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repmgrd: add configuration option "always_promote"

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In certain corner cases, it's possible repmgrd may end up monitoring
a standby which was a former primary, but the node record has not
yet been updated.

Previously repmgrd would abort the promotion with a cryptic message
about being unable to find a node record for node_id -1 (the
default value for an unknown node id).

This commit addes a new configuration option "always_promote", which
determines whether repmgrd should promote the node in this case.
The default is "false", to effectively maintain the existing behaviour.

Logging output has also been improved to make it clearer what has
happened when this situation occurs.
This commit is contained in:
Ian Barwick
2020-09-29 14:13:03 +09:00
parent 16eeae700c
commit ce229beff8
8 changed files with 130 additions and 11 deletions
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73
repmgrd-physical.c
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@@ -764,9 +764,25 @@ check_primary_status(int degraded_monitoring_elapsed)
}
else
{
appendPQExpBuffer(&event_details,
_("node has become a standby, monitoring connection to upstream node %i"),
local_node_info.upstream_node_id);
if (local_node_info.upstream_node_id == UNKNOWN_NODE_ID)
{
/*
* If upstream_node_id is not set, it's possible that following a switchover
* of some kind (possibly forced in some way), the updated node record has
* not yet propagated to the local node. In this case however we can safely
* assume we're monitoring the primary.
*/
appendPQExpBuffer(&event_details,
_("node has become a standby, monitoring connection to primary node %i"),
primary_node_id);
}
else
{
appendPQExpBuffer(&event_details,
_("node has become a standby, monitoring connection to upstream node %i"),
local_node_info.upstream_node_id);
}
}
create_event_notification(new_primary_conn,
@@ -3199,6 +3215,7 @@ update_monitoring_history(void)
if (primary_last_wal_location >= replication_info.last_wal_receive_lsn)
{
replication_lag_bytes = (long long unsigned int) (primary_last_wal_location - replication_info.last_wal_receive_lsn);
log_debug("replication lag in bytes is: %llu", replication_lag_bytes);
}
else
{
@@ -3482,6 +3499,14 @@ do_upstream_standby_failover(void)
}
/*
* This promotes the local node using the "promote_command" configuration
* parameter, which must be either "repmgr standby promote" or a script which
* at some point executes "repmgr standby promote".
*
* TODO: make "promote_command" and execute the same code used by
* "repmgr standby promote".
*/
static FailoverState
promote_self(void)
{
@@ -3504,13 +3529,43 @@ promote_self(void)
sleep(config_file_options.promote_delay);
}
record_status = get_node_record(local_conn, local_node_info.upstream_node_id, &failed_primary);
if (record_status != RECORD_FOUND)
if (local_node_info.upstream_node_id == UNKNOWN_NODE_ID)
{
log_error(_("unable to retrieve metadata record for failed upstream (ID: %i)"),
local_node_info.upstream_node_id);
return FAILOVER_STATE_PROMOTION_FAILED;
/*
* This is a corner-case situation where the repmgr metadata on the
* promotion candidate is outdated and the local node's upstream_node_id
* is not set. This is often an indication of potentially serious issues,
* such as the local node being very far behind the primary, or not being
* attached at all.
*
* In this case it may be desirable to restore the original primary.
* This behaviour can be controlled by the "always_promote" configuration option.
*/
if (config_file_options.always_promote == false)
{
log_error(_("this node (ID: %i) does not have its upstream_node_id set, not promoting"),
local_node_info.node_id);
log_detail(_("the local node's metadata has not been updated since it became a standby"));
log_hint(_("set \"always_promote\" to \"true\" to force promotion in this situation"));
return FAILOVER_STATE_PROMOTION_FAILED;
}
else
{
log_warning(_("this node (ID: %i) does not have its upstream_node_id set, promoting anyway"),
local_node_info.node_id);
log_detail(_("\"always_promote\" is set to \"true\" "));
}
}
else
{
record_status = get_node_record(local_conn, local_node_info.upstream_node_id, &failed_primary);
if (record_status != RECORD_FOUND)
{
log_error(_("unable to retrieve metadata record for failed upstream (ID: %i)"),
local_node_info.upstream_node_id);
return FAILOVER_STATE_PROMOTION_FAILED;
}
}
/* the presence of this command has been established already */