Home | About | Sematext search-lucene.com search-hadoop.com
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB
 Search Hadoop and all its subprojects:

Switch to Threaded View
MapReduce >> mail # user >> Is there any way to partially process HDFS edits?


Copy link to this message
-
Re: Is there any way to partially process HDFS edits?
A simple estimate puts the total number of blocks somewhere around 500,000.
Due to an HBase bug (HBASE-9648), there were approximately 50,000,000 files
that were created and quickly deleted (about 10/sec for 6 weeks) in the
cluster, and that activity is what is contained in the edits.

Since those files don't exist (quickly created and deleted), shouldn't they
be inconsequential to the memory requirements of the namenode as it starts
up.

--Tom
On Thu, Sep 26, 2013 at 10:25 AM, Nitin Pawar <[EMAIL PROTECTED]>wrote:

> Can you share how many blocks does your cluster have? how many
> directories? how many files?
>
> There is a JIRA https://issues.apache.org/jira/browse/HADOOP-1687 which
> explains how much RAM will be used for your namenode.
> Its pretty old by hadoop version but its a good starting point.
>
> According to Cloudera's blog "A good rule of thumb is to assume 1GB of
> NameNode memory for every 1 million blocks stored in the distributed file
> system"
>
> http://blog.cloudera.com/blog/2013/08/how-to-select-the-right-hardware-for-your-new-hadoop-cluster/
>
>
>
> On Thu, Sep 26, 2013 at 9:26 PM, Tom Brown <[EMAIL PROTECTED]> wrote:
>
>> It ran again for about 15 hours before dying again. I'm seeing what extra
>> RAM resources we can throw at this VM (maybe up to 32GB), but until then
>> I'm trying to figure out if I'm hitting some strange bug.
>>
>> When the edits were originally made (over the course of 6 weeks), the
>> namenode only had 512MB and was able to contain the filesystem completely
>> in memory. I don't understand why it's running out of memory. If 512MB was
>> enough while the edits were first made, shouldn't it be enough to process
>> them again?
>>
>> --Tom
>>
>>
>> On Thu, Sep 26, 2013 at 6:05 AM, Harsh J <[EMAIL PROTECTED]> wrote:
>>
>>> Hi Tom,
>>>
>>> The edits are processed sequentially, and aren't all held in memory.
>>> Right now there's no mid-way-checkpoint when it is loaded, such that
>>> it could resume only with remaining work if interrupted. Normally this
>>> is not a problem in deployments given that SNN or SBN runs for
>>> checkpointing the images and keeping the edits collection small
>>> periodically.
>>>
>>> If your NameNode is running out of memory _applying_ the edits, then
>>> the cause is not the edits but a growing namespace. You most-likely
>>> have more files now than before, and thats going to take up permanent
>>> memory from the NameNode heap size.
>>>
>>> On Thu, Sep 26, 2013 at 3:00 AM, Tom Brown <[EMAIL PROTECTED]> wrote:
>>> > Unfortunately, I cannot give it that much RAM. The machine has 4GB
>>> total
>>> > (though could be expanded somewhat-- it's a VM).
>>> >
>>> > Though if each edit is processed sequentially (in a streaming form),
>>> the
>>> > entire edits file will never be in RAM at once.
>>> >
>>> > Is the edits file format well defined (could I break off 100MB chunks
>>> and
>>> > process them individually to achieve the same result as processing the
>>> whole
>>> > thing at once)?
>>> >
>>> > --Tom
>>> >
>>> >
>>> > On Wed, Sep 25, 2013 at 1:53 PM, Ravi Prakash <[EMAIL PROTECTED]>
>>> wrote:
>>> >>
>>> >> Tom! I would guess that just giving the NN JVM lots of memory (64Gb /
>>> >> 96Gb) should be the easiest way.
>>> >>
>>> >>
>>> >> ________________________________
>>> >> From: Tom Brown <[EMAIL PROTECTED]>
>>> >> To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
>>> >> Sent: Wednesday, September 25, 2013 11:29 AM
>>> >> Subject: Is there any way to partially process HDFS edits?
>>> >>
>>> >> I have an edits file on my namenode that is 35GB. This is quite a bit
>>> >> larger than it should be (the secondary namenode wasn't running for
>>> some
>>> >> time, and HBASE-9648 caused a huge number of additional edits).
>>> >>
>>> >> The first time I tried to start the namenode, it chewed on the edits
>>> for
>>> >> about 4 hours and then ran out of memory. I have increased the memory
>>> >> available to the namenode (was 512MB, now 2GB), and started the
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB