CODEWITHSUNDEEP
javaexceptionldapreconnect
Anand
Anand

Reputation: 419

How to reconnect when the LDAP server is restarted?

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

Upvotes: 9

Views: 9866

Answers (4)

Oueslati Bechir
Oueslati Bechir

Reputation: 970

You should note that this is related essentially to LDAP connection pooling. As defined here:

A connection is retrieved from the pool, used, returned to the pool, and then, retrieved again from the pool for another Context instance.

Thus, the reuse of a previous connection may cause such problem:

You may test the behavior without using LDAP connection pooling by setting 

com.sun.jndi.ldap.connect.pool=false

Also, another possible cause may be the timeout of reading the LDAP operations. In fact, the reading operation is not notified about the closure of the LDAP server after a specific timeout. For more information, you may take a look at this link

Upvotes: -1

user207421
user207421

Reputation: 310840

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.

Upvotes: 2

lordoku
lordoku

Reputation: 1112

We had this problem at work. The solution we came up with (may not be the best answer). Was to create a watchdog thread that would check the connection at some fixed rate. If the connection did not work, it would re-initialize the connection with LDAP.

Upvotes: 0

Terry Gardner
Terry Gardner

Reputation: 11134

The UnboundID LDAP SDK provides a means to auto-connect wherein that auto-reconnect operation is invisible to the client.

Upvotes: 0

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