[tor-bugs] #20335 [Metrics/CollecTor]: ReferenceChecker causes OOM

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#20335: ReferenceChecker causes OOM
-------------------------------+---------------------
 Reporter:  iwakeh             |          Owner:
     Type:  defect             |         Status:  new
 Priority:  Medium             |      Milestone:
Component:  Metrics/CollecTor  |        Version:
 Severity:  Normal             |     Resolution:
 Keywords:                     |  Actual Points:
Parent ID:                     |         Points:
 Reviewer:                     |        Sponsor:
-------------------------------+---------------------

Comment (by karsten):

 Replying to [comment:4 iwakeh]:
 > Steps to reproduce (from #18910, the discussion should take place here):
 >
 [https://gitweb.torproject.org/user/iwakeh/collector.git/commit/?h=task-18910
 -first-sync&id=5eb89c10a0a720c1fa4eb806e5d5b5f2dee75b65 Collector branch]:
 Run the jar in a new location, i.e. with empty recent and out. Configure
 relaydescs and sync. RunOnce will be sufficient the OOM heap dump contains
 very many Reference objects. (Your assumption in one of the previous
 comments hinted in the right direction, I think, but I couldn't verify
 that yet.)

 Hmm, I didn't run out of memory while checking references.  And I don't
 quite understand how that would happen in an initial run, because the
 reference checker is run before the sync manager even starts to run.

 I did run out of heap space while reading descriptors in a second run:

 {{{
 $ java -DLOGBASE=log -jar collector-1.1.0-dev.jar
 2016-10-13 12:54:55,995 ERROR o.t.d.i.DescriptorReaderImpl:192 Bug:
 uncaught exception or error while reading descriptors: Java heap space
 java.lang.OutOfMemoryError: Java heap space
         at java.util.Arrays.copyOf(Arrays.java:3236) ~[na:1.8.0_102]
         at
 java.io.ByteArrayOutputStream.grow(ByteArrayOutputStream.java:118)
 ~[na:1.8.0_102]
         at
 java.io.ByteArrayOutputStream.ensureCapacity(ByteArrayOutputStream.java:93)
 ~[na:1.8.0_102]
         at
 java.io.ByteArrayOutputStream.write(ByteArrayOutputStream.java:153)
 ~[na:1.8.0_102]
         at
 org.torproject.descriptor.impl.DescriptorReaderImpl$DescriptorReaderRunnable.readFile(DescriptorReaderImpl.java:378)
 ~[collector-1.1.0-dev.jar:1.1.0-dev-5eb89c1]
         at
 org.torproject.descriptor.impl.DescriptorReaderImpl$DescriptorReaderRunnable.readDescriptors(DescriptorReaderImpl.java:284)
 ~[collector-1.1.0-dev.jar:1.1.0-dev-5eb89c1]
         at
 org.torproject.descriptor.impl.DescriptorReaderImpl$DescriptorReaderRunnable.run(DescriptorReaderImpl.java:188)
 ~[collector-1.1.0-dev.jar:1.1.0-dev-5eb89c1]
         at java.lang.Thread.run(Thread.java:745) [na:1.8.0_102]
 }}}

 Can you try to put the reference checker back in and see if you still run
 out of memory somewhere?  I'm not yet convinced that it's the reference
 checker that is to blame here.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20335#comment:7>
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