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https://issues.apache.org/jira/browse/GIRAPH-306?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13437607#comment-13437607
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Avery Ching commented on GIRAPH-306:
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>Yeah that was the impression I had too. Just to clarify, as of the recent
>Netty upgrades + this one, we are in no way >attempting to handle worker
>restarts with any grace right? This is all purely connection reliability for
>healthy worker nodes?
Yeah, this is purely for reliability of connections and requests, nothing else.
>I am having a lot more trouble scaling out to more workers than I used to. I
>know you guys had mentioned this, but I have >not been testing again until the
>last few days and its definitely gotten trickier, not the least of which
>because I'm >having trouble getting logs to see what happened during a fail. I
>don't have dumps I saved from those jobs, but if I see >more I will put them
>here.
Here's a trick you can try. Add -Dmapred.map.max.attempts=1 to ensure that any
failure will fail the job. Then you can see the logs for the failed task and
try to figure out what the problem is.
>Mostly the logs I get are reconnection logs after reincarnation in which they
>all fail (of course) and no logs for the >failed portion of the run that
>triggered the worker to reincarnate.
The above should help us narrow down your problem. =)
> Netty requests should be reliable and implement exactly once semantics
> ----------------------------------------------------------------------
>
> Key: GIRAPH-306
> URL: https://issues.apache.org/jira/browse/GIRAPH-306
> Project: Giraph
> Issue Type: Improvement
> Reporter: Avery Ching
> Priority: Critical
> Attachments: GIRAPH-306.patch
>
>
> One of the biggest scalability challenges is getting Giraph to run reliably
> on a large number of tasks (i.e. > 200). Several problems exist:
> 1) If the connection fails after the initial connection was made, the job
> will die.
> 2) Requests must be completed exactly once. This is difficult to implement,
> but required since we cannot have multiple retried requests succeed (i.e. a
> vertex gets more messages than expected).
> 3) Sometimes there are unresolved addresses, causing failure.
> This patch addresses these issues by re-establishing failed connections and
> keep tracking of every request sent to every worker. If the request fails or
> passes a timeout, it will be resent. The server will keep track of requests
> that succeeded to insure that the same request won't be processed more than
> once. The structure for keeping track of the succeeded requests on the
> server is efficient for handling increasing request ids (IncreasingBitSet).
> For handling unresolved addresses, I added retry logic to keep trying to
> resolve the problem.
> This patch also adds several unit tests that use fault injection to simulate
> a lost response or a closed channel exception on the server. It also has
> unittests for IncreasingBitSet to insure it is working correctly and
> efficiently.
> This passes all unittests (including the new ones). Additionally, I have
> some experience results as well.
> Previously, I was unable to run reliably with more than 200 workers. With
> this change I can reliably run 500+ workers. I also ran with 600 workers
> successfully. This is a really big reliability win for us.
> I can see the code working to do reconnections and re-issue requests when
> necessary. It's very cool.
> I.e.
> 2012-08-18 00:16:52,109 INFO org.apache.giraph.comm.NettyClient:
> checkAndFixChannel: Fixing disconnected channel to
> xxx.xxx.xxx.xxx/xx.xx.xx.xx:30455, open = false, bound = false
> 2012-08-18 00:16:52,111 INFO org.apache.giraph.comm.NettyClient:
> checkAndFixChannel: Connected to xxx.xxx.xxx.xxx/xxx.xxx.xxx.xxx:30455!
> 2012-08-18 00:16:52,123 INFO org.apache.giraph.comm.NettyClient:
> checkAndFixChannel: Fixing disconnected channel to
> xxx.xxx.xxx.xxx/xxx.xxx.xxx.xxx, open = false, bound = false
> 2012-08-18 00:16:52,124 INFO org.apache.giraph.comm.NettyClient:
> checkAndFixChannel: Connected to xxx.xxx.xxx.xxx/xxx.xxx.xxx.xxx:30117!
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