CC'ing  pfeldman@chromium.org for further inputs. 

Thanks!

cc: pwnall@ who had opinions.

I got into a situation in my application where navigator.storage.estimate() was reporting I was using 23gb. I went to devtools to see where all that was going, and it was attributing it all to CacheStorage. From inspecting my caches, none of them were using over a few MB. So I'm seeing a factor of over 1000x from what appears to be there, to what its reporting is there. This is causing issues in my application because I'm hitting various Quota errors.

I dont think this is actually a devtools issue. I think that CacheStorage is contributing very erroneously to Quota API.

#3: I think you're hitting a separate Cache Storage bug.

I think this issue tracks addressing confusions like the one discussed in https://crbug.com/795735#c5 TL;DR: the backing stores we use involve logs, so the actual disk usage of each storage feature does not precisely match the amount of data stored by the application / user.

#5 pwnall@ : how do you explain the repro at https://bugs.chromium.org/p/chromium/issues/detail?id=795134#c9 ?

#6: To be clear -- I did not intend to imply that comment #3 does not point to a valid bug. My intention was to state that the #3 seems to describe a bug in cache storage accounting, which is a separate issue (that can be fixed quickly).

I think this issue covers the fact that, even with perfect quota accounting, the disk space taken by our backing stores is not perfectly related to the sum of the sizes of the items that the user / application has written to the stores. While this reality is fairly non-negotiable, we would still like to get to a point where our quota system behaves in a way that matches developers' intuition. This is a fairly subtle problem that is unlikely to have a quick and easy fix.

Leaving comment #3 of this thread aside, how would you categorise the behaviour seen in the following (and other related repros in that thread):

https://bugs.chromium.org/p/chromium/issues/detail?id=795134#c9

Bug, or just a mismatch between developer expectation and reality?

#8: I'm afraid it's all mismatch between developer expectations and reality. One of my colleagues will follow up on that bug shortly.

In general, please try to file one bug per issue (visible issue with a different repro). I would rather close bugs as duplicate than have to look for repros in the middle of a bug thread.

Thank you for reporting bugs!

pwnall@ well if this isn't a browser bug, then hopefully you or your colleague will be able to educate us as to how to alter our code to prevent the Cache Usage from increasing uncontrollably (until it hits the Quota limit) in the repro provided at https://bugs.chromium.org/p/chromium/issues/detail?id=795134#c9.  

So far as I can see, that repro is just mimicking "normal" behaviour (open tab, load page, close tab, repeat) and yet the cache usage just keeps rising.  There must be some way of forcibly recovering the cache storage that is being reported as "used" which actually isn't?

#10: The only increasing storage usage I see when using the page linked to from https://bugs.chromium.org/p/chromium/issues/detail?id=795134#c9 is IndexedDB usage, not CacheStorage usage. I believe that it's a separate issue, and (if it's a bug) it needs to be filed separately.

Duplicating into  issue 847462  which details a feature request for clarifying quota usage by opaque responses