perl

[Bash Coder]

I never saw a reply to this question on the list, so this is a *bump*...

On 12/4/06, matt DiMeo <mattdimeo at yahoo.com> wrote:
>
> There's a minor (depending on application) reliability issue with the perl
> client (I have version 1.18).
>
> Basically if a host dies, every request to it will take one second to
> timeout.  The client is smart about marking a memcached as down if it can't
> initally connect to it, but when it already has a connection, it'll just
> keep retrying.
>
> This is because the _dead_sock sub is only passed a $dead_for parameter
> (20+rand seconds) on initial connect; if an already-connected socket fails,
> it gets undef and doesn't mark the host bad.
>
> You can simulate this behavior by running memcached in non-daemon mode and
> hitting ctrl-z; every request to that server will then take a full second to
> fail (the select timeout is 1s).
>
> Most applications would probably just slow down, but our system can't
> tolerate average response times of over about 400ms (we fill up all our
> worker processes), so we kinda fall over.
>
> I've fixed this locally by modifying all the _dead_sock calls to pass an
> appropriate $dead_for value.
>
> I'm also planning to add support for optionally replacing the %host_dead
> hash with an IPC::ShareLite object, which would allow the information about
> which hosts are up or down to be shared between clients on the same host.
>
> So, a couple questions:
> 1. Can anyone tell me why _dead_sock isn't always passed a $down_for time?
> 2. If not, let's fix it (which isn't actually a question).
> 3. Would anyone else be interested in the IPC::ShareLite stuff?
>
> Thanks,
> -m@


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