dbutils.c

/*
 * dbutils.c - Database connection/management functions
 * Copyright (C) 2ndQuadrant, 2010-2012
 *
 * 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 <unistd.h>

#include "repmgr.h"
#include "strutil.h"
#include "log.h"

PGconn *
establishDBConnection(const char *conninfo, const bool exit_on_error)
{
	/* Make a connection to the database */
	PGconn *conn = NULL;
	char    connection_string[MAXLEN];

	strcpy(connection_string, conninfo);
	strcat(connection_string, " fallback_application_name='repmgr'");
	conn = PQconnectdb(connection_string);

	/* Check to see that the backend connection was successfully made */
	if ((PQstatus(conn) != CONNECTION_OK))
	{
		log_err(_("Connection to database failed: %s\n"),
		        PQerrorMessage(conn));

		if (exit_on_error)
		{
			PQfinish(conn);
			exit(ERR_DB_CON);
		}
	}

	return conn;
}

PGconn *
establishDBConnectionByParams(const char *keywords[], const char *values[],const bool exit_on_error)
{
	/* Make a connection to the database */
	PGconn *conn = PQconnectdbParams(keywords, values, true);

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

	return conn;
}

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

	res = PQexec(conn, "SELECT pg_is_in_recovery()");

	if (PQresultStatus(res) != PGRES_TUPLES_OK)
	{
		log_err(_("Can't query server mode: %s"),
		        PQerrorMessage(conn));
		PQclear(res);
		PQfinish(conn);
		exit(ERR_DB_QUERY);
	}

	if (PQntuples(res) == 1 && strcmp(PQgetvalue(res, 0, 0), "t") == 0)
		result = true;

	PQclear(res);
	return result;
}


bool
is_witness(PGconn *conn, char *schema, char *cluster, int node_id)
{
	PGresult   *res;
	bool		result = false;
	char		sqlquery[QUERY_STR_LEN];

	sqlquery_snprintf(sqlquery, "SELECT witness from %s.repl_nodes where cluster = '%s' and id = %d",
	                  schema, cluster, node_id);
	res = PQexec(conn, sqlquery);
	if (PQresultStatus(res) != PGRES_TUPLES_OK)
	{
		log_err(_("Can't query server mode: %s"), PQerrorMessage(conn));
		PQclear(res);
		PQfinish(conn);
		exit(ERR_DB_QUERY);
	}

	if (PQntuples(res) == 1 && strcmp(PQgetvalue(res, 0, 0), "t") == 0)
		result = true;

	PQclear(res);
	return result;
}


/* check the PQStatus and try to 'select 1' to confirm good connection */
bool
is_pgup(PGconn *conn, int timeout)
{
	char		sqlquery[QUERY_STR_LEN];
	/* Check the connection status twice in case it changes after reset */
	bool		twice = false;

	/* Check the connection status twice in case it changes after reset */
	for (;;)
	{
		if (PQstatus(conn) != CONNECTION_OK)
		{
			if (twice)
				return false;
			PQreset(conn);  // reconnect
			twice = true;
		}
		else
		{
			/*
			* Send a SELECT 1 just to check if the connection is OK
			*/
			if (!CancelQuery(conn, timeout))
				goto failed;
			if (wait_connection_availability(conn, timeout) != 1)
				goto failed;

			sqlquery_snprintf(sqlquery, "SELECT 1");
			if (PQsendQuery(conn, sqlquery) == 0)
			{
				log_warning(_("PQsendQuery: Query could not be sent to primary. %s\n"),
				            PQerrorMessage(conn));
				goto failed;
			}
			if (wait_connection_availability(conn, timeout) != 1)
				goto failed;

			break;

failed:
			// we need to retry, because we might just have loose the connection once
			if (twice)
				return false;
			PQreset(conn);  // reconnect
			twice = true;
		}
	}
	return true;
}


/*
 * 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)
	{
		log_err(_("Version check PQexec failed: %s"),
		        PQerrorMessage(conn));
		PQclear(res);
		PQfinish(conn);
		exit(ERR_DB_QUERY);
	}

	major_version1 = atoi(PQgetvalue(res, 0, 0));
	major_version2 = PQgetvalue(res, 0, 1);

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

	PQclear(res);

	return major_version;
}


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

	sqlquery_snprintf(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)
	{
		log_err(_("GUC setting check PQexec failed: %s"),
		        PQerrorMessage(conn));
		PQclear(res);
		PQfinish(conn);
		exit(ERR_DB_QUERY);
	}
	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[QUERY_STR_LEN];

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

	res = PQexec(conn, sqlquery);
	if (PQresultStatus(res) != PGRES_TUPLES_OK)
	{
		log_err(_("Get cluster size PQexec failed: %s"),
		        PQerrorMessage(conn));
		PQclear(res);
		PQfinish(conn);
		exit(ERR_DB_QUERY);
	}
	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
 *
 * NB: If master_conninfo_out may be NULL.  If it is non-null, it is assumed to
 * point to allocated memory of MAXCONNINFO in length, and the master server
 * connection string is placed there.
 */
PGconn *
getMasterConnection(PGconn *standby_conn, char *schema, char *cluster,
                    int *master_id, char *master_conninfo_out)
{
	PGconn		*master_conn	 = NULL;
	PGresult	*res1;
	PGresult	*res2;
	char		 sqlquery[QUERY_STR_LEN];
	char		 master_conninfo_stack[MAXCONNINFO];
	char		*master_conninfo = &*master_conninfo_stack;
	char		 schema_quoted[MAXLEN];

	int		 i;

	/*
	 * If the caller wanted to get a copy of the connection info string, sub
	 * out the local stack pointer for the pointer passed by the caller.
	 */
	if (master_conninfo_out != NULL)
		master_conninfo = master_conninfo_out;

	/*
	 * XXX: This is copied in at least two other procedures
	 *
	 * Assemble the unquoted schema name
	 */
	{
		char *identifier = PQescapeIdentifier(standby_conn, schema,
		                                      strlen(schema));

		maxlen_snprintf(schema_quoted, "%s", identifier);
		PQfreemem(identifier);
	}

	/* find all nodes belonging to this cluster */
	log_info(_("finding node list for cluster '%s'\n"),
	         cluster);

	sqlquery_snprintf(sqlquery, "SELECT id, conninfo FROM %s.repl_nodes "
	                  " WHERE cluster = '%s' and not witness",
	                  schema_quoted, cluster);

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

	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, 1), MAXCONNINFO);
		log_info(_("checking role of cluster node '%s'\n"),
		         master_conninfo);
		master_conn = establishDBConnection(master_conninfo, false);

		if (PQstatus(master_conn) != CONNECTION_OK)
			continue;

		/*
		 * Can't use the is_standby() function here because on error that
		 * function closes the connection passed and exits.  This still
		 * needs to close master_conn first.
		 */
		res2 = PQexec(master_conn, "SELECT pg_is_in_recovery()");

		if (PQresultStatus(res2) != PGRES_TUPLES_OK)
		{
			log_err(_("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;
}


/*
 * wait until current query finishes ignoring any results, this could be an async command
 * or a cancelation of a query
 * return 1 if Ok; 0 if any error ocurred; -1 if timeout reached
 */
int
wait_connection_availability(PGconn *conn, int timeout)
{
	PGresult   *res;

	while(timeout-- >= 0)
	{
		if (PQconsumeInput(conn) == 0)
		{
			log_warning(_("PQconsumeInput: Query could not be sent to primary. %s\n"),
			            PQerrorMessage(conn));
			return 0;
		}

		if (PQisBusy(conn) == 0)
		{
			res = PQgetResult(conn);
			if (res == NULL)
				break;
			PQclear(res);
		}
		sleep(1);
	}
	if (timeout >= 0)
		return 1;
	else
		return -1;
}


bool
CancelQuery(PGconn *conn, int timeout)
{
	char errbuf[ERRBUFF_SIZE];
	PGcancel *pgcancel;

	if (wait_connection_availability(conn, timeout) != 1)
		return false;

	pgcancel = PQgetCancel(conn);

	if (pgcancel != NULL)
	{
		/*
		 * PQcancel can only return 0 if socket()/connect()/send()
 		 * fails, in any of those cases we can assume something
		 * bad happened to the connection
		 */
		if (PQcancel(pgcancel, errbuf, ERRBUFF_SIZE) == 0)
		{
			log_warning(_("Can't stop current query: %s\n"), errbuf);
			PQfreeCancel(pgcancel);
			return false;
		}

		PQfreeCancel(pgcancel);
	}

	return true;
}