[plugin-response-cache] Allow return "null" when cache backend is unavailable

[PhantomRay]

I am using plugin-response-cache to implement redis cache backend. The plugin makes redis or other cache backend a hard dependency. This means when the apollo server lost connection to redis server, any incoming requests will fail. It would be good to allow the redis client to retry connection. At the same time, any queries with cache control should still function by bypassing cache.

This can be achieved easily by adding try-catch block to this line.

let serializedValue = undefined;
try {
  serializedValue = await cache.get(key);
  if (serializedValue === undefined) {
    return null;
  }
} catch (err) {
  return null;
}

Is it worth to add this feature? Meanwhile, if apollo server losts redis connection, the service is totally unusable.

[PhantomRay]

It could be addressed in @apollo/utils.keyvadapter.

I created an issue there. apollographql/apollo-utils#211

[glasser]

Thanks, I mentioned on that issue that you can opt in to this functionality via ErrorsAreMissesCache. apollographql/apollo-utils#211 (comment)

[PhantomRay]

Hi @glasser, thanks for the useful info. I implemented the feature according to official docs https://www.apollographql.com/docs/apollo-server/performance/cache-backends/

It would be great if this is mentioned there.

[glasser]

Makes sense — care to submit a PR against https://github.com/apollographql/apollo-server/blob/main/docs/source/performance/cache-backends.mdx ?

[PhantomRay]

@glasser I will add it soon.