This is the second post on my little “Cassandra – Getting Started” series covering the installation and basic configuration of Cassandra. Cassandra is extremely easy to set up, especially compared to HBase. All you got to do is to download, extract, edit a single XML-file and run. But let us take it step by step.

You can download Cassandra directly from it’s (her?) website. At the time of the submission of this post, version 0.4.1 was the most recent stable. Note that you need Java 6 installed to run Cassandra which I assume here as properly installed.

After extracting Cassandra to some folder (on my Windows box I placed it directly in D:\cassandra), the only file you need to edit is conf/storage-conf.xml. While Cassandra is engineered to run on a large number of machines in a network, we start it here as a single node with the default parameter set, so that most of the settings are ok for now.

If your are not on a Unix-like system, you need to update the folders where Cassandra is supposed to store the data. If your using Windows (like me), then find the following lines in conf/storage-conf.xml and change the paths to something sensible

<CommitLogDirectory>/var/lib/cassandra/commitlog</CommitLogDirectory>
<DataFileDirectories>
      <DataFileDirectory>/var/lib/cassandra/data</DataFileDirectory>
</DataFileDirectories>
<CalloutLocation>/var/lib/cassandra/callouts</CalloutLocation>
<BootstrapFileDirectory>/var/lib/cassandra/bootstrap</BootstrapFileDirectory>
<StagingFileDirectory>/var/lib/cassandra/staging</StagingFileDirectory>

like for example my settings:

<CommitLogDirectory>D:/cassandra/data/commitlog</CommitLogDirectory>
<DataFileDirectories>
       <DataFileDirectory>D:/cassandra/data/data</DataFileDirectory>
</DataFileDirectories>
<CalloutLocation>D:/cassandra/data/callouts</CalloutLocation>
<BootstrapFileDirectory>D:/cassandra/data/bootstrap</BootstrapFileDirectory>
<StagingFileDirectory>D:/cassandra/data/staging</StagingFileDirectory>

Let’s take Cassandra for a spin and check if she starts up correctly. For Mac OS, Linux, etc. users, simply change to the bin directory of Cassandra and run ./cassandra. As an aside for the impatient, I start Cassanda with sudo to avoid trouble with the Cassandras system.log.

Windows users, however, that use the command line (meaning not Cygwin) cannot start it just like that. The cassandra.bat didnt work for me on my Vista box if executed with bin being the current working directory (probably due to the CASSANDRA_HOME environment variable that get’s incorrectly set in the batch file). BUT it works perfect if you call bin\cassandra.bat from Cassandra’s main directory above bin. So if you are on Windows, change to the directory where you extracted Cassandra and execute bin\cassandra.bat.

Cassandras output on startup will look similar to this (here on Mac OS):

Schabbys-MacBook-Pro:bin johannes$ sudo ./cassandra
Schabbys-MacBook-Pro:bin johannes$ Listening for transport dt_socket at address: 8888
DEBUG - Loading settings from ./../conf/storage-conf.xml
DEBUG - Syncing log with a period of 1000
DEBUG - opening keyspace Keyspace1
DEBUG - adding Super1 as 0
DEBUG - adding Standard2 as 1
DEBUG - adding Standard1 as 2
DEBUG - adding StandardByUUID1 as 3
DEBUG - adding LocationInfo as 4
DEBUG - adding HintsColumnFamily as 5
DEBUG - opening keyspace system
DEBUG - INDEX LOAD TIME for /Users/johannes/cassandra/data/system/LocationInfo-1-Data.db: 0 ms.
DEBUG - INDEX LOAD TIME for /Users/johannes/cassandra/data/system/LocationInfo-2-Data.db: 0 ms.
DEBUG - INDEX LOAD TIME for /Users/johannes/cassandra/data/system/LocationInfo-3-Data.db: 0 ms.
INFO - Replaying /Users/johannes/cassandra/commitlog/CommitLog-1257980407451.log
DEBUG - Replaying /Users/johannes/cassandra/commitlog/CommitLog-1257980407451.log starting at 117
DEBUG - Reading mutation at 117
DEBUG - replaying mutation for system.L: {ColumnFamily(LocationInfo [Generation,])}
INFO - Flushing Memtable(LocationInfo)@228828460
DEBUG - Submitting LocationInfo for compaction
INFO - Completed flushing Memtable(LocationInfo)@228828460
INFO - Compacting [/Users/johannes/cassandra/data/system/LocationInfo-1-Data.db,/Users/johannes/cassandra/data/system/LocationInfo-2-Data.db,/Users/johannes/cassandra/data/system/LocationInfo-3-Data.db,/Users/johannes/cassandra/data/system/LocationInfo-4-Data.db]
DEBUG - index size for bloom filter calc for file  : /Users/johannes/cassandra/data/system/LocationInfo-1-Data.db   : 256
DEBUG - index size for bloom filter calc for file  : /Users/johannes/cassandra/data/system/LocationInfo-2-Data.db   : 512
DEBUG - index size for bloom filter calc for file  : /Users/johannes/cassandra/data/system/LocationInfo-3-Data.db   : 768
DEBUG - index size for bloom filter calc for file  : /Users/johannes/cassandra/data/system/LocationInfo-4-Data.db   : 1024
DEBUG - Expected bloom filter size : 1024
INFO - Compacted to /Users/johannes/cassandra/data/system/LocationInfo-5-Data.db.  0/255 bytes for 0/1 keys read/written.  Time: 150ms.
DEBUG - collecting Generation:false:4@3
DEBUG - collecting Token:false:16@0
INFO - Saved Token found: 160533723849634883377008460059010504450
DEBUG - Starting to listen on 127.0.0.1:7001
DEBUG - Binding thrift service to localhost:9160

I think that’s it. Leave a comment if you run in trouble or check the nice If Something Goes Wrong page in the Cassandra Wiki.