Loop in client results in NPE + CommunicationException Request: 1 cancelled

• Key: DIRSERVER-391
• Type: Bug
• Status: Closed
• Resolution: Fixed
• Priority: Major
• Assignee: Alex Karasulu
• Reporter: David Geleyn

Description

The source code that fails is too complicated to add here, so I've made a test program that results in the same behaviour.

This program doesn't do anything useful. It checks twice whether Alex Karasulu is an administrator and repeats this for a thousand times. It results in an CommunicationException at client side and a NPE at server side. I added both stacktraces at the end. I also added the code that starts up the LDAP server.

I googled to find some explanation for the "Request 1: Cancelled", but I didn't find an useful explanation. There was some topic on a forum that mentionned that the number of connections was reached. Can this be the problem?

After the NPE (which is never a good thing), new server requests will be processed. It's only the thread that handles the request that fails (i guess).

============= SAMPLE CLIENT CODE
public static void main(String[] args) throws Exception
{
        final Properties env = new Properties();
        env.put(Context.INITIAL_CONTEXT_FACTORY,
"com.sun.jndi.ldap.LdapCtxFactory");
        env.put(Context.PROVIDER_URL, "ldap://david:389");
        env.put(Context.SECURITY_AUTHENTICATION, "simple");
        env.put("java.naming.ldap.version", "3");
        env.put(Context.SECURITY_PRINCIPAL, "uid=admin,ou=system");
        env.put(Context.SECURITY_CREDENTIALS, "secret");
        int positive = 0;
 
        for (int i = 0; i < 1000; i++)
        {
                // Try to authenticate user.
                DirContext userContext = new InitialDirContext(env);
 
                final SearchControls constraints = new SearchControls();
                constraints.setDerefLinkFlag(true);
                constraints.setSearchScope(SearchControls.SUBTREE_SCOPE);
                String filter =
"(&(cn=administrators)(uniqueMember=uid=akarasulu,ou=users,ou=system))";
                NamingEnumeration enum =
userContext.search("ou=groups,ou=system", filter, constraints);
                enum = userContext.search("ou=groups,ou=system", filter,
constraints);
 
                if (enum.hasMoreElements()) positive++;
                userContext.close();
        }
        System.out.println(positive);
 
}

============= SERVER STARTUP CODE
// Start the LDAP server
Properties env = new Properties();
env.setProperty(Context.PROVIDER_URL, "ou=system");
env.setProperty(Context.INITIAL_CONTEXT_FACTORY,
"org.apache.ldap.server.jndi.ServerContextFactory");
try
{
        new InitialDirContext(env);
}
catch (NamingException e)
{
        e.printStackTrace();
}

============= CLIENT STACK TRACE
javax.naming.CommunicationException: Request: 1 cancelled
        at com.sun.jndi.ldap.LdapRequest.getReplyBer(LdapRequest.java:60)
        at com.sun.jndi.ldap.Connection.readReply(Connection.java:405)
        at com.sun.jndi.ldap.LdapClient.ldapBind(LdapClient.java:340)
        at com.sun.jndi.ldap.LdapClient.authenticate(LdapClient.java:193)
        at com.sun.jndi.ldap.LdapCtx.connect(LdapCtx.java:2640)
        at com.sun.jndi.ldap.LdapCtx.<init>(LdapCtx.java:290)
        at
com.sun.jndi.ldap.LdapCtxFactory.getUsingURL(LdapCtxFactory.java:175)
        at
com.sun.jndi.ldap.LdapCtxFactory.getUsingURLs(LdapCtxFactory.java:193)
        at
com.sun.jndi.ldap.LdapCtxFactory.getLdapCtxInstance(LdapCtxFactory.java:136)
        at
com.sun.jndi.ldap.LdapCtxFactory.getInitialContext(LdapCtxFactory.java:66)
        at
javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:662)
        at
javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:243)
        at javax.naming.InitialContext.init(InitialContext.java:219)
        at javax.naming.InitialContext.<init>(InitialContext.java:195)
        at
javax.naming.directory.InitialDirContext.<init>(InitialDirContext.java:80)
        at id.security.authentication.service.ldap.Test.main(Test.java:34)

============= SERVER STACK TRACE
java.lang.NullPointerException
        at
sun.nio.ch.WindowsSelectorImpl$SubSelector.processFDSet(WindowsSelectorImpl.java:321)
        at
sun.nio.ch.WindowsSelectorImpl$SubSelector.processSelectedKeys(WindowsSelectorImpl.java:290)
        at
sun.nio.ch.WindowsSelectorImpl$SubSelector.access$2800(WindowsSelectorImpl.java:253)
        at
sun.nio.ch.WindowsSelectorImpl.updateSelectedKeys(WindowsSelectorImpl.java:439)
        at
sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:145)
        at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:59)
        at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:70)
        at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:74)
        at
org.apache.apseda.input.TCPInputManager.run(TCPInputManager.java:158)
        at java.lang.Thread.run(Thread.java:534)