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Add troubleshooting guide for http_resp_hdr_len #519
We recently had an issue where Varnish would serve some pages (startlingly quickly), and give a backend fetch error (503) on others. It turns out that it is due to the length of the cache tags list being longer than the maximum header length that varnish expects.
Fortunately, this is configurable.
Attached is a screenshot of what the change looks like once compiled.
@maxbucknell I need more context from your /etc/sysconfig/varnish file. I do not have Varnish installed right now and I need to know in particular:
@xcomSteveJohnson the default /etc/sysconfig/varnish file looks like this:
That option could/should be added after the
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Feb 11, 2016
Also, there is a typo in the first line:
Should be "8192 bytes".
It would also be handy to have a recommendation on what to set this value to. Setting it to 64000 will give you the same error if you have a category with around 3050 products (every product tag is about 21 characters long). While that's a lot, it's totally conceivable.
I wrote a blog post on the topic, wherein I suppose that a sensible value is the product count of your largest category multiplied by 30. This gives you room to grow and keeps memory usage in check, since I suspect increasing this parameter to something really large will have an adverse impact on memory consumption of Varnish.