A Java Open Client application is creating many Apache HTTP Async Client IO dispatcher threads when connecting to a PASOE instance. The threads look similar to the following:

Windows
java.lang.Thread.State: RUNNABLE
at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(java.base@11.0.14.1/Native Method)
at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(java.base@11.0.14.1/WindowsSelectorImpl.java:357)
at sun.nio.ch.WindowsSelectorImpl.doSelect(java.base@11.0.14.1/WindowsSelectorImpl.java:182)
at sun.nio.ch.SelectorImpl.lockAndDoSelect(java.base@11.0.14.1/SelectorImpl.java:124)
- locked <0x000000062623aa20> (a sun.nio.ch.Util$2)
- locked <0x000000062623a8a0> (a sun.nio.ch.WindowsSelectorImpl)
at sun.nio.ch.SelectorImpl.select(java.base@11.0.14.1/SelectorImpl.java:136)
at org.apache.http.impl.nio.reactor.AbstractIOReactor.execute(AbstractIOReactor.java:255)
at org.apache.http.impl.nio.reactor.BaseIOReactor.execute(BaseIOReactor.java:104)
at org.apache.http.impl.nio.reactor.AbstractMultiworkerIOReactor$Worker.run(AbstractMultiworkerIOReactor.java:591)
at java.lang.Thread.run( java.base@11.0.14.1/Thread.java:829) (mailto:java.base@11.0.14.1/Thread.java:829))


Linux
java.lang.Thread.State: RUNNABLE
at sun.nio.ch.EPoll.wait(java.base@11.0.14.1/Native Method)
at sun.nio.ch.EPollSelectorImpl.doSelect(java.base@11.0.14.1/EPollSelectorImpl.java:118)
at sun.nio.ch.SelectorImpl.lockAndDoSelect(java.base@11.0.14.1/SelectorImpl.java:129)
- locked <0x00000006830982f8> (a sun.nio.ch.Util$2)
- locked <0x00000006830982a8> (a sun.nio.ch.EPollSelectorImpl)
at sun.nio.ch.SelectorImpl.select(java.base@11.0.14.1/SelectorImpl.java:141)
at org.apache.http.impl.nio.reactor.AbstractMultiworkerIOReactor.execute(AbstractMultiworkerIOReactor.java:340)
at org.apache.http.impl.nio.conn.PoolingNHttpClientConnectionManager.execute(PoolingNHttpClientConnectionManager.java:221)
at org.apache.http.impl.nio.client.CloseableHttpAsyncClientBase$1.run(CloseableHttpAsyncClientBase.java:64)
at java.lang.Thread.run(java.base@11.0.14.1/Thread.java:840)

Using one of the following commands to generate a thread dump of the Java Open Client application:

jstack -l <pid> > threaddump.txt
jcmd <pid> Thread.print -l > threaddump.txt

If the java Open Client code is running inside an application server like Apache Tomcat, then it may cause the Tomcat server to run out of resources and become unable to process client requests anymore.

The Apache Async HTTP Client creates an IO thread pool to process IO events. By default it creates one thread per CPU core. So for each Java Open Client connection to a PASOE instance, a number of IO dispatcher threads is created which is equal to the number of logical processors available on the machine. For example, if a Java Open Client application is run on a machine with 22 logical processors, then 22 IO dispatcher threads will be created when the Java Open Client application makes a connection to a PASOE instance. This happens when the AppObject is instantiated, for example:

OpenAppObject dynAO = new OpenAppObject(myConnection, "");

So when using Java Open Client within an application server like Tomcat, the amount of IO dispatcher threads will be multiplied by the amount of Java Open Client connections to a PASOE instance.

Upgrade to OpenEdge 12.8 or later where the Apache HTTP Async Client IO dispatcher threads are limited to one IO dispatcher thread per Java Open Client AppObject.

A new undocumented Java system property was added in OpenEdge 12.2.5 to configure the amount of Apache HTTP Async Client IO dispatcher threads per Java Open Client AppObject. Set the "com.progress.openedge.apacheHTTPIOThreadCount" system property to 1 to limit the Java Open Client application to one thread per AppObject. For example, run the following before instantiating the AppObject:

System.setProperty("com.progress.openedge.apacheHTTPIOThreadCount", "1");

Alternatively, set the following JVM parameter when starting the Java application:

-Dcom.progress.openedge.apacheHTTPIOThreadCount=1