There really aren't a lot of log messages that can explain why tablets for other tables went offline except the following:
2016-04-11 13:32:18,258 [tserver.TabletServerResourceManager$AssignmentWatcher]
WARN : tserver:instance-accumulo-3 Assignment for 2<< has been running for at
least 973455566ms
java.lang.Exception: Assignment of 2<<
at sun.misc.Unsafe.park(Native Method)
at java.util.concurrent.locks.LockSupport.park(Unknown Source)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(Unknown
Source)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(Unknown
Source)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(Unknown
Source)
at java.util.concurrent.locks.ReentrantLock$FairSync.lock(Unknown Source)
at java.util.concurrent.locks.ReentrantLock.lock(Unknown Source)
at
org.apache.accumulo.tserver.TabletServer.acquireRecoveryMemory(TabletServer.java:2230)
at
org.apache.accumulo.tserver.TabletServer.access$2600(TabletServer.java:252)
at
org.apache.accumulo.tserver.TabletServer$AssignmentHandler.run(TabletServer.java:2150)
at
org.apache.accumulo.fate.util.LoggingRunnable.run(LoggingRunnable.java:35)
at
org.apache.accumulo.tserver.ActiveAssignmentRunnable.run(ActiveAssignmentRunnable.java:61)
at org.apache.htrace.wrappers.TraceRunnable.run(TraceRunnable.java:57)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at
org.apache.accumulo.fate.util.LoggingRunnable.run(LoggingRunnable.java:35)
at java.lang.Thread.run(Unknown Source)
Table 2<< here doesn't have the issue with minc failing and so shouldn’t be
offline. These messages happened on a restart of a tserver if that offers any
clues. All the nodes were rebooted at that time due to a power failure. I'm
assuming that it's tablet went offline soon after this message first appeared
in the logs.
Other tidbit of note is that the Accumulo operates for hours/days without
taking the tablets offline even though minc is failing and it's the crash of a
tserver due to OutOfMemory situation in one case that seems to have taken the
tablet offline. Is it safe to assume that other tservers are not able to pick
up the tablets that are failing minc from a crashed tserver?
-----Original Message-----
From: Josh Elser [mailto:[email protected]]
Sent: Friday, April 08, 2016 10:52 AM
To: [email protected]
Subject: Re: Fwd: why compaction failure on one table brings other tables
offline, how to recover
Billie Rinaldi wrote:
> *From:* Jayesh Patel
> *Sent:* Thursday, April 07, 2016 4:36 PM
> *To:* '[email protected] <mailto:[email protected]>'
> <[email protected] <mailto:[email protected]>>
> *Subject:* RE: why compaction failure on one table brings other tables
> offline, how to recover____
>
> __ __
>
> I have a 3 node Accumulo 1.7 cluster with a few small tables (few MB
> in size at most).____
>
> __ __
>
> I had one of those table fail minc because I had configured a
> SummingCombiner with FIXEDLEN but had smaller values:____
>
> MinC failed (trying to convert to long, but byte array isn't long
> enough, wanted 8 found 1) to create
> hdfs://instance-accumulo:8020/accumulo/tables/1/default_tablet/F0002bc
> s.rf_tmp
> retrying ...____
>
> __ __
>
> I have learned since to set the ‘lossy’ parameter to true to avoid this.
> *Why is the default value for it false* if it can cause catastrophic
> failure that you’ll read about ahead.____
I'm pretty sure I told you this on StackOverflow, but if you're not writing
8-byte long values, don't used FIXEDLEN. Use VARLEN instead.
> However, this brought other the tablets for other tables offline
> without any apparent errors or warnings. *Can someone please explain
> why?*____
Can you provide logs? We are not wizards :)
> In order to recover from this, I did a ‘droptable’ from the shell on
> the affected tables, but they all got stuck in the ‘DELETING’ state.
> I was able to finally delete them using zkcli ‘rmr’ command. *Is there
> a better way?____*
Again, not sure why they would have gotten stuck in the deleting phase without
more logs/context (nor how far along in the deletion process they got). It's
possible that there were still entries in the accumulo.metadata table.
> I’m assuming there is a more proper way because when I created the
> tables again (with the same name), they went back to having a single
> offline tablet right away. *Is this because there are “traces” of the
> old table left behind that affect the new table even though the new
> table has a different table id?* I ended up wiping out hdfs and
> recreating the accumulo instance. ____
Accumulo uses monotonically increasing IDs to identify tables. The
human-readable names are only there for your benefit. Creating a table with the
same name would not cause a problem. It sounds like you got the metadata table
in a bad state or have tabletservers in a bad state (if you haven't restarted
them).
> It seems that a small bug, writing 1 byte value instead of 8 bytes,
> caused us to dump the whole accumulo instance. Luckily the data
> wasn’t that important, but this whole episode makes us wonder why
> doing things the right way (assuming there is a right way) wasn’t
> obvious or if Accumulo is just very fragile.____
>
Causing Accumulo to be unable to flush data from memory to disk in a minor
compaction is a very bad idea. One that we cannot automatically recover from
because of the combiner configuration you set.
If you can provide logs and stack traces from the Accumulo services, we can try
to help you further. This is not normal. If you don't believe me, take a look
at the distributed tests we run each release where we write hundreds of
gigabytes of data across many servers while randomly killing Accumulo processes.
>
> Please ask away any questions/clarification you might have. We’ll
> appreciate any input you might have so we make educated decisions
> about using Accumulo going forward.____
>
> __ __
>
> Thank you,____
>
> Jayesh____
>
>
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