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dbutils.c
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dbutils.c
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/*
* dbutils.c - Database connection/management functions
* Copyright (C) 2ndQuadrant, 2010-2015
*
* 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 <time.h>
#include <sys/time.h>
#include "repmgr.h"
#include "config.h"
#include "strutil.h"
#include "log.h"
char repmgr_schema[MAXLEN] = "";
char repmgr_schema_quoted[MAXLEN] = "";
PGconn *
establish_db_connection(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'");
log_debug(_("connecting to: '%s'\n"), connection_string);
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 *
establish_db_connection_by_params(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
check_cluster_schema(PGconn *conn)
{
PGresult *res;
char sqlquery[QUERY_STR_LEN];
sqlquery_snprintf(sqlquery,
"SELECT 1 FROM pg_namespace WHERE nspname = '%s'",
get_repmgr_schema());
log_debug(_("check_cluster_schema(): %s\n"), sqlquery);
res = PQexec(conn, sqlquery);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_err(_("check_cluster_schema(): unable to check cluster schema: %s\n"),
PQerrorMessage(conn));
PQclear(res);
return false;
}
if (PQntuples(res) == 0)
{
/* schema doesn't exist */
log_debug(_("check_cluster_schema(): schema '%s' doesn't exist\n"), get_repmgr_schema());
PQclear(res);
return false;
}
PQclear(res);
return true;
}
int
is_standby(PGconn *conn)
{
PGresult *res;
int result = 0;
res = PQexec(conn, "SELECT pg_is_in_recovery()");
if (res == NULL || PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_err(_("Can't query server mode: %s"),
PQerrorMessage(conn));
result = -1;
}
else if (PQntuples(res) == 1 && strcmp(PQgetvalue(res, 0, 0), "t") == 0)
result = 1;
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 (!cancel_query(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 lost the
* connection once
*/
if (twice)
return false;
PQreset(conn); /* reconnect */
twice = true;
}
}
return true;
}
/*
* Return the id of the active master node, or NODE_NOT_FOUND if no
* record available.
*
* This reports the value stored in the database only and
* does not verify whether the node is actually available
*/
int
get_master_node_id(PGconn *conn, char *cluster)
{
char sqlquery[QUERY_STR_LEN];
PGresult *res;
int retval;
sqlquery_snprintf(sqlquery,
"SELECT id "
" FROM %s.repl_nodes "
" WHERE cluster = '%s' "
" AND type = 'master' "
" AND active IS TRUE ",
get_repmgr_schema_quoted(conn),
cluster);
res = PQexec(conn, sqlquery);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_err(_("get_master_node_id(): query failed\n%s\n"),
PQerrorMessage(conn));
retval = NODE_NOT_FOUND;
}
else if (PQntuples(res) == 0)
{
log_warning(_("get_master_node_id(): no active primary found\n"));
retval = NODE_NOT_FOUND;
}
else
{
retval = atoi(PQgetvalue(res, 0, 0));
}
PQclear(res);
return retval;
}
/*
* Return the server version number for the connection provided
*/
int
get_server_version(PGconn *conn, char *server_version)
{
PGresult *res;
res = PQexec(conn,
"SELECT current_setting('server_version_num'), "
" current_setting('server_version')");
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_err(_("unable to determine server version number:\n%s"),
PQerrorMessage(conn));
PQclear(res);
return -1;
}
if(server_version != NULL)
strcpy(server_version, PQgetvalue(res, 0, 0));
return atoi(PQgetvalue(res, 0, 0));
}
int
guc_set(PGconn *conn, const char *parameter, const char *op,
const char *value)
{
PGresult *res;
char sqlquery[QUERY_STR_LEN];
int retval = 1;
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));
retval = -1;
}
else if (PQntuples(res) == 0)
{
retval = 0;
}
PQclear(res);
return retval;
}
/**
* Just like guc_set except with an extra parameter containing the name of
* the pg datatype so that the comparison can be done properly.
*/
int
guc_set_typed(PGconn *conn, const char *parameter, const char *op,
const char *value, const char *datatype)
{
PGresult *res;
char sqlquery[QUERY_STR_LEN];
int retval = 1;
sqlquery_snprintf(sqlquery,
"SELECT true FROM pg_settings "
" WHERE name = '%s' AND setting::%s %s '%s'::%s",
parameter, datatype, op, value, datatype);
res = PQexec(conn, sqlquery);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_err(_("GUC setting check PQexec failed: %s"),
PQerrorMessage(conn));
retval = -1;
}
else if (PQntuples(res) == 0)
{
retval = 0;
}
PQclear(res);
return retval;
}
bool
get_cluster_size(PGconn *conn, char *size)
{
PGresult *res;
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 (res == NULL || PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_err(_("get_cluster_size(): PQexec failed: %s"),
PQerrorMessage(conn));
PQclear(res);
return false;
}
strncpy(size, PQgetvalue(res, 0, 0), MAXLEN);
PQclear(res);
return true;
}
bool
get_pg_setting(PGconn *conn, const char *setting, char *output)
{
char sqlquery[QUERY_STR_LEN];
PGresult *res;
int i;
bool success = true;
sqlquery_snprintf(sqlquery,
"SELECT name, setting "
" FROM pg_settings WHERE name = '%s'",
setting);
log_debug(_("get_pg_setting(): %s\n"), sqlquery);
res = PQexec(conn, sqlquery);
if (res == NULL || PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_err(_("get_pg_setting() - PQexec failed: %s"),
PQerrorMessage(conn));
PQclear(res);
return false;
}
for (i = 0; i < PQntuples(res); i++)
{
if (strcmp(PQgetvalue(res, i, 0), setting) == 0)
{
strncpy(output, PQgetvalue(res, i, 1), MAXLEN);
success = true;
break;
}
else
{
log_err(_("unknown parameter: %s"), PQgetvalue(res, i, 0));
}
}
if(success == true)
{
log_debug(_("get_pg_setting(): returned value is '%s'\n"), output);
}
PQclear(res);
return success;
}
/*
* get_upstream_connection()
*
* Returns connection to node's upstream node
*
* NOTE: will attempt to connect even if node is marked as inactive
*/
PGconn *
get_upstream_connection(PGconn *standby_conn, char *cluster, int node_id,
int *upstream_node_id_ptr, char *upstream_conninfo_out)
{
PGconn *upstream_conn = NULL;
PGresult *res;
char sqlquery[QUERY_STR_LEN];
char upstream_conninfo_stack[MAXCONNINFO];
char *upstream_conninfo = &*upstream_conninfo_stack;
/*
* 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 (upstream_conninfo_out != NULL)
upstream_conninfo = upstream_conninfo_out;
sqlquery_snprintf(sqlquery,
" SELECT un.conninfo, un.name, un.id "
" FROM %s.repl_nodes un "
"INNER JOIN %s.repl_nodes n "
" ON (un.id = n.upstream_node_id AND un.cluster = n.cluster)"
" WHERE n.cluster = '%s' "
" AND n.id = %i ",
get_repmgr_schema_quoted(standby_conn),
get_repmgr_schema_quoted(standby_conn),
cluster,
node_id);
log_debug("get_upstream_connection(): %s\n", sqlquery);
res = PQexec(standby_conn, sqlquery);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_err(_("unable to get conninfo for upstream server: %s\n"),
PQerrorMessage(standby_conn));
PQclear(res);
return NULL;
}
if(!PQntuples(res))
{
log_notice(_("no record found for upstream server"));
PQclear(res);
return NULL;
}
strncpy(upstream_conninfo, PQgetvalue(res, 0, 0), MAXCONNINFO);
if(upstream_node_id_ptr != NULL)
*upstream_node_id_ptr = atoi(PQgetvalue(res, 0, 1));
PQclear(res);
log_debug("conninfo is: '%s'\n", upstream_conninfo);
upstream_conn = establish_db_connection(upstream_conninfo, false);
if (PQstatus(upstream_conn) != CONNECTION_OK)
{
log_err(_("unable to connect to upstream node: %s\n"),
PQerrorMessage(upstream_conn));
return NULL;
}
return upstream_conn;
}
/*
* 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 *
get_master_connection(PGconn *standby_conn, 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;
int i,
node_id;
if(master_id != NULL)
{
*master_id = NODE_NOT_FOUND;
}
/* 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 type != 'witness' ",
get_repmgr_schema_quoted(standby_conn),
cluster);
res1 = PQexec(standby_conn, sqlquery);
if (PQresultStatus(res1) != PGRES_TUPLES_OK)
{
log_err(_("unable to retrieve node records: %s\n"),
PQerrorMessage(standby_conn));
PQclear(res1);
return NULL;
}
for (i = 0; i < PQntuples(res1); i++)
{
/* initialize with the values of the current node being processed */
node_id = atoi(PQgetvalue(res1, i, 0));
strncpy(master_conninfo, PQgetvalue(res1, i, 1), MAXCONNINFO);
log_info(_("checking role of cluster node '%i'\n"),
node_id);
master_conn = establish_db_connection(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(_("unable to retrieve 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);
log_debug(_("get_master_connection(): current master node is %i\n"), node_id);
if(master_id != NULL)
{
*master_id = node_id;
}
return master_conn;
}
else
{
/* if it is a standby, clear info */
PQclear(res2);
PQfinish(master_conn);
}
}
/*
* 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, long long timeout)
{
PGresult *res;
fd_set read_set;
int sock = PQsocket(conn);
struct timeval tmout,
before,
after;
struct timezone tz;
/* recalc to microseconds */
timeout *= 1000000;
while (timeout > 0)
{
if (PQconsumeInput(conn) == 0)
{
log_warning(_("wait_connection_availability: could not receive data from connection. %s\n"),
PQerrorMessage(conn));
return 0;
}
if (PQisBusy(conn) == 0)
{
do
{
res = PQgetResult(conn);
PQclear(res);
} while (res != NULL);
break;
}
tmout.tv_sec = 0;
tmout.tv_usec = 250000;
FD_ZERO(&read_set);
FD_SET(sock, &read_set);
gettimeofday(&before, &tz);
if (select(sock, &read_set, NULL, NULL, &tmout) == -1)
{
log_warning(
_("wait_connection_availability: select() returned with error: %s"),
strerror(errno));
return -1;
}
gettimeofday(&after, &tz);
timeout -= (after.tv_sec * 1000000 + after.tv_usec) -
(before.tv_sec * 1000000 + before.tv_usec);
}
if (timeout >= 0)
{
return 1;
}
log_warning(_("wait_connection_availability: timeout reached"));
return -1;
}
bool
cancel_query(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)
return false;
/*
* 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;
}
char *
get_repmgr_schema(void)
{
return repmgr_schema;
}
char *
get_repmgr_schema_quoted(PGconn *conn)
{
if(strcmp(repmgr_schema_quoted, "") == 0)
{
char *identifier = PQescapeIdentifier(conn, repmgr_schema,
strlen(repmgr_schema));
maxlen_snprintf(repmgr_schema_quoted, "%s", identifier);
PQfreemem(identifier);
}
return repmgr_schema_quoted;
}
bool
create_replication_slot(PGconn *conn, char *slot_name)
{
char sqlquery[QUERY_STR_LEN];
PGresult *res;
/*
* Check whether slot exists already; if it exists and is active, that
* means another active standby is using it, which creates an error situation;
* if not we can reuse it as-is
*/
sqlquery_snprintf(sqlquery,
"SELECT active, slot_type "
" FROM pg_replication_slots "
" WHERE slot_name = '%s' ",
slot_name);
res = PQexec(conn, sqlquery);
if (!res || PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_err(_("unable to query pg_replication_slots: %s\n"),
PQerrorMessage(conn));
PQclear(res);
return false;
}
if(PQntuples(res))
{
if(strcmp(PQgetvalue(res, 0, 1), "physical") != 0)
{
log_err(_("Slot '%s' exists and is not a physical slot\n"),
slot_name);
PQclear(res);
}
if(strcmp(PQgetvalue(res, 0, 0), "f") == 0)
{
PQclear(res);
log_debug(_("Replication slot '%s' exists but is inactive; reusing\n"),
slot_name);
return true;
}
PQclear(res);
log_err(_("Slot '%s' already exists as an active slot\n"),
slot_name);
return false;
}
sqlquery_snprintf(sqlquery,
"SELECT * FROM pg_create_physical_replication_slot('%s')",
slot_name);
log_debug(_("create_replication_slot(): Creating slot '%s' on primary\n"), slot_name);
res = PQexec(conn, sqlquery);
if (!res || PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_err(_("unable to create slot '%s' on the primary node: %s\n"),
slot_name,
PQerrorMessage(conn));
PQclear(res);
return false;
}
PQclear(res);
return true;
}
bool
start_backup(PGconn *conn, char *first_wal_segment, bool fast_checkpoint)
{
char sqlquery[QUERY_STR_LEN];
PGresult *res;
sqlquery_snprintf(sqlquery,
"SELECT pg_xlogfile_name(pg_start_backup('repmgr_standby_clone_%ld', %s))",
time(NULL),
fast_checkpoint ? "TRUE" : "FALSE");
log_debug(_("standby clone: %s\n"), sqlquery);
res = PQexec(conn, sqlquery);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_err(_("unable to start backup: %s\n"), PQerrorMessage(conn));
PQclear(res);
return false;
}
if (first_wal_segment != NULL)
{
char *first_wal_seg_pq = PQgetvalue(res, 0, 0);
size_t buf_sz = strlen(first_wal_seg_pq);
first_wal_segment = malloc(buf_sz + 1);
xsnprintf(first_wal_segment, buf_sz + 1, "%s", first_wal_seg_pq);
}
PQclear(res);
return true;
}
bool
stop_backup(PGconn *conn, char *last_wal_segment)
{
char sqlquery[QUERY_STR_LEN];
PGresult *res;
sqlquery_snprintf(sqlquery, "SELECT pg_xlogfile_name(pg_stop_backup())");
res = PQexec(conn, sqlquery);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_err(_("unable to stop backup: %s\n"), PQerrorMessage(conn));
PQclear(res);
return false;
}
if (last_wal_segment != NULL)
{
char *last_wal_seg_pq = PQgetvalue(res, 0, 0);
size_t buf_sz = strlen(last_wal_seg_pq);
last_wal_segment = malloc(buf_sz + 1);
xsnprintf(last_wal_segment, buf_sz + 1, "%s", last_wal_seg_pq);
}
PQclear(res);
return true;
}
bool
set_config_bool(PGconn *conn, const char *config_param, bool state)
{
char sqlquery[QUERY_STR_LEN];
PGresult *res;
sqlquery_snprintf(sqlquery,
"SET %s TO %s",
config_param,
state ? "TRUE" : "FALSE");
res = PQexec(conn, sqlquery);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
{
log_err("unable to set '%s': %s\n", config_param, PQerrorMessage(conn));
PQclear(res);
return false;
}
PQclear(res);
return true;
}
/*
* copy_configuration()
*
* Copy records in master's `repl_nodes` table to witness database
*
* This is used by `repmgr` when setting up the witness database, and
* `repmgrd` after a failover event occurs
*/
bool
copy_configuration(PGconn *masterconn, PGconn *witnessconn, char *cluster_name)
{
char sqlquery[MAXLEN];
PGresult *res;
int i;
sqlquery_snprintf(sqlquery, "TRUNCATE TABLE %s.repl_nodes", get_repmgr_schema_quoted(witnessconn));
log_debug("copy_configuration: %s\n", sqlquery);
res = PQexec(witnessconn, sqlquery);
if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
{
fprintf(stderr, "Cannot clean node details in the witness, %s\n",
PQerrorMessage(witnessconn));
return false;
}
sqlquery_snprintf(sqlquery,
"SELECT id, type, upstream_node_id, name, conninfo, priority, slot_name FROM %s.repl_nodes",
get_repmgr_schema_quoted(masterconn));
res = PQexec(masterconn, sqlquery);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
fprintf(stderr, "Can't get configuration from master: %s\n",
PQerrorMessage(masterconn));
PQclear(res);
return false;
}
for (i = 0; i < PQntuples(res); i++)
{
bool node_record_created;
char *witness = PQgetvalue(res, i, 4);
log_debug(_("copy_configuration(): %s\n"), witness);
node_record_created = create_node_record(witnessconn,
"copy_configuration",
atoi(PQgetvalue(res, i, 0)),
PQgetvalue(res, i, 1),
strlen(PQgetvalue(res, i, 2))
? atoi(PQgetvalue(res, i, 2))
: NO_UPSTREAM_NODE,
cluster_name,
PQgetvalue(res, i, 3),
PQgetvalue(res, i, 4),
atoi(PQgetvalue(res, i, 5)),
strlen(PQgetvalue(res, i, 6))
? PQgetvalue(res, i, 6)
: NULL
);
if (node_record_created == false)
{
fprintf(stderr, "Unable to copy node record to witness database: %s\n",
PQerrorMessage(witnessconn));
return false;
}
}
PQclear(res);
return true;
}
/*
* create_node_record()
*
* Create an entry in the `repl_nodes` table.
*
* XXX we should pass the record parameters as a struct.
*/
bool
create_node_record(PGconn *conn, char *action, int node, char *type, int upstream_node, char *cluster_name, char *node_name, char *conninfo, int priority, char *slot_name)
{
char sqlquery[QUERY_STR_LEN];
char upstream_node_id[MAXLEN];
char slot_name_buf[MAXLEN];
PGresult *res;
if(upstream_node == NO_UPSTREAM_NODE)
{
/*
* No explicit upstream node id provided for standby - attempt to
* get primary node id
*/
if(strcmp(type, "standby") == 0)
{
int primary_node_id = get_master_node_id(conn, cluster_name);
maxlen_snprintf(upstream_node_id, "%i", primary_node_id);
}
else
{
maxlen_snprintf(upstream_node_id, "%s", "NULL");
}
}
else
{
maxlen_snprintf(upstream_node_id, "%i", upstream_node);
}
if(slot_name != NULL && slot_name[0])
{
maxlen_snprintf(slot_name_buf, "'%s'", slot_name);
}