[jira] [Updated] (TS-4278) HostDB sync causes active transactions to block for 100's of ms

["Leif Hedstrom (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TS-4278?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Leif Hedstrom updated TS-4278:
------------------------------
    Fix Version/s: 6.2.0

> HostDB sync causes active transactions to block for 100's of ms
> ---------------------------------------------------------------
>
>                 Key: TS-4278
>                 URL: https://issues.apache.org/jira/browse/TS-4278
>             Project: Traffic Server
>          Issue Type: Bug
>          Components: HostDB
>            Reporter: Susan Hinrichs
>             Fix For: 6.2.0
>
>
> When HostDB syncs to disk (by default every two minutes), active transactions will block when they reach HttpSM::do_hostdb_lookup.  This is because do_hostdb_lookup calls hostDBProcessor.getbyname_imm which attempts to get the bucket locks.   The delays generally last for 500-1200ms.  This blocks the event loop so no other actions will be performed by the net handler until the lock is dropped.
> I'm assuming that the bucket locks are grabbed by the sync logic.  When I increased proxy.config.cache.hostdb.sync_frequency to 1200, the every two minute slow down went away.  Fortunately proxy.config.cache.hostdb.sync_frequency set to 0 seems to completely eliminate the sync, which will be my suggested solution internally.
> I tried reducing the size of the hostdb table, but that didn't seem to affect the delay time.
> The delay only reliably exhibited on loaded system.  Running my httperf test case on a machine with no other activity did not show the delays.



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