Apache Cassandra on a Raspberry Pi

One of the  reason I got hold of a Raspberry Pi (the $35 arm based Linux

machine) was to play around with building a cluster of them  for handling

"Big Data".  This is a real exercise in tinkering, very much a “what if” scenario.  The first thing I wanted to play with was getting Apache Cassandra to run on  the Pi.  Of course Cassandra is built with Java, there is no java on the Pi out of the box.    Several people suggested building Openjdk (http://openjdk.java.net/) but I plumbed for Oracle’s java SE for  embedded available here:

http://www.oracle.com/technetwork/java/embedded/downloads/javase/index.html

Download Java SE for Embedded 7 (ARMv6/7 Linux - Headless )and install it on the PI.  Once done and with the path and java_home correctly set you should be able to run the java on your pi.

Next get hold of a version of Apache Cassandra (http://cassandra.apache.org/)  I was using version 1.1.0.  Install it as usual.    If yo u try and run Cassandra from the bin directory it will fail to start with the serror:

“Invalid initial eden size: -Xmn0M”

The problem is that cassandra-env.sh is trying to work out the heap size by getting the  amount of memory on the machine and multiplying it it by the number of processors (line 69)

max_sensible_yg_in_mb=`expr $max_sensible_yg_per_core_in_mb "*" $system_cpu_cores`

The number of system cpu cores (line 22 or there abouts):

system_cpu_cores=`egrep -c 'processor([[:space:]]+):.*' /proc/cpuinfo`

is failing on the Pi (there is no processor line in /proc/cpuinfo).  For now I’ve manually altered cassanda-env.sh  to report only on core. 

system_cpu_cores=1

Cassandra now runs on the Pi.     There must be a better way of doing this( my Linux programming is failing me for the moment)  but for now I’m just tinkering so it will do.

Next up, try and get some performance figures for the Pi running Cassanadra.

Update

The correct way to fix this is to add change the Linux section of cassandra-env.sh to

           system_memory_in_mb=`free -m | awk '/Mem:/ {print $2}'`

            system_cpu_cores=`egrep -c 'processor([[:space:]]+):.*' /proc/cpuinfo`

            if [ "$system_cpu_cores" -lt "1" ]

            then

               system_cpu_cores="1"

            fi

            echo "Linux"

            echo "memory" $system_memory_in_mb

            echo "cores" $system_cpu_cores