Re: contention during XMLReaderFactory.createXMLReader

Hi Andrew,

Creating a new XML parser can be very expensive. The ClassLoader used to 
create the parser and its internal components might block or spend a long 
time searching its "classpath" for META-INF/services files. This is why 
it's generally a good idea to cache and reuse [1] XML parser instances.

Thanks.

[1] 
http://www.ibm.com/developerworks/xml/library/x-perfap2/index.html#reuse

Michael Glavassevich
XML Technologies and WAS Development
IBM Toronto Lab
E-mail: [email protected]
E-mail: [email protected]

Andrew Welch <[email protected]> wrote on 11/12/2013 07:48:47 AM:

> Hi,
> 
> A colleague was doing some performance testing and discovered some
> contention at this line of my code:
> 
> XMLReaderFactory.createXMLReader("org.apache.xerces.parsers.SAXParser");
> 
> ...which was surprising : ) He informed me it was doing a blocking
> operation every time.
> 
> Anyway, he went away and went through the Xerces source and found that
> if the "org.apache.xerces.xni.parser.XMLParserConfiguration" system
> property is not set it does indeed do a blocking operation (in
> parsers.ObjectFactory)
> 
> To demonstrate this, run the below code with and without the system
> property set:
> 
> public static void main(String... args) throws Exception {
> 
>     //System.setProperty
> ("org.apache.xerces.xni.parser.XMLParserConfiguration",
>     //        "org.apache.xerces.parsers.XIncludeParserConfiguration");
> 
>     long start = System.nanoTime();
> 
>     for (int i = 0; i <= 10000; i++) {
>         XMLReaderFactory.createXMLReader
> ("org.apache.xerces.parsers.SAXParser");
>     }
> 
>     long end = System.nanoTime();
>     double millis = (end - start) * 1e-6;
> 
>     System.out.println(millis);
> 
> }
> 
> On my machine it consistently takes around ~2000ms without the system
> property, and ~1300ms with.
> 
> This is present in both 2.9 and 2.11 as far as I can see.
> 
> 
> 
> 
> -- 
> Andrew Welch
> http://andrewjwelch.com
> 
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