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repmgrd: monitor standbys attached to primary

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This functionality enables repmgrd (when running on the primary) to
monitor connected child nodes. It will log connections and disconnections
and generate events.

Additionally, repmgrd can execute a custom script if the number of connected
child nodes falls below a configurable threshold. This script can be used
e.g. to "fence" the primary following a failover situation where a new primary
has been promoted and all standbys are now child nodes of that primary.
This commit is contained in:
Ian Barwick
2019-04-22 16:16:59 +09:00
parent 64c4cb81d5
commit 5a90513878
9 changed files with 917 additions and 5 deletions
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56
dbutils.c
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@@ -1575,6 +1575,7 @@ identify_system(PGconn *repl_conn, t_system_identification *identification)
return true;
}
TimeLineHistoryEntry *
get_timeline_history(PGconn *repl_conn, TimeLineID tli)
{
@@ -1672,6 +1673,46 @@ get_timeline_history(PGconn *repl_conn, TimeLineID tli)
}
bool
get_child_nodes(PGconn *conn, int node_id, NodeInfoList *node_list)
{
PQExpBufferData query;
PGresult *res = NULL;
bool success = true;
initPQExpBuffer(&query);
appendPQExpBuffer(&query,
" SELECT n.node_id, n.type, n.upstream_node_id, n.node_name, n.conninfo, n.repluser, "
" n.slot_name, n.location, n.priority, n.active, n.config_file, "
" '' AS upstream_node_name, "
" CASE WHEN sr.application_name IS NULL THEN FALSE ELSE TRUE END AS attached "
" FROM repmgr.nodes n "
" LEFT JOIN pg_catalog.pg_stat_replication sr "
" ON sr.application_name = n.node_name "
" WHERE n.upstream_node_id = %i ",
node_id);
log_verbose(LOG_DEBUG, "get_active_sibling_node_records():\n%s", query.data);
res = PQexec(conn, query.data);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_db_error(conn, query.data, _("get_active_sibling_records(): unable to execute query"));
success = false;
}
termPQExpBuffer(&query);
/* this will return an empty list if there was an error executing the query */
_populate_node_records(res, node_list);
PQclear(res);
return success;
}
/* =============================== */
/* repmgrd shared memory functions */
/* =============================== */
@@ -2273,9 +2314,18 @@ _populate_node_record(PGresult *res, t_node_info *node_info, int row, bool init_
node_info->active = atobool(PQgetvalue(res, row, 9));
snprintf(node_info->config_file, sizeof(node_info->config_file), "%s", PQgetvalue(res, row, 10));
/* This won't normally be set */
/* These are only set by certain queries */
snprintf(node_info->upstream_node_name, sizeof(node_info->upstream_node_name), "%s", PQgetvalue(res, row, 11));
if (PQgetisnull(res, row, 12))
{
node_info->attached = NODE_ATTACHED_UNKNOWN;
}
else
{
node_info->attached = atobool(PQgetvalue(res, row, 12)) ? NODE_ATTACHED : NODE_DETACHED;
}
/* Set remaining struct fields with default values */
if (init_defaults == true)
@@ -2398,7 +2448,7 @@ get_node_record_with_upstream(PGconn *conn, int node_id, t_node_info *node_info)
initPQExpBuffer(&query);
appendPQExpBuffer(&query,
" SELECT n.node_id, n.type, n.upstream_node_id, n.node_name, n.conninfo, n.repluser, "
" n.slot_name, n.location, n.priority, n.active, n.config_file, un.node_name AS upstream_node_name "
" n.slot_name, n.location, n.priority, n.active, n.config_file, un.node_name AS upstream_node_name, NULL AS attached "
" FROM repmgr.nodes n "
" LEFT JOIN repmgr.nodes un "
" ON un.node_id = n.upstream_node_id"
@@ -2698,7 +2748,7 @@ get_all_node_records_with_upstream(PGconn *conn, NodeInfoList *node_list)
appendPQExpBufferStr(&query,
" SELECT n.node_id, n.type, n.upstream_node_id, n.node_name, n.conninfo, n.repluser, "
" n.slot_name, n.location, n.priority, n.active, n.config_file, un.node_name AS upstream_node_name "
" n.slot_name, n.location, n.priority, n.active, n.config_file, un.node_name AS upstream_node_name, NULL AS attached "
" FROM repmgr.nodes n "
" LEFT JOIN repmgr.nodes un "
" ON un.node_id = n.upstream_node_id"