Clear cache when serving NWB files to Neurosift and other services

[rly]

Describe the issue

A user I am working with was iteratively creating NWB files and using NWB GUIDE > Neurosift to visualize the file. The NWB file is only ~75 MB. The user would modify the file but the changes were not reflected in NWB GUIDE > Neurosift. The file was indeed changed as confirmed by PyNWB. It turns out that Electron has a cache and something, probably the NWB file, is being cached and served when the file with the same path (but different create/modify date and size) is requested.

See https://stackoverflow.com/a/44675132/20177

Deleting /Users/<user>/Library/Application Support/NWB GUIDE/Cache was insufficient, but deleting /Users/<user>/Library/Application Support/NWB GUIDE/ worked.

It might be that if the file is much larger, it would not be cached.

GUIDE should clear the Electron cache (or not use the cache) when serving NWB files to Neurosift and other services like DANDI Upload.

Steps to Reproduce

^

Operating System

Mac

GUIDE Version

1.0.4

Code of Conduct

Yes

Did you confirm this issue was not already reported?

Yes

[rly]

It looks like the structure of the NWB file is cached in the browser/Electron's IndexedDB in the neurosift-hdf5-cache database, so changes to the structure, e.g., renaming groups, adding columns to a table, changing attributes, will not be reflected unless the cache is cleared.

It seems that changing values of datasets is reflected, however.

Disabling the cache / deleting the storage data is especially important now that after #970, when serving files to Neurosift, different files might map to the same URL. For example, "http://127.0.0.1:4242//files/0:/processing" might be created when loading a file on the first run of NWB GUIDE. After GUIDE is closed and reopened and a new file is explored with Neurosift, "http://127.0.0.1:4242//files/0:/processing" should point to a new file, but the key/value pairs were cached, and so the incorrect values will be loaded. Indeed, I tested this and on the second load of File B, the hierarchy of file A from the first load was shown.

[rly]

I thought #975 resolved this but it did not. It seems like even though indexedDB.deleteDatabase("neurosift-hdf5-cache") is indeed run when the Neurosift page is launched, this command does not actually delete the database. Manual inspection shows that when an NWB file is loaded into the Neurosift page, it still holds all of the old entries. I tried many different ways to try to delete the database from GUIDE. I think the command has to come from the neurosift.app origin. This makes sense. Otherwise, one website can open and/or delete another website's persistent data...

So we'll have to take a different approach. Instead of <host>/files/<index>, I propose we use <host>/files/<random string that is unlikely to collide>. We can't use file names because of the + sign issue, we shouldn't use the same ID for a file when opening it multiple times because the file may have changed between opens and so the cache is invalid, and we can't use values that might have been used previously due to the above caching issue. So a random string seems best.