Previously, if PostgreSQL was not running on the node, repmgrd and
pause status were shown as "0", implying their status was known.
This brings the csv output in line with the human-readable output,
which displays "n/a" in this case.
Specifically, if WAL replay is paused *and* WAL is pending replay,
this node cannot be promoted until WAL replay is unpaused. In this
state it is not a suitable promotion candidate in a failover situation.
The initial implementation was designed to fall back to "manual"
start/stop of repmgrd if the "repmgrd_service_..._command" parameters
were not set.
However on reflection, this is too much of a potential footgun, so
we will mandate provision of these parameters.
repmgr will attempt to construct appropriate commands to start
and stop repmgrd, but usually it's preferable for them to be explicitly
defined, particularly if repmgr is installed from packages.
This suppresses display of the usually lengthy "conninfo" column, mainly
useful for generating a compact table suitable for pasting into emails,
chats etc. without messy line breaks.
Implements GitHub #521.
In some circumstances, e.g. while performing a switchover, it is essential
that repmgrd does not take any kind of failover action, as this will put
the cluster into an incorrect state.
Previously it was necessary to stop repmgrd on all nodes (or at least
those nodes which repmgrd would consider as promotion candidates), however
this is a cumbersome and potentially risk-prone operation, particularly if the
replication cluster contains more than a couple of servers.
To prevent this issue from occurring, this patch introduces the ability
to "pause" repmgrd on all nodes wth a single command ("repmgr daemon pause")
which notifies repmgrd not to take any failover action until the node
is "unpaused" ("repmgr daemon unpause").
"repmgr daemon status" provides an overview of each node and whether repmgrd
is running, and if so whether it is paused.
"repmgr standby switchover" has been modified to automatically pause repmgrd
while carrying out the switchover.
See documentation for further details.
