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In dcb.c:dcb_close DCB is removed either before or after the call dcb->func.close. Since mysql backend protocol sends COM_QUIT and thus, writes to backend DCB, it is kept in DCB_STATE_POLLING until the write is completed.

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dcb.h: define ERRHAND temporarily since changes are still behind that macro
Defined two error handling actions in router.h: ERRACT_NEW_COMMECTION and ERRACT_REPLY_CLIENT.
Failed database is logged at expanding frequence to error and to message log due changes in mysql_mon.c. Added two new members in MONITOR_SERVERS: mon_err_count, and mon_prev_status so that each backend can be treated individually.

Error handling: if mysql_backend.c:dcb_read fails, router's handleError is called instead of closing session.
	If mysql_client.c:SESSION_ROUTE_QUERY fails router's handleError is called instead of sending error to client.

	readwritesplit.c:select_connect_backend_servers is modified so that in can be called during active router session. When called, it attempts to find one master and maximum number of configured slaves in correct state if necessary.
	When handleError needs to replace failed unit it now calls select_connect_backend_servers.
This commit is contained in:
VilhoRaatikka
2014-06-08 19:36:12 +03:00
parent 916b763685
commit 889bdd4f8c
8 changed files with 298 additions and 121 deletions
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206
server/modules/routing/readwritesplit/readwritesplit.c
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@ -91,6 +91,8 @@ static void handleError(
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 uint8_t getCapabilities (ROUTER* inst, void* router_session);
@ -425,14 +427,12 @@ static void* newSession(
SESSION* session)
{
backend_ref_t* backend_ref; /*< array of backend references (DCB,BACKEND,cursor) */
backend_ref_t* master_ref = NULL; /*< pointer to selected master */
BACKEND** b;
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 conf_max_nslaves; /*< value from configuration file */
int i;
const int min_nservers = 1; /*< hard-coded for now */
static uint64_t router_client_ses_seq; /*< ID for client session */
@ -478,9 +478,7 @@ static void* newSession(
client_rses->rses_autocommit_enabled = true;
client_rses->rses_transaction_active = false;
/** count servers */
b = router->servers;
while (*(b++) != NULL) router_nservers++;
router_nservers = router_get_servercount(router);
/** With too few servers session is not created */
if (router_nservers < min_nservers ||
@ -558,6 +556,7 @@ static void* newSession(
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 = BREF_NOT_USED;
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;
@ -565,22 +564,8 @@ static void* newSession(
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;
}
/**
* 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.
*/
if (client_rses->rses_config.rw_max_slave_conn_count > 0)
{
conf_max_nslaves = client_rses->rses_config.rw_max_slave_conn_count;
}
else
{
conf_max_nslaves =
(router_nservers*client_rses->rses_config.rw_max_slave_conn_percent)/100;
}
max_nslaves = MIN(router_nservers-1, MAX(1, conf_max_nslaves));
}
max_nslaves = rses_get_max_slavecount(client_rses, router_nservers);
spinlock_init(&client_rses->rses_lock);
client_rses->rses_backend_ref = backend_ref;
@ -770,7 +755,10 @@ static void freeSession(
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,
@ -1401,10 +1389,10 @@ static bool select_connect_backend_servers(
select_criteria_t select_criteria,
SESSION* session,
ROUTER_INSTANCE* router)
{
{
bool succp = true;
bool master_found = false;
bool master_connected = false;
bool master_found;
bool master_connected;
int slaves_found = 0;
int slaves_connected = 0;
int i;
@ -1418,6 +1406,20 @@ static bool select_connect_backend_servers(
succp = false;
goto return_succp;
}
/** Master is already chosen and connected. This is slave failure case */
if (*p_master_ref != NULL &&
(*p_master_ref)->bref_state == BREF_IN_USE)
{
master_found = true;
master_connected = true;
}
/** New session or master failure case */
else
{
master_found = false;
master_connected = false;
}
/** Check slave selection criteria and set compare function */
p = criteria_cmpfun[select_criteria];
@ -1502,7 +1504,7 @@ static bool select_connect_backend_servers(
i++)
{
BACKEND* b = backend_ref[i].bref_backend;
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Examine server "
@ -1514,6 +1516,7 @@ static bool select_connect_backend_servers(
b->backend_conn_count,
router->bitmask)));
if (SERVER_IS_RUNNING(b->backend_server) &&
((b->backend_server->status & router->bitmask) ==
router->bitvalue))
@ -1522,33 +1525,43 @@ static bool select_connect_backend_servers(
SERVER_IS_SLAVE(b->backend_server))
{
slaves_found += 1;
backend_ref[i].bref_dcb = dcb_connect(
b->backend_server,
session,
b->backend_server->protocol);
if (backend_ref[i].bref_dcb != NULL)
/** Slave is already connected */
if (backend_ref[i].bref_state == BREF_IN_USE)
{
slaves_connected += 1;
backend_ref[i].bref_state = 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);
}
/** New slave connection is taking place */
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 */
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;
backend_ref[i].bref_state = 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 */
}
}
}
else if (!master_connected &&
@ -1584,18 +1597,18 @@ static bool select_connect_backend_servers(
/* handle connect error */
}
}
else
{
succp = false;
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Unable to establish "
"connection with server %s:%d, %s",
b->backend_server->name,
b->backend_server->port,
STRSRVSTATUS(b->backend_server))));
/* handle connect error */
}
}
else
{
succp = false;
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Unable to establish "
"connection with server %s:%d, %s",
b->backend_server->name,
b->backend_server->port,
STRSRVSTATUS(b->backend_server))));
/* handle connect error */
}
} /*< for */
@ -2496,12 +2509,40 @@ static void handleError (
int action,
bool *succp)
{
DCB* client_dcb = NULL;
SESSION* session = backend_dcb->session;
DCB* client_dcb = NULL;
SESSION* session = backend_dcb->session;
ROUTER_INSTANCE* router = (ROUTER_INSTANCE *)instance;
ROUTER_CLIENT_SES* rses = (ROUTER_CLIENT_SES *)router_session;
client_dcb = session->client;
CHK_DCB(client_dcb);
ss_dassert(client_dcb != NULL);
switch (action) {
case ERRACT_NEW_CONNECTION:
{
int router_nservers;
int max_nslaves;
router_nservers = router_get_servercount(router);
max_nslaves = rses_get_max_slavecount(rses, router_nservers);
*succp = select_connect_backend_servers(
&rses->rses_master_ref,
rses->rses_backend_ref,
router_nservers,
max_nslaves,
rses->rses_config.rw_slave_select_criteria,
session,
router);
ss_dassert(*succp);
}
break;
default:
*succp = false;
break;
}
}
static void print_error_packet(
@ -2555,3 +2596,42 @@ static void print_error_packet(
while ((buf = gwbuf_consume(buf, GWBUF_LENGTH(buf))) != NULL);
}
}
static int router_get_servercount(
ROUTER_INSTANCE* router)
{
int router_nservers = 0;
BACKEND** b = router->servers;
/** count servers */
while (*(b++) != NULL) router_nservers++;
return router_nservers;
}
/**
* 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;
}