Varnish intermittently returns incomplete images

[Batanun B]

also... could you explain this part for me? "so it had to truncate it and throw it away"
Why does it have to truncate it? Why not avoid caching it, and returning it as is, from the backend, untouched?
________________________________
From: Guillaume Quintard <guillaume at varnish-software.com>
Sent: Friday, May 8, 2020 7:34 PM
To: Batanun B <batanun at hotmail.com>
Cc: varnish-misc at varnish-cache.org <varnish-misc at varnish-cache.org>
Subject: Re: Varnish intermittently returns incomplete images

Hi,

Do you have objects that are sensibly smaller that your images in your cache?

What you are describing sounds like LRU failure (check nuke_limit in "varnishadm param.show"), basically, on a miss, varnish couldn't evict enough objects and make room for the new object, so it had to truncate it and throw it away.

If that's the issue, you can increase nuke_limit, or get a bigger cache, or segregate small and large objects into different storages.

--
Guillaume Quintard


On Fri, May 8, 2020 at 10:14 AM Batanun B <batanun at hotmail.com<mailto:batanun at hotmail.com>> wrote:
Our Varnish (test environment) intermittently returns incomplete images. So the binary content is not complete. When requesting the image from the backend directly (using curl), the complete image is returned every time (I tested 1000 times using a script).

This happens intermittently. Sometimes Varnish returns the complete image, sometimes half of it, sometimes 20% etc... The incomplete image is returned quickly, so I don't think there is a timeout involved (we have not configured any specific timeout in varnish).

I see nothing special in varnishlog when this happens. But I don't know how to troubleshoot this in a good way. Any suggestions?
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