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doc(RetryFlow): explain with more details (#29229)

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yiksanchan 2020-07-28 08:44:53 -07:00 • committed by GitHub
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17
akka-stream/src/main/scala/akka/stream/scaladsl/RetryFlow.scala
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@ -19,12 +19,17 @@ object RetryFlow {
* The retry condition is controlled by the `decideRetry` function. It takes the originally emitted
* element and the response emitted by `flow`, and may return a request to be retried.
*
* The implementation of the `RetryFlow` requires that `flow` follows one-in-one-out semantics,
* the [[akka.stream.scaladsl.Flow Flow]] may not filter elements,
* nor emit more than one element per incoming element. The `RetryFlow` will fail if two elements are
* emitted from the `flow`, it will be stuck "forever" if nothing is emitted. Just one element will
* be emitted into the `flow` at any time. The `flow` needs to emit an element before the next
* will be emitted to it.
* The implementation of the `RetryFlow` requires that `flow` follows strict first-in-first-out and
* one-in-one-out semantics, i.e., the [[akka.stream.scaladsl.Flow Flow]] may neither filter elements,
* nor emit more than one element per incoming element. The `RetryFlow` will fail if two elements
* are emitted for one incoming element. Any sort of batching, grouping, or filtering
* will make it hang forever.
*
* Just one element will be emitted into the `flow` at any time.
* Let's say the flow is handling an element, either first-time executing some calculation, or retrying.
* The next element won't be emitted into the flow until the current element has been finished processing.
* By finished, it means either succeed the very first attempt, succeed after a few attempts, or get dropped after
* using up [[maxRetries]] retries.
*
* @param minBackoff minimum duration to backoff between issuing retries
* @param maxBackoff maximum duration to backoff between issuing retries