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From Bill Farner <wfar...@apache.org>
Subject Re: mesos-log health check HTTP endpoint
Date Fri, 17 Jun 2016 14:05:17 GMT
If i recall correctly, the current implementation of the mesos log requires
that the callers handle mutually-exclusive access for reads and writes.
This means that non-leading schdulers may not read or write to perform the
check you describe.

What's the behavior of the scheduler when it starts and the log replica is
non-VOTING?  I thought the log open() call would fail, and the scheduler
process would exit (giving a strong signal that the scheduler is not
healthy).

On Fri, Jun 17, 2016 at 2:44 AM, Martin Hrabovčin <
martin.hrabovcin@gmail.com> wrote:

> Hello,
>
> I was asking same question in #aurora channel and I still haven't found an
> answer so I am bringing this in mailing list with a proposal.
>
> Is there a way to check the state of mesos-log (whether the its writable in
> VOTING state) through some HTTP check outside of aurora process on a
> non-leading aurora instance? We are trying to create external check that
> would determine whether the mesos-log is ready in case of aurora rolling
> update. When adding new instance to existing aurora cluster and we want to
> make sure that mesos-log is replicated and replica is ready to serve reads
> and writes. Currently we’re grep-ing java process log and looking for
> “Persisted replica status to VOTING”.
>
> I was pointed to /vars endpoint but I haven't found obvious answer there.
>
> I'd like to propose creating new HTTP endpoint "/loghealth" that would
> similarly to "/leaderhealth" return 200 when mesos-log is ready and 503 in
> case when mesos log throws exception. As for implementation I was thinking
> about doing simple read from log or write noop to log directly.
>
> Thanks!
>

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