This helps provide a better picture of the state of the cluster, i.e.
making it more obvious whether there's been a timeline divergence.
This also provides infrastructure for further improvements in cluster
status display and diagnosis.
Note this is only available in PostgreSQL 9.6 and later as it relies
on the SQL functions for interrogating pg_control, which can be executed
remotely. As PostgreSQL 9.5 will shortly be the only community-supported
version without these functions, it's not worth the effort of trying
to duplicate their functionality.
Previously repmgr would happily clone from whatever server
it found at the provided source server address. We should
ensure that a standby can only be cloned from a node which
is part of the main replication cluster.
This check fetches a list of nodes from the source server,
connects to the first non-witness server it finds, and
compares the system identifiers of the source node and the
node it has connected to. If there is a mismatch, then the
source server is clearly not part of the main replication
cluster, and is most likely the witness server.
When showing node information, check if the node's copy of its
record shows a different upstream to the one expected according
to the node where the command is executed.
This helps visualise situations where the cluster is in an
unexpected state, and provide a better idea of the actual state.
For example, if a cluster has divided somehow and a set of nodes are
following a new primary, when running "cluster show" etc., repmgr
will now show the name of the primary those nodes are actually
following, rather than the now outdated node name recorded
on the other side of the split. A warning will also be issued
about the situation.
In Barman mode, if there is an existing, populated data directory, and
the "--force" option is provided, the entire directory was being deleted,
and later recreated as part of the rsync process, but with the default
permissions.
Fix this by recreating the data directory with the correct permissions
after deleting it.
This enable selection of the method repmgrd uses to check whether the upstream
node is available. Possible values are:
- "ping" (default): uses PQping() to check server availability
- "connection": executes a query on the connection to check server
availability (similar to repmgr3.x).
With long-running copy operations, it's possible the connection(s) to
the primary/source server may go away for some reason, so recheck
their availability before attempting to reuse.
We only want to check the status of physical replication slots
to determine whether a streaming replication standby has become
detached and there is therefore a risk of uncontrolled WAL buildup
on the local node.
It's not feasible to second-guess the state of logical replication
slots.
If, for whatever reason, repmgrd is not running on a node, but that
node qualifies as promotion candidate, failover will not take place
as that node will never promote itself.
We therefore discount nodes where repmgrd is running as promotion
candidates, which will ensure one node is always promoted.
There is a slight risk here that the node(s) where repmgrd is not running
are further ahead, leading to a timeline fork. It might be possible
to mitigate that by having the "election" leader perform the promote
(or follow) operation.
Previously, if the witness server connection details were provided
to "repmgr witness register" rather than those of the primary server,
repmgr a) write the node record to the witness server rather than
the primary, and b) would loop indefinitely trying to copy the
node table to itself.
Addresses GitHub #538.
Ensure repmgr checks the standby (promotion candidate) is currently
attached to the primary (demotion candidate).
Addresses issue reported in GitHub #519.
Immediately after the demotion candidate (primary) has shut down, we can't
be absolutely sure that the walreceiver has flushed all WAL to disk, so
checking pg_last_wal_receive_lsn() at that point might not reflect
the actual last available WAL location.
To handle this, we'll loop for a while (timeout controlled by configuration
parameter "wal_receive_check_timeout") before finally deciding whether
the standby is still behind the shut-down primary.
Addresses issue raised in GitHub #518.
The switchover will fail if the data_directory parameter in repmgr.conf
on the remote node (demotion candidate) is incorrectly configured.
We use the previously added "repmgr node check --data-directory-config
to verify this, and abort early if an issue is discovered.
Implements GitHub #523.
Previously, if connection URIs were in use and "repmgr standby switchover"
was executed, repmgr would pass the connection URI as-is to the demotion
candidate to execute "repmgr node rejoin". However the presence of
unescaped ampersands in the connection URI was causing the rejoin command
to be incorrectly executed.
Addresses GitHub #525.
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.
repmgr requires that the same "major version" (e.g. 4.3) is present
on all nodes, otherwise - particularly in the case of repmgrd - it's
highly likely things won't work as expected.
Implements part of GitHub #515.
Previously it would refuse to start if the primary was not reachable,
the thinking being that it's pointless trying to monitor an incomplete
cluster.
However following an aborted failover situation, repmgrd will restart
monitoring and on the witness server, this will lead to it aborting
itself due to to continuing absence of primary.
To resolve this, witness repmgrd will now start monitoring in degraded
mode if no primary is found in the hope a primary will reappear at
some point.
Previously repmgr would abort with an unhelpful message about being
unable to parse CSV output.
With this commit, it will continue running, and display a list of
inaccessible nodes as an addendum to the main output (unless --csv
or --terse options are specified).
Addresses GitHub #246.
