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https://issues.apache.org/jira/browse/GIRAPH-306?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13437585#comment-13437585
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Eli Reisman 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?
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.
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.
> 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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