Robert Kanter created OOZIE-2651:
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Summary: Set javax.xml.parsers.DocumentBuilderFactory sys prop to
make XML handling faster
Key: OOZIE-2651
URL: https://issues.apache.org/jira/browse/OOZIE-2651
Project: Oozie
Issue Type: Improvement
Components: core
Affects Versions: trunk
Reporter: Robert Kanter
Assignee: Robert Kanter
Fix For: 4.3.0
We noticed from some jstacks that Oozie was spending a lot of time looking for
XML related jars (we do a lot of XML parsing in Oozie and Hadoop code). For
instance, we'd see hundreds of threads blocked here
{noformat}
"pool-5-thread-57" prio=10 tid=0x00007f9579923000 nid=0x6b7f waiting for
monitor entry [0x00007f94225e3000]
java.lang.Thread.State: BLOCKED (on object monitor)
at
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1559)
- waiting to lock <0x0000000500026148> (a
org.apache.catalina.loader.WebappClassLoader)
at
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1526)
at
javax.xml.parsers.FactoryFinder.getProviderClass(FactoryFinder.java:117)
at javax.xml.parsers.FactoryFinder.newInstance(FactoryFinder.java:178)
at
javax.xml.parsers.FactoryFinder.findJarServiceProvider(FactoryFinder.java:333)
at javax.xml.parsers.FactoryFinder.find(FactoryFinder.java:255)
at
javax.xml.parsers.DocumentBuilderFactory.newInstance(DocumentBuilderFactory.java:121)
at
org.apache.hadoop.conf.Configuration.loadResource(Configuration.java:2526)
at
org.apache.hadoop.conf.Configuration.loadResources(Configuration.java:2503)
at
org.apache.hadoop.conf.Configuration.getProps(Configuration.java:2409)
- locked <0x00000007eac5ea28> (a org.apache.hadoop.conf.Configuration)
at org.apache.hadoop.conf.Configuration.set(Configuration.java:1144)
at org.apache.hadoop.conf.Configuration.set(Configuration.java:1116)
at org.apache.oozie.util.XConfiguration.copy(XConfiguration.java:206)
...
{noformat}
There's nothing we can do about the lock at the {{WebappClassLoader}}, but by
setting the {{javax.xml.parsers.DocumentBuilderFactory}} system property to
{{org.apache.xerces.jaxp.DocumentBuilderFactoryImpl}}, we can speed this up a
lot by getting rid of all of the searching that it's doing to find the
implementation.
See
https://docs.oracle.com/javase/7/docs/api/javax/xml/parsers/DocumentBuilderFactory.html#newInstance()
and
https://www.databasesandlife.com/java-always-explicitly-specify-which-xml-parser-to-use/
In our testing, we had a metric around creating a new {{JobClient}}, which
eventually calls this code, and it dropped from ~3min max to ~2sec max.
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