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From David Medinets <>
Subject Re: ingest problems
Date Tue, 11 Feb 2014 16:55:13 GMT
My cluster ingests data every night. We use a map-reduce program to
generate rFiles. Then import those files into Accumulo. No hiccups. No
instability. I've also used map-reduce to directly write mutations. Haven't
seen any issues there either.

What is the average load on the servers while the ingest runs?
How large are the mutations?
What are your heap sizes?
How much memory do the servers have?
Can you move beyond a three node cluster?
Are you querying while writing to the same table?

On Tue, Feb 11, 2014 at 11:28 AM, Josh Elser <> wrote:

> On 2/11/14, 11:10 AM, Kesten Broughton wrote:
>> Hi there,
>> We have been experimenting with accumulo for about two months now.  Our
>> biggest painpoint has been on ingest.
>> Often we will have ingest process fail 2 or 3 times 3/4 of the way
>> through an ingest and then on a final try it works, without any changes.
> Funny, most times I hear that people consider Accumulo to handles ingest
> fairly well, but let's see what we can do to help.
> We need a bit more information than what you provided here though: what's
> your "ingest process"? Are you using some other workflow library? Are you
> running MapReduce? Do you just have a Java class with a main method that
> uses a BatchWriter?
> The fact that it "works sometimes" implies that the problem might be
> resource related.
>  Once the ingest works, the cluster is usually stable for querying for
>> weeks or months only requiring the occasional if there is a
>> problem.
>> Sometimes our ingest can be 24 hours long, and we need a stronger ingest
>> story to be able to commit to accumulo.
> You should be able to run ingest 24/7 with Accumulo without it falling
> over (I do regularly to stress-test it). The limitation should only be the
> disk-space you have available.
>  Our cluster architecture has been:
>> 3 hdfs datanodes overlaid with name node, secondary nn and accumulo
>> master each collocated with a datanode, and a zookeeper server on each.
>> We realize this is not optimal and are transitioning to separate
>> hardware for zookeepers and name/secondary/accumulomaster nodes.
>> However, the big concern is that sometimes a failed ingest will bork the
>> whole cluster and we have to re-init accumulo with an accumulo init
>> destroying all our data.
>> We have experienced this on at least three different clusters of this
>> description.
> Can you be more specific than "bork the whole cluster"? Unless you're
> hitting a really nasty bug, there shouldn't be any way that a client
> writing data into Accumulo will destroy an instance.
>  The most recent attempt was on a 65GB dataset.   The cluster had been up
>> for over 24 hours.  The ingest test takes 40 mins and about 5 mins
>> in, one of the datanodes failed.
>> There were no error logs on the failed node, and the two other nodes had
>> logs filled with zookeeper connection errors.  We were unable to recover
>> the cluster and had to re-init.
> Check both the log4j logs and the stdout/stderr redirection files for the
> datanode process. Typically, if you get an OOME, log4j gets torn down
> before that exception can be printed to the normal log files. "Silent"
> failures seem indicative of lack of physical resources (over-subscribed the
> node) on the box or insufficient resources provided to the processes (-Xmx
> was too small for the process).
>  I know a vague description of problems is difficult to respond to, and
>> the next time we have an ingest failure, i will bring specifics forward.
>>   But I'm writing to know if
>> 1.  Ingest failures are a known fail point for accumulo, or if we are
>> perhaps unlucky/mis-configured.
> No -- something else is going on here.
>  2.  Are there any guidelines for capturing ingest failures / determining
>> root causes when errors don't show up in the logs
> For any help request, be sure to gather Accumulo, Hadoop and ZooKeeper
> versions, OS and Java versions. Capturing log files and stdout/stderr files
> are important; beware that if you restart the Accumulo process on that
> node, it will overwrite the stdout/stderr files, so make sure to copy them
> out of the way.
>  3.  Are there any means of checkpointing a data ingest, so that if a
>> failure were to occur at hour 23.5 we could roll back to hour 23 and
>> continue.  Client code could checkpoint and restart at the last one, but
>> if the underlying accumulo cluster can't be recovered, that's of no use.
> You can do anything you want in your client ingest code :)
> Assuming that you're using a BatchWriter, if you manually call flush() and
> it returns without Exception, you can assume that all data up to that point
> written with that BatchWriter instance is "ingested". This can easily
> extrapolated: if you're ingesting CSV files, ensure that a flush() happens
> every 1000lines and denote that somewhere that your ingest process can
> advance itself to the appropriate place in the CSV file and proceed from
> where it left off.
>  thanks,
>> kesten

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