# LatencyView.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.nhttp.util;

    import org.apache.synapse.commons.jmx.MBeanRegistrar;

    import java.util.ArrayList;
    import java.util.Calendar;
    import java.util.Date;
    import java.util.List;
    import java.util.concurrent.Executors;
    import java.util.concurrent.ScheduledExecutorService;
    import java.util.concurrent.ThreadFactory;
    import java.util.concurrent.TimeUnit;

    /**
     * <p>LatencyView provides statistical information related to the latency (overhead) incurred by
     * the Synapse NHTTP transport, when mediating messages back and forth. Statistics are available
     * under two main categories, namely short term data and long term data. Short term data is
     * statistical information related to the last 15 minutes of execution and these metrics are
     * updated every 5 seconds. Long term data is related to the last 24 hours of execution and
     * they are updated every 5 minutes. Two timer tasks and a single threaded scheduled executor
     * is used to perform these periodic calculations.</p>
     *
     * <p>Latency calculation for a single invocation is carried out by taking timestamps on
     * following events:</p>
     *
     * <ul>
     *  <li>t1 - Receiving a new request (ServerHandler#requestReceived)</li>
     *  <li>t2 - Obtaining a connection to forward the request (ClientHandler#processConnection)</li>
     *  <li>t3 - Reading the complete response from the backend server (ClientHandler#inputReady)</li>
     *  <li>t4 - Writing the complete response to the client (ServerHandler#outputReady)</li>
     * <ul>
     *
     * <p>Having taken these timestamps, the latency for the invocation is calculated as follows:<br/>
     *    Latency = (t4 - t1) - (t3 - t2)
     * </p>
     *
     */
    public class LatencyView implements LatencyViewMBean {

        private static final int SMALL_DATA_COLLECTION_PERIOD = 5;
        private static final int LARGE_DATA_COLLECTION_PERIOD = 5 * 60;

        /** Keeps track of th last reported latency value */
        private LatencyParameter lastLatency = new LatencyParameter(true);

        /** -Following are used to calculate BackEnd(Be) latency - */
        /** Keeps track of th last reported BE latency value */
        private LatencyParameter lastLatencyBe = new LatencyParameter(true);

        private LatencyParameter serverDecodeLatency;

        private LatencyParameter serverEncodeLatency;

        private LatencyParameter clientEncodeLatency;

        private LatencyParameter clientDecodeLatency;

        private LatencyParameter serverWorkerWaitTime;

        private LatencyParameter clientWorkerWaitTime;

        private LatencyParameter requestMediationLatency;

        private LatencyParameter responseMediationLatency;

        private List<LatencyParameter> latencies = new ArrayList<LatencyParameter>(10);

        /** Scheduled executor on which data collectors are executed */
        private ScheduledExecutorService scheduler;

        private Date resetTime = Calendar.getInstance().getTime();

        private String latencyMode;
        private String name;

        public LatencyView(final String latencyMode, boolean isHttps) {
            this(latencyMode, isHttps, "", false);
        }

        public LatencyView(final String latencyMode, boolean isHttps, final String namePostfix, final boolean showAdvancedParameters) {
            this.latencyMode = latencyMode;
            name = "nio-http" + (isHttps ? "s" : "") + namePostfix;

            scheduler =  Executors.newSingleThreadScheduledExecutor(new ThreadFactory() {
                public Thread newThread(Runnable r) {
                    return new Thread(r, latencyMode + "-" + name + "-latency-view");
                }
            });

            scheduler.scheduleAtFixedRate(new ShortTermDataCollector(), SMALL_DATA_COLLECTION_PERIOD,
                    SMALL_DATA_COLLECTION_PERIOD, TimeUnit.SECONDS);
            scheduler.scheduleAtFixedRate(new LongTermDataCollector(), LARGE_DATA_COLLECTION_PERIOD,
                    LARGE_DATA_COLLECTION_PERIOD, TimeUnit.SECONDS);
            boolean registered = false;
            try {
                registered = MBeanRegistrar.getInstance().registerMBean(this, this.latencyMode, name);
            } finally {
                if (!registered) {
                    scheduler.shutdownNow();
                }
            }
            registerAllLatencies(showAdvancedParameters);
        }

        public void destroy() {
            MBeanRegistrar.getInstance().unRegisterMBean(latencyMode, name);
            if (!scheduler.isShutdown()) {
                scheduler.shutdownNow();
            }
        }

        /**
         * Report the timestamp values captured during mediating messages back and forth
         *
         * @param reqArrival The request arrival time
         * @param reqDeparture The request departure time (backend connection establishment)
         * @param resArrival The resoponse arrival time
         * @param resDeparture The response departure time
         */
        private void notifyTimes(long reqArrival, long reqDeparture,
                                 long resArrival, long resDeparture) {
            long latencyBe = (resArrival - reqDeparture);
            long latency = (resDeparture - reqArrival) - latencyBe;
            lastLatency.update(latency);
            lastLatencyBe.update(latencyBe);
        }

        public void notifyTimes(LatencyCollector collector) {
            lastLatency.update(collector.getLatency());
            lastLatencyBe.update(collector.getBackendLatency());
            serverDecodeLatency.update(collector.getServerDecodeLatency());
            clientEncodeLatency.update(collector.getClientEncodeLatency());
            clientDecodeLatency.update(collector.getClientDecodeLatency());
            serverEncodeLatency.update(collector.getServerEncodeLatency());
            serverWorkerWaitTime.update(collector.getServerWorkerQueuedTime());
            clientWorkerWaitTime.update(collector.getClientWorkerQueuedTime());
            requestMediationLatency.update(collector.getServerWorkerLatency());
            responseMediationLatency.update(collector.getClientWorkerLatency());
        }

        private void registerAllLatencies(boolean recordAdditionalLatencies) {
            latencies.add(lastLatency);
            latencies.add(lastLatencyBe);
            serverDecodeLatency = new LatencyParameter(recordAdditionalLatencies);
            serverEncodeLatency = new LatencyParameter(recordAdditionalLatencies);
            clientEncodeLatency = new LatencyParameter(recordAdditionalLatencies);
            clientDecodeLatency = new LatencyParameter(recordAdditionalLatencies);
            serverWorkerWaitTime = new LatencyParameter(recordAdditionalLatencies);
            clientWorkerWaitTime = new LatencyParameter(recordAdditionalLatencies);
            requestMediationLatency = new LatencyParameter(recordAdditionalLatencies);
            responseMediationLatency = new LatencyParameter(recordAdditionalLatencies);
            latencies.add(serverDecodeLatency);
            latencies.add(clientEncodeLatency);
            latencies.add(clientDecodeLatency);
            latencies.add(serverEncodeLatency);
            latencies.add(serverWorkerWaitTime);
            latencies.add(clientWorkerWaitTime);
            latencies.add(requestMediationLatency);
            latencies.add(responseMediationLatency);
        }

        public double getAvg_Latency() {
            return lastLatency.getAllTimeAverage();
        }

        public double getAvg_Client_To_Esb_RequestReadTime() {
            return serverDecodeLatency.getAllTimeAverage();
        }

        public double getAvg_Esb_To_BackEnd_RequestWriteTime() {
            return clientEncodeLatency.getAllTimeAverage();
        }

        public double getAvg_BackEnd_To_Esb_ResponseReadTime() {
            return clientDecodeLatency.getAllTimeAverage();
        }

        public double getAvg_Esb_To_Client_ResponseWriteTime() {
            return serverEncodeLatency.getAllTimeAverage();
        }

        public double get1m_Avg_Client_To_Esb_RequestReadTime() {
            return serverDecodeLatency.getAverageLatency1m();
        }

        public double get1m_Avg_Esb_To_BackEnd_RequestWriteTime() {
            return clientEncodeLatency.getAverageLatency1m();
        }

        public double get1m_Avg_BackEnd_To_Esb_ResponseReadTime() {
            return clientDecodeLatency.getAverageLatency1m();
        }

        public double get1m_Avg_Esb_To_Client_ResponseWriteTime() {
            return serverEncodeLatency.getAverageLatency1m();
        }

        public double get5m_Avg_Client_To_Esb_RequestReadTime() {
            return serverDecodeLatency.getAverageLatency5m();
        }

        public double get5m_Avg_Esb_To_BackEnd_RequestWriteTime() {
            return clientEncodeLatency.getAverageLatency5m();
        }

        public double get5m_Avg_BackEnd_To_Esb_ResponseReadTime() {
            return clientDecodeLatency.getAverageLatency5m();
        }

        public double get5m_Avg_Esb_To_Client_ResponseWriteTime() {
            return serverEncodeLatency.getAverageLatency5m();
        }

        public double get15m_Avg_Client_To_Esb_RequestReadTime() {
            return serverDecodeLatency.getAverageLatency15m();
        }

        public double get15m_Avg_Esb_To_BackEnd_RequestWriteTime() {
            return clientEncodeLatency.getAverageLatency15m();
        }

        public double get15m_Avg_BackEnd_To_Esb_ResponseReadTime() {
            return clientDecodeLatency.getAverageLatency15m();
        }

        public double get15m_Avg_Esb_To_Client_ResponseWriteTime() {
            return serverEncodeLatency.getAverageLatency15m();
        }

        public double getAvg_ClientWorker_QueuedTime() {
            return clientWorkerWaitTime.getAllTimeAverage();
        }

        public double get1m_Avg_ClientWorker_QueuedTime() {
            return clientWorkerWaitTime.getAverageLatency1m();
        }

        public double get5m_Avg_ClientWorker_QueuedTime() {
            return clientWorkerWaitTime.getAverageLatency5m();
        }

        public double get15m_Avg_ClientWorker_QueuedTime() {
            return clientWorkerWaitTime.getAverageLatency15m();
        }

        public double getAvg_ServerWorker_QueuedTime() {
            return serverWorkerWaitTime.getAllTimeAverage();
        }

        public double get1m_Avg_ServerWorker_QueuedTime() {
            return serverWorkerWaitTime.getAverageLatency1m();
        }

        public double get5m_Avg_ServerWorker_QueuedTime() {
            return serverWorkerWaitTime.getAverageLatency5m();
        }

        public double get15m_Avg_ServerWorker_QueuedTime() {
            return serverWorkerWaitTime.getAverageLatency15m();
        }

        public double get1m_Avg_Latency() {
            return lastLatency.getAverageLatency1m();
        }

        public double get5m_Avg_Latency() {
            return lastLatency.getAverageLatency5m();
        }

        public double get15m_Avg_Latency() {
            return lastLatency.getAverageLatency15m();
        }

        public double get1h_Avg_Latency() {
            return lastLatency.getAverageLatency1h();
        }

        public double get8h_Avg_Latency() {
            return lastLatency.getAverageLatency8h();
        }

        public double get24h_Avg_Latency() {
            return lastLatency.getAverageLatency24h();
        }

        public double getAvg_Latency_BackEnd() {
            return lastLatencyBe.getAllTimeAverage();
        }

        public double get1m_Avg_Latency_BackEnd() {
            return lastLatencyBe.getAverageLatency1m();
        }

        public double get5m_Avg_Latency_BackEnd() {
            return lastLatencyBe.getAverageLatency5m();
        }

        public double get15m_Avg_Latency_BackEnd() {
            return lastLatencyBe.getAverageLatency15m();
        }

        public double get1h_Avg_Latency_BackEnd() {
            return lastLatencyBe.getAverageLatency1h();
        }

        public double get8h_Avg_Latency_BackEnd() {
            return lastLatencyBe.getAverageLatency8h();
        }

        public double get24h_Avg_Latency_BackEnd() {
            return lastLatencyBe.getAverageLatency24h();
        }

        public double get1h_Avg_Client_To_Esb_RequestReadTime() {
            return serverDecodeLatency.getAverageLatency1h();
        }

        public double get1h_Avg_Esb_To_BackEnd_RequestWriteTime() {
            return clientEncodeLatency.getAverageLatency1h();
        }

        public double get1h_Avg_BackEnd_To_Esb_ResponseReadTime() {
            return clientDecodeLatency.getAverageLatency1h();
        }

        public double get1h_Avg_Esb_To_Client_ResponseWriteTime() {
            return serverEncodeLatency.getAverageLatency1h();
        }

        public double get1h_Avg_ServerWorker_QueuedTime() {
            return serverWorkerWaitTime.getAverageLatency1h();
        }

        public double get1h_Avg_ClientWorker_QueuedTime() {
            return clientWorkerWaitTime.getAverageLatency1h();
        }

        public double get8h_Avg_Client_To_Esb_RequestReadTime() {
            return serverDecodeLatency.getAverageLatency8h();
        }

        public double get8h_Avg_Esb_To_BackEnd_RequestWriteTime() {
            return clientEncodeLatency.getAverageLatency8h();
        }

        public double get8h_Avg_BackEnd_To_Esb_ResponseReadTime() {
            return clientDecodeLatency.getAverageLatency8h();
        }

        public double get8h_Avg_Esb_To_Client_ResponseWriteTime() {
            return serverEncodeLatency.getAverageLatency8h();
        }

        public double get8h_Avg_ServerWorker_QueuedTime() {
            return serverWorkerWaitTime.getAverageLatency8h();
        }

        public double get8h_Avg_ClientWorker_QueuedTime() {
            return clientWorkerWaitTime.getAverageLatency8h();
        }

        public double get24h_Avg_Client_To_Esb_RequestReadTime() {
            return serverDecodeLatency.getAverageLatency24h();
        }

        public double get24h_Avg_Esb_To_BackEnd_RequestWriteTime() {
            return clientEncodeLatency.getAverageLatency24h();
        }

        public double get24h_Avg_BackEnd_To_Esb_ResponseReadTime() {
            return clientDecodeLatency.getAverageLatency24h();
        }

        public double get24h_Avg_Esb_To_Client_ResponseWriteTime() {
            return serverEncodeLatency.getAverageLatency24h();
        }

        public double get24h_Avg_ServerWorker_QueuedTime() {
            return serverWorkerWaitTime.getAverageLatency24h();
        }

        public double get24h_Avg_ClientWorker_QueuedTime() {
            return clientWorkerWaitTime.getAverageLatency24h();
        }

        public double getAvg_request_Mediation_Latency() {
            return requestMediationLatency.getAllTimeAverage();
        }

        public double getAvg_response_Mediation_Latency() {
            return responseMediationLatency.getAllTimeAverage();
        }

        public double get1m_Avg_request_Mediation_Latency() {
            return requestMediationLatency.getAverageLatency1m();
        }

        public double get1m_Avg_response_Mediation_Latency() {
            return responseMediationLatency.getAverageLatency1m();
        }

        public double get5m_Avg_request_Mediation_Latency() {
            return requestMediationLatency.getAverageLatency5m();
        }

        public double get5m_Avg_response_Mediation_Latency() {
            return responseMediationLatency.getAverageLatency5m();
        }

        public double get15m_Avg_request_Mediation_Latency() {
            return requestMediationLatency.getAverageLatency15m();
        }

        public double get15m_Avg_response_Mediation_Latency() {
            return responseMediationLatency.getAverageLatency15m();
        }

        public double get1h_Avg_request_Mediation_Latency() {
            return requestMediationLatency.getAverageLatency1h();
        }

        public double get1h_Avg_response_Mediation_Latency() {
            return responseMediationLatency.getAverageLatency1h();
        }

        public double get8h_Avg_request_Mediation_Latency() {
            return requestMediationLatency.getAverageLatency8h();
        }

        public double get8h_Avg_response_Mediation_Latency() {
            return responseMediationLatency.getAverageLatency8h();
        }

        public double get24h_Avg_request_Mediation_Latency() {
            return requestMediationLatency.getAverageLatency24h();
        }

        public double get24h_Avg_response_Mediation_Latency() {
            return responseMediationLatency.getAverageLatency24h();
        }

        public void reset() {
            for (LatencyParameter latency : latencies) {
                latency.reset();
            }
            resetTime = Calendar.getInstance().getTime();
        }

        public Date getLastResetTime() {
            return resetTime;
        }

        private class ShortTermDataCollector implements Runnable {
            public void run() {
                for (LatencyParameter latency : latencies) {
                    latency.updateCache();
                }
            }
        }

        private class LongTermDataCollector implements Runnable {
            public void run() {
                for (LatencyParameter latency : latencies) {
                    latency.updateLongTermCache();
                }
            }
        }
    }