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From "Will Glass-Husain" <wglasshus...@gmail.com>
Subject Re: Velocity Performance and Concurrency issues
Date Thu, 24 Jul 2008 23:39:23 GMT
One big problem is that you are using Velocity.evaluate() which is not
recommended for high-volume use.

If you store your templates as text files and use a ResourceLoader to
retrieve as a Template object, Velocity has very efficient caching.
You can store your templates as files (use FileResourceLoader), in the
classpath (ClasspathResourceLoader), or in a database
(DatasourceResourceLoader).

The (unreleased) Velocity 1.6 (in source control trunk) contains
further improvements.  But you should see order of magnitude
improvements from retrieving your templates with a ResourceLoader (and
the caching option on) vs. Velocity.evaluate().

See the developer's manual for more details.

WILL


On Thu, Jul 24, 2008 at 3:46 PM, Malcolm Edgar <malcolm.edgar@gmail.com> wrote:
> Hi Auge,
>
> On the Velocity development list there is some ongoing work to address
> this issue. I would recommend that you try the performance patches and
> get in contact with these people.
>
> https://issues.apache.org/jira/browse/VELOCITY-606
>
> regards Malcolm Edgar
>
> On Fri, Jul 25, 2008 at 7:53 AM, Raymond Auge <rauge@liferay.com> wrote:
>> Hello All,
>>
>> My name is ray Augé. I am an engineer working for Liferay, Inc. on the
>> Liferay Portlet project.
>>
>> We have a critical issue with Velocity performance where under large
>> load Velocity becomes a bottleneck for scalability.
>>
>> Now, I'm fairly certain that this is perhaps because we are using
>> Velocity in a way which may not leverage its scalability features.
>>
>> Allow me to explain the problem and our usage.
>>
>> Under heavy load we hit a max throughput and thread dumps during this
>> time are completely filled with BLOCKED threads as bellow:
>>
>> [snip]
>> "http-80-Processor47" daemon prio=10 tid=0x00002aabbdb90400 nid=0x5a59
>> waiting for monitor entry [0x0000000044c72000..0x0000000044c74a80]
>>   java.lang.Thread.State: BLOCKED (on object monitor)
>>        at
>> org.apache.velocity.util.introspection.IntrospectorBase.getMethod(IntrospectorBase.java:103)
>>        - waiting to lock <0x00002aaad093d940> (a
>> org.apache.velocity.util.introspection.IntrospectorCacheImpl)
>>        at
>> org.apache.velocity.util.introspection.Introspector.getMethod(Introspector.java:101)
>>        at
>> org.apache.velocity.util.introspection.UberspectImpl.getMethod(UberspectImpl.java:165)
>>        at
>> org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:184)
>>        at
>> org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:203)
>>        at
>> org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:294)
>>        at
>> org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:318)
>>        at org.apache.velocity.app.Velocity.evaluate(Velocity.java:322)
>>        at org.apache.velocity.app.Velocity.evaluate(Velocity.java:195)
>>        at
>> com.liferay.portlet.layoutconfiguration.util.RuntimePortletUtil.processTemplate(RuntimePortletUtil.java:238)
>>        at
>> com.liferay.portlet.layoutconfiguration.util.RuntimePortletUtil.processTemplate(RuntimePortletUtil.java:194)
>>        at
>> org.apache.jsp.html.portal.layout.view.portlet_jsp._jspService(portlet_jsp.java:801)
>> [/snip]
>>
>> Now here is what the Velocity usage looks like for that particular
>> thread:
>>
>>                TemplateProcessor processor = new TemplateProcessor(
>>                        servletContext, request, response, portletId);
>>
>>                VelocityContext vc = new VelocityContext();
>>
>>                vc.put("processor", processor);
>>
>>                // Wrap a bunch of puts...
>>
>>                VelocityVariables.insertVariables(vc, request);
>>
>>                 // many more puts here...
>>                vc.put(...);
>>                vc.put(..);
>>
>>                StringWriter sw = new StringWriter();
>>
>>                try {
>>                        Velocity.evaluate(
>>                                vc, sw, RuntimePortletUtil.class.getName(), content);
>>                }
>>                catch (Exception e) {
>>                        _log.error(e, e);
>>
>>                        throw e;
>>                }
>>
>>                 // eventually do
>>                 return sw.toString();
>>
>> etc..
>>
>> Is there an obvious miss-use of Velocity than anyone can identify here?
>>
>> Wondering if we are supposed to re-use a common inner context? IF so,
>> would it be a singleton? a pool of re-usable contexts? something else?
>>
>> Many thanks for any input,
>>
>>
>> ----------------------------------
>> Raymond Augé
>> Software Engineer
>> Liferay, Inc.
>> Enterprise. Open Source. For Life.
>> ----------------------------------
>>
>> Liferay Meetup 2008 – Los Angeles
>>
>> August 1, 2008
>>
>> Meet and brainstorm with the creators of Liferay Portal, our partners
>> and other members of our community!
>>
>> The day will consist of a series of technical sessions presented by our
>> integration and services partners. There is time set aside for Q&A and
>> corporate brainstorming to give the community a chance to give feedback
>> and make suggestions!
>>
>> View Event Details
>>
>> Register Now
>>
>
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>



-- 
Forio Business Simulations

Will Glass-Husain
wglass@forio.com
www.forio.com

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