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Roman,

According to documentation [1] this setting is responsible for the amount
of time to wait a lock to be released before trying to check if it is, in
fact, a deadlock. This time just allows not to spend resources for
unnecessary checks.
If a lock is not a deadlock, this check will just skip it and request will
continue to wait for a lock to be released until lock_timeout is exceeded.

[1] http://www.postgresql.org/docs/9.3/static/runtime-config-locks.html

Vladimir Kozhukalov

On Mon, Mar 21, 2016 at 7:39 PM, Roman Prykhodchenko <me at romcheg.me> wrote:

> Folks,
>
> We have been analyzing a bunch of random failures in Fuel tests and
> encountered several ones caused by detector raising errors occasionally
> [1]. After attempts to reproduce the same behavior have failed we’ve
> decided to run the same test suit on overloaded nodes. Those test-runs
> allowed us to catch the same behavior we’ve seen on CI slaves. After
> analyzing both PostgreSQL logs and Nailgun’s code we’ve found no reasons
> for those deadlocks to occur.
>
> Thinking about the facts mentioned we came up with the idea that those
> random deadlocks occur in cases when CI slaves are overloaded by other jobs
> and transactions start hitting deadlock timeout. Thus I propose to change
> PostgreSQL’s deadlock_timeout value from the default one to 3-5 seconds.
> That will slow down tests, if they run on an overloaded CI slave but will
> help to avoid random and false-positive deadlock warnings.
>
>
> References:
>
> 1. https://bugs.launchpad.net/fuel/+bug/1556070
>
>
> - romcheg
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