19 September 2012

Do Coherence Aggregators Failover?


Coherence provides three possibilities for clients to execute code over entries in the data grid.
  • Entry Processors
  • Invocation Service
  • Aggregators

Entry Processors

The behaviour of Coherence's Entry Processors is well documented, they provide a lock-free programming model and a guarantee to apply any cache entry mutations as a single atomic operation.  An entry processor is created by a client and executed against a key, a set of keys or a filter.  In a partitioned cache execution takes place in parallel and should a primary node for a key fail while executing a processor the task is automatically migrated to a back-up.  An Entry Processor provides a "once and only once" guarantee and offers a powerful strategy for performing multiple updates concurrently.

10 September 2012

Book Review: HBase Administration Cookbook

Publisher: Packt Publishing
Language : English
Paperback : 332 pages [ 235mm x 191mm ]
Release Date : August 2012
ISBN : 1849517142
ISBN 13 : 9781849517140
Author(s) : Yifeng Jiang
Available at : Packt Publishing Website, Amazon



HBase is an Apache project designed to enable realtime access to very large datasets. 
In order to enable this it leverages components from the Hadoop projects HDFS (distributed, massive scale, fault taulerant file system modelled on GFS), Zookeeper and Hadoop MapReduce

3 September 2012

Out Of Memory Exception First Response


In any business, it’s a wise decision to not only plan for outages in production but to expect them. When problems do occur, particularly for production systems, time taken to resolve the issue is always key, whether that means time taken to restore the affected system to a stable, consistent and usable state or a root cause analysis to determine the causes and preventative measures to put in place.
When opening a support ticket, then, it is very important to reduce the amount of time wasted by waiting for support to tell you what data they need to diagnose the problem.
This post will provide a basic guide to some useful first steps following a Java OutOfMemory exception which should help get things moving quickly.