It's possible that a node was registered with "use_replication_slots=false"
but that was later changed to "use_replication_slots=true". If the node
was not subsequently re-registered, the node record will contain an empty
slot name, which will cause any slot creation operation during
"standby follow" or "node rejoin" to fail.
To prevent this happening, check for an empty slot name and automatically
set before proceeding.
Addresses GitHub #343.
If a connection was provided for a database other than the "repmgr"
database, error was logged but execution continued, resulting in
the connection being finished twice.
Addresses GitHub #358.
If --force-rewind is used in conjunction with "repmgr node rejoin",
any replication slots present on the source node will be copied too;
it's essential to remove these to prevent stale slots being extant
when the node starts up.
We do this at file system level *before* the server starts to minimize
the risk of any problems.
Addresses GitHub #334
As that's what we really want to know. Also return "UNCLEAN_SHUTDOWN"
if that's the case, rather than "RUNNING" which is confusing, even
though it's a command for internal use.
There are now too many options to sensibly fit into general --help
output; we'll add separate output for each repmgr command, e.g.
"repmgr node --help".
"standby follow" was originally co-opted to start up a demoted node;
this functionality is now delegated to "node rejoin", with the core
functionality of "standby follow" implemented as an internal function.
If the current primary (demotion candidate) still has any files to archive,
it will delay the shutdown until all files are archived. If there is a
substantial number of files, and/or the archive command executes slowly,
this will probably lead to an unwelcome delay in the switchover process.
The repmgr3 implementation required the promotion candidate (standby)
to directly work with the demotion candidate's data directory,
directly execute server control commands etc.
Here we delegated a lot more of that work to the repmgr on the
demotion candidate, which reduces the amount of back-and-forth
over SSH and generally makes things cleaner and smoother.
In particular the repmgr on the demotion candidate will carry
out a thorough check that the node is shut down and report
the last checkpoint LSN to the promotion candidate; this
can then be used to determine whether pg_rewind needs to be
executed on the demoted primary before reintegrating it back
into the cluster (todo).
Also implement "--dry-run" for this action, which will sanity-check the
nodes as far as possible without executing the switchover.
Additionally some of the new repmgr node commands (or command options)
introduced for this can be also executed by the user to obtain
additional information about the status of each node.
