Cassandra 2.0 Available
Written by Kay Ewbank   
Tuesday, 10 September 2013

Apache has released Cassandra 2.0, the new version of the NoSQL distributed database. Improvements include lightweight transactions, triggers and enhancements to the Cassandra Query Language.

Apache Cassandra has grown in popularity and is now used in applications at Adobe, CERN, Comcast, eBay, GoDaddy, HP, IBM, Instagram, Netflix, Plaxo, and Sony.

 

cassandra

 

According to the  Apache Software Foundation announcement of the new version, the lightweight transaction support means Cassandra now has operation linearizability similar to the serializable isolation level offered by relational databases, which prevents conflicts during concurrent requests.

The DataStax Developer blog has a good description of how lightweight transactions in Cassandra work, but essentially, the system uses the Paxos consensus protocol. Essentially, a node proposes making a change to a value. The proposal is sent to participating replicas, and those replicas promise not to accept any other proposed changes (for the moment). If a majority of the nodes promise to accept the proposer’s change, it can proceed to do the change. However, if the majority of the replicated nodes included an earlier proposed change with their response, then that is the value the proposing node goes with.

Cassandra extends the Paxos consensus protocol with a third phase; the commit/acknowledge phase. This does mean that it takes four round trips to provide a linear transaction, but so long as you don’t need to many atomic transactions in your application, it works.

Triggers are the next improvement, and remain a work in progress with a warning of changes to come in Cassandra 2.1. However, the triggers currently rely on logged batches to implement a flexible, atomic, eventually consistent mechanism for reacting to – and augmenting – write operations.

The CQL enhancements add cursors and improved index support. There’s support for the new triggers, and some support for the new lightweight transactions. This support is exposed through the support of the IF keyword in INSERT, UPDATE and DELETE statements. The extra support for indexes lets you use columns for secondary indexes that are already used as primary key columns.

Other improvements include

  • Improved compaction, keeping read performance from deteriorating under heavy write load
  • Eager retries to avoid query timeouts by sending redundant requests to other replicas if too much time elapses on the original request
  • Custom Thrift server implementation based on LMAX Disruptor that achieves lower message processing latencies and better throughput with flexible buffer allocation strategies.

Source code, documentation, and related resources are available on the Apache Cassandra site.

 

 cassandraicon

Paxos consensus protocol

Related Articles

Cassandra 1.0 with Increased Performance

Cassandra with CQL

 

To be informed about new articles on I Programmer, install the I Programmer Toolbar, subscribe to the RSS feed, follow us on, Twitter, Facebook, Google+ or Linkedin,  or sign up for our weekly newsletter.

 

blog comments powered by Disqus

 

Banner


Imagine Cup Winners 2014
09/08/2014

The finals of the Imagine Cup were recently held in Seattle attended by 34 teams, 125 students in all, representing 34 countries. Winners of the Imagine Cup, Team Eyenaemia will be meeting with Bill G [ ... ]



Google's Blink Not Implementing W3C Pointer Events
18/08/2014

Since it split away from the WebKit render engine to create Blink, Google has been free to pick and choose what gets implemented. Now we have the news that it has decided to ignore the W3C spec for to [ ... ]


More News

Last Updated ( Tuesday, 10 September 2013 )
 
 

   
RSS feed of news items only
I Programmer News
Copyright © 2014 i-programmer.info. All Rights Reserved.
Joomla! is Free Software released under the GNU/GPL License.