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/*
* dbutils.c - Database connection/management functions
* Copyright (C) 2ndQuadrant, 2010-2011
*
* 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"
#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;

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

PQclear(res);
return result;
}



bool
is_witness(PGconn *conn, char *schema, char *cluster, int node_id)
{
PGresult *res;
bool result;
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 (strcmp(PQgetvalue(res, 0, 0), "f") == 0)
result = false;
else
result = true;

PQclear(res);
return result;
}


/* check the PQStatus and try to 'select 1' to confirm good connection */
bool
is_pgup(PGconn *conn)
{
PGresult *res;
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 connection is OK
* the PQstatus() won't catch disconnected connection
* XXXX
* the error message can be used by repmgrd
*/
sqlquery_snprintf(sqlquery, "SELECT 1");
res = PQexec(conn, sqlquery);
// we need to retry, because we might just have loose the connection once
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_err(_("PQexec failed: %s\n"), PQerrorMessage(conn));
PQclear(res);
if (twice)
return false;
PQreset(conn); // reconnect
twice = true;
}
else
{
PQclear(res);
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, int id, 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 * FROM %s.repl_nodes "
" WHERE cluster = '%s' and id <> %d and not witness",
schema_quoted, cluster, id);

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, 2), 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;
}
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