David M. Lyle commented on METRON-322:
> Global Batching and Flushing
> Key: METRON-322
> URL: https://issues.apache.org/jira/browse/METRON-322
> Project: Metron
> Issue Type: Improvement
> Reporter: Ajay Yadav
> Assignee: Matt Foley
> All Writers and other bolts that maintain an internal "batch" queue, need to
> have a timeout flush, to prevent messages from low-volume telemetries from
> sitting in their queues indefinitely. Storm has a timeout value
> (topology.message.timeout.secs) that prevents it from waiting for too long.
> If the Writer does not process the queue before the timeout, then Storm
> recycles the tuples through the topology. This has multiple undesirable
> consequences, including data duplication and waste of compute resources. We
> would like to be able to specify an interval after which the queues would
> flush, even if the batch size is not met.
> We will utilize the Storm Tick Tuple to trigger timeout flushing, following
> the recommendations of the article at
> Since every Writer processes its queue somewhat differently, every bolt that
> has a "batchSize" parameter will be given a "batchTimeout" parameter too. It
> will default to 1/2 the value of "topology.message.timeout.secs", as
> recommended, and will ignore settings larger than the default, which could
> cause failure to flush in time. In the Enrichment topology, where two
> Writers may be placed one after the other (enrichment and threat intel), the
> default timeout interval will be 1/4 the value of
> "topology.message.timeout.secs". The default value of
> "topology.message.timeout.secs" in Storm is 30 seconds.
> In addition, Storm provides a limit on the number of pending messages that
> have not been acked. If more than "topology.max.spout.pending" messages are
> waiting in a topology, then Storm will recycle them through the topology.
> However, the default value of "topology.max.spout.pending" is null, and if
> set to non-null value, the user can manage the consequences by setting
> batchSize limits appropriately. Having the timeout flush will also
> ameliorate this issue. So we do not need to address
> "topology.max.spout.pending" directly in this task.
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