Github user acommuni commented on the pull request:
https://github.com/apache/storm/pull/700#issuecomment-195988246
In case external system is down, it could be interesting to pause the Spout
for an amount of time. The state "OPEN" of the CB could be directly linked to
the spout. I don't know if the implementation of the back pressure is
manageable through public API. But it would be a nice enhancement to be able to
implement Circuit Breaker algorithm with bolt and spout.
Error count and timeout generated by request to external system can be
detected by the bolt using those external component and could be propagated to
the spout. In case the amount of consecutive error reaches a defined value the
spout could be paused by the bolt for an amout of time (CLOSE to OPEN state).
After sleeping the spout is considered in HALF OPEN state. If new error occurs
spout sleeps for another amount of time else it goes to CLOSE state and
continue to read new tuples.
Being able to use Circuit breaker framework like Hystrix could be a nice
enhancement of the back pressure feature.
https://github.com/Netflix/Hystrix
https://github.com/Netflix/Hystrix/wiki/How-it-Works
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