Map-Reduce on top of cassandra

[Or Yanay <or...@peer39.com>]

Hi All,

I am trying to write some map-reduce tasks so I can find out stuff like - how many records have X status?
I am using 0.7.0 and have 5 nodes with ~100G of data on each node.

I have written the code based on the word_count example and the map-reduce is running successfully BUT is extremely slow (about 2 hours for the simplest key count).

I am now looking to track down the slowness and tune my process, or explore alternative ways to achieve the same goal.

Can anyone point me to a way to tune my map-reduce job?
Does anyone have any experience exploring Cassandra data with Hadoop cluster configuration? ( As suggested in http://wiki.apache.org/cassandra/HadoopSupport#ClusterConfig)

Thanks,
Orr

RE: Map-Reduce on top of cassandra

[Or Yanay <or...@peer39.com>]

Worked like a charm!
I have installed hadoop on my Cassandra nodes and ran the MR using Hadoop job tracker.

A simple key count improved from ~2 hours to about 25 minutes (150M keys and ~100G on each node)

Thanks Jeremy.

-----Original Message-----
From: Jeremy Hanna [mailto:jeremy.hanna1234@gmail.com] 
Sent: Monday, March 14, 2011 8:42 PM
To: user@cassandra.apache.org
Subject: Re: Map-Reduce on top of cassandra

Just for the sake of updating this thread - Orr didn't yet have task trackers on the Cassandra nodes so most of the time was likely due to copying the ~100G of data to the hadoop cluster prior to processing.  They're going to try after installing task trackers on the nodes.

On Mar 14, 2011, at 10:06 AM, Or Yanay wrote:

> Hi All,
>  
> I am trying to write some map-reduce tasks so I can find out stuff like - how many records have X status?
> I am using 0.7.0 and have 5 nodes with ~100G of data on each node.
>  
> I have written the code based on the word_count example and the map-reduce is running successfully BUT is extremely slow (about 2 hours for the simplest key count).
>  
> I am now looking to track down the slowness and tune my process, or explore alternative ways to achieve the same goal.
>  
> Can anyone point me to a way to tune my map-reduce job?
> Does anyone have any experience exploring Cassandra data with Hadoop cluster configuration? ( As suggested inhttp://wiki.apache.org/cassandra/HadoopSupport#ClusterConfig)
>  
> Thanks,
> Orr
>  

Re: Map-Reduce on top of cassandra

[Jeremy Hanna <je...@gmail.com>]

Just for the sake of updating this thread - Orr didn't yet have task trackers on the Cassandra nodes so most of the time was likely due to copying the ~100G of data to the hadoop cluster prior to processing.  They're going to try after installing task trackers on the nodes.

On Mar 14, 2011, at 10:06 AM, Or Yanay wrote:

> Hi All,
>  
> I am trying to write some map-reduce tasks so I can find out stuff like – how many records have X status?
> I am using 0.7.0 and have 5 nodes with ~100G of data on each node.
>  
> I have written the code based on the word_count example and the map-reduce is running successfully BUT is extremely slow (about 2 hours for the simplest key count).
>  
> I am now looking to track down the slowness and tune my process, or explore alternative ways to achieve the same goal.
>  
> Can anyone point me to a way to tune my map-reduce job?
> Does anyone have any experience exploring Cassandra data with Hadoop cluster configuration? ( As suggested inhttp://wiki.apache.org/cassandra/HadoopSupport#ClusterConfig)
>  
> Thanks,
> Orr
>  

Re: Map-Reduce on top of cassandra

[Jeremy Hanna <je...@gmail.com>]

Can you go into the #cassandra channel and ask your question?  See if jeromatron or driftx are around.  That way there can be a back and forth about settings and things.

http://webchat.freenode.net/?channels=#cassandra

On Mar 14, 2011, at 10:06 AM, Or Yanay wrote:

> Hi All,
>  
> I am trying to write some map-reduce tasks so I can find out stuff like – how many records have X status?
> I am using 0.7.0 and have 5 nodes with ~100G of data on each node.
>  
> I have written the code based on the word_count example and the map-reduce is running successfully BUT is extremely slow (about 2 hours for the simplest key count).
>  
> I am now looking to track down the slowness and tune my process, or explore alternative ways to achieve the same goal.
>  
> Can anyone point me to a way to tune my map-reduce job?
> Does anyone have any experience exploring Cassandra data with Hadoop cluster configuration? ( As suggested inhttp://wiki.apache.org/cassandra/HadoopSupport#ClusterConfig)
>  
> Thanks,
> Orr
>