Question

OutOfMemoryError When creating *large* Velocity report...

Asked by: burtonrhodes

I have a webapp (tomcat, struts 2, hibernate, sql server) that creates a report for a user using the apache velocity engine (version 1.6.2).  The report is formatted in HTML and served to the user as a webpage.  The problem happens when the user decides to create a report for many contacts in the database (1000+).  Currently I am limiting the user to 250 records when creating a report, but do not want this limitation.

I have an example of the code I am using below - it should be pretty basic Velocity stuff.  I've also included the error stack trace in an attachment in case that's of use.  Is there another way to do this?

(I am currently testing this on Jetty, but don't want to test on tomcat servers until I know a possible solution)

StringWriter writer = new StringWriter();
 
// Create the velocity context and add variables
VelocityContext context = new VelocityContext();
context.put("contacts", contacts);
 
// Get the template
String templateFileName = "contactDetail.vm";
InputStream in = ReportCreatorServiceImpl.class.getResourceAsStream(velocityPath + templateFileName);
if (in==null) {
	throw new Exception ("Velocity template not found.");
}
InputStreamReader reader = new InputStreamReader(in);
 
// Do the merge
Velocity.init();
Velocity.evaluate(context, writer, "LOG", reader);  // <----- !!! ERROR HERE!!!!!
return writer.toString();

                                  
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Asked On
2009-10-25 at 20:37:32ID24842556
Tags

OutOfMemoryError Velocity Java

Topic

eXO Velocity

Participating Experts
1
Points
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Comments
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Answers

 

by: arevuriPosted on 2009-10-25 at 21:07:05ID: 25659609

There is no heap memory available to store your data. Increase the heap memory using JVM parameters for your tomcat. Check your cataline configuration files to set these value

Heap memory can be set using (This requires your system has sufficient RAM)

-Xms1024m indicates 1GB of minimum memory
-Xmx2048m indicates 2GB of maximum memory

This above parameters tells the JVM that how much memory of the machine should be allocated for your application.

Also you need to optimize your code not to store so much data in memory. Check if there is any duplicate data in mulitple objects. If so clean up the same.

-Revuri

 

by: burtonrhodesPosted on 2009-10-26 at 06:19:44ID: 25661914

Precisely - I am trying to "clean up my code" to optimize.  The problem is that this report inherently uses a lot of memory - it basically displays the entire database if a user requests it.  I am trying to accomplish this report without having to increase the memory.  For example, is there a way to write the report directly to a file and not to memory?  My preferred method would be to "stream" the report to the user without creating the entire report in memory and then serving it up to the user.  I can't seem to find a way in Velocity to do either ("file" or return a "stream").  Any suggestions?

 

by: burtonrhodesPosted on 2009-10-26 at 06:47:26ID: 25662160

I found this thread and may have the same issue.  I have a #foreach loop for each contact record and may be overloading the cache?  However, this thread doesn't tell me how do actually make the change.  Any ideas?

http://archives.devshed.com/forums/java-118/out-of-memory-error-using-gzipoutputstream-211326.html

 

by: arevuriPosted on 2009-10-26 at 08:50:40ID: 25663491

Usually, in practical, any UI report will have limited number of records shown based on some search criteria. Alsonumber of records to be displayed in each page are restricted.

In case if client needs the entire data as a report, an excel,csv,flat file formated report would be generated and FTPd' to the desired location.

If you are allowed to use above practices, I would suggest to go with that.

However for your purpose, you can create a File on the server where your application runs and Write the file on to the WEB page by setting appropriate content-type. Whenever you access the WEB page then your browser will prompt to save the file. I am not sure how to do this in Velocity, in case of servlets, directly we can write onto the servlet and this servlet can be called on to browser using HTML/DHTML coding.

I will get back to you on this, if I found something related to this.

BTW, can you tell me what is total size of your report (in KB ) and what is the allocated memory for JVM in your tomcat server.

Regards,
-Revuri

 

by: burtonrhodesPosted on 2009-10-27 at 17:35:03ID: 25679081

I changed the heap size on Maven_opts variable and everything completed fine.  Of course, when the page loaded on IE it basically "broke" it because the HTML page was so large.  I think I will maintain my 500 record limit.  There already is an export feature to xls so I guess I will do that instead.  I apprecaite your willingness to help and I guess your suggestion to limit is the best thing to do.

20120131-EE-VQP-002

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