Looking for way to monitor dsync, confirm it is or isn't running

[Rich Wales]

Earlier, I asked:

>> I would like to be able to run some sort of periodic health check to
>> confirm that dsync is (or is not) running properly between the two
>> sites, and alert me if dsync is failing or lagging excessively. Does
>> anyone know of a tool to do this?

and Michael Grimm replied:

> doveadm replicator status
> 
> If those numbers tend to become significantly larger than 0, then
> replication has issues. I do not use that for health checking . . .
> but used it once in a while when suspecting issues with replication.

Thanks.

As a followup question:  If "doveadm replicator status" shows problems,
are there any commands available to pinpoint exactly which request(s)
is/are causing the problem(s)?

One of the sites I am administering, for example, has been reporting
1 "queued 'full resync' requests" and 9 "waiting 'failed' requests" for
the past couple of days.  But I have no idea how to resolve the issue.
Suggestions welcome.

Rich Wales
richw at richw.org