Mercurial > hg > blitz_condensed

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>


  <title>Blitz Overview</title>
</head>


<body>


<h1>Blitz - Javaspaces Made Simple</h1>


<p>The <a href="http://www.dancres.org/blitz/index.html">Blitz</a> JavaSpaces<sup>TM</sup>
implementation aims to provide a rich set of features to make the
development &amp; deployment of JavaSpaces technology easier, more
efficient and more fun to experiment with.
</p>


<p>The Blitz Project is the first <a href="http://www.jini.org/">Jini<sup>TM</sup></a> 2.x compliant JavaSpace to be made available under an <a href="http://www.opensource.org/">OpenSource</a> <a href="LICENSE.TXT">license</a>.</p>


<h2>Key features</h2>


<ul>


  <li>Ease of installation.</li>


  <li>Jini 2.x enabled.</li>


  <li>Use of established VM principles.</li>


  <li>Smart indexing.</li>


  <li>Tuneable persistence.</li>


  <li>Tools.</li>


  <li>Entry Browsing.</li>


  <li>Embeddable Space support.</li>


  <li>Active/Passive/Manual lease cleanup.</li>


  <li>Built for experimentation and expansion.</li>


  <li>Easy integration with the Inca X IDE &amp; Runtime Environment.</li>


</ul>


<h3>Ease of installation</h3>

Blitz aims to make installation simpler by not relying on other visible
services such as RDBMS products (which tend to require significant
admininistration knowledge of both the RDBMS and the OS) and providing
default configurations which make it useful out of the box.

<h3>JINI 2.x Enabled</h3>


First-class support for a variety of security configurations and deployment environments.

<h3>Use of established VM Principles</h3>


<p>Blitz's central abstraction for Entry storage is based on the
classic Virtual Memory (VM) concept such that a set of Entry's are
cached in memory at any one time and then paged, as required, according
to an algorithm which typically bases it's decisions on usage patterns.
&nbsp;In addition, readahead can be supported such that we can fault in
a collection of potentially matching Entry's when the cache has
provided no suitable candidates.
</p>


<p>This re-use of an OS concept allows Blitz to take advantage of a
huge body of existing research with respect to effective caching in the
face of varying application behaviour (some will have hotspots, some
will be random, some will reference things strictly in order).</p>


<p>Different JavaSpace applications will have common sets of behaviour
from a cache usage perspective. Blitz architecture makes it possible to
support several different cache management strategies and allow an
astute user to pick the one most suited to their application behaviour.
</p>


<h3>Smart Indexing</h3>


<p>Blitz uses on disk and in-memory Entry storage, which is fully indexed automatically and keeps search times to a minimum.
</p>


<h3>Tunable persistence</h3>


<p>Disk space is now cheap &amp; efficient both in speed and
reliability which reduces the motivation for developing a memory-only
JavaSpace. The basic performance limit for a persistent space is
related to guarenteeing consistency which is determined by the speed
with which a system can force log entries to disk. Blitz tackles these
problems by providing a range of profiles (Storage Models) giving
different tradeoffs between data-integrity and speed.</p>


<ul>


  <li>VM-style caching with full consistent logging to ensure all changes are durable - full persistence.</li>


  <li>VM-style caching with periodic flushing (after x seconds) - ensuring all changes x seconds ago are persistent.</li>


  <li>VM-style caching with no logging - if your cache is big enough to
hold the working-set of Entry's for your application, no paging occurs
so all work is performed in memory with no disk access required -
transient.</li>


</ul>


<h3>Tools</h3>


A selection of tools are provided to assist developers and administrators:

<ol>


  <li>Dashboard - GUI tool which displays useful information such as
the number of instances of each type, number of currently active
transactions, operation totals and memory consumption.</li>


  <li>SyncAndShutdown - Flushes all updates to disk and shuts down a Blitz JavaSpaces instance.</li>


  <li>DumpEntries - Displays the current contents of a Blitz JavaSpaces instance optionally unpacking and displaying each Entry.</li>


  <li>Cleanup - Clears all Entry's from the Blitz JavaSpaces instance
and removes all schema information allowing for re-definition of Entry
structure with no restart required.</li>


  <li>EntrySizer - assists in calculating Blitz JVM memory footprint</li>


</ol>


<h3>Entry Browsing</h3>


<p>Blitz JavaSpaces supports <code>com.sun.jini.outrigger.JavaSpaceAdmin</code> allowing appropriate Service Browsers (e.g. Inca X's community browser) to view and manipulate the Entry's within an instance.</p>


<h3>Embeddable Space support</h3>

Certain multi-threaded applications, running in a single JVM, can
benefit from the use of JavaSpaces. In these situations, having the
JavaSpace available as a remote service is undesirable. This feature
allows an application to run Blitz locally, within it's own JVM,
providing a performance boost.

<h3>Active/Passive lease cleanup</h3>


<p>In high-performance applications, the cost of tracking lease expiry
and clearing expired entries from disk may affect throughput
sufficiently that it is more economical to accept that some disk-space
will be lost to expired entries. Conversely, in environments where
disk-space is at a premium, it may be more appropriate to expend
processor and disk time doing full cleanup of expired entries.</p>


<p>Blitz provides three options for handling lease expiry processing:</p>


<ol>


  <li>When an expired entry is loaded into cache-memory, it will be
marked for deletion at the next cache flush. This has the effect of
cleaning up entries which are slowing down the speed of searches.
(passive cleanup)</li>


  <li>Occasional background scans of disk storage to find and remove
expired entry's that never get into cache. This has the effect of
conserving disk space. (active cleanup)</li>


  <li>User requested background scans of disk storage to find and remove expired entry's. (manual cleanup)</li>


</ol>


<p><b>Note</b>: the active cleanup code by default, is turned <em>off</em>.  It can be turned on by setting the <code>leaseReapInterval</code> variable in the configuration file to a non-zero value.</p>


<p><b>Note</b>: the manual cleanup code by default, is turned <em>off</em>.  It can be turned on by setting the <code>leaseReapInterval</code> variable in the configuration file to <code>org.dancres.blitz.lease.LeaseReaper.MANUAL_REAP</code>.</p>


<h3>Built for experimentation and expansion</h3>

Because Blitz is open-source, should the need arise, you can make
whatever changes you desire. The design is based on a small number of
generic abstractions making it easy (hopefully) to get to grips with
the code.

<h3>Easy integration with the Inca X IDE &amp; Runtime Environment</h3>


The <a href="http://www.incax.com/">Inca X</a> team have been testing
Blitz and have built an installer to integrate it into all versions of
their IDE &amp; Runtime Environment.

<h2>Maturing with further development</h2>


<p>Looking at RDBMS technology, one can see that it has reached
maturity - these are some of the defining characteristics of such a
market:
</p>


<ul>


  <li>A few dominant vendors.</li>


  <li>A large body of technical research.</li>


  <li>Established benchmarks.</li>


  <li>Large number of common features between vendors.</li>


  <li>A large body of knowledge with respect to application development and how to get appropriate performance.</li>


</ul>


<p>The maturity of the RDBMS market is in marked contrast to the
JavaSpaces technology where there's still a substantial amount of work
to be done.
</p>


<p>Blitz is intended to be a vehicle for furthering the development of
JavaSpaces technology covering issues as diverse as internal
implementation, application development (usage patterns, frameworks
etc) and administration/deployment.
</p>


<h2>About Blitz</h2>


The Blitz project was started by Dan Creswell.

<h3>Credits</h3>


Blitz uses:

<ol>


	<li><a href="http://gee.cs.oswego.edu/dl/classes/EDU/oswego/cs/dl/util/concurrent/intro.html">Doug Lea's util.concurrent package</a></li>


	<li><a href="http://teatrove.sourceforge.net/trove.html">TeaTrove</a></li>


	<li><a href="http://www.prevayler.org/">Prevayler</a></li>


	<li><a href="http://www.sleepycat.com/">Berkeley Db and Berkeley Db Java Edition</a></li>


</ol>


<p></p>

<div align="center"><a href="../index.html">Back to Documentation</a></div>


<p><i>Java and all Java-based marks are trademarks or registered trademarks of Sun Microsystems, Inc. in the U. S. and other countries</i></p>


</body>
</html>
author	Dominic Cleal <dominic-cleal@cdo2.com>
date	Thu, 05 Aug 2010 11:07:25 +0100
parents	3dc0c5604566
children