PH65108: Z/OS LIBERTY 24.0.0.6 WITH JAVA 17 REPORTS CWWKX0201E ON CONNECTION REST JAVA.NET.UNKNOWNHOSTEXCEPTION

APAR status

• Closed as program error.

Error description

• Customer may encounter BPXI039I SYSTEM LIMIT INET MAXSOCKETS HAS
  REACHED % OF ITS CURRENT CAPACITY
  
  Liberty:
  
  CWWKB0108I: IBM CORP product WAS FOR Z/OS version 24.0.0.6
  successfully registered with z/OS.
  
  Java version:
  
  JRE 17 z/OS s390x-64 (build 17.0.11+9) IBM Semeru Runtime
  Certified Edition for z/OS
  JAVA VM NAME	- IBM J9 VM
  JAVA VM VERSION	- z/OS-Release-17.0.11.0-b02
  
  CWWKX0201E: The WebSphere Java Management Extensions REST client
  encountered an error while preparing the request to the ser
  ver for URL    on connection rest
  
  null 3
  java.net.UnknownHostException:
  
  	at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.ja
  va:577)
  	at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.
  java:327)
  	at java.base/java.net.Socket.connect(Socket.java:633)
  	at java.base/sun.security.ssl.SSLSocketImpl.connect(SSLSocketI
  mpl.java:304)
  	at java.base/sun.security.ssl.BaseSSLSocketImpl.connect(BaseSS
  LSocketImpl.java:174)
  	at java.base/sun.net.NetworkClient.doConnect(NetworkClient.jav
  a:183)
  	at java.base/sun.net.www.http.HttpClient.openServer(HttpClient
  .java:533)
  	at java.base/sun.net.www.http.HttpClient.openServer(HttpClient
  .java:638)
  	at java.base/sun.net.www.protocol.https.HttpsClient.<init>(Htt
  psClient.java:266)
  	at java.base/sun.net.www.protocol.https.HttpsClient.New(HttpsC
  lient.java:380)
  	at java.base/sun.net.www.protocol.https.AbstractDelegateHttpsU
  RLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnectio
  n.java
  :193)
  	at java.base/sun.net.www.protocol.http.HttpURLConnection.plain
  Connect0(HttpURLConnection.java:1242)
  	at java.base/sun.net.www.protocol.http.HttpURLConnection.plain
  Connect(HttpURLConnection.java:1128)
  	at java.base/sun.net.www.protocol.https.AbstractDelegateHttpsU
  RLConnection.connect(AbstractDelegateHttpsURLConnection.java:17
  9)
  	at java.base/sun.net.www.protocol.http.HttpURLConnection.getOu
  tputStream0(HttpURLConnection.java:1451)
  	at java.base/sun.net.www.protocol.http.HttpURLConnection.getOu
  tputStream(HttpURLConnection.java:1422)
  	at java.base/sun.net.www.protocol.https.HttpsURLConnectionImpl
  .getOutputStream(HttpsURLConnectionImpl.java:220)
  	at com.ibm.ws.jmx.connector.client.rest.internal.RESTMBeanServ
  erConnection.invoke(RESTMBeanServerConnection.java:1137)
  	at com.ibm.ws.collective.repository.client.internal.RemoteConn
  ectionHelperImpl.doInvoke(RemoteConnectionHelperImpl.java:396)
  	at com.ibm.ws.collective.repository.client.internal.RemoteConn
  ectionHelperImpl.invoke(RemoteConnectionHelperImpl.java:246)
  	at com.ibm.ws.collective.repository.client.internal.RemoteRepo
  sitoryConnection.accessMBean(RemoteRepositoryConnection.java:87
  3)
  

Local fix

• The workaround is to set Java property
  -Djdk.net.usePlainSocketImpl=true
  
  which you can put in the jvm.options file as noted here:
  [Customizing the Liberty environment - IBM Documentation]
  ( https://www.ibm.com/docs/en/was-liberty/zos?topic=manually-cu
  stomizing-liberty-environment)
  
  As noted below, the property will only work on Semeru 17. It
  will not work on Semeru 21 because the legacy socket
  implementation was completely removed in OpenJDK 21.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:  Users of IBM WebSphere Application          *
  *                  Server Liberty with the restConnector-2.0,  *
  *                  collectiveMember-1.0 or                     *
  *                  collectiveController-1.0 features enabled   *
  *                  feature enabled                             *
  ****************************************************************
  * PROBLEM DESCRIPTION: A WebSphere Liberty server encounters   *
  *                      external network problems (such as      *
  *                      DNS resolution failures), causing       *
  *                      UnknownHostExceptions. The WebSphere    *
  *                      Liberty server may then consume         *
  *                      excessive numbers of TCP/IP sockets,    *
  *                      which can exceed system wide limits.    *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  WebSphere Liberty logs/FFDs will likely record
  UnknownHostExceptions. System tools such as nestat will then
  show rapid growth in the number of open TCP/IP sockets,
  possibly followed by errors such as 'too many open files' in
  WebSphere Liberty or system logs.
  

Problem conclusion

• The code was updated to reduce the number of retries when
  network errors errors are detected, which reduces the number
  of open sockets.
  The fix for this APAR is targeted for inclusion in fix pack
  WebSphere Liberty 25.0.0.4. For more information, see
  'Recommended Updates for WebSphere Application Server':
  https://www.ibm.com/support/pages/node/715553
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  WAS LIBERTY COR

• Fixed component ID

  5725L2900

Applicable component levels