Github user ctubbsii commented on the issue:
https://github.com/apache/accumulo/pull/242
> An old, standby monitor would return HTTP/503 (unavailable) to signify
that it isn't polling data from the master and (thus) is useless to observe.
Does the new REST API still do this?
No, it does not. "Standby" monitors will function as normal (except for log
receiving), because it may be desirable to have multiple monitors. The 503
response code was added in ACCUMULO-4424 for 2.0.0, and has never been
released, so this won't break anyone. The monitor has never fit into the same
active/standby HA paradigm that applies to the other services, because its
features do not require exclusivity. The active/standby single-instance
situation for the monitor was only introduced for log receiving (so Accumulo
could identify and automatically forward logs to the monitor), which introduced
some kind of exclusivity (but for logs only). I believe we've made sufficient
improvements to the log forwarding features, so that it's no longer necessary
to impose exclusivity restrictions on all monitor features simply for log
forwarding.
We can probably still do something to improve the way we inform users about
log forwarding exclusivity. For example: we could provide
`monitor.log.receiver={WITH_LOCK,ON,OFF}` (default: WITH_LOCK) config, and have
the 503 response on the REST endpoint for logs, and display a message on the
log view based on whether it receives 503 or 200 from the AJAX call. That
should be a separate task, if we do that.
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