Make timeout for opening IndexedDB configurable

[loicraux]

Have you read the FAQ and checked for duplicate open issues?
Yes

Is your feature request related to a problem? Please describe.

We have an Electron application for downloading films and watching them offline, which uses shaka-player and its offline storage.

I've noticed in our users' application logs an increasing number of INDEXED_DB_INIT_TIMED_OUT errors (code 9017), which occur when window.indexedDB.open takes more than 5 seconds to call the onsuccess callback.

This 5-second timeout is hardcoded in the shaka-player code. It had already been increased from 2 seconds to 5 seconds by this Pull Request: #4984

It seems established that the performance of window.indexedDB.open is proportional to the size of the DB and the tables that need to be loaded (and probably also impacted by the performance of the user's machine). See for example this source.

I think that users encounter this error due to a combination of a large number of films downloaded and the lower performance of their machine.

Describe the solution you'd like

I think it would be a good idea to be able to set the value of this timeout in the shaka-player configuration. It would be optional in the configuration, with a default value of 5 seconds.

It would also be desirable to be able to deactivate this timeout completely. In this case it would be set to false in the shaka-player configuration.

Describe alternatives you've considered

No alternative solution considered.

Additional context

N/A

Are you planning to send a PR to add it?

It looks as a fairly easy PR, so yes I could send one to add this feature.

[avelad]

I agree, please @loicraux send your PR :)

[loicraux]

Thanks @avelad , I am working on the PR

[loicraux]

@avelad I'm actually a little confused about how to implement this new timeout configuration feature for offline storage initialization.

I thought it would be more straightforward...

I was thinking of adding this property:

 * @property {number} initializationTimeout
 *   The timeout in seconds before the initialization of the offline storage
 *   is rejected because it takes too long. Zero means there is no timeout.
 *   Defaults to <code>5</code>.

.... to shaka.extern.OfflineConfiguration and then simply use it in the code...

This timeout is used by the implementation of StorageMechanism#init in lib/offline/indexeddb/storage_mechanism.js.

This API StorageMechanism#init is called in two places:

1. method init of shaka.offline.StorageMuxer.
2. by the implementation of erase() in lib/offline/indexeddb/storage_mechanism.js itself.

The method init of shaka.offline.StorageMuxer is basically used by 3 parts of the code:

1. offline/storage.js : high-level API for managing offline storage, for store and list APIs
2. offline/offline_scheme.js : NetworkingEngine plugin to manage offline:// schemes
3. and eventually offline/offline_manifest_parser.js, the manifest parser for manifests which mime type is 'application/x-offline-manifest'

Case 1 is easy, offline/storage.js of course has access to the OfflineConfiguration

Case 2. is tricky : the plugin only has access to retryParameters via the Request, correct me if I'm wrong.

And so is case 3. : the offline manifest parser could implement shaka.extern.ManifestParser#configure, but it would be passed a shaka.extern.ManifestConfiguration, not the OfflineConfiguration...

So I am a bit stuck about how to implement this timeout feature in a clean way... Your suggestions would be welcome before I proceed further.

I also thought about passing this initialization timeout setting somehow to the factory function of the StorageMechanism in lib/offline/indexeddb/storage_mechanism.js when it registers itself in the storage mechanisms registry, but again at this point I don't have access to the OfflineConfiguration either... Factories are called in lib/offline/storage_muxer.js#init(), so I don't have access to the OfflineConfiguration again...

(Furthermore, this timeout for initialization is a bit specific to the StorageMechanism based on IndexedDB. It is probably nonsense for some potential other storage mechanisms...)

[avelad]

I created #8366

You can set shaka.offline.indexeddb.StorageMechanismOpenTimeout = 150; before any interaction with the API. :)