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MaxScale/server/modules/routing/readwritesplit/readwritesplit.c
Markus Makela 1432677406 Fix regression in prepared statement routing 
The prepared statements were router according to the real type instead of
being router to the master. This was caused by the change in the route
target function.
2016-11-21 23:05:46 +02:00

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/*
* Copyright (c) 2016 MariaDB Corporation Ab
*
* Use of this software is governed by the Business Source License included
* in the LICENSE.TXT file and at www.mariadb.com/bsl.
*
* Change Date: 2019-07-01
*
* On the date above, in accordance with the Business Source License, use
* of this software will be governed by version 2 or later of the General
* Public License.
*/
#include <stdio.h>
#include <strings.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <maxscale/router.h>
#include "readwritesplit.h"
#include "rwsplit_internal.h"
#include <maxscale/log_manager.h>
#include <maxscale/query_classifier.h>
#include <maxscale/dcb.h>
#include <maxscale/spinlock.h>
#include <maxscale/modinfo.h>
#include <maxscale/modutil.h>
#include <maxscale/alloc.h>
MODULE_INFO info =
{
MODULE_API_ROUTER, MODULE_GA, ROUTER_VERSION,
"A Read/Write splitting router for enhancement read scalability"
};
/**
* @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. It also contains functions that are directly called
* by the entry point functions. Some of these are used by functions in other
* modules of the read write split router, others are used only within this
* module.
*
* @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
* 09/09/2015 Martin Brampton Modify error handler
* 25/09/2015 Martin Brampton Block callback processing when no router
* session in the DCB
* 03/08/2016 Martin Brampton Extract the API functions, move the rest
*
* @endverbatim
*/
/** Maximum number of slaves */
#define MAX_SLAVE_COUNT 255
static char *version_str = "V1.1.0";
/*
* The functions that implement the router module API
*/
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 diagnostics(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 uint64_t getCapabilities(void);
/*
* End of the API functions; now the module structure that links to them.
* Note that the function names are chosen to exactly match the names used in
* the definition of ROUTER_OBJECT. This is not obligatory, but is done to
* make it easier to track the connection between calls and functions.
*/
static ROUTER_OBJECT MyObject =
{
createInstance,
newSession,
closeSession,
freeSession,
routeQuery,
diagnostics,
clientReply,
handleError,
getCapabilities,
NULL
};
/*
* Declaration of functions that are used only within this module, and are
* not part of the API.
*/
static void refreshInstance(ROUTER_INSTANCE *router,
CONFIG_PARAMETER *singleparam);
static void free_rwsplit_instance(ROUTER_INSTANCE *router);
static bool rwsplit_process_router_options(ROUTER_INSTANCE *router,
char **options);
static void handle_error_reply_client(SESSION *ses, ROUTER_CLIENT_SES *rses,
DCB *backend_dcb, GWBUF *errmsg);
static bool handle_error_new_connection(ROUTER_INSTANCE *inst,
ROUTER_CLIENT_SES **rses,
DCB *backend_dcb, GWBUF *errmsg);
static bool have_enough_servers(ROUTER_CLIENT_SES *rses, const int min_nsrv,
int router_nsrv, ROUTER_INSTANCE *router);
static bool create_backends(ROUTER_CLIENT_SES *rses, backend_ref_t** dest, int* n_backend);
/**
* Implementation of the mandatory version entry point
*
* @return version string of the module
*/
char *version()
{
return version_str;
}
/**
* The module initialization routine, called when the module
* is first loaded.
*/
void ModuleInit()
{
MXS_NOTICE("Initializing statement-based read/write split router module.");
}
/**
* The module entry point routine. It is this routine that
* must return 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;
}
/*
* Now we implement the API functions
*/
/**
* @brief Create an instance of the read/write router (API).
*
* Create an instance of read/write statement router within the MaxScale. One
* instance of the router is required for each service that is defined in the
* configuration as using this router. One instance of the router will handle
* multiple connections (or router sessions).
*
* @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;
CONFIG_PARAMETER *param;
if ((router = MXS_CALLOC(1, sizeof(ROUTER_INSTANCE))) == NULL)
{
return NULL;
}
router->service = service;
spinlock_init(&router->lock);
/*
* Until we know otherwise assume we have some available slaves.
*/
router->available_slaves = true;
/** Enable strict multistatement handling by default */
router->rwsplit_config.rw_strict_multi_stmt = true;
/** By default, the client connection is closed immediately when a master
* failure is detected */
router->rwsplit_config.rw_master_failure_mode = RW_FAIL_INSTANTLY;
/** Call this before refreshInstance */
if (options && !rwsplit_process_router_options(router, options))
{
free_rwsplit_instance(router);
return NULL;
}
/** These options cancel each other out */
if (router->rwsplit_config.rw_disable_sescmd_hist &&
router->rwsplit_config.rw_max_sescmd_history_size > 0)
{
router->rwsplit_config.rw_max_sescmd_history_size = 0;
}
/**
* Set default value for max_slave_connections as 100%. This way
* LEAST_CURRENT_OPERATIONS allows us to balance evenly across all the
* configured slaves.
*/
router->rwsplit_config.rw_max_slave_conn_count = MAX_SLAVE_COUNT;
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;
/** Set default values */
router->rwsplit_config.rw_use_sql_variables_in = CONFIG_SQL_VARIABLES_IN;
param = config_get_param(service->svc_config_param, "use_sql_variables_in");
if (param != NULL)
{
refreshInstance(router, param);
}
return (ROUTER *)router;
}
/**
* @brief Associate a new session with this instance of the router (API).
*
* The session is used to store all the data required by the router for a
* particular client connection. The instance of the router that relates to a
* particular service is passed as the first parameter. The second parameter is
* the session that has been created in response to the request from a client
* for a connection. The passed session contains generic information; this
* function creates the session structure that holds router specific data.
* There is often a one to one relationship between sessions and router
* sessions, although it is possible to create configurations where a
* connection is handled by multiple routers, one after another.
*
* @param instance The router instance data
* @param session The MaxScale session (generic connection data)
* @return Session specific data for this session, i.e. a router session
*/
static void *newSession(ROUTER *router_inst, SESSION *session)
{
ROUTER_INSTANCE *router = (ROUTER_INSTANCE *)router_inst;
ROUTER_CLIENT_SES *client_rses = (ROUTER_CLIENT_SES *)MXS_CALLOC(1, sizeof(ROUTER_CLIENT_SES));
if (client_rses == NULL)
{
return NULL;
}
#if defined(SS_DEBUG)
client_rses->rses_chk_top = CHK_NUM_ROUTER_SES;
client_rses->rses_chk_tail = CHK_NUM_ROUTER_SES;
#endif
client_rses->router = router;
client_rses->client_dcb = session->client_dcb;
client_rses->rses_autocommit_enabled = true;
client_rses->rses_transaction_active = false;
client_rses->have_tmp_tables = false;
client_rses->forced_node = NULL;
spinlock_init(&client_rses->rses_lock);
memcpy(&client_rses->rses_config, &router->rwsplit_config, sizeof(client_rses->rses_config));
int router_nservers = router->service->n_dbref;
const int min_nservers = 1; /*< hard-coded for now */
if (!have_enough_servers(client_rses, min_nservers, router_nservers, router))
{
MXS_FREE(client_rses);
return NULL;
}
/**
* Create backend reference objects for this session.
*/
backend_ref_t *backend_ref;
if (!create_backends(client_rses, &backend_ref, &router_nservers))
{
MXS_FREE(client_rses);
return NULL;
}
int max_nslaves = rses_get_max_slavecount(client_rses, router_nservers);
int max_slave_rlag = rses_get_max_replication_lag(client_rses);
client_rses->rses_backend_ref = backend_ref;
client_rses->rses_nbackends = router_nservers; /*< # of backend servers */
backend_ref_t *master_ref = NULL; /*< pointer to selected master */
if (!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, false))
{
/**
* Master and at least <min_nslaves> slaves must be found if the router is
* in the strict mode. If sessions without master are allowed, only
* <min_nslaves> slaves must be found.
*/
MXS_FREE(client_rses->rses_backend_ref);
MXS_FREE(client_rses);
return NULL;
}
/** Copy backend pointers to router session. */
client_rses->rses_master_ref = master_ref;
if (client_rses->rses_config.rw_max_slave_conn_percent)
{
int n_conn = 0;
double pct = (double)client_rses->rses_config.rw_max_slave_conn_percent / 100.0;
n_conn = MXS_MAX(floor((double)client_rses->rses_nbackends * pct), 1);
client_rses->rses_config.rw_max_slave_conn_count = n_conn;
}
router->stats.n_sessions += 1;
return (void *)client_rses;
}
/**
* @brief Close a router session (API).
*
* Close a session with the router, this is the mechanism by which a router
* may cleanup data structure etc. The instance of the router that relates to
* the relevant service is passed, along with the router session that is to
* be closed. Typically the function is used in conjunction with freeSession
* which will release the resources used by a router session (see below).
*
* @param instance The router instance data
* @param session The router session being closed
*/
static void closeSession(ROUTER *instance, void *router_session)
{
ROUTER_CLIENT_SES *router_cli_ses = (ROUTER_CLIENT_SES *)router_session;
CHK_CLIENT_RSES(router_cli_ses);
if (!router_cli_ses->rses_closed && rses_begin_locked_router_action(router_cli_ses))
{
/**
* Mark router session as closed. @c rses_closed is checked at the start
* of every API function to quickly stop the processing of closed sessions.
*/
router_cli_ses->rses_closed = true;
for (int i = 0; i < router_cli_ses->rses_nbackends; i++)
{
backend_ref_t *bref = &router_cli_ses->rses_backend_ref[i];
if (BREF_IS_IN_USE(bref))
{
/** This backend is in use and it needs to be closed */
DCB *dcb = bref->bref_dcb;
CHK_DCB(dcb);
ss_dassert(dcb->session->state == SESSION_STATE_STOPPING);
if (BREF_IS_WAITING_RESULT(bref))
{
/** This backend was executing a query when the session was closed */
bref_clear_state(bref, BREF_WAITING_RESULT);
}
bref_clear_state(bref, BREF_IN_USE);
bref_set_state(bref, BREF_CLOSED);
dcb_close(dcb);
/** Decrease server reference connection count */
atomic_add(&bref->ref->connections, -1);
}
else
{
ss_dassert(!BREF_IS_WAITING_RESULT(bref));
/** This should never be true unless a backend reference is taken
* out of use before clearing the BREF_WAITING_RESULT state */
if (BREF_IS_WAITING_RESULT(bref))
{
MXS_WARNING("A closed backend was expecting a result, this should not be possible. "
"Decrementing active operation counter for this backend.");
bref_clear_state(bref, BREF_WAITING_RESULT);
}
}
}
rses_end_locked_router_action(router_cli_ses);
}
}
/**
* @brief Free a router session (API).
*
* When a router session has been closed, freeSession can be called to free
* allocated resources.
*
* @param router_instance The router instance the session belongs to
* @param router_client_session Client session
*
*/
static void freeSession(ROUTER *router_instance, void *router_client_session)
{
ROUTER_CLIENT_SES *router_cli_ses = (ROUTER_CLIENT_SES *)router_client_session;
/**
* For each property type, walk through the list, finalize properties
* and free the allocated memory.
*/
for (int 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;
}
}
MXS_FREE(router_cli_ses->rses_backend_ref);
MXS_FREE(router_cli_ses);
return;
}
/**
* @brief Mark a backend reference as failed
*
* @param bref Backend reference to close
* @param fatal Whether the failure was fatal
*/
void close_failed_bref(backend_ref_t *bref, bool fatal)
{
if (BREF_IS_WAITING_RESULT(bref))
{
bref_clear_state(bref, BREF_WAITING_RESULT);
}
bref_clear_state(bref, BREF_QUERY_ACTIVE);
bref_clear_state(bref, BREF_IN_USE);
bref_set_state(bref, BREF_CLOSED);
if (fatal)
{
bref_set_state(bref, BREF_FATAL_FAILURE);
}
if (sescmd_cursor_is_active(&bref->bref_sescmd_cur))
{
sescmd_cursor_set_active(&bref->bref_sescmd_cur, false);
}
if (bref->bref_pending_cmd)
{
gwbuf_free(bref->bref_pending_cmd);
bref->bref_pending_cmd = NULL;
}
}
/**
* @brief The main routing entry point for a query (API)
*
* The routeQuery function will make the routing decision based on the contents
* of the instance, session and the query itself. The query always represents
* a complete MariaDB/MySQL packet because we define the RCAP_TYPE_STMT_INPUT in
* getCapabilities().
*
* @param instance Router instance
* @param router_session Router session associated with the client
* @param querybuf Buffer containing the query
* @return 1 on success, 0 on error
*/
static int routeQuery(ROUTER *instance, void *router_session, GWBUF *querybuf)
{
ROUTER_INSTANCE *inst = (ROUTER_INSTANCE *) instance;
ROUTER_CLIENT_SES *rses = (ROUTER_CLIENT_SES *) router_session;
int rval = 0;
CHK_CLIENT_RSES(rses);
if (rses->rses_closed)
{
closed_session_reply(querybuf);
}
else
{
live_session_reply(&querybuf, rses);
if (route_single_stmt(inst, rses, querybuf))
{
rval = 1;
}
}
if (querybuf != NULL)
{
gwbuf_free(querybuf);
}
return rval;
}
/**
* @brief Diagnostics routine (API)
*
* Print query router statistics to the DCB passed in
*
* @param instance The router instance
* @param dcb The DCB for diagnostic output
*/
static void diagnostics(ROUTER *instance, DCB *dcb)
{
ROUTER_INSTANCE *router = (ROUTER_INSTANCE *)instance;
char *weightby;
double master_pct = 0.0, slave_pct = 0.0, all_pct = 0.0;
if (router->stats.n_queries > 0)
{
master_pct = ((double)router->stats.n_master / (double)router->stats.n_queries) * 100.0;
slave_pct = ((double)router->stats.n_slave / (double)router->stats.n_queries) * 100.0;
all_pct = ((double)router->stats.n_all / (double)router->stats.n_queries) * 100.0;
}
dcb_printf(dcb, "\tNumber of router sessions: %d\n",
router->stats.n_sessions);
dcb_printf(dcb, "\tCurrent no. of router sessions: %d\n",
router->service->stats.n_current);
dcb_printf(dcb, "\tNumber of queries forwarded: %d\n",
router->stats.n_queries);
dcb_printf(dcb, "\tNumber of queries forwarded to master: %d (%.2f%%)\n",
router->stats.n_master, master_pct);
dcb_printf(dcb, "\tNumber of queries forwarded to slave: %d (%.2f%%)\n",
router->stats.n_slave, slave_pct);
dcb_printf(dcb, "\tNumber of queries forwarded to all: %d (%.2f%%)\n",
router->stats.n_all, all_pct);
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 (SERVER_REF *ref = router->service->dbref; ref; ref = ref->next)
{
dcb_printf(dcb, "\t\t%-20s %3.1f%% %-6d %-6d %d\n",
ref->server->unique_name, (float)ref->weight / 10,
ref->server->stats.n_current, ref->connections,
ref->server->stats.n_current_ops);
}
}
}
/**
* @brief Client Reply routine (API)
*
* 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_INSTANCE *router_inst;
ROUTER_CLIENT_SES *router_cli_ses;
sescmd_cursor_t *scur = NULL;
backend_ref_t *bref;
router_cli_ses = (ROUTER_CLIENT_SES *)router_session;
router_inst = (ROUTER_INSTANCE *)instance;
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))
{
gwbuf_free(writebuf);
goto lock_failed;
}
/** Holding lock ensures that router session remains open */
ss_dassert(backend_dcb->session != NULL);
client_dcb = backend_dcb->session->client_dcb;
/** 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)
{
gwbuf_free(writebuf);
/** 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);
#if !defined(FOR_BUG548_FIX_ONLY)
/** This makes the issue becoming visible in poll.c */
if (bref == NULL)
{
/** Unlock router session */
rses_end_locked_router_action(router_cli_ses);
goto lock_failed;
}
#endif
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))
{
check_session_command_reply(writebuf, scur, bref);
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.
*/
bool rconn = false;
writebuf = sescmd_cursor_process_replies(writebuf, bref, &rconn);
if (rconn && !router_inst->rwsplit_config.rw_disable_sescmd_hist)
{
select_connect_backend_servers(
&router_cli_ses->rses_master_ref, router_cli_ses->rses_backend_ref,
router_cli_ses->rses_nbackends,
router_cli_ses->rses_config.rw_max_slave_conn_count,
router_cli_ses->rses_config.rw_max_slave_replication_lag,
router_cli_ses->rses_config.rw_slave_select_criteria,
router_cli_ses->rses_master_ref->bref_dcb->session,
router_cli_ses->router,
true);
}
}
/**
* 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.
*/
/** 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;
MXS_INFO("Backend %s:%d processed reply and starts to execute active cursor.",
bref->ref->server->name, bref->ref->server->port);
succp = execute_sescmd_in_backend(bref);
if (!succp)
{
MXS_INFO("Backend %s:%d failed to execute session command.",
bref->ref->server->name, bref->ref->server->port);
}
}
else if (bref->bref_pending_cmd != NULL) /*< non-sescmd is waiting to be routed */
{
int ret;
CHK_GWBUF(bref->bref_pending_cmd);
if ((ret = bref->bref_dcb->func.write(bref->bref_dcb,
gwbuf_clone(bref->bref_pending_cmd))) == 1)
{
ROUTER_INSTANCE* inst = (ROUTER_INSTANCE *)instance;
atomic_add(&inst->stats.n_queries, 1);
/**
* Add one query response waiter to backend reference
*/
bref_set_state(bref, BREF_QUERY_ACTIVE);
bref_set_state(bref, BREF_WAITING_RESULT);
}
else
{
char* sql = modutil_get_SQL(bref->bref_pending_cmd);
if (sql)
{
MXS_ERROR("Routing query \"%s\" failed.", sql);
MXS_FREE(sql);
}
else
{
MXS_ERROR("Failed to route query.");
}
}
gwbuf_free(bref->bref_pending_cmd);
bref->bref_pending_cmd = NULL;
}
/** Unlock router session */
rses_end_locked_router_action(router_cli_ses);
lock_failed:
return;
}
/**
* @brief Get router capabilities (API)
*
* Return a bit map indicating the characteristics of this particular router.
* In this case, the only bit set indicates that the router wants to receive
* data for routing as whole SQL statements.
*
* @return RCAP_TYPE_STMT_INPUT.
*/
static uint64_t getCapabilities(void)
{
return RCAP_TYPE_STMT_INPUT;
}
/*
* This is the end of the API functions, and the start of functions that are
* used by the API functions and also used in other modules of the router
* code. Their prototypes are included in rwsplit_internal.h since these
* functions are not intended for use outside the read write split router.
*/
/**
* @brief 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.
*
*/
bool rses_begin_locked_router_action(ROUTER_CLIENT_SES *rses)
{
bool succp = false;
if (rses == NULL)
{
return 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 */
/**
* @brief Releases router client session lock.
*
* Parameters:
* @param rses - <usage>
* <description>
*
* @return void
*
*/
void rses_end_locked_router_action(ROUTER_CLIENT_SES *rses)
{
CHK_CLIENT_RSES(rses);
spinlock_release(&rses->rses_lock);
}
/*
* @brief Clear one or more bits in the backend reference state
*
* The router session holds details of the backend servers that are
* involved in the routing for this particular service. Each backend
* server has a state bit string, and this function (along with
* bref_set_state) is used to manage the state.
*
* @param bref The backend reference to be modified
* @param state A bit string where the 1 bits indicate bits that should
* be turned off in the bref state.
*/
void bref_clear_state(backend_ref_t *bref, bref_state_t state)
{
if (bref == NULL)
{
MXS_ERROR("[%s] Error: NULL parameter.", __FUNCTION__);
return;
}
if ((state & BREF_WAITING_RESULT) && (bref->bref_state & BREF_WAITING_RESULT))
{
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->ref->server->stats.n_current_ops, -1);
ss_dassert(prev2 > 0);
if (prev2 <= 0)
{
MXS_ERROR("[%s] Error: negative current operation count in backend %s:%u",
__FUNCTION__, bref->ref->server->name,
bref->ref->server->port);
}
}
}
bref->bref_state &= ~state;
}
/*
* @brief Set one or more bits in the backend reference state
*
* The router session holds details of the backend servers that are
* involved in the routing for this particular service. Each backend
* server has a state bit string, and this function (along with
* bref_clear_state) is used to manage the state.
*
* @param bref The backend reference to be modified
* @param state A bit string where the 1 bits indicate bits that should
* be turned on in the bref state.
*/
void bref_set_state(backend_ref_t *bref, bref_state_t state)
{
if (bref == NULL)
{
MXS_ERROR("[%s] Error: NULL parameter.", __FUNCTION__);
return;
}
if ((state & BREF_WAITING_RESULT) && (bref->bref_state & BREF_WAITING_RESULT) == 0)
{
int prev1;
int prev2;
/** Increase waiter count */
prev1 = atomic_add(&bref->bref_num_result_wait, 1);
ss_dassert(prev1 >= 0);
if (prev1 < 0)
{
MXS_ERROR("[%s] Error: negative number of connections waiting for "
"results in backend %s:%u", __FUNCTION__,
bref->ref->server->name, bref->ref->server->port);
}
/** Increase global operation count */
prev2 = atomic_add(&bref->ref->server->stats.n_current_ops, 1);
ss_dassert(prev2 >= 0);
if (prev2 < 0)
{
MXS_ERROR("[%s] Error: negative current operation count in backend %s:%u",
__FUNCTION__, bref->ref->server->name, bref->ref->server->port);
}
}
bref->bref_state |= state;
}
/**
* @brief Free resources belonging to a property
*
* Property is freed at the end of router client session.
*
* @param prop The property whose resources are to be released
*/
void rses_property_done(rses_property_t *prop)
{
if (prop == NULL)
{
MXS_ERROR("[%s] Error: NULL parameter.", __FUNCTION__);
return;
}
CHK_RSES_PROP(prop);
switch (prop->rses_prop_type)
{
case RSES_PROP_TYPE_SESCMD:
mysql_sescmd_done(&prop->rses_prop_data.sescmd);
break;
case RSES_PROP_TYPE_TMPTABLES:
hashtable_free(prop->rses_prop_data.temp_tables);
break;
default:
MXS_DEBUG("%lu [rses_property_done] Unknown property type %d "
"in property %p", pthread_self(), prop->rses_prop_type, prop);
ss_dassert(false);
break;
}
MXS_FREE(prop);
}
/**
* @brief Get count of backend servers that are slaves.
*
* 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.
*
* @param rses Router client session
* @param router_nservers The number of backend servers in total
*/
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 = MXS_MIN(router_nservers - 1, MXS_MAX(1, conf_max_nslaves));
return max_nslaves;
}
/*
* @brief Get the maximum replication lag for this router
*
* @param rses Router client session
* @return Replication lag from configuration or very large number
*/
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;
}
/**
* @brief Find a back end reference that matches the given DCB
*
* Finds out if there is a backend reference pointing at the DCB given as
* parameter.
*
* @param rses router client session
* @param dcb DCB
*
* @return backend reference pointer if succeed or NULL
*/
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;
}
/**
* @brief Call hang up function
*
* Calls hang-up function for DCB if it is not both running and in
* master/slave/joined/ndb role. Called by DCB's callback routine.
*
* @param dcb DCB relating to a backend server
* @param reason The reason for the state change
* @param data Data is a backend reference structure belonging to this router
*
* @return 1 for success, 0 for failure
*/
int router_handle_state_switch(DCB *dcb, DCB_REASON reason, void *data)
{
backend_ref_t *bref;
int rc = 1;
SERVER *srv;
CHK_DCB(dcb);
if (NULL == dcb->session->router_session)
{
/*
* The following processing will fail if there is no router session,
* because the "data" parameter will not contain meaningful data,
* so we have no choice but to stop here.
*/
return 0;
}
bref = (backend_ref_t *)data;
CHK_BACKEND_REF(bref);
srv = bref->ref->server;
if (SERVER_IS_RUNNING(srv) && SERVER_IS_IN_CLUSTER(srv))
{
goto return_rc;
}
MXS_DEBUG("%lu [router_handle_state_switch] %s %s:%d in state %s",
pthread_self(), STRDCBREASON(reason), srv->name, srv->port,
STRSRVSTATUS(srv));
CHK_SESSION(((SESSION *)dcb->session));
if (dcb->session->router_session)
{
CHK_CLIENT_RSES(((ROUTER_CLIENT_SES *)dcb->session->router_session));
}
switch (reason)
{
case DCB_REASON_NOT_RESPONDING:
dcb->func.hangup(dcb);
break;
default:
break;
}
return_rc:
return rc;
}
/*
* The end of the functions used here and elsewhere in the router; start of
* functions that are purely internal to this module, i.e. are called directly
* or indirectly by the API functions and not used elsewhere.
*/
/**
* @brief Process router options
*
* @param router Router instance
* @param options Router options
* @return True on success, false if a configuration error was found
*/
static bool rwsplit_process_router_options(ROUTER_INSTANCE *router,
char **options)
{
int i;
char *value;
select_criteria_t c;
if (options == NULL)
{
return true;
}
bool success = true;
for (i = 0; options[i]; i++)
{
if ((value = strchr(options[i], '=')) == NULL)
{
MXS_ERROR("Unsupported router option \"%s\" for readwritesplit router.", options[i]);
success = false;
}
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)
{
MXS_ERROR("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));
success = false;
}
else
{
router->rwsplit_config.rw_slave_select_criteria = c;
}
}
else if (strcmp(options[i], "max_sescmd_history") == 0)
{
router->rwsplit_config.rw_max_sescmd_history_size = atoi(value);
}
else if (strcmp(options[i], "disable_sescmd_history") == 0)
{
router->rwsplit_config.rw_disable_sescmd_hist = config_truth_value(value);
}
else if (strcmp(options[i], "master_accept_reads") == 0)
{
router->rwsplit_config.rw_master_reads = config_truth_value(value);
}
else if (strcmp(options[i], "strict_multi_stmt") == 0)
{
router->rwsplit_config.rw_strict_multi_stmt = config_truth_value(value);
}
else if (strcmp(options[i], "master_failure_mode") == 0)
{
if (strcasecmp(value, "fail_instantly") == 0)
{
router->rwsplit_config.rw_master_failure_mode = RW_FAIL_INSTANTLY;
}
else if (strcasecmp(value, "fail_on_write") == 0)
{
router->rwsplit_config.rw_master_failure_mode = RW_FAIL_ON_WRITE;
}
else if (strcasecmp(value, "error_on_write") == 0)
{
router->rwsplit_config.rw_master_failure_mode = RW_ERROR_ON_WRITE;
}
else
{
MXS_ERROR("Unknown value for 'master_failure_mode': %s", value);
success = false;
}
}
else
{
MXS_ERROR("Unknown router option \"%s=%s\" for readwritesplit router.",
options[i], value);
success = false;
}
}
} /*< for */
return success;
}
/**
* @brief Router error handling routine (API)
*
* 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 errmsgbuf The error message to reply
* @param backend_dcb The backend DCB
* @param action The action: ERRACT_NEW_CONNECTION or
* ERRACT_REPLY_CLIENT
* @param succp Result of action: true iff router can continue
*
* 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 *problem_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(problem_dcb);
/** Don't handle same error twice on same DCB */
if (problem_dcb->dcb_errhandle_called)
{
/** we optimistically assume that previous call succeed */
/*
* The return of true is potentially misleading, but appears to
* be safe with the code as it stands on 9 Sept 2015 - MNB
*/
*succp = true;
return;
}
else
{
problem_dcb->dcb_errhandle_called = true;
}
session = problem_dcb->session;
bool close_dcb = true;
if (session == NULL || rses == NULL)
{
*succp = false;
}
else if (DCB_ROLE_CLIENT_HANDLER == problem_dcb->dcb_role)
{
*succp = false;
}
else
{
CHK_SESSION(session);
CHK_CLIENT_RSES(rses);
switch (action)
{
case ERRACT_NEW_CONNECTION:
{
if (!rses_begin_locked_router_action(rses))
{
close_dcb = false; /* With the assumption that if the router session is closed,
* then so is the dcb.
*/
*succp = false;
break;
}
/**
* If master has lost its Master status error can't be
* handled so that session could continue.
*/
if (rses->rses_master_ref && rses->rses_master_ref->bref_dcb == problem_dcb)
{
SERVER *srv = rses->rses_master_ref->ref->server;
backend_ref_t *bref = get_bref_from_dcb(rses, problem_dcb);
bool can_continue = false;
if (rses->rses_config.rw_master_failure_mode != RW_FAIL_INSTANTLY &&
(bref == NULL || !BREF_IS_WAITING_RESULT(bref)))
{
/** The failure of a master is not considered a critical
* failure as partial functionality still remains. Reads
* are allowed as long as slave servers are available
* and writes will cause an error to be returned.
*
* If we were waiting for a response from the master, we
* can't be sure whether it was executed or not. In this
* case the safest thing to do is to close the client
* connection. */
can_continue = true;
}
else if (!SERVER_IS_MASTER(srv) && !srv->master_err_is_logged)
{
MXS_ERROR("Server %s:%d lost the master status. Readwritesplit "
"service can't locate the master. Client sessions "
"will be closed.", srv->name, srv->port);
srv->master_err_is_logged = true;
}
*succp = can_continue;
if (bref != NULL)
{
CHK_BACKEND_REF(bref);
close_failed_bref(bref, true);
}
else
{
MXS_ERROR("Server %s:%d lost the master status but could not locate the "
"corresponding backend ref.", srv->name, srv->port);
}
}
else
{
/**
* This is called in hope of getting replacement for
* failed slave(s).
*/
*succp = handle_error_new_connection(inst, &rses, problem_dcb, errmsgbuf);
}
dcb_close(problem_dcb);
close_dcb = false;
rses_end_locked_router_action(rses);
break;
}
case ERRACT_REPLY_CLIENT:
{
handle_error_reply_client(session, rses, problem_dcb, errmsgbuf);
close_dcb = false;
*succp = false; /*< no new backend servers were made available */
break;
}
default:
ss_dassert(!true);
*succp = false;
break;
}
}
if (close_dcb)
{
dcb_close(problem_dcb);
}
}
/**
* @brief Handle an error reply for a client
*
* @param ses Session
* @param rses Router session
* @param backend_dcb DCB for the backend server that has failed
* @param errmsg GWBUF containing the error message
*/
static void handle_error_reply_client(SESSION *ses, ROUTER_CLIENT_SES *rses,
DCB *backend_dcb, GWBUF *errmsg)
{
session_state_t sesstate;
DCB *client_dcb;
backend_ref_t *bref;
spinlock_acquire(&ses->ses_lock);
sesstate = ses->state;
client_dcb = ses->client_dcb;
spinlock_release(&ses->ses_lock);
if (rses_begin_locked_router_action(rses))
{
/**
* If bref exists, mark it closed
*/
if ((bref = get_bref_from_dcb(rses, backend_dcb)) != NULL)
{
CHK_BACKEND_REF(bref);
if (BREF_IS_IN_USE(bref))
{
close_failed_bref(bref, false);
dcb_close(backend_dcb);
}
}
else
{
// All dcbs should be associated with a backend reference.
ss_dassert(!true);
}
rses_end_locked_router_action(rses);
}
else
{
// The session has already been closed, hence the dcb has been
// closed as well.
}
if (sesstate == SESSION_STATE_ROUTER_READY)
{
CHK_DCB(client_dcb);
client_dcb->func.write(client_dcb, gwbuf_clone(errmsg));
}
}
/**
* Check if there is backend reference pointing at failed DCB, and reset its
* flags. Then clear DCB's callback and finally : try to find replacement(s)
* for failed slave(s).
*
* This must be called with router lock.
*
* @param inst router instance
* @param rses router client session
* @param dcb failed DCB
* @param errmsg error message which is sent to client if it is waiting
*
* @return true if there are enough backend connections to continue, false if
* not
*/
static bool handle_error_new_connection(ROUTER_INSTANCE *inst,
ROUTER_CLIENT_SES **rses,
DCB *backend_dcb, GWBUF *errmsg)
{
ROUTER_CLIENT_SES *myrses;
SESSION *ses;
int max_nslaves;
int max_slave_rlag;
backend_ref_t *bref;
bool succp;
myrses = *rses;
ss_dassert(SPINLOCK_IS_LOCKED(&myrses->rses_lock));
ses = backend_dcb->session;
CHK_SESSION(ses);
/**
* If bref == NULL it has been replaced already with another one.
*/
if ((bref = get_bref_from_dcb(myrses, backend_dcb)) == NULL)
{
succp = true;
goto return_succp;
}
CHK_BACKEND_REF(bref);
/**
* If query was sent through the bref and it is waiting for reply from
* the backend server it is necessary to send an error to the client
* because it is waiting for reply.
*/
if (BREF_IS_WAITING_RESULT(bref))
{
DCB *client_dcb = ses->client_dcb;
client_dcb->func.write(client_dcb, gwbuf_clone(errmsg));
}
close_failed_bref(bref, false);
/**
* 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;
}
/**
* 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);
max_nslaves = rses_get_max_slavecount(myrses, myrses->rses_nbackends);
max_slave_rlag = rses_get_max_replication_lag(myrses);
/**
* Try to get replacement slave or at least the minimum
* number of slave connections for router session.
*/
if (inst->rwsplit_config.rw_disable_sescmd_hist)
{
succp = have_enough_servers(myrses, 1, myrses->rses_nbackends, inst) ? true : false;
}
else
{
succp = select_connect_backend_servers(&myrses->rses_master_ref,
myrses->rses_backend_ref,
myrses->rses_nbackends,
max_nslaves, max_slave_rlag,
myrses->rses_config.rw_slave_select_criteria,
ses, inst, true);
}
return_succp:
return succp;
}
/**
* @brief Calculate whether we have enough servers to route a query
*
* @param p_rses Router session
* @param min_nsrv Minimum number of servers that is sufficient
* @param nsrv Actual number of servers
* @param router Router instance
*
* @return bool - whether enough, side effect is error logging
*/
static bool have_enough_servers(ROUTER_CLIENT_SES *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 ||
MXS_MAX((rses)->rses_config.rw_max_slave_conn_count,
(router_nsrv * (rses)->rses_config.rw_max_slave_conn_percent) /
100) < min_nsrv)
{
if (router_nsrv < min_nsrv)
{
MXS_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
{
int pct = (rses)->rses_config.rw_max_slave_conn_percent / 100;
int nservers = router_nsrv * pct;
if ((rses)->rses_config.rw_max_slave_conn_count < min_nsrv)
{
MXS_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,
(rses)->rses_config.rw_max_slave_conn_count, min_nsrv);
}
if (nservers < min_nsrv)
{
double dbgpct = ((double)min_nsrv / (double)router_nsrv) * 100.0;
MXS_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,
(rses)->rses_config.rw_max_slave_conn_percent, dbgpct);
}
}
succp = false;
}
else
{
succp = true;
}
return succp;
}
/**
* @brief Refresh the instance by the given parameter value.
*
* Used by createInstance and newSession
*
* @param router Router instance
* @param singleparam Parameter fo be reloaded
*
* Note: this part is not done. Needs refactoring.
*/
static void refreshInstance(ROUTER_INSTANCE *router,
CONFIG_PARAMETER *singleparam)
{
CONFIG_PARAMETER *param;
bool refresh_single;
config_param_type_t paramtype;
if (singleparam != NULL)
{
param = singleparam;
refresh_single = true;
}
else
{
param = router->service->svc_config_param;
refresh_single = false;
}
paramtype = config_get_paramtype(param);
while (param != NULL)
{
/** Catch unused parameter types */
ss_dassert(paramtype == COUNT_TYPE || paramtype == PERCENT_TYPE ||
paramtype == SQLVAR_TARGET_TYPE);
if (paramtype == COUNT_TYPE)
{
if (strncmp(param->name, "max_slave_connections", MAX_PARAM_LEN) == 0)
{
int val;
bool succp;
router->rwsplit_config.rw_max_slave_conn_percent = 0;
succp = config_get_valint(&val, param, NULL, paramtype);
if (succp)
{
router->rwsplit_config.rw_max_slave_conn_count = val;
}
}
else if (strncmp(param->name, "max_slave_replication_lag",
MAX_PARAM_LEN) == 0)
{
int val;
bool succp;
succp = config_get_valint(&val, param, NULL, paramtype);
if (succp)
{
router->rwsplit_config.rw_max_slave_replication_lag = val;
}
}
}
else if (paramtype == PERCENT_TYPE)
{
if (strncmp(param->name, "max_slave_connections", MAX_PARAM_LEN) == 0)
{
int val;
bool succp;
router->rwsplit_config.rw_max_slave_conn_count = 0;
succp = config_get_valint(&val, param, NULL, paramtype);
if (succp)
{
router->rwsplit_config.rw_max_slave_conn_percent = val;
}
}
}
else if (paramtype == SQLVAR_TARGET_TYPE)
{
if (strncmp(param->name, "use_sql_variables_in", MAX_PARAM_LEN) == 0)
{
target_t valtarget;
bool succp;
succp = config_get_valtarget(&valtarget, param, NULL, paramtype);
if (succp)
{
router->rwsplit_config.rw_use_sql_variables_in = valtarget;
}
}
}
if (refresh_single)
{
break;
}
param = param->next;
}
}
/*
* @brief Release resources when createInstance fails to complete
*
* Internal to createInstance
*
* @param router Router instance
*
*/
static void free_rwsplit_instance(ROUTER_INSTANCE *router)
{
if (router)
{
MXS_FREE(router);
}
}
/**
* @brief Create backend server references
*
* This creates a new set of backend references for the client session. Currently
* this is only used on startup but it could be used to dynamically change the
* set of used servers.
*
* @param rses Client router session
* @param dest Destination where the array of backens is stored
* @param n_backend Number of items in the array
* @return True on success, false on error
*/
static bool create_backends(ROUTER_CLIENT_SES *rses, backend_ref_t** dest, int* n_backend)
{
backend_ref_t *backend_ref = (backend_ref_t *)MXS_CALLOC(1, *n_backend * sizeof(backend_ref_t));
if (backend_ref == NULL)
{
return false;
}
int i = 0;
for (SERVER_REF *sref = rses->router->service->dbref; sref && i < *n_backend; sref = sref->next)
{
if (sref->active)
{
#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].ref = sref;
/** store pointers to sescmd list to both cursors */
backend_ref[i].bref_sescmd_cur.scmd_cur_rses = rses;
backend_ref[i].bref_sescmd_cur.scmd_cur_active = false;
backend_ref[i].bref_sescmd_cur.scmd_cur_ptr_property =
&rses->rses_properties[RSES_PROP_TYPE_SESCMD];
backend_ref[i].bref_sescmd_cur.scmd_cur_cmd = NULL;
i++;
}
}
if (i < *n_backend)
{
MXS_INFO("The service reported %d servers but only took %d into use.", *n_backend, i);
*n_backend = i;
}
*dest = backend_ref;
return true;
}
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