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Re: [pcp] pmcd restart race condition

To: Ken McDonell <kenj@xxxxxxxxxxxxxxxx>, Martins Innus <minnus@xxxxxxxxxxx>
Subject: Re: [pcp] pmcd restart race condition
From: Nathan Scott <nathans@xxxxxxxxxx>
Date: Mon, 5 Oct 2015 19:36:01 -0400 (EDT)
Cc: PCP <pcp@xxxxxxxxxxx>
Delivered-to: pcp@xxxxxxxxxxx
In-reply-to: <5612DAA5.9090403@xxxxxxxxxxxxxxxx>
References: <560EB93A.6020606@xxxxxxxxxxx> <y0my4flump3.fsf@xxxxxxxx> <00bd01d0fd56$189950a0$49cbf1e0$@internode.on.net> <5612D405.2030701@xxxxxxxxxxx> <5612DAA5.9090403@xxxxxxxxxxxxxxxx>
Reply-to: Nathan Scott <nathans@xxxxxxxxxx>
Thread-index: 1JtFhF/7JL6DopOhmLSdJx1ZV4lBBg==
Thread-topic: pmcd restart race condition
Hi guys,

----- Original Message -----
> [...]
> Good news Martins.
> 
> I've reviewed the script again in the light of Frank's suggestions and
> moved some other "do only once" tasks after the _pmda_setup call into
> the same conditional block.
> 
> I am still concerned about running _pmda_setup in the background ... I
> think it is safe, but it just does not feel right.
> 
> Let's wait on Nathan's input to see if there is a real performance
> reason to maintained the backgrounding of _pmda_setup.

The problem was reported by someone who wanted to be able to spin up VMs
quickly, which were preconfigured to have pmcd installed and a (at least
one) custom PMDA which had a slow Install.  For some reason they couldn't
make the Install faster, it was impractical for them to pre-configure the
PMDA (namespace install, etc) because of the way they prepared the system
images & Install was measured as being the longest part of their instance
bootup (10 - 20 seconds IIRC).

Since we have in-tree PMDAs with long check_delay ./Install settings too,
this seemed like something we should be doing in the background anyway.

Great to hear its looking fixed, thanks!

cheers.

--
Nathan

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