[Discussion] How to dedupe concurrent memoizable requests? about apollo-datasource-http

[llc1123]

I have submitted a PR #37 memoizing promises and it looks good.

[bradleymorris]

Why is it not possible to just memoize the original promise? It seems what needs to be done is that the response Promise needs to be created and inserted into the memoization cache Prior to request execution.

That way, any subsequent queries checking the memo cache will fetch the promise and wait for the original execution to complete (and then likewise 'share' the response).

[llc1123]

I don't think storing the promise in cache is a good idea. How do you deal with promise rejection?

@StarpTech What do you think?

[bradleymorris]

I don't think I see the problem you're alluding to in regards to promise rejection. The memoization store is different from the 'proper' cache and nothing is serialized or written to disk with the dedicated alloc/quicklru memoization cache, as far as I am aware.

So if the promise is rejected, any executions awaiting the promise will be notified as they typically would be, even if they are late arrivers and await promise fulfillment after the promise was either fulfilled or rejected.

I could be over-simplifying something, here, but I think that the Apollo out-of-box REST data source might do something similar to avoid this problem as well.

[bradleymorris]

@llc1123 Thank you for your time and effort on this. Hopefully it gets merged and released soon!