No no, with Varnish open-source you really want all your stuff in memory anyway. What I meant is really to have two storages based on object size.
Imagine you have a 50MB object that needs to be stored, and your nuke_limit is 50. If you only have one store, then you could easily evict 50 100KB objects, forcing you to fail the transaction. But if you have a pool that is dedicated to bigger objects, you know that each object you evict from it is at least 1MB big, so you cannot fail the transaction due to nuke_limit -- Guillaume Quintard On Fri, May 8, 2020 at 11:50 AM Batanun B <bata...@hotmail.com> wrote: > ok. Interesting. 🙂 > > 99.99% of the time that this is happening (after adjusting the cache > sizes), I would say that it would be only a single user requesting the > image. So it would make sense it it was possible to configure Varnish so it > could handle that scenario in a better way. What happens when multiple > users request the same resource, and this nuke problem happens is less of a > problem, and those times a broken could be acceptable (but preferably it > would start serving each request separately, uncached, fetching from the > backend each time). > > I will increase the cache size, and look into splitting it into two > storages. But, I'm guessing you mean that the small objects should be > cached in-memory, and the larger ones on disk? It would make much more > sense if it cached less "popular" objects on disk, and more "popular" > objects in memory, and only considering the object size when the in-memory > cache starts to get full. Is it possible to configure Varnish to handle > that in a smart and dynamic way? > ------------------------------ > *From:* Guillaume Quintard <guilla...@varnish-software.com> > *Sent:* Friday, May 8, 2020 8:33 PM > *To:* Batanun B <bata...@hotmail.com> > *Cc:* varnish-misc@varnish-cache.org <varnish-misc@varnish-cache.org> > *Subject:* Re: Varnish intermittently returns incomplete images > > Good question. This is because by default varnish streams the response, so > it starts sending what it has, even though it's unsure it can actually > deliver. When the eviction strikes, it just aborts the transaction. > > The problem with "just" passing the data to the user is that there may be > more than one and things get really complicated. > > Getting a bigger cache would help, and segregating the storages (smaller > than 1MB, and bigger than 1MB for example) would too > -- > Guillaume Quintard > > > On Fri, May 8, 2020 at 11:28 AM Batanun B <bata...@hotmail.com> wrote: > > 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 <guilla...@varnish-software.com> > *Sent:* Friday, May 8, 2020 7:34 PM > *To:* Batanun B <bata...@hotmail.com> > *Cc:* varnish-misc@varnish-cache.org <varnish-misc@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 <bata...@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? > _______________________________________________ > varnish-misc mailing list > varnish-misc@varnish-cache.org > https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc > > _______________________________________________ > varnish-misc mailing list > varnish-misc@varnish-cache.org > https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc > > _______________________________________________ > varnish-misc mailing list > varnish-misc@varnish-cache.org > https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc >
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