[xep-support] XEP 371 multi-threading

[Duncan, David]

Hi,

 I have another performance question. In regard to my previous email
concerning multi-threading, i have discovered that using Oracle OCI driver
causes problems in a muli-threaded application. I believe this is the main
cause for my performance issues and not the xep driver. However i have a
question regarding xep internal transformation step. I use xep to transform
an xml file to xsl-fo and then render the pdf, so i use xep to perform 2
steps. I was wondering if performance gains could be achieved by separating
out the transform step? Perhaps I could use Xalan or Saxon to do the
transform and pass xep the xslfo to render? I beleive xep uses JAXP...and
maybe using another transformation engine (with freedom to optimise the
engine) woudl help. Im also looking at stylesheet improvement such as,
 
	 - Don't use "//" (descendant axes) patterns near the root of a
large document. 
	 - Use xsl:key elements and the key() function as an efficient way
to retrieve node sets. 
	 - Where possible, use pattern matching rather than xsl:if or
xsl:when statements. 
	 - xsl:for-each is fast because it does not require pattern
matching. 
	 - Keep in mind that xsl:sort prevents incremental processing. 
	 - When you create variables, 
	 - <xsl:variable name="fooElem" select="foo"/>
		is usually faster than 
	 - <xsl:variable
name="fooElem"><xsl:value-of-select="foo"/></xsl:variable> 
	 - The use of index predicates within match patterns can be
expensive. 

If anyone has any suggestions or comments that would be much appreciated.

Thanks,
David.
-----Original Message-----
From: owner-xep-support at renderx.com
[mailto:owner-xep-support at renderx.com]On Behalf Of Duncan, David
Sent: Tuesday, March 02, 2004 10:41 AM
To: 'xep-support at renderx.com'
Subject: [xep-support] XEP 371 multi-threading


Hi,

 I am having a major performance problem when upgraded to xep 371. I may
have amde some code errors which ill investigate, but my initial finding
appear to show problems with multi-threading on a mulitiple cpu machine.
Basically i launch a single JVM which initialises XEP bu loading XEP system
properties and by calling com.renderx.xep.gen.backends.H4PDF.init().

Then ,multiple threads are spawned each creating a PrintPublisher class
(note this is a publisher per xsl file. ie we cache the print publisher
object for multiple transforms using the same xsl template),

class DMSPrintPublisher {

	private static final Logger s_logger =
Logger.getLogger(BatchPublishingClient.class);  // log4j is thread-safe
	private static FOTransformer foTransformer;
	private FormatterImpl formatter;
	
    public DMSPrintPublisher(String template, Properties xepProps) throws
CorrespondenceException {
        InputSource xsl = new InputSource();
        InputStream templateInputStream = new
ByteArrayInputStream(template.getBytes());
        xsl.setByteStream(templateInputStream);
        SAXSource saxSource = new SAXSource(xsl);
        
        try {
        	this.formatter = new FormatterImpl(xepProps,
com.renderx.xep.lib.Logger.NULL_LOGGER);
            foTransformer = new FOTransformer(saxSource, formatter);
            foTransformer.setLogger(com.renderx.xep.lib.Logger.NULL_LOGGER);

			foTransformer.setParameter("signature_location",
System.getProperty(DMSConstants.SIGNATURE_LOCATION));
        	
        } catch (Exception e) {
            throw new CorrespondenceException("Could not set up
transformation engine: " + e.getMessage(), e);
        }

    public void publish(String documentData, OutputStream dest) throws
PublishException {
      try {
      	InputStream dataInputStream = new
ByteArrayInputStream(documentData.getBytes());
       	StreamSource xml = new StreamSource(dataInputStream);
            FOTarget foTarget = new FOTarget(dest, "PDF");
            foTransformer.transform(xml, foTarget);
            dataInputStream.close();
            dest.close();
            formatter.cleanup();
        } catch (Exception exc) {
            throw new PublishException(ErrorCodes.RECOVERABLE_SYSTEM_ERROR,
"Failed to perform transform: " + exc.getMessage(), exc);
        }
    }	
 }

My main concern is that when using xep 361 interface we saw the
multi-threaded process being shared across a 4 cpu unix box (running
Solaris8). However, using xep371 (along with code changes due to new
interface), we see 1 cpu maxed out and the rest idle. This reduces
performance by 4 fold. 

Perhaps I have made some errors in coding the publisher...maybe I should
create one FOTransformer (initialised by xep properties) instead of 1 for
each publisher object? Bu this seems to be a side issue. Are you aware of
any potential multi-threading issues with the new version of xep?

Many thanks for your support,

David.





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