Details
-
Bug
-
Status: Resolved
-
Minor
-
Resolution: Fixed
-
0.9.2-incubating, 0.9.1-incubating, 0.9.3
-
None
Description
I am fairly new to storm, but I observed some behavior which I believe may be unintended and wanted to report it...
I was experimenting with using storm on a topology which had large numbers of threads (30) and was running on a single node for test purposes and noticed that even when no tuples were being processed, there was over 100% CPU utilization.
I became concerned and investigated by attempting to reproduce with a very simple topology. I took the WordCountTopology from storm-starter and ran it in an Ubuntu VM. I increased the sleep time in the RandomSentenceSpout that feeds the topology to 10 seconds so that there was effectively no work to do. I then modified the topology so that there were 30 threads for each bolt and only one instance of the spout. When I ran the topology I noticed that there was again 100% CPU usage when idle even on this very simple topology. After extensive experimentation (netty vs. zeromq, 0.9.3, 0.9.2, 0.9.1, multiple JVM versions) I used yourkit and found that the high utilization was coming from DisruptorQueue.consumeBatchWhenAvailable where there is this code:
final long availableSequence = _barrier.waitFor(nextSequence, 10, TimeUnit.MILLISECONDS);
I increased to 100 ms and was able to reduce the CPU utilization when idle. I am new to storm, so I am not sure what affect modifying this number has. I Is this expected behavior from storm? I would like to propose modifying the code so that this wait is configurable if possible...
Thank You
