Cache as fallback

[ycrumeyrolle]

I'd like to have the following behaviour :
I execute a first request. The request succeed. I retrieve the data,
and store it in the cache.
I execute a second request. The request succeed. I retrieve the data,
and store it in the cache.

The server became unavailable.
I execute a third request. The request fail. I retrieve the data from
the cache.
Further requests will retrieve data from the cache until the request
succeed.

The server became available.
I execute a final request. The request succeed. I retrieve the data,
and store it in the cache.

I'd like to use the cache as a fallback when the server is not
available.
Is it possible with a custom cache definition or by any other way ?

[Scott González]

You should be able to do this with a custom cache type. You'll want to cache the value on success and inspect the error code on error to determine if you want to treat it as a success anyway (because of the cache). This is pretty different from all of the built-in cache types since you'll never short-circuit the request from the cache. I'd suggest looking at how the in-memory cache is implemented to get an idea of how to implement a custom cache: https://github.com/appendto/amplify/blob/64fd940805f5eeced23cc7a56ab7fb6eef7d23de/request/amplify.request.js#L284