[jira] [Resolved] (SLING-3321) Incorrect caching/timeout behavior with slow health check

["Carsten Ziegeler (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SLING-3321?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Carsten Ziegeler resolved SLING-3321.
-------------------------------------

       Resolution: Fixed
    Fix Version/s: Health Check Core 1.0.8

I've changed the handling of futures completely - now only final results are cached and the managing of futures is synchronized to avoid double creation/running of futures when the same check is requested in parallel

> Incorrect caching/timeout behavior with slow health check
> ---------------------------------------------------------
>
>                 Key: SLING-3321
>                 URL: https://issues.apache.org/jira/browse/SLING-3321
>             Project: Sling
>          Issue Type: Bug
>          Components: Health Check
>    Affects Versions: Health Check Core 1.0.8
>            Reporter: Bertrand Delacretaz
>            Assignee: Carsten Ziegeler
>             Fix For: Health Check Core 1.0.8
>
>         Attachments: SLING-3321-log.txt
>
>
> We might not need to fix this right now, just making a note of some tests I did with the SlowHealthCheckSample.
> By default SlowHealthCheckSample takes 1200-3700 msec to execute, and I have set the cache lifetime to 5 seconds.
> With these settings, executing the health check every second should always provide a result: even if a particular execute call takes more than the default 2 seconds execution timeout, an older cached result should still be available as 3700 (max execution time) + 1000 (execution period) is smaller than 5000 (time to live in cache)
> I'll attach an execution log which shows that this is not the case. I see two problems:
> # A result which times out is cached and reused, even though the actual execution might have finished in the meantime. We then get a timeout result and the actual result is thrown away. There's no " execution counter=2" result in my log for example.
> # There's no way to say "execute the health check, but if it times out use an older result if still valid". We might need an execution option for that, as you don't always want that.
> I think this is a realistic use case, checking external systems for example might have that kind of timing characteristics. I should be able to call the executor for such an HC every second, for example, and get a result every time,.



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