# ActiveConnectionMonitor.java

    /*
    *  Licensed to the Apache Software Foundation (ASF) under one
    *  or more contributor license agreements.  See the NOTICE file
    *  distributed with this work for additional information
    *  regarding copyright ownership.  The ASF licenses this file
    *  to you under the Apache License, Version 2.0 (the
    *  "License"); you may not use this file except in compliance
    *  with the License.  You may obtain a copy of the License at
    *
    *   http://www.apache.org/licenses/LICENSE-2.0
    *
    *  Unless required by applicable law or agreed to in writing,
    *  software distributed under the License is distributed on an
    *   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    *  KIND, either express or implied.  See the License for the
    *  specific language governing permissions and limitations
    *  under the License.
    */
    package org.apache.synapse.transport.passthru.util;

    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.apache.http.impl.nio.reactor.DefaultListeningIOReactor;
    import org.apache.synapse.transport.passthru.jmx.PassThroughTransportMetricsCollector;

    import java.io.IOException;

    /**
     * PassThroughTransport ActiveConnectionMonitor
     */
    public class ActiveConnectionMonitor implements Runnable {

       private static final Log log = LogFactory.getLog(ActiveConnectionMonitor.class);

       /* Delay between each monitoring tasks */
       private PassThroughTransportMetricsCollector pttMetricsCollector;
       private DefaultListeningIOReactor ioReactor;

       /* Maximum Active Connections */
       private int maxActive;

       public ActiveConnectionMonitor(PassThroughTransportMetricsCollector metrics, DefaultListeningIOReactor ior, int maxActiveConnections) {
            ioReactor = ior;
            pttMetricsCollector = metrics;
            maxActive = maxActiveConnections;
        }

        public void run() {
            try {
                if (maxActive > 0) {
                    if (log.isDebugEnabled()) {
                        log.debug("Active Connection Count : " + pttMetricsCollector.getActiveConnectionCount());
                    }

                    if (pttMetricsCollector.getActiveConnectionCount() > maxActive) {
                        log.warn("Pausing the Listening IOReactor : Too many open connections than the max_open_connections limit.");
                        ioReactor.pause();
                    } else {
                        ioReactor.resume();
                    }
                }
            } catch (IOException e) {
                log.warn("Active Connection Monitor Task - IO Error while pausing/resuming the IOReactor ");
            }
        }
    }