Jenkins Becomes Unreachable After LDAP UnknownHostException – Memory Cache Issue?

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Hi Jenkins Community,

I’m experiencing an issue where Jenkins becomes completely unreachable, even though systemctl status jenkins shows the service as active. This happens after the following log entries are repeatedly generated:

WARNING h.p.a.LDAPSearchBuilder#searchOne: JENKINS-42687 The user we are looking for might exist
java.net.UnknownHostException: InterEXT.local
        at java.base/java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:229)
        at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
        at java.base/java.net.Socket.connect(Socket.java:609)
        at java.base/sun.security.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:305)
        at java.naming/com.sun.jndi.ldap.Connection.createConnectionSocket(Connection.java:340)
        at java.naming/com.sun.jndi.ldap.Connection.createSocket(Connection.java:282)
        at java.naming/com.sun.jndi.ldap.Connection.<init>(Connection.java:229)
        at java.naming/com.sun.jndi.ldap.LdapClient.<init>(LdapClient.java:137)
        at java.naming/com.sun.jndi.ldap.LdapClient.getInstance(LdapClient.java:1616)
Caused: javax.naming.CommunicationException: InterEXT.local:636 [Root exception is java.net.UnknownHostException: InterEXT.local]

Jenkins Version: 2.246.3

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Issue Details:

  • Jenkins is configured to integrate with Active Directory.
  • The Domain Controller is explicitly set as ldap.intertech.com.tr:636.
  • The logs indicate that Jenkins is trying to reach InterEXT.local, which is not defined anywhere in the configuration.
  • After these log entries, Jenkins becomes completely unreachable in the browser, although the service remains active.
  • Restarting Jenkins temporarily resolves the issue, but it recurs after some time.