Akka stream map with retry

问题

How can i retry if mapping/processing of an element in the stream fails?

I have tried setting the decider in materializer but it does not offer retry. It simply maps exception to Supervision stage.

Thanks

回答1:

Consider it as a tip rather than complete answer. I recently implement similar functionality with futures and mapAsync. There is a library called retry for retrying futures with different strategies such as pause or back off. But this method have a problem that because akka streams use bounded buffers, if all futures that mapAsync is buffered are failing, your pipeline will stop processing.

Another approach to this problem is building a flow with feedback loop that pushes failed messages back to start. This is better solution since failed ones won't block your pipeline, however, I found that it is harder to implement backoff strategy this way.

回答2:

From akka-stream 2.4.4 you can use recoverWithRetries (docs here).

This basically allows you to provide

1. the number of retry attempts
2. alternative source(s) to switch to depending on the occurred failure

It's available for both Source and Flow.

来源：https://stackoverflow.com/questions/35868862/akka-stream-map-with-retry