROR,
"Warning : Couldn't connect to any of the %d "
"slaves. Routing to %s only.",
slaves_found,
(is_synced_master ? "Galera nodes" : "Master"))));
LOGIF(LM, (skygw_log_write(
LOGFILE_MESSAGE,
"* Warning : Couldn't connect to any of the %d "
"slaves. Routing to %s only.",
slaves_found,
(is_synced_master ? "Galera nodes" : "Master"))));
}
else if (slaves_found == 0)
{
LOGIF(LE, (skygw_log_write(
LOGFILE_ERROR,
"Warning : Couldn't find any slaves from existing "
"%d servers. Routing to %s only.",
router_nservers,
(is_synced_master ? "Galera nodes" : "Master"))));
LOGIF(LM, (skygw_log_write(
LOGFILE_MESSAGE,
"* Warning : Couldn't find any slaves from existing "
"%d servers. Routing to %s only.",
router_nservers,
(is_synced_master ? "Galera nodes" : "Master"))));
}
else if (slaves_connected < max_nslaves)
{
LOGIF(LT, (skygw_log_write_flush(
LOGFILE_TRACE,
"Note : Couldn't connect to maximum number of "
"slaves. Connected successfully to %d slaves "
"of %d of them.",
slaves_connected,
slaves_found)));
}
if (LOG_IS_ENABLED(LT))
{
for (i=0; i<router_nservers; i++)
{
BACKEND* b = backend_ref[i].bref_backend;
if (BREF_IS_IN_USE((&backend_ref[i])))
{
backend_type_t btype = BACKEND_TYPE(b);
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Selected %s in \t%s:%d",
(btype == BE_MASTER ? "master" :
(btype == BE_SLAVE ? "slave" :
"unknown node type")),
b->backend_server->name,
b->backend_server->port)));
}
} /* for */
}
}
/**
* Failure cases
*/
else
{
succp = false;
if (!master_found)
{
LOGIF(LE, (skygw_log_write(
LOGFILE_ERROR,
"Error : Couldn't find suitable %s from %d "
"candidates.",
(is_synced_master ? "Galera node" : "Master"),
router_nservers)));
LOGIF(LM, (skygw_log_write(
LOGFILE_MESSAGE,
"Error : Couldn't find suitable %s from %d "
"candidates.",
(is_synced_master ? "Galera node" : "Master"),
router_nservers)));
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Error : Couldn't find suitable %s from %d "
"candidates.",
(is_synced_master ? "Galera node" : "Master"),
router_nservers)));
}
else if (!master_connected)
{
LOGIF(LE, (skygw_log_write(
LOGFILE_ERROR,
"Error : Couldn't connect to any %s although "
"there exists at least one %s node in the "
"cluster.",
(is_synced_master ? "Galera node" : "Master"),
(is_synced_master ? "Galera node" : "Master"))));
LOGIF(LM, (skygw_log_write(
LOGFILE_MESSAGE,
"Error : Couldn't connect to any %s although "
"there exists at least one %s node in the "
"cluster.",
(is_synced_master ? "Galera node" : "Master"),
(is_synced_master ? "Galera node" : "Master"))));
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Error : Couldn't connect to any %s although "
"there exists at least one %s node in the "
"cluster.",
(is_synced_master ? "Galera node" : "Master"),
(is_synced_master ? "Galera node" : "Master"))));
}
if (slaves_connected < min_nslaves)
{
LOGIF(LE, (skygw_log_write(
LOGFILE_ERROR,
"Error : Couldn't establish required amount of "
"slave connections for router session.")));
LOGIF(LM, (skygw_log_write(
LOGFILE_MESSAGE,
"Error : Couldn't establish required amount of "
"slave connections for router session.")));
}
/** Clean up connections */
for (i=0; i<router_nservers; i++)
{
if (BREF_IS_IN_USE((&backend_ref[i])))
{
ss_dassert(backend_ref[i].bref_backend->backend_conn_count > 0);
/** disconnect opened connections */
dcb_close(backend_ref[i].bref_dcb);
bref_clear_state(&backend_ref[i], BREF_IN_USE);
/** Decrease backend's connection counter. */
atomic_add(&backend_ref[i].bref_backend->backend_conn_count, -1);
}
}
master_connected = false;
slaves_connected = 0;
}
return_succp:
return succp;
}
/**
* Create a generic router session property strcture.
*/
static rses_property_t* rses_property_init(
rses_property_type_t prop_type)
{
rses_property_t* prop;
prop = (rses_property_t*)calloc(1, sizeof(rses_property_t));
if (prop == NULL)
{
goto return_prop;
}
prop->rses_prop_type = prop_type;
#if defined(SS_DEBUG)
prop->rses_prop_chk_top = CHK_NUM_ROUTER_PROPERTY;
prop->rses_prop_chk_tail = CHK_NUM_ROUTER_PROPERTY;
#endif
return_prop:
CHK_RSES_PROP(prop);
return prop;
}
/**
* Property is freed at the end of router client session.
*/
static void rses_property_done(
rses_property_t* prop)
{
CHK_RSES_PROP(prop);
switch (prop->rses_prop_type) {
case RSES_PROP_TYPE_SESCMD:
mysql_sescmd_done(&prop->rses_prop_data.sescmd);
break;
default:
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [rses_property_done] Unknown property type %d "
"in property %p",
pthread_self(),
prop->rses_prop_type,
prop)));
ss_dassert(false);
break;
}
free(prop);
}
/**
* Add property to the router_client_ses structure's rses_properties
* array. The slot is determined by the type of property.
* In each slot there is a list of properties of similar type.
*
* Router client session must be locked.
*/
static void rses_property_add(
ROUTER_CLIENT_SES* rses,
rses_property_t* prop)
{
rses_property_t* p;
CHK_CLIENT_RSES(rses);
CHK_RSES_PROP(prop);
ss_dassert(SPINLOCK_IS_LOCKED(&rses->rses_lock));
prop->rses_prop_rsession = rses;
p = rses->rses_properties[prop->rses_prop_type];
if (p == NULL)
{
rses->rses_properties[prop->rses_prop_type] = prop;
}
else
{
while (p->rses_prop_next != NULL)
{
p = p->rses_prop_next;
}
p->rses_prop_next = prop;
}
}
/**
* Router session must be locked.
* Return session command pointer if succeed, NULL if failed.
*/
static mysql_sescmd_t* rses_property_get_sescmd(
rses_property_t* prop)
{
mysql_sescmd_t* sescmd;
CHK_RSES_PROP(prop);
ss_dassert(prop->rses_prop_rsession == NULL ||
SPINLOCK_IS_LOCKED(&prop->rses_prop_rsession->rses_lock));
sescmd = &prop->rses_prop_data.sescmd;
if (sescmd != NULL)
{
CHK_MYSQL_SESCMD(sescmd);
}
return sescmd;
}
/**
static void rses_begin_locked_property_action(
rses_property_t* prop)
{
CHK_RSES_PROP(prop);
spinlock_acquire(&prop->rses_prop_lock);
}
static void rses_end_locked_property_action(
rses_property_t* prop)
{
CHK_RSES_PROP(prop);
spinlock_release(&prop->rses_prop_lock);
}
*/
/**
* Create session command property.
*/
static mysql_sescmd_t* mysql_sescmd_init (
rses_property_t* rses_prop,
GWBUF* sescmd_buf,
unsigned char packet_type,
ROUTER_CLIENT_SES* rses)
{
mysql_sescmd_t* sescmd;
CHK_RSES_PROP(rses_prop);
/** Can't call rses_property_get_sescmd with uninitialized sescmd */
sescmd = &rses_prop->rses_prop_data.sescmd;
sescmd->my_sescmd_prop = rses_prop; /*< reference to owning property */
#if defined(SS_DEBUG)
sescmd->my_sescmd_chk_top = CHK_NUM_MY_SESCMD;
sescmd->my_sescmd_chk_tail = CHK_NUM_MY_SESCMD;
#endif
/** Set session command buffer */
sescmd->my_sescmd_buf = sescmd_buf;
sescmd->my_sescmd_packet_type = packet_type;
return sescmd;
}
static void mysql_sescmd_done(
mysql_sescmd_t* sescmd)
{
CHK_RSES_PROP(sescmd->my_sescmd_prop);
gwbuf_free(sescmd->my_sescmd_buf);
memset(sescmd, 0, sizeof(mysql_sescmd_t));
}
/**
* All cases where backend message starts at least with one response to session
* command are handled here.
* Read session commands from property list. If command is already replied,
* discard packet. Else send reply to client. In both cases move cursor forward
* until all session command replies are handled.
*
* Cases that are expected to happen and which are handled:
* s = response not yet replied to client, S = already replied response,
* q = query
* 1. q+ for example : select * from mysql.user
* 2. s+ for example : set autocommit=1
* 3. S+
* 4. sq+
* 5. Sq+
* 6. Ss+
* 7. Ss+q+
* 8. S+q+
* 9. s+q+
*/
static GWBUF* sescmd_cursor_process_replies(
GWBUF* replybuf,
backend_ref_t* bref)
{
mysql_sescmd_t* scmd;
sescmd_cursor_t* scur;
scur = &bref->bref_sescmd_cur;
ss_dassert(SPINLOCK_IS_LOCKED(&(scur->scmd_cur_rses->rses_lock)));
scmd = sescmd_cursor_get_command(scur);
CHK_GWBUF(replybuf);
/**
* Walk through packets in the message and the list of session
* commands.
*/
while (scmd != NULL && replybuf != NULL)
{
/** Faster backend has already responded to client : discard */
if (scmd->my_sescmd_is_replied)
{
bool last_packet = false;
CHK_GWBUF(replybuf);
while (!last_packet)
{
int buflen;
buflen = GWBUF_LENGTH(replybuf);
last_packet = GWBUF_IS_TYPE_RESPONSE_END(replybuf);
/** discard packet */
replybuf = gwbuf_consume(replybuf, buflen);
}
/** Set response status received */
bref_clear_state(bref, BREF_WAITING_RESULT);
}
/** Response is in the buffer and it will be sent to client. */
else if (replybuf != NULL)
{
/** Mark the rest session commands as replied */
scmd->my_sescmd_is_replied = true;
}
if (sescmd_cursor_next(scur))
{
scmd = sescmd_cursor_get_command(scur);
}
else
{
scmd = NULL;
/** All session commands are replied */
scur->scmd_cur_active = false;
}
}
ss_dassert(replybuf == NULL || *scur->scmd_cur_ptr_property == NULL);
return replybuf;
}
/**
* Get the address of current session command.
*
* Router session must be locked */
static mysql_sescmd_t* sescmd_cursor_get_command(
sescmd_cursor_t* scur)
{
mysql_sescmd_t* scmd;
ss_dassert(SPINLOCK_IS_LOCKED(&(scur->scmd_cur_rses->rses_lock)));
scur->scmd_cur_cmd = rses_property_get_sescmd(*scur->scmd_cur_ptr_property);
CHK_MYSQL_SESCMD(scur->scmd_cur_cmd);
scmd = scur->scmd_cur_cmd;
return scmd;
}
/** router must be locked */
static bool sescmd_cursor_is_active(
sescmd_cursor_t* sescmd_cursor)
{
bool succp;
ss_dassert(SPINLOCK_IS_LOCKED(&sescmd_cursor->scmd_cur_rses->rses_lock));
succp = sescmd_cursor->scmd_cur_active;
return succp;
}
/** router must be locked */
static void sescmd_cursor_set_active(
sescmd_cursor_t* sescmd_cursor,
bool value)
{
ss_dassert(SPINLOCK_IS_LOCKED(&sescmd_cursor->scmd_cur_rses->rses_lock));
/** avoid calling unnecessarily */
ss_dassert(sescmd_cursor->scmd_cur_active != value);
sescmd_cursor->scmd_cur_active = value;
}
/**
* Clone session command's command buffer.
* Router session must be locked
*/
static GWBUF* sescmd_cursor_clone_querybuf(
sescmd_cursor_t* scur)
{
GWBUF* buf;
ss_dassert(scur->scmd_cur_cmd != NULL);
buf = gwbuf_clone(scur->scmd_cur_cmd->my_sescmd_buf);
CHK_GWBUF(buf);
return buf;
}
static bool sescmd_cursor_history_empty(
sescmd_cursor_t* scur)
{
bool succp;
CHK_SESCMD_CUR(scur);
if (scur->scmd_cur_rses->rses_properties[RSES_PROP_TYPE_SESCMD] == NULL)
{
succp = true;
}
else
{
succp = false;
}
return succp;
}
static void sescmd_cursor_reset(
sescmd_cursor_t* scur)
{
ROUTER_CLIENT_SES* rses;
CHK_SESCMD_CUR(scur);
CHK_CLIENT_RSES(scur->scmd_cur_rses);
rses = scur->scmd_cur_rses;
scur->scmd_cur_ptr_property = &rses->rses_properties[RSES_PROP_TYPE_SESCMD];
CHK_RSES_PROP((*scur->scmd_cur_ptr_property));
scur->scmd_cur_active = false;
scur->scmd_cur_cmd = &(*scur->scmd_cur_ptr_property)->rses_prop_data.sescmd;
}
static bool execute_sescmd_history(
backend_ref_t* bref)
{
bool succp;
sescmd_cursor_t* scur;
CHK_BACKEND_REF(bref);
scur = &bref->bref_sescmd_cur;
CHK_SESCMD_CUR(scur);
if (!sescmd_cursor_history_empty(scur))
{
sescmd_cursor_reset(scur);
succp = execute_sescmd_in_backend(bref);
}
else
{
succp = true;
}
return succp;
}
/**
* If session command cursor is passive, sends the command to backend for
* execution.
*
* Returns true if command was sent or added successfully to the queue.
* Returns false if command sending failed or if there are no pending session
* commands.
*
* Router session must be locked.
*/
static bool execute_sescmd_in_backend(
backend_ref_t* backend_ref)
{
DCB* dcb;
bool succp;
int rc = 0;
sescmd_cursor_t* scur;
if (BREF_IS_CLOSED(backend_ref))
{
succp = false;
goto return_succp;
}
dcb = backend_ref->bref_dcb;
CHK_DCB(dcb);
CHK_BACKEND_REF(backend_ref);
/**
* Get cursor pointer and copy of command buffer to cursor.
*/
scur = &backend_ref->bref_sescmd_cur;
/** Return if there are no pending ses commands */
if (sescmd_cursor_get_command(scur) == NULL)
{
succp = false;
LOGIF(LT, (skygw_log_write_flush(
LOGFILE_TRACE,
"Cursor had no pending session commands.")));
goto return_succp;
}
if (!sescmd_cursor_is_active(scur))
{
/** Cursor is left active when function returns. */
sescmd_cursor_set_active(scur, true);
}
#if defined(SS_DEBUG)
LOGIF(LT, tracelog_routed_query(scur->scmd_cur_rses,
"execute_sescmd_in_backend",
backend_ref,
sescmd_cursor_clone_querybuf(scur)));
{
GWBUF* tmpbuf = sescmd_cursor_clone_querybuf(scur);
uint8_t* ptr = GWBUF_DATA(tmpbuf);
unsigned char cmd = MYSQL_GET_COMMAND(ptr);
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [execute_sescmd_in_backend] Just before write, fd "
"%d : cmd %s.",
pthread_self(),
dcb->fd,
STRPACKETTYPE(cmd))));
gwbuf_free(tmpbuf);
}
#endif /*< SS_DEBUG */
switch (scur->scmd_cur_cmd->my_sescmd_packet_type) {
case MYSQL_COM_CHANGE_USER:
rc = dcb->func.auth(
dcb,
NULL,
dcb->session,
sescmd_cursor_clone_querybuf(scur));
break;
case MYSQL_COM_QUERY:
case MYSQL_COM_INIT_DB:
default:
/**
* Mark session command buffer, it triggers writing
* MySQL command to protocol
*/
gwbuf_set_type(scur->scmd_cur_cmd->my_sescmd_buf, GWBUF_TYPE_SESCMD);
rc = dcb->func.write(
dcb,
sescmd_cursor_clone_querybuf(scur));
break;
}
LOGIF(LT, (skygw_log_write_flush(
LOGFILE_TRACE,
"%lu [execute_sescmd_in_backend] Routed %s cmd %p.",
pthread_self(),
STRPACKETTYPE(scur->scmd_cur_cmd->my_sescmd_packet_type),
scur->scmd_cur_cmd)));
if (rc == 1)
{
succp = true;
}
else
{
succp = false;
}
return_succp:
return succp;
}
/**
* Moves cursor to next property and copied address of its sescmd to cursor.
* Current propery must be non-null.
* If current property is the last on the list, *scur->scmd_ptr_property == NULL
*
* Router session must be locked
*/
static bool sescmd_cursor_next(
sescmd_cursor_t* scur)
{
bool succp = false;
rses_property_t* prop_curr;
rses_property_t* prop_next;
ss_dassert(scur != NULL);
ss_dassert(*(scur->scmd_cur_ptr_property) != NULL);
ss_dassert(SPINLOCK_IS_LOCKED(
&(*(scur->scmd_cur_ptr_property))->rses_prop_rsession->rses_lock));
/** Illegal situation */
if (scur == NULL ||
*scur->scmd_cur_ptr_property == NULL ||
scur->scmd_cur_cmd == NULL)
{
/** Log error */
goto return_succp;
}
prop_curr = *(scur->scmd_cur_ptr_property);
CHK_MYSQL_SESCMD(scur->scmd_cur_cmd);
ss_dassert(prop_curr == mysql_sescmd_get_property(scur->scmd_cur_cmd));
CHK_RSES_PROP(prop_curr);
/** Copy address of pointer to next property */
scur->scmd_cur_ptr_property = &(prop_curr->rses_prop_next);
prop_next = *scur->scmd_cur_ptr_property;
ss_dassert(prop_next == *(scur->scmd_cur_ptr_property));
/** If there is a next property move forward */
if (prop_next != NULL)
{
CHK_RSES_PROP(prop_next);
CHK_RSES_PROP((*(scur->scmd_cur_ptr_property)));
/** Get pointer to next property's sescmd */
scur->scmd_cur_cmd = rses_property_get_sescmd(prop_next);
ss_dassert(prop_next == scur->scmd_cur_cmd->my_sescmd_prop);
CHK_MYSQL_SESCMD(scur->scmd_cur_cmd);
CHK_RSES_PROP(scur->scmd_cur_cmd->my_sescmd_prop);
}
else
{
/** No more properties, can't proceed. */
goto return_succp;
}
if (scur->scmd_cur_cmd != NULL)
{
succp = true;
}
else
{
ss_dassert(false); /*< Log error, sescmd shouldn't be NULL */
}
return_succp:
return succp;
}
static rses_property_t* mysql_sescmd_get_property(
mysql_sescmd_t* scmd)
{
CHK_MYSQL_SESCMD(scmd);
return scmd->my_sescmd_prop;
}
static void tracelog_routed_query(
ROUTER_CLIENT_SES* rses,
char* funcname,
backend_ref_t* bref,
GWBUF* buf)
{
uint8_t* packet = GWBUF_DATA(buf);
unsigned char packet_type = packet[4];
size_t len;
size_t buflen = GWBUF_LENGTH(buf);
char* querystr;
char* startpos = (char *)&packet[5];
BACKEND* b;
backend_type_t be_type;
DCB* dcb;
CHK_BACKEND_REF(bref);
b = bref->bref_backend;
CHK_BACKEND(b);
dcb = bref->bref_dcb;
CHK_DCB(dcb);
be_type = BACKEND_TYPE(b);
if (GWBUF_IS_TYPE_MYSQL(buf))
{
len = packet[0];
len += 256*packet[1];
len += 256*256*packet[2];
if (packet_type == '\x03')
{
querystr = (char *)malloc(len);
memcpy(querystr, startpos, len-1);
querystr[len-1] = '\0';
LOGIF(LT, (skygw_log_write_flush(
LOGFILE_TRACE,
"%lu [%s] %d bytes long buf, \"%s\" -> %s:%d %s dcb %p",
pthread_self(),
funcname,
buflen,
querystr,
b->backend_server->name,
b->backend_server->port,
STRBETYPE(be_type),
dcb)));
free(querystr);
}
else if (packet_type == '\x22' ||
packet_type == 0x22 ||
packet_type == '\x26' ||
packet_type == 0x26 ||
true)
{
querystr = (char *)malloc(len);
memcpy(querystr, startpos, len-1);
querystr[len-1] = '\0';
LOGIF(LT, (skygw_log_write_flush(
LOGFILE_TRACE,
"%lu [%s] %d bytes long buf, \"%s\" -> %s:%d %s dcb %p",
pthread_self(),
funcname,
buflen,
querystr,
b->backend_server->name,
b->backend_server->port,
STRBETYPE(be_type),
dcb)));
free(querystr);
}
}
gwbuf_free(buf);
}
/**
* Return rc, rc < 0 if router session is closed. rc == 0 if there are no
* capabilities specified, rc > 0 when there are capabilities.
*/
static uint8_t getCapabilities (
ROUTER* inst,
void* router_session)
{
ROUTER_CLIENT_SES* rses = (ROUTER_CLIENT_SES *)router_session;
uint8_t rc;
if (!rses_begin_locked_router_action(rses))
{
rc = 0xff;
goto return_rc;
}
rc = rses->rses_capabilities;
rses_end_locked_router_action(rses);
return_rc:
return rc;
}
/**
* Execute in backends used by current router session.
* Save session variable commands to router session property
* struct. Thus, they can be replayed in backends which are
* started and joined later.
*
* Suppress redundant OK packets sent by backends.
*
* The first OK packet is replied to the client.
* Return true if succeed, false is returned if router session was closed or
* if execute_sescmd_in_backend failed.
*/
static bool route_session_write(
ROUTER_CLIENT_SES* router_cli_ses,
GWBUF* querybuf,
ROUTER_INSTANCE* inst,
unsigned char packet_type,
skygw_query_type_t qtype)
{
bool succp;
rses_property_t* prop;
backend_ref_t* backend_ref;
int i;
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Session write, query type\t%s, packet type %s, "
"routing to all servers.",
STRQTYPE(qtype),
STRPACKETTYPE(packet_type))));
backend_ref = router_cli_ses->rses_backend_ref;
/**
* These are one-way messages and server doesn't respond to them.
* Therefore reply processing is unnecessary and session
* command property is not needed. It is just routed to all available
* backends.
*/
if (packet_type == MYSQL_COM_STMT_SEND_LONG_DATA ||
packet_type == MYSQL_COM_QUIT ||
packet_type == MYSQL_COM_STMT_CLOSE)
{
int rc;
succp = true;
/** Lock router session */
if (!rses_begin_locked_router_action(router_cli_ses))
{
succp = false;
goto return_succp;
}
for (i=0; i<router_cli_ses->rses_nbackends; i++)
{
DCB* dcb = backend_ref[i].bref_dcb;
if (BREF_IS_IN_USE((&backend_ref[i])))
{
rc = dcb->func.write(dcb, gwbuf_clone(querybuf));
if (rc != 1)
{
succp = false;
}
}
}
rses_end_locked_router_action(router_cli_ses);
gwbuf_free(querybuf);
goto return_succp;
}
/** Lock router session */
if (!rses_begin_locked_router_action(router_cli_ses))
{
rses_property_done(prop);
succp = false;
goto return_succp;
}
/**
* Additional reference is created to querybuf to
* prevent it from being released before properties
* are cleaned up as a part of router sessionclean-up.
*/
prop = rses_property_init(RSES_PROP_TYPE_SESCMD);
mysql_sescmd_init(prop, querybuf, packet_type, router_cli_ses);
/** Add sescmd property to router client session */
rses_property_add(router_cli_ses, prop);
for (i=0; i<router_cli_ses->rses_nbackends; i++)
{
if (BREF_IS_IN_USE((&backend_ref[i])))
{
sescmd_cursor_t* scur;
scur = backend_ref_get_sescmd_cursor(&backend_ref[i]);
/**
* Add one waiter to backend reference.
*/
bref_set_state(get_bref_from_dcb(router_cli_ses,
backend_ref[i].bref_dcb),
BREF_WAITING_RESULT);
/**
* Start execution if cursor is not already executing.
* Otherwise, cursor will execute pending commands
* when it completes with previous commands.
*/
if (sescmd_cursor_is_active(scur))
{
succp = true;
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Backend %s:%d already executing sescmd.",
backend_ref[i].bref_backend->backend_server->name,
backend_ref[i].bref_backend->backend_server->port)));
}
else
{
succp = execute_sescmd_in_backend(&backend_ref[i]);
if (!succp)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Failed to execute session "
"command in %s:%d",
backend_ref[i].bref_backend->backend_server->name,
backend_ref[i].bref_backend->backend_server->port)));
}
}
}
}
/** Unlock router session */
rses_end_locked_router_action(router_cli_ses);
atomic_add(&inst->stats.n_all, 1);
return_succp:
return succp;
}
#if defined(NOT_USED)
static bool router_option_configured(
ROUTER_INSTANCE* router,
const char* optionstr,
void* data)
{
bool succp = false;
char** option;
option = router->service->routerOptions;
while (option != NULL)
{
char* value;
if ((value = strchr(options[i], '=')) == NULL)
{
break;
}
else
{
*value = 0;
value++;
if (strcmp(options[i], "slave_selection_criteria") == 0)
{
if (GET_SELECT_CRITERIA(value) == (select_criteria_t *)*data)
{
succp = true;
break;
}
}
}
}
return succp;
}
#endif /*< NOT_USED */
static void rwsplit_process_router_options(
ROUTER_INSTANCE* router,
char** options)
{
int i;
char* value;
select_criteria_t c;
for (i = 0; options[i]; i++)
{
if ((value = strchr(options[i], '=')) == NULL)
{
LOGIF(LE, (skygw_log_write(
LOGFILE_ERROR, "Warning : Unsupported "
"router option \"%s\" for "
"readwritesplit router.",
options[i])));
}
else
{
*value = 0;
value++;
if (strcmp(options[i], "slave_selection_criteria") == 0)
{
c = GET_SELECT_CRITERIA(value);
ss_dassert(
c == LEAST_GLOBAL_CONNECTIONS ||
c == LEAST_ROUTER_CONNECTIONS ||
c == LEAST_BEHIND_MASTER ||
c == LEAST_CURRENT_OPERATIONS ||
c == UNDEFINED_CRITERIA);
if (c == UNDEFINED_CRITERIA)
{
LOGIF(LE, (skygw_log_write(
LOGFILE_ERROR, "Warning : Unknown "
"slave selection criteria \"%s\". "
"Allowed values are LEAST_GLOBAL_CONNECTIONS, "
"LEAST_ROUTER_CONNECTIONS, "
"LEAST_BEHIND_MASTER,"
"and LEAST_CURRENT_OPERATIONS.",
STRCRITERIA(router->rwsplit_config.rw_slave_select_criteria))));
}
else
{
router->rwsplit_config.rw_slave_select_criteria = c;
}
}
}
} /*< for */
}
/**
* Error Handler routine to resolve backend failures. If it succeeds then there
* are enough operative backends available and connected. Otherwise it fails,
* and session is terminated.
*
* @param instance The router instance
* @param router_session The router session
* @param message The error message to reply
* @param backend_dcb The backend DCB
* @param action The action: REPLY, REPLY_AND_CLOSE, NEW_CONNECTION
* @param succp Result of action.
*
* Even if succp == true connecting to new slave may have failed. succp is to
* tell whether router has enough master/slave connections to continue work.
*/
static void handleError (
ROUTER* instance,
void* router_session,
GWBUF* errmsgbuf,
DCB* backend_dcb,
error_action_t action,
bool* succp)
{
SESSION* session;
ROUTER_INSTANCE* inst = (ROUTER_INSTANCE *)instance;
ROUTER_CLIENT_SES* rses = (ROUTER_CLIENT_SES *)router_session;
CHK_DCB(backend_dcb);
#if defined(SS_DEBUG)
backend_dcb->dcb_errhandle_called = true;
#endif
session = backend_dcb->session;
if (session != NULL)
CHK_SESSION(session);
switch (action) {
case ERRACT_NEW_CONNECTION:
{
if (rses != NULL)
CHK_CLIENT_RSES(rses);
if (!rses_begin_locked_router_action(rses))
{
*succp = false;
return;
}
*succp = handle_error_new_connection(inst,
rses,
backend_dcb,
errmsgbuf);
rses_end_locked_router_action(rses);
break;
}
case ERRACT_REPLY_CLIENT:
{
*succp = handle_error_reply_client(session, errmsgbuf);
break;
}
default:
*succp = false;
break;
}
}
static bool handle_error_reply_client(
SESSION* ses,
GWBUF* errmsg)
{
session_state_t sesstate;
DCB* client_dcb;
bool succp;
spinlock_acquire(&ses->ses_lock);
sesstate = ses->state;
client_dcb = ses->client;
spinlock_release(&ses->ses_lock);
if (sesstate == SESSION_STATE_ROUTER_READY)
{
CHK_DCB(client_dcb);
client_dcb->func.write(client_dcb, errmsg);
}
succp = false; /** false because new servers aren's selected. */
return succp;
}
/**
* This must be called with router lock
*/
static bool handle_error_new_connection(
ROUTER_INSTANCE* inst,
ROUTER_CLIENT_SES* rses,
DCB* backend_dcb,
GWBUF* errmsg)
{
SESSION* ses;
int router_nservers;
int max_nslaves;
int max_slave_rlag;
backend_ref_t* bref;
bool succp;
ss_dassert(SPINLOCK_IS_LOCKED(&rses->rses_lock));
ses = backend_dcb->session;
CHK_SESSION(ses);
bref = get_bref_from_dcb(rses, backend_dcb);
/** failed DCB has already been replaced */
if (bref == NULL)
{
succp = true;
goto return_succp;
}
/**
* Error handler is already called for this DCB because
* it's not polling anymore. It can be assumed that
* it succeed because rses isn't closed.
*/
if (backend_dcb->state != DCB_STATE_POLLING)
{
succp = true;
goto return_succp;
}
CHK_BACKEND_REF(bref);
if (BREF_IS_WAITING_RESULT(bref))
{
DCB* client_dcb;
client_dcb = ses->client;
client_dcb->func.write(client_dcb, errmsg);
bref_clear_state(bref, BREF_WAITING_RESULT);
}
bref_clear_state(bref, BREF_IN_USE);
bref_set_state(bref, BREF_CLOSED);
/**
* Remove callback because this DCB won't be used
* unless it is reconnected later, and then the callback
* is set again.
*/
dcb_remove_callback(backend_dcb,
DCB_REASON_NOT_RESPONDING,
&router_handle_state_switch,
(void *)bref);
router_nservers = router_get_servercount(inst);
max_nslaves = rses_get_max_slavecount(rses, router_nservers);
max_slave_rlag = rses_get_max_replication_lag(rses);
/**
* Try to get replacement slave or at least the minimum
* number of slave connections for router session.
*/
succp = select_connect_backend_servers(
&rses->rses_master_ref,
rses->rses_backend_ref,
router_nservers,
max_nslaves,
max_slave_rlag,
rses->rses_config.rw_slave_select_criteria,
ses,
inst);
return_succp:
return succp;
}
static void print_error_packet(
ROUTER_CLIENT_SES* rses,
GWBUF* buf,
DCB* dcb)
{
#if defined(SS_DEBUG)
if (GWBUF_IS_TYPE_MYSQL(buf))
{
while (gwbuf_length(buf) > 0)
{
/**
* This works with MySQL protocol only !
* Protocol specific packet print functions would be nice.
*/
uint8_t* ptr = GWBUF_DATA(buf);
size_t len = MYSQL_GET_PACKET_LEN(ptr);
if (MYSQL_GET_COMMAND(ptr) == 0xff)
{
SERVER* srv = NULL;
backend_ref_t* bref = rses->rses_backend_ref;
int i;
char* bufstr;
for (i=0; i<rses->rses_nbackends; i++)
{
if (bref[i].bref_dcb == dcb)
{
srv = bref[i].bref_backend->backend_server;
}
}
ss_dassert(srv != NULL);
bufstr = strndup(&ptr[7], len-3);
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Backend server %s:%d responded with "
"error : %s",
srv->name,
srv->port,
bufstr)));
free(bufstr);
}
buf = gwbuf_consume(buf, len+4);
}
}
else
{
while ((buf = gwbuf_consume(buf, GWBUF_LENGTH(buf))) != NULL);
}
#endif /*< SS_DEBUG */
}
static int router_get_servercount(
ROUTER_INSTANCE* inst)
{
int router_nservers = 0;
BACKEND** b = inst->servers;
/** count servers */
while (*(b++) != NULL) router_nservers++;
return router_nservers;
}
static bool have_enough_servers(
ROUTER_CLIENT_SES** p_rses,
const int min_nsrv,
int router_nsrv,
ROUTER_INSTANCE* router)
{
bool succp;
/** With too few servers session is not created */
if (router_nsrv < min_nsrv ||
MAX((*p_rses)->rses_config.rw_max_slave_conn_count,
(router_nsrv*(*p_rses)->rses_config.rw_max_slave_conn_percent)/100)
< min_nsrv)
{
if (router_nsrv < min_nsrv)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Unable to start %s service. There are "
"too few backend servers available. Found %d "
"when %d is required.",
router->service->name,
router_nsrv,
min_nsrv)));
}
else
{
double pct = (*p_rses)->rses_config.rw_max_slave_conn_percent/100;
double nservers = (double)router_nsrv*pct;
if ((*p_rses)->rses_config.rw_max_slave_conn_count < min_nsrv)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Unable to start %s service. There are "
"too few backend servers configured in "
"MaxScale.cnf. Found %d when %d is required.",
router->service->name,
(*p_rses)->rses_config.rw_max_slave_conn_count,
min_nsrv)));
}
if (nservers < min_nsrv)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Unable to start %s service. There are "
"too few backend servers configured in "
"MaxScale.cnf. Found %d%% when at least %.0f%% "
"would be required.",
router->service->name,
(*p_rses)->rses_config.rw_max_slave_conn_percent,
min_nsrv/(((double)router_nsrv)/100))));
}
}
free(*p_rses);
*p_rses = NULL;
succp = false;
}
else
{
succp = true;
}
return succp;
}
/**
* Find out the number of read backend servers.
* Depending on the configuration value type, either copy direct count
* of slave connections or calculate the count from percentage value.
*/
static int rses_get_max_slavecount(
ROUTER_CLIENT_SES* rses,
int router_nservers)
{
int conf_max_nslaves;
int max_nslaves;
CHK_CLIENT_RSES(rses);
if (rses->rses_config.rw_max_slave_conn_count > 0)
{
conf_max_nslaves = rses->rses_config.rw_max_slave_conn_count;
}
else
{
conf_max_nslaves =
(router_nservers*rses->rses_config.rw_max_slave_conn_percent)/100;
}
max_nslaves = MIN(router_nservers-1, MAX(1, conf_max_nslaves));
return max_nslaves;
}
static int rses_get_max_replication_lag(
ROUTER_CLIENT_SES* rses)
{
int conf_max_rlag;
CHK_CLIENT_RSES(rses);
/** if there is no configured value, then longest possible int is used */
if (rses->rses_config.rw_max_slave_replication_lag > 0)
{
conf_max_rlag = rses->rses_config.rw_max_slave_replication_lag;
}
else
{
conf_max_rlag = ~(1<<31);
}
return conf_max_rlag;
}
static backend_ref_t* get_bref_from_dcb(
ROUTER_CLIENT_SES* rses,
DCB* dcb)
{
backend_ref_t* bref;
int i = 0;
CHK_DCB(dcb);
CHK_CLIENT_RSES(rses);
bref = rses->rses_backend_ref;
while (i<rses->rses_nbackends)
{
if (bref->bref_dcb == dcb)
{
break;
}
bref++;
i += 1;
}
if (i == rses->rses_nbackends)
{
bref = NULL;
}
return bref;
}
static int router_handle_state_switch(
DCB* dcb,
DCB_REASON reason,
void* data)
{
backend_ref_t* bref;
int rc = 1;
ROUTER_CLIENT_SES* rses;
SESSION* ses;
SERVER* srv;
CHK_DCB(dcb);
bref = (backend_ref_t *)data;
CHK_BACKEND_REF(bref);
srv = bref->bref_backend->backend_server;
if (SERVER_IS_RUNNING(srv) && SERVER_IS_IN_CLUSTER(srv))
{
goto return_rc;
}
ses = dcb->session;
CHK_SESSION(ses);
rses = (ROUTER_CLIENT_SES *)dcb->session->router_session;
CHK_CLIENT_RSES(rses);
switch (reason) {
case DCB_REASON_NOT_RESPONDING:
dcb->func.hangup(dcb);
break;
default:
break;
}
return_rc:
return rc;
}
static sescmd_cursor_t* backend_ref_get_sescmd_cursor (
backend_ref_t* bref)
{
sescmd_cursor_t* scur;
CHK_BACKEND_REF(bref);
scur = &bref->bref_sescmd_cur;
CHK_SESCMD_CUR(scur);
return scur;
}
#if defined(PREP_STMT_CACHING)
#define MAX_STMT_LEN 1024
static prep_stmt_t* prep_stmt_init(
prep_stmt_type_t type,
void* id)
{
prep_stmt_t* pstmt;
pstmt = (prep_stmt_t *)calloc(1, sizeof(prep_stmt_t));
if (pstmt != NULL)
{
#if defined(SS_DEBUG)
pstmt->pstmt_chk_top = CHK_NUM_PREP_STMT;
pstmt->pstmt_chk_tail = CHK_NUM_PREP_STMT;
#endif
pstmt->pstmt_state = PREP_STMT_ALLOC;
pstmt->pstmt_type = type;
if (type == PREP_STMT_NAME)
{
pstmt->pstmt_id.name = strndup((char *)id, MAX_STMT_LEN);
}
else
{
pstmt->pstmt_id.seq = 0;
}
}
CHK_PREP_STMT(pstmt);
return pstmt;
}
static void prep_stmt_done(
prep_stmt_t* pstmt)
{
CHK_PREP_STMT(pstmt);
if (pstmt->pstmt_type == PREP_STMT_NAME)
{
free(pstmt->pstmt_id.name);
}
free(pstmt);
}
static bool prep_stmt_drop(
prep_stmt_t* pstmt)
{
CHK_PREP_STMT(pstmt);
pstmt->pstmt_state = PREP_STMT_DROPPED;
return true;
}
#endif /*< PREP_STMT_CACHING */
/********************************
* This routine returns the root master server from MySQL replication tree
* Get the root Master rule:
*
* find server with the lowest replication depth level
* and the SERVER_MASTER bitval
* Servers are checked even if they are in 'maintenance'
*
* @param servers The list of servers
* @param router_nservers The number of servers
* @return The Master found
*
*/
static BACKEND *get_root_master(backend_ref_t *servers, int router_nservers) {
int i = 0;
BACKEND * master_host = NULL;
for (i = 0; i< router_nservers; i++) {
BACKEND* b = NULL;
b = servers[i].bref_backend;
if (b && (b->backend_server->status & (SERVER_MASTER|SERVER_MAINT)) == SERVER_MASTER) {
if (master_host && b->backend_server->depth < master_host->backend_server->depth) {
master_host = b;
} else {
if (master_host == NULL) {
master_host = b;
}
}
}
}
return master_host;
}
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