How to reconnect when the LDAP server is restarted?

Question

I have a situation where through a Java program, I create a javax.naming.ldap.LdapContext and do a search() operation on it - which makes an underlying connection. Then I put the Java app thread to sleep, during which I restart the LDAP server (OpenLDAP, just to note). When the App thread wakes up and tries to do any operation on the LdapContext created earlier, it throws "CommunicationException: Connection is closed".

What I want is to be able to re-establish the connection.

I see that LdapContext has a reconnect() method - where I pass controls as null. However, this does not have any effect. What I saw in the Sun LDAP implementation that during the time when the LDAP server was restarted, the ConnectionPool maintained by the Sun implementation marked the underlying com.sun.jndi.ldap.LdapClient instance with a "usable=false". Upon reconnect() call - it simply calls ensureOpen(), which again checks if the usable flag is false or not - if it's false; then it throws CommunicationException - so back to square one.

My question is: how does a Java app survive an external LDAP server restart? Is creation of new LdapContext again is the only way out? Appreciate any insights.

Here is the stacktrace of the exception:

javax.naming.CommunicationException: connection closed [Root exception is java.io.IOException: connection closed]; remaining name 'uid=foo,ou=People,dc=example,dc=com'
at com.sun.jndi.ldap.LdapCtx.doSearch(LdapCtx.java:1979)
at com.sun.jndi.ldap.LdapCtx.searchAux(LdapCtx.java:1824)
at com.sun.jndi.ldap.LdapCtx.c_search(LdapCtx.java:1749)
at com.sun.jndi.toolkit.ctx.ComponentDirContext.p_search(ComponentDirContext.java:368)
at com.sun.jndi.toolkit.ctx.PartialCompositeDirContext.search(PartialCompositeDirContext.java:338)
at com.sun.jndi.toolkit.ctx.PartialCompositeDirContext.search(PartialCompositeDirContext.java:321)
at javax.naming.directory.InitialDirContext.search(InitialDirContext.java:248)
Caused by: java.io.IOException: connection closed
at com.sun.jndi.ldap.LdapClient.ensureOpen(LdapClient.java:1558)
at com.sun.jndi.ldap.LdapClient.search(LdapClient.java:504)
at com.sun.jndi.ldap.LdapCtx.doSearch(LdapCtx.java:1962)
... 26 more

Answer 1

Just enable JNDI connection pooling and it will all be taken care of for you behind the scenes. See the JNDI Guide to Features and the LDAP Provider documentation. It's controlled by just a couple of properties.