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https://issues.apache.org/jira/browse/HAMA-633?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13438472#comment-13438472
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Thomas Jungblut commented on HAMA-633:
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The problem wasn't there before and I would really like to fix the root of the
problem. How would transferring the superstep number solve the problem? They
arrive too late to get added to the _right_ queue.
So it would be better to send how many messages come from that peer, so that
the other has to wait for all messages to arrive. We can give them a sequence
id to know on the other side which messages haven't arrived yet. Before all
messages have arrived, it makes no sense to get into the last end barrier.
> Fix CI Failure
> --------------
>
> Key: HAMA-633
> URL: https://issues.apache.org/jira/browse/HAMA-633
> Project: Hama
> Issue Type: Bug
> Components: bsp core
> Affects Versions: 0.5.0
> Reporter: Thomas Jungblut
> Fix For: 0.6.0
>
>
> The current nightly fails because it seems to read messages that actually
> belong to the previous superstep.
> This is reproducable also in the local runner, so this is no problem of the
> specific RPC implementations. The problem could also be in the GraphJobRunner.
> This is going to be expressed by a nullpointer exception, when a non-master
> tasks gets a aggregation message (which actually just belongs to the master).
> {noformat}
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________ 0 / hama.2;0 / 4
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________+ true
> janus.apache.org:61002
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________++ VAL=0.0
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________ 1 / hama.2;1 / 4
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________+ true
> janus.apache.org:61002
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________++ VAL=0.0
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________ 0 / hama.2;0 / 7
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________+ true
> janus.apache.org:61002
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________++
> VAL=0.4572019638123739
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________ 1 / hama.2;1 / 7
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________+ true
> janus.apache.org:61002
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________++
> VAL=0.44247448197562855
> 12/08/17 23:05:52 INFO server.PrepRequestProcessor: Got user-level
> KeeperException when processing sessionid:0x13936d5d8cc0002 type:create
> cxid:0x3de zxid:0xfffffffffffffffe txntype:unknown reqpath:n/a Error
> Path:/bsp/job_201208172305_0001/sync/51 Error:KeeperErrorCode = NodeExists
> for /bsp/job_201208172305_0001/sync/51
> 12/08/17 23:05:52 INFO server.PrepRequestProcessor: Got user-level
> KeeperException when processing sessionid:0x13936d5d8cc0002 type:create
> cxid:0x3e8 zxid:0xfffffffffffffffe txntype:unknown reqpath:n/a Error
> Path:/bsp/job_201208172305_0001/sync/51/ready Error:KeeperErrorCode =
> NodeExists for /bsp/job_201208172305_0001/sync/51/ready
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________ 0 / hama.2;0 / 4
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________+ true
> janus.apache.org:61002
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________++ VAL=0.0
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________ 1 / hama.2;1 / 4
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________+ true
> janus.apache.org:61002
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________++ VAL=0.0
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________ 0 / hama.2;0 / 7
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________+ true
> janus.apache.org:61002
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________++ VAL=0.457610574551534
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________ 1 / hama.2;1 / 7
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________+ true
> janus.apache.org:61002
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________++
> VAL=0.2675231554874198
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________ 0 / hama.2;0 / 11
> 12/08/17 23:05:52 INFO graph.GraphJobRunner: _________+ NULL! false
> janus.apache.org:61001
> 12/08/17 23:05:52 ERROR bsp.BSPTask: Error running bsp setup and bsp function.
> java.lang.NullPointerException
> at
> org.apache.hama.graph.GraphJobRunner.parseMessages(GraphJobRunner.java:373)
> at org.apache.hama.graph.GraphJobRunner.bsp(GraphJobRunner.java:209)
> at org.apache.hama.bsp.BSPTask.runBSP(BSPTask.java:166)
> at org.apache.hama.bsp.BSPTask.run(BSPTask.java:143)
> at
> org.apache.hama.bsp.GroomServer$BSPPeerChild.main(GroomServer.java:1271)
> 12/08/17 23:05:52 INFO server.PrepRequestProcessor: Processed session
> termination for sessionid: 0x13936d5d8cc0002
> {noformat}
> It is very difficult to track this down, my ideas were:
> - It changes the host because of fault tolerance (contra arguments: its
> turned off and the port is smaller than the other one)
> - Messaging is broken (would also explain why pagerank does not converge
> anymore)
> Some more info:
> I know that this happens when the master tasks sends a message with the
> updated aggregator values to every slave. (line 239). Then this only message
> should be consumed arround line 246 cc.
> But it still remains in the buffer and will be consumed after all computation
> in line 209 in the parseMessages.
> Even clearing the buffer is not fixing it.
> The worst problem is, that this is not reproducable, the failure seems to
> happen just in only two to three tenth of all builds. Seems like some really
> nasty edge case.
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