dbutils.c

/*
 * dbutils.c - Database connection/management functions
 * Copyright (C) 2ndQuadrant, 2010
 *
 * This program 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, either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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, see <http://www.gnu.org/licenses/>.
 *
 */

#include "repmgr.h"

#define MAXQUERY 8192
#define MAXCONNINFO 1024

PGconn *
establishDBConnection(const char *conninfo, const bool exit_on_error)
{
	/* Make a connection to the database */
	PGconn *conn = PQconnectdb(conninfo);

	/* Check to see that the backend connection was successfully made */
	if ((PQstatus(conn) != CONNECTION_OK))
	{
		fprintf(stderr, "Connection to database failed: %s",
		        PQerrorMessage(conn));
		if (exit_on_error)
		{
			PQfinish(conn);
			exit(1);
		}
	}

	return conn;
}



bool
is_standby(PGconn *conn)
{
	PGresult   *res;
	bool		result;

	res = PQexec(conn, "SELECT pg_is_in_recovery()");
	if (PQresultStatus(res) != PGRES_TUPLES_OK)
	{
		fprintf(stderr, "Can't query server mode: %s", PQerrorMessage(conn));
		PQclear(res);
		PQfinish(conn);
		exit(1);
	}

	if (strcmp(PQgetvalue(res, 0, 0), "f") == 0)
		result = false;
	else
		result = true;

	PQclear(res);
	return result;
}


/*
 * If postgreSQL version is 9 or superior returns the major version
 * if 8 or inferior returns an empty string
 */
char *
pg_version(PGconn *conn, char* major_version)
{
	PGresult	*res;

	int			major_version1;
	char		*major_version2;

	res = PQexec(conn, "WITH pg_version(ver) AS (SELECT split_part(version(), ' ', 2)) "
	             "SELECT split_part(ver, '.', 1), split_part(ver, '.', 2) FROM pg_version");
	if (PQresultStatus(res) != PGRES_TUPLES_OK)
	{
		fprintf(stderr, "PQexec failed: %s", PQerrorMessage(conn));
		PQclear(res);
		PQfinish(conn);
		exit(1);
	}
	major_version1 = atoi(PQgetvalue(res, 0, 0));
	major_version2 = PQgetvalue(res, 0, 1);
	PQclear(res);

	if (major_version1 >= 9)
	{
		/* form a major version string */
		snprintf(major_version, MAXVERSIONSTR, "%d.%s", major_version1, major_version2);
	}
	else
		strcpy(major_version, "");

	return major_version;
}


bool
guc_setted(PGconn *conn, const char *parameter, const char *op, const char *value)
{
	PGresult	*res;
	char		sqlquery[MAXQUERY];

	sprintf(sqlquery, "SELECT true FROM pg_settings "
	        " WHERE name = '%s' AND setting %s '%s'",
	        parameter, op, value);

	res = PQexec(conn, sqlquery);
	if (PQresultStatus(res) != PGRES_TUPLES_OK)
	{
		fprintf(stderr, "PQexec failed: %s", PQerrorMessage(conn));
		PQclear(res);
		PQfinish(conn);
		exit(1);
	}
	if (PQntuples(res) == 0)
	{
		PQclear(res);
		return false;
	}
	PQclear(res);

	return true;
}


const char *
get_cluster_size(PGconn *conn)
{
	PGresult	*res;
	const char		*size;
	char		sqlquery[MAXQUERY];

	sprintf(sqlquery, "SELECT pg_size_pretty(SUM(pg_database_size(oid))::bigint) "
	        "  FROM pg_database ");

	res = PQexec(conn, sqlquery);
	if (PQresultStatus(res) != PGRES_TUPLES_OK)
	{
		fprintf(stderr, "PQexec failed: %s", PQerrorMessage(conn));
		PQclear(res);
		PQfinish(conn);
		exit(1);
	}
	size = PQgetvalue(res, 0, 0);
	PQclear(res);
	return size;
}

/*
 * get a connection to master by reading repl_nodes, creating a connection
 * to each node (one at a time) and finding if it is a master or a standby
 */
PGconn *
getMasterConnection(PGconn *standby_conn, int id, char *cluster, int *master_id)
{
	PGconn	 *master_conn = NULL;
	PGresult *res1;
	PGresult *res2;
	char 	 sqlquery[MAXQUERY];
	char	 master_conninfo[MAXCONNINFO];
	int		 i;

	/* find all nodes belonging to this cluster */
	sprintf(sqlquery, "SELECT * FROM repmgr_%s.repl_nodes "
	        " WHERE cluster = '%s' and id <> %d",
	        cluster, cluster, id);

	res1 = PQexec(standby_conn, sqlquery);
	if (PQresultStatus(res1) != PGRES_TUPLES_OK)
	{
		fprintf(stderr, "Can't get nodes info: %s\n", PQerrorMessage(standby_conn));
		PQclear(res1);
		PQfinish(standby_conn);
		exit(1);
	}

	for (i = 0; i < PQntuples(res1); i++)
	{
		/* initialize with the values of the current node being processed */
		*master_id = atoi(PQgetvalue(res1, i, 0));
		strncpy(master_conninfo, PQgetvalue(res1, i, 2), MAXCONNINFO);
		master_conn = establishDBConnection(master_conninfo, false);
		if (PQstatus(master_conn) != CONNECTION_OK)
			continue;

		/*
		 * I can't use the is_standby() function here because on error that
		   * function closes the connection i pass and exit, but i still need to close
		 * standby_conn
		 */
		res2 = PQexec(master_conn, "SELECT pg_is_in_recovery()");
		if (PQresultStatus(res2) != PGRES_TUPLES_OK)
		{
			fprintf(stderr, "Can't get recovery state from this node: %s\n", PQerrorMessage(master_conn));
			PQclear(res2);
			PQfinish(master_conn);
			continue;
		}

		/* if false, this is the master */
		if (strcmp(PQgetvalue(res2, 0, 0), "f") == 0)
		{
			PQclear(res2);
			PQclear(res1);
			return master_conn;
		}
		else
		{
			/* if it is a standby clear info */
			PQclear(res2);
			PQfinish(master_conn);
			*master_id = -1;
		}
	}

	/* If we finish this loop without finding a master then
	 * we doesn't have the info or the master has failed (or we
	 * reached max_connections or superuser_reserved_connections,
	 * anything else i'm missing?),
	 * Probably we will need to check the error to know if we need
	 * to start failover procedure or just fix some situation on the
	 * standby.
	 */
	PQclear(res1);
	return NULL;
}