[DIRMINA-1086] IoSessions closed by filterChain.fireExceptionCaught(e) are kept in memory

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Not A Problem
• Affects Version/s: 2.0.17
• Component/s: Core
• Environment: mina in ApacheDS
• Assignee: Unassigned
• Reporter: Wenxiang Qiu
• Created: 04/Jun/18 09:01
• Updated: 19/Feb/19 16:41
• Resolved: 19/Feb/19 16:41

Description

I'm using ApacheDS, I found this problem and am not sure if it's a mina issue or an ApacheDS issue.

 

AbstractPollingIoProcessor#read looks like this:

 

private void read(S session) {
    IoSessionConfig config = session.getConfig();
    int bufferSize = config.getReadBufferSize();
    IoBuffer buf = IoBuffer.allocate(bufferSize);

    final boolean hasFragmentation = session.getTransportMetadata().hasFragmentation();

    try {
        /* omitted */

        if (ret < 0) {
            IoFilterChain filterChain = session.getFilterChain();
            filterChain.fireInputClosed();
        }
    } catch (Exception e) {
        if ((e instanceof IOException) &&
(!(e instanceof PortUnreachableException)
|| !AbstractDatagramSessionConfig.class.isAssignableFrom(config.getClass())
|| ((AbstractDatagramSessionConfig) config).isCloseOnPortUnreachable())) {
            scheduleRemove(session);
        }

        IoFilterChain filterChain = session.getFilterChain();
        filterChain.fireExceptionCaught(e);
    }
}

 

When an exception occurs with an LDAP connection, e.g. Connection reset by peer, catch block is entered and ExcpetionCaught gets fired:

filterChain.fireExceptionCaught(e);

The session is thus closed by LdapProtocolHandler#exceptionCaught:

public void exceptionCaught( IoSession session, Throwable cause )
{
    if ( cause.getCause() instanceof ResponseCarryingMessageException )
    {
        ResponseCarryingMessageException rcme = ( ResponseCarryingMessageException ) cause.getCause();

        if ( rcme.getResponse() != null )
        {
            session.write( rcme.getResponse() );
            return;
        }
    }

    LOG.warn( "Unexpected exception forcing session to close: sending disconnect notice to client.", cause );

    session.write( NoticeOfDisconnect.PROTOCOLERROR );
    LdapSession ldapSession = this.ldapServer.getLdapSessionManager().removeLdapSession( session );
    cleanUpSession( ldapSession );
    session.close( true );
}

Although this session is scheduled for removal, due to its state being closing, AbstractPollingIoProcessor#removeSessions does nothing about this session:

case CLOSING:
    // Skip if channel is already closed
    // In any case, remove the session from the queue
    removedSessions++;
    break;

Consequence is that this session is kept forever in IoServiceListenerSupport.managedSessions, and as its size grows, this ConcurrentMap can take up quite a large amount of memory.