Roshan Naik created STORM-1351:
----------------------------------
Summary: 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
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 'backoff', '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.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
