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/*-------------------------------------------------------------------------
* sync_thread.c
*
* Implementation of the thread that generates SYNC events.
*
* Copyright (c) 2003-2009, PostgreSQL Global Development Group
* Author: Jan Wieck, Afilias USA INC.
*
*
*-------------------------------------------------------------------------
*/
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <signal.h>
#include <sys/types.h>
#ifndef WIN32
#include <unistd.h>
#include <sys/time.h>
#endif
#include "slon.h"
/* ----------
* Global variables
* ----------
*/
int sync_interval;
int sync_interval_timeout;
/* ----------
* slon_localSyncThread
*
* Generate SYNC event if local database activity created new log info.
* ----------
*/
void *
syncThread_main(void *dummy)
{
SlonConn *conn;
char last_actseq_buf[64];
SlonDString query1;
SlonDString query2;
PGconn *dbconn;
PGresult *res;
int timeout_count;
slon_log(SLON_INFO,
"syncThread: thread starts\n");
/*
* Connect to the local database
*/
if ((conn = slon_connectdb(rtcfg_conninfo, "local_sync")) == NULL)
slon_retry();
dbconn = conn->dbconn;
monitor_state("local_sync", 0, conn->conn_pid, "thread main loop", 0, "n/a");
/*
* We don't initialize the last known action sequence to the actual value.
* This causes that we create a SYNC event allways on startup, just in
* case.
*/
last_actseq_buf[0] = '\0';
/*
* Build the query that starts a transaction and retrieves the last value
* from the action sequence.
*/
dstring_init(&query1);
slon_mkquery(&query1,
"start transaction;"
"set transaction isolation level serializable;"
"lock table %s.sl_event_lock;"
"select last_value from %s.sl_action_seq;",
rtcfg_namespace, rtcfg_namespace);
/*
* Build the query that calls createEvent() for the SYNC
*/
dstring_init(&query2);
slon_mkquery(&query2,
"select %s.createEvent('_%s', 'SYNC', NULL);",
rtcfg_namespace, rtcfg_cluster_name);
timeout_count = (sync_interval_timeout == 0) ? 0 :
sync_interval_timeout - sync_interval;
while (sched_wait_time(conn, SCHED_WAIT_SOCK_READ, sync_interval) == SCHED_STATUS_OK)
{
/*
* Start a serializable transaction and get the last value from the
* action sequence number.
*/
res = PQexec(dbconn, dstring_data(&query1));
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
slon_log(SLON_FATAL,
"syncThread: \"%s\" - %s",
dstring_data(&query1), PQresultErrorMessage(res));
PQclear(res);
slon_retry();
break;
}
/*
* Check if it's identical to the last known seq or if the sync
* interval timeout has arrived.
*/
if (sync_interval_timeout != 0)
timeout_count -= sync_interval;
if (strcmp(last_actseq_buf, PQgetvalue(res, 0, 0)) != 0 ||
timeout_count < 0)
{
/*
* Action sequence has changed, generate a SYNC event and read the
* resulting currval of the event sequence.
*/
monitor_state("local_sync", 0, conn->conn_pid, "GenSync", 0, "n/a");
strcpy(last_actseq_buf, PQgetvalue(res, 0, 0));
PQclear(res);
res = PQexec(dbconn, dstring_data(&query2));
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
slon_log(SLON_FATAL,
"syncThread: \"%s\" - %s",
dstring_data(&query2), PQresultErrorMessage(res));
PQclear(res);
slon_retry();
break;
}
slon_log(SLON_DEBUG2,
"syncThread: new sl_action_seq %s - SYNC %s\n",
last_actseq_buf, PQgetvalue(res, 0, 0));
PQclear(res);
/*
* Commit the transaction
*/
res = PQexec(dbconn, "commit transaction;");
if (PQresultStatus(res) != PGRES_COMMAND_OK)
{
slon_log(SLON_FATAL,
"syncThread: \"commit transaction;\" - %s",
PQresultErrorMessage(res));
PQclear(res);
slon_retry();
}
PQclear(res);
/*
* Restart the timeout on a sync.
*/
timeout_count = (sync_interval_timeout == 0) ? 0 :
sync_interval_timeout - sync_interval;
}
else
{
/*
* No database activity detected - rollback.
*/
PQclear(res);
res = PQexec(dbconn, "rollback transaction;");
if (PQresultStatus(res) != PGRES_COMMAND_OK)
{
slon_log(SLON_FATAL,
"syncThread: \"rollback transaction;\" - %s",
PQresultErrorMessage(res));
PQclear(res);
slon_retry();
}
PQclear(res);
}
monitor_state("local_sync", 0, conn->conn_pid, "thread main loop", 0, "n/a");
}
dstring_free(&query1);
dstring_free(&query2);
slon_disconnectdb(conn);
slon_log(SLON_INFO, "syncThread: thread done\n");
pthread_exit(NULL);
}
/*
* Local Variables:
* tab-width: 4
* c-indent-level: 4
* c-basic-offset: 4
* End:
*/
|
