my.jorgecuadros.com reads customer data from the Oracle VPS replica, and a
replica that has silently stopped applying serves stale balances rather
than erroring — so "is it replicating" needed an answer that is not a
human squinting at SHOW REPLICA STATUS.
Runs entirely against the replica over ssh, so it needs no credentials for
the galactus master, and exits non-zero on failure so it can be driven from
cron or a monitor.
It deliberately does not trust the two fields an operator reaches for first.
Replica_IO_Running reports Yes while the SQL thread is stopped, because the
network thread is still downloading binlog it will never apply — verified by
stopping SQL_THREAD and watching IO stay Yes. Seconds_Behind_Source reads 0
both when there is nothing to apply and when nothing is connected. The
trustworthy signal is GTID_SUBTRACT(Retrieved, Executed): binlog fetched but
not applied.
NULL lag means either thread is down, so it is reported as "not applying"
rather than blamed on a specific thread — the thread fields above already
say which, and guessing there produced a wrong diagnosis.
Uses sed rather than `head -n1`; on this machine `head` resolves to LWP's
HTTP head(1), which mangles the pipeline instead of failing.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
rmancinasandClaude Opus 5
7bec2a13d8