iOS cache not entirely cleared when calling clearAll()

[jvanderwee]

Version

4.1.1

Summary

Two possible issues:

• request is cached for mutations with .doNotStore(true)
• request is still in cache after calling apolloClient.apolloStore.clearAll()

Steps to reproduce the behavior

1. Call a mutation with .doNotStore(true), e.g.

apolloClient
    .mutation(FooMutation())
    .doNotStore(true)
    .execute()

2. Grep ~/Library/Developer/CoreSimulator/Devices/<id>/data/Containers/Data/Application/<id>/Library/Caches/<id>/Cache.db-wal for "mutation"

• mutation request is present in cache

3. Call apolloClient.apolloStore.clearAll()
4. Grep as above

• mutation request still present in cache

Logs

(Your logs here)

[BoD]

Hi! I could not reproduce on my end, but a couple of remarks:

• you mention that you're looking at the .db-wal file but you should be looking at the .db file.
• you mention you see FooMutation in the cache, but we don't store references to the operation names anywhere - only the field names should be in there

You can check the contents of the db by opening it with the cache viewer of the Apollo IDE plugin, or with sqlite3 on the command line and by executing select * from records;

[jvanderwee]

Hey @BoD 👋 I think this might be the NSURLCache. Wondering if it would be possible to prevent the NSURLRequest from caching data if we set doNotStore(true)?

[jvanderwee]

You're right about not seeing "FooMutation", but I do see the operation name. I've edited above

[BoD]

Oh I see - doNotStore() and clearAll() are actually about the normalized cache and are not related to the HTTP cache.

The HTTP responses should not be cached actually as we set a NSURLRequestReloadIgnoringCacheData policy on the requests here. Are you positive the responses are actually cached? (Maybe this can be confirmed by going to airplane mode, or by using a tool like Charles Proxy).

In general there's not really a reason to use both an HTTP cache and the normalized cache at the same time, the normalized cache being sufficient. I think passing NSURLSessionConfiguration.ephemeralSessionConfiguration() to the constructor of DefaultHttpEngine should disable any disk storage.

[jvanderwee]

Yes they are definitely cached.

I think NSURLRequestReloadIgnoringCacheData means that data is not read from the cache, but data can still be cached - https://medium.com/swiftblade/urlrequest-can-be-cached-regardless-of-cachepolicy-f33b25d96c63

I wonder if nil could be passed to the willCacheResponse completion handler here?

[BoD]

Thanks for checking! That makes sense.

Can you try ephemeralSessionConfiguration()?

Something like

val client = ApolloClient.Builder()
    .httpEngine(
      DefaultHttpEngine(nsUrlSessionConfiguration = NSURLSessionConfiguration.ephemeralSessionConfiguration())
    )
   (...)
  .build()

If it works we may want to use that by default, as there's no reason to write to a cache that is never read.

[jvanderwee]

no sign of the mutation in the cache after making that change 🙌

[BoD]

Thanks for checking! Do you want to open a PR to use that by default?

[BoD]

Thanks for the PR, I just merged it! I'll close this issue then.

[github-actions]

Do you have any feedback for the maintainers? Please tell us by taking a one-minute survey. Your responses will help us understand Apollo Kotlin usage and allow us to serve you better.