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https://issues.apache.org/jira/browse/STORM-1351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15027571#comment-15027571
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Robert Joseph Evans commented on STORM-1351:
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What do you mean by topology runner? If you want different backoff logic
ISpoutWaitStrategy would be the consumer of that data as [~ptgoetz] has pointed
out. But, I don't see much value in backing off for a different amount of time
when there is no data vs. there is an error. The wait strategy is trying to
pick up the next tuple to process as quickly as possible without overwhelming
the downstream system. A single 1 ms wait works really well for this. Adding
more of a wait in most cases is to avoid doing a DDOS on the system you are
consuming data from. That does not seem to be the case here.
If you want to communicate error conditions or similar problems to an end user
or a monitoring/alerting system a metric would be preferable. Spouts can
already register their own metrics for reporting errors, and the latest version
of storm includes a system metric that includes counts as to why nextTuple was
not called.
> Storm spouts and bolts need a way to communicate problems back to toplogy
> runner
> --------------------------------------------------------------------------------
>
> Key: STORM-1351
> URL: https://issues.apache.org/jira/browse/STORM-1351
> Project: Apache Storm
> Issue Type: Bug
> Components: storm-core
> Reporter: Roshan Naik
> Assignee: Roshan Naik
>
> A spout can be having a problem generating a tuple in nextTuple() because
> -a) there is no data to generate currently
> - b) there is some I/O issues it is experiencing
> If the spout returns immediately from the nextTuple() call then the
> nextTuple() will be invoked immediately leading to CPU spike. The CPU spike
> would last till the situation is remedied by new coming data or the i/o
> issues getting resolved.
> Currently to work around this, the spouts will have to implement a
> exponential backoff mechanism internally. There are two problems with this:
> - each spout needs to implement this backoff logic
> - since nextTuple() has an internal sleep and takes longer to return, the
> latency metrics computation gets thrown off
> *Thoughts for Solution:*
> The spout should be able to indicate a 'no data', 'experiencing error' or
> 'all good' status back to the caller of nextTuple() so that the right backoff
> logic can kick in.
> - The most natural way to do this is using the return type of the nextTuple
> method. Currently nextTuple() returns void. However, this will break source
> and binary compat since the new storm will not be able to invoke the methods
> on the unmodified spouts. This breaking change can only be considered as an
> option only prior to v1.0.
> - Alternatively this can be done by providing an additional method on the
> collector to indicate the condition to the topology runner. The spout can
> invoke this explicitly. the metrics can then also account for 'no data' and
> 'error attempts'
> - Alternatively - The toplogy runner may just examine the collector if there
> was new data generated by the nextTuple() call. In this case it cannot
> distinguish between errors v/s no incoming data.
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