Updating VMODs with zero downtime

Carlos Abalde carlos.abalde at gmail.com
Mon Jul 28 13:38:49 CEST 2014

On 28 Jul 2014, at 12:21, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:

>> Lately I've been wondering about the possibility of updating Varnish 
>> VMODs with zero downtime. Being able of reloading VCL with zero downtime 
>> is a great Varnish Feature; it reminds me a lot to hot code replacement 
>> ...
> Just reload your VCL and the VMODs should be updated too.


That’s great. However, I’ve been testing with Varnish 3.0.3 running in CentOS 6.5, using a minimal VCL importing the example VMOD (https://github.com/varnish/libvmod-example) to generate a synthetic response using the example.hello() method. After changing the “Hello” string included in the VMOD by something else, recompiling and reinstalling the VMOD, the behaviour does not change when reloading the service. Only a restart of the service seems to work to update the VMOD.

Maybe I’m missing something here. I’ll do some more testing using the CLI…


Carlos Abalde.
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