repmgrd
configuration
repmgrd configuration
To use repmgrd, its associated function library must be
included in postgresql.conf with:
shared_preload_libraries = 'repmgr'
Changing this setting requires a restart of PostgreSQL; for more details see
the PostgreSQL documentation.
Additionally the following repmgrd options *must* be set in
repmgr.conf (adjust configuration file locations as appropriate):
failover=automatic
promote_command='repmgr standby promote -f /etc/repmgr.conf --log-to-file'
follow_command='repmgr standby follow -f /etc/repmgr.conf --log-to-file --upstream-node-id=%n'
Note that the --log-to-file option will cause
output generated by the &repmgr; command, when executed by repmgrd,
to be logged to the same destination configured to receive log output for repmgrd.
See repmgr.conf.sample for further repmgrd-specific settings.
When failover is set to automatic, upon detecting failure
of the current primary, repmgrd will execute one of
promote_command or follow_command,
depending on whether the current server is to become the new primary, or
needs to follow another server which has become the new primary. Note that
these commands can be any valid shell script which results in one of these
two actions happening, but if &repmgr;'s standby follow or
standby promote
commands are not executed (either directly as shown here, or from a script which
performs other actions), the &repmgr; metadata will not be updated and
&repmgr; will no longer function reliably.
The follow_command should provide the --upstream-node-id=%n
option to repmgr standby follow; the %n will be replaced by
repmgrd with the ID of the new primary node. If this is not provided, &repmgr;
will attempt to determine the new primary by itself, but if the
original primary comes back online after the new primary is promoted, there is a risk that
repmgr standby follow will result in the node continuing to follow
the original primary.
repmgrd connection settings
In addition to the &repmgr; configuration settings, parameters in the
conninfo string influence how &repmgr; makes a network connection to
PostgreSQL. In particular, if another server in the replication cluster
is unreachable at network level, system network settings will influence
the length of time it takes to determine that the connection is not possible.
In particular explicitly setting a parameter for connect_timeout
should be considered; the effective minimum value of 2
(seconds) will ensure that a connection failure at network level is reported
as soon as possible, otherwise depending on the system settings (e.g.
tcp_syn_retries in Linux) a delay of a minute or more
is possible.
For further details on conninfo network connection
parameters, see the
PostgreSQL documentation.
repmgrd log rotation
To ensure the current repmgrd logfile does not grow
indefinitely, configure your system's logrotate to
regularly rotate it.
Sample configuration to rotate logfiles weekly with retention for
up to 52 weeks and rotation forced if a file grows beyond 100Mb:
/var/log/postgresql/repmgr-9.6.log {
missingok
compress
rotate 52
maxsize 100M
weekly
create 0600 postgres postgres
}