Hi Juho -- I'm doing something similar. In my case, I want to execute async requests concurrently for inputs associated with different keys but issue them sequentially for any given key. The way I do it is to create a keyed stream and use it as an input to an async function. In this arrangement, all the inputs for a given key are handled by a single instance of the async function; inside that function instance, I use a map to keep track of any in-flight requests for a given key. When a new input comes in for a key, if there is an existing in-flight request for that key, the future that is constructed for the new request is constructed as [existing request].then([new request]) so that the new one is only executed once the in-flight request completes. The futures are constructed in such a way that they maintain the map properly after completing.
On Mon, Jun 19, 2023 at 10:55 AM Juho Autio <juho.au...@rovio.com.invalid> wrote: > I need to make some slower external requests in parallel, so Async I/O > helps greatly with that. However, I also need to make the requests in a > certain order per key. Is that possible with Async I/O? > > The documentation[1] talks about preserving the stream order of > results, but it doesn't discuss the order of the async requests. I tried to > use AsyncDataStream.orderedWait, but the order of async requests seems to > be random – the order of calls gets shuffled even if I > use AsyncDataStream.orderedWait. > > If that is by design, would there be any suggestion how to work around > that? I was thinking of collecting all events of the same key into a > List, so that the async operator gets a list instead of individual events. > There are of course some downsides with using a List, so I would rather > have something better. > > In a nutshell my code is: > > AsyncDataStream.orderedWait(stream.keyBy(key), asyncFunction) > > The asyncFunction extends RichAsyncFunction. > > Thanks! > > [1] > > https://nightlies.apache.org/flink/flink-docs-master/docs/dev/datastream/operators/asyncio/#order-of-results > > (Sorry if it's not appropriate to post this type of question to the dev > mailing list. I tried the Flink users list with no luck.) >
