[jira] [Updated] (OOZIE-2651) Set javax.xml.parsers.DocumentBuilderFactory sys prop to make XML handling faster

["Robert Kanter (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/OOZIE-2651?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Robert Kanter updated OOZIE-2651:
---------------------------------
    Fix Version/s:     (was: 4.3.0)

> 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
>         Attachments: OOZIE-2651.001.patch
>
>
> 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 also calls {{DocumentBuilderFactory.newInstance}}, and it dropped from ~3min max to ~2sec max (not an exact test of the savings here).  And we also didn't see so much blocking on this in the jstacks anymore.



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