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From Ethan Rowe <et...@the-rowes.com>
Subject Re: New node unable to stream (0.8.5)
Date Thu, 15 Sep 2011 18:51:02 GMT
>
>
> Cool.  We've deactivated all tasks against these nodes and will scrub them
> all in parallel, apply the encryption options you specified, and see where
> that gets us.  Thanks for the assistance.
>

To follow up:
* We scrubbed all the nodes
* We applied the encryption options specified
* A repair is continuing (for about an hour so far, perhaps more) on the
new, problematic node; it's successfully streaming data from its neighbors
and has built up a roughly equivalent data volume on disk

We'll see if the data is fully restored once this process completes.  Even
if it isn't, it seems likely that the cluster will be in a healthy state
soon, so we can reimport as necessary and we'll be out of the woods.

Now that I've said all that, something will inevitably go wrong, but until
that happens, thanks again for the feedback.
- Ethan



>> On Thu, Sep 15, 2011 at 8:40 AM, Ethan Rowe <ethan@the-rowes.com> wrote:
>> > On Thu, Sep 15, 2011 at 9:21 AM, Jonathan Ellis <jbellis@gmail.com>
>> wrote:
>> >>
>> >> Where did the data loss come in?
>> >
>> > The outcome of the analytical jobs run overnight while some of these
>> repairs
>> > were (not) running is consistent with what I would expect if perhaps
>> 20-30%
>> > of the source data was missing.  Given the strong consistency model
>> we're
>> > using, this is surprising to me, since the jobs did not report any read
>> or
>> > write failures.  I wonder if this is a consequence of the dead node
>> missing
>> > and the new node being operational but having received basically none of
>> its
>> > hinted handoff streams.  Perhaps with streaming fixed the data will
>> > reappear, which would be a happy outcome, but if not, I can reimport the
>> > critical stuff from files.
>> >>
>> >> Scrub is safe to run in parallel.
>> >
>> > Is it somewhat analogous to a major compaction in terms of I/O impact,
>> with
>> > perhaps less greedy use of disk space?
>> >
>> >>
>> >> On Thu, Sep 15, 2011 at 8:08 AM, Ethan Rowe <ethan@the-rowes.com>
>> wrote:
>> >> > After further review, I'm definitely going to scrub all the original
>> >> > nodes
>> >> > in the cluster.
>> >> > We've lost some data as a result of this situation.  It can be
>> restored,
>> >> > but
>> >> > the question is what to do with the problematic new node first.  I
>> don't
>> >> > particularly care about the data that's on it, since I'm going to
>> >> > re-import
>> >> > the critical data from files anyway, and then I can recreate
>> derivative
>> >> > data
>> >> > afterwards.  So it's purely a matter of getting the cluster healthy
>> >> > again as
>> >> > quickly as possible so I can begin that import process.
>> >> > Any issue with running scrubs on multiple nodes at a time, provided
>> they
>> >> > aren't replication neighbors?
>> >> > On Thu, Sep 15, 2011 at 8:18 AM, Ethan Rowe <ethan@the-rowes.com>
>> wrote:
>> >> >>
>> >> >> I just noticed the following from one of Jonathan Ellis' messages
>> >> >> yesterday:
>> >> >>>
>> >> >>> Added to NEWS:
>> >> >>>
>> >> >>>    - After upgrading, run nodetool scrub against each node
before
>> >> >>> running
>> >> >>>      repair, moving nodes, or adding new ones.
>> >> >>
>> >> >>
>> >> >> We did not do this, as it was not indicated as necessary in the
news
>> >> >> when
>> >> >> we were dealing with the upgrade.
>> >> >> So perhaps I need to scrub everything before going any further,
>> though
>> >> >> the
>> >> >> question is what to do with the problematic node.  Additionally,
it
>> >> >> would be
>> >> >> helpful to know if scrub will affect the hinted handoffs that have
>> >> >> accumulated, as these seem likely to be part of the set of failing
>> >> >> streams.
>> >> >> On Thu, Sep 15, 2011 at 8:13 AM, Ethan Rowe <ethan@the-rowes.com>
>> >> >> wrote:
>> >> >>>
>> >> >>> Here's a typical log slice (not terribly informative, I fear):
>> >> >>>>
>> >> >>>>  INFO [AntiEntropyStage:2] 2011-09-15 05:41:36,106
>> >> >>>> AntiEntropyService.java (l
>> >> >>>> ine 884) Performing streaming repair of 1003 ranges with
/
>> 10.34.90.8
>> >> >>>> for
>> >> >>>> (299
>> >> >>>>
>> >> >>>>
>> >> >>>>
>> 90798416657667504332586989223299634,54296681768153272037430773234349600451]
>> >> >>>>  INFO [AntiEntropyStage:2] 2011-09-15 05:41:36,427 StreamOut.java
>> >> >>>> (line
>> >> >>>> 181)
>> >> >>>> Stream context metadata
>> >> >>>> [/mnt/cassandra/data/events_production/FitsByShip-g-1
>> >> >>>> 0-Data.db sections=88 progress=0/11707163 - 0%,
>> >> >>>> /mnt/cassandra/data/events_pr
>> >> >>>> oduction/FitsByShip-g-11-Data.db sections=169 progress=0/6133240
-
>> >> >>>> 0%,
>> >> >>>> /mnt/c
>> >> >>>> assandra/data/events_production/FitsByShip-g-6-Data.db
sections=1
>> >> >>>> progress=0/
>> >> >>>> 6918814 - 0%,
>> >> >>>> /mnt/cassandra/data/events_production/FitsByShip-g-12-Data.db
s
>> >> >>>> ections=260 progress=0/9091780 - 0%], 4 sstables.
>> >> >>>>  INFO [AntiEntropyStage:2] 2011-09-15 05:41:36,428
>> >> >>>> StreamOutSession.java
>> >> >>>> (lin
>> >> >>>> e 174) Streaming to /10.34.90.8
>> >> >>>> ERROR [Thread-56] 2011-09-15 05:41:38,515
>> >> >>>> AbstractCassandraDaemon.java
>> >> >>>> (line
>> >> >>>> 139) Fatal exception in thread Thread[Thread-56,5,main]
>> >> >>>> java.lang.NullPointerException
>> >> >>>>         at
>> >> >>>> org.apache.cassandra.net.IncomingTcpConnection.stream(IncomingTcpC
>> >> >>>> onnection.java:174)
>> >> >>>>         at
>> >> >>>> org.apache.cassandra.net.IncomingTcpConnection.run(IncomingTcpConn
>> >> >>>> ection.java:114)
>> >> >>>
>> >> >>> Not sure if the exception is related to the outbound streaming
>> above;
>> >> >>> other nodes are actively trying to stream to this node, so
perhaps
>> it
>> >> >>> comes
>> >> >>> from those and temporal adjacency to the outbound stream is
just
>> >> >>> coincidental.  I have other snippets that look basically identical
>> to
>> >> >>> the
>> >> >>> above, except if I look at the logs to which this node is trying
to
>> >> >>> stream,
>> >> >>> I see that it has concurrently opened a stream in the other
>> direction,
>> >> >>> which
>> >> >>> could be the one that the exception pertains to.
>> >> >>>
>> >> >>> On Thu, Sep 15, 2011 at 7:41 AM, Sylvain Lebresne
>> >> >>> <sylvain@datastax.com>
>> >> >>> wrote:
>> >> >>>>
>> >> >>>> On Thu, Sep 15, 2011 at 1:16 PM, Ethan Rowe <ethan@the-rowes.com>
>> >> >>>> wrote:
>> >> >>>> > Hi.
>> >> >>>> >
>> >> >>>> > We've been running a 7-node cluster with RF 3, QUORUM
>> reads/writes
>> >> >>>> > in
>> >> >>>> > our
>> >> >>>> > production environment for a few months.  It's been
consistently
>> >> >>>> > stable
>> >> >>>> > during this period, particularly once we got out maintenance
>> >> >>>> > strategy
>> >> >>>> > fully
>> >> >>>> > worked out (per node, one repair a week, one major
compaction a
>> >> >>>> > week,
>> >> >>>> > the
>> >> >>>> > latter due to the nature of our data model and usage).
 While
>> this
>> >> >>>> > cluster
>> >> >>>> > started, back in June or so, on the 0.7 series, it's
been
>> running
>> >> >>>> > 0.8.3 for
>> >> >>>> > a while now with no issues.  We upgraded to 0.8.5
two days ago,
>> >> >>>> > having
>> >> >>>> > tested the upgrade in our staging cluster (with an
otherwise
>> >> >>>> > identical
>> >> >>>> > configuration) previously and verified that our application's
>> >> >>>> > various
>> >> >>>> > use
>> >> >>>> > cases appeared successful.
>> >> >>>> >
>> >> >>>> > One of our nodes suffered a disk failure yesterday.
 We
>> attempted
>> >> >>>> > to
>> >> >>>> > replace
>> >> >>>> > the dead node by placing a new node at OldNode.initial_token
- 1
>> >> >>>> > with
>> >> >>>> > auto_bootstrap on.  A few things went awry from there:
>> >> >>>> >
>> >> >>>> > 1. We never saw the new node in bootstrap mode; it
became
>> available
>> >> >>>> > pretty
>> >> >>>> > much immediately upon joining the ring, and never
reported a
>> >> >>>> > "joining"
>> >> >>>> > state.  I did verify that auto_bootstrap was on.
>> >> >>>> >
>> >> >>>> > 2. I mistakenly ran repair on the new node rather
than
>> removetoken
>> >> >>>> > on
>> >> >>>> > the
>> >> >>>> > old node, due to a delightful mental error.  The repair
got
>> nowhere
>> >> >>>> > fast, as
>> >> >>>> > it attempts to repair against the down node which
throws an
>> >> >>>> > exception.
>> >> >>>> >  So I
>> >> >>>> > interrupted the repair, restarted the node to clear
any pending
>> >> >>>> > validation
>> >> >>>> > compactions, and...
>> >> >>>> >
>> >> >>>> > 3. Ran removetoken for the old node.
>> >> >>>> >
>> >> >>>> > 4. We let this run for some time and saw eventually
that all the
>> >> >>>> > nodes
>> >> >>>> > appeared to be done various compactions and were stuck
at
>> >> >>>> > streaming.
>> >> >>>> > Many
>> >> >>>> > streams listed as open, none making any progress.
>> >> >>>> >
>> >> >>>> > 5.  I observed an Rpc-related exception on the new
node (where
>> the
>> >> >>>> > removetoken was launched) and concluded that the streams
were
>> >> >>>> > broken
>> >> >>>> > so the
>> >> >>>> > process wouldn't ever finish.
>> >> >>>> >
>> >> >>>> > 6. Ran a "removetoken force" to get the dead node
out of the
>> mix.
>> >> >>>> > No
>> >> >>>> > problems.
>> >> >>>> >
>> >> >>>> > 7. Ran a repair on the new node.
>> >> >>>> >
>> >> >>>> > 8. Validations ran, streams opened up, and again things
got
>> stuck
>> >> >>>> > in
>> >> >>>> > streaming, hanging for over an hour with no progress.
>> >> >>>> >
>> >> >>>> > 9. Musing that lingering tasks from the removetoken
could be a
>> >> >>>> > factor,
>> >> >>>> > I
>> >> >>>> > performed a rolling restart and attempted a repair
again.
>> >> >>>> >
>> >> >>>> > 10. Same problem.  Did another rolling restart and
attempted a
>> >> >>>> > fresh
>> >> >>>> > repair
>> >> >>>> > on the most important column family alone.
>> >> >>>> >
>> >> >>>> > 11. Same problem.  Streams included CFs not specified,
so I
>> guess
>> >> >>>> > they
>> >> >>>> > must
>> >> >>>> > be for hinted handoff.
>> >> >>>> >
>> >> >>>> > In concluding that streaming is stuck, I've observed:
>> >> >>>> > - streams will be open to the new node from other
nodes, but the
>> >> >>>> > new
>> >> >>>> > node
>> >> >>>> > doesn't list them
>> >> >>>> > - streams will be open to the other nodes from the
new node, but
>> >> >>>> > the
>> >> >>>> > other
>> >> >>>> > nodes don't list them
>> >> >>>> > - the streams reported may make some initial progress,
but then
>> >> >>>> > they
>> >> >>>> > hang at
>> >> >>>> > a particular point and do not move on for an hour
or more.
>> >> >>>> > - The logs report repair-related activity, until NPEs
on
>> incoming
>> >> >>>> > TCP
>> >> >>>> > connections show up, which appear likely to be the
culprit.
>> >> >>>>
>> >> >>>> Can you send the stack trace from those NPE.
>> >> >>>>
>> >> >>>> >
>> >> >>>> > I can provide more exact details when I'm done commuting.
>> >> >>>> >
>> >> >>>> > With streaming broken on this node, I'm unable to
run repairs,
>> >> >>>> > which
>> >> >>>> > is
>> >> >>>> > obviously problematic.  The application didn't suffer
any
>> >> >>>> > operational
>> >> >>>> > issues
>> >> >>>> > as a consequence of this, but I need to review the
overnight
>> >> >>>> > results
>> >> >>>> > to
>> >> >>>> > verify we're not suffering data loss (I doubt we are).
>> >> >>>> >
>> >> >>>> > At this point, I'm considering a couple options:
>> >> >>>> > 1. Remove the new node and let the adjacent node take
over its
>> >> >>>> > range
>> >> >>>> > 2. Bring the new node down, add a new one in front
of it, and
>> >> >>>> > properly
>> >> >>>> > removetoken the problematic one.
>> >> >>>> > 3. Bring the new node down, remove all its data except
for the
>> >> >>>> > system
>> >> >>>> > keyspace, then bring it back up and repair it.
>> >> >>>> > 4. Revert to 0.8.3 and see if that helps.
>> >> >>>> >
>> >> >>>> > Recommendations?
>> >> >>>> >
>> >> >>>> > Thanks.
>> >> >>>> > - Ethan
>> >> >>>> >
>> >> >>>
>> >> >>
>> >> >
>> >> >
>> >>
>> >>
>> >>
>> >> --
>> >> Jonathan Ellis
>> >> Project Chair, Apache Cassandra
>> >> co-founder of DataStax, the source for professional Cassandra support
>> >> http://www.datastax.com
>> >
>> >
>>
>>
>>
>> --
>> Jonathan Ellis
>> Project Chair, Apache Cassandra
>> co-founder of DataStax, the source for professional Cassandra support
>> http://www.datastax.com
>>
>
>

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