NAME
FAILOVER - Fail a broken replication set over to a backup node
SYNOPSIS
FAILOVER (options);
DESCRIPTION
The FAILOVER command causes the backup node to take over all sets that
currently originate on the failed node. slonik will contact all other
direct subscribers of the failed node to determine which node has the
highest sync status for each set. If another node has a higher sync
status than the backup node, the replication will first be redirected
so that the backup node replicates against that other node, before
assuming the origin role and allowing update activity.
After successful failover, all former direct subscribers of the failed
node become direct subscribers of the backup node. The failed node is
abandoned, and can and should be removed from the configuration with
SLONIK DROP NODE(7).
ID = ival
ID of the failed node
BACKUP NODE = ival
Node ID of the node that will take over all sets originating on
the failed node
This uses “schemadocfailednode( integer, integer )” [not available as a
man page].
EXAMPLE
FAILOVER (
ID = 1,
BACKUP NODE = 2
);
LOCKING BEHAVIOUR
Exclusive locks on each replicated table will be taken out on both the
new origin node as replication triggers are changed. If the new origin
was not completely up to date, and replication data must be drawn from
some other node that is more up to date, the new origin will not become
usable until those updates are complete.
DANGEROUS/UNINTUITIVE BEHAVIOUR
This command will abandon the status of the failed node. There is no
possibility to let the failed node join the cluster again without
rebuilding it from scratch as a slave. If at all possible, you would
likely prefer to use SLONIK MOVE SET(7) instead, as that does not
abandon the failed node.
If there are many nodes in a cluster, and failover includes dropping
out additional nodes (e.g. when it is necessary to treat all nodes at a
site including an origin as well as subscribers as failed), it is
necessary to carefully sequence the actions, as described in “ Failover
With Complex Node Set ” [not available as a man page].
VERSION INFORMATION
This command was introduced in Slony-I 1.0
In version 2.0, the default BACKUP NODE value of 1 was removed, so it
is mandatory to provide a value for this parameter.
12 May 2010 SLONIK FAILOVER(7)