co.cask.tigon.sql.internal.HealthInspector.java Source code

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Here is the source code for co.cask.tigon.sql.internal.HealthInspector.java

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/*
 * Copyright  2014 Cask Data, Inc.
 *
 * Licensed 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 co.cask.tigon.sql.internal;

import co.cask.tigon.sql.conf.Constants;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import com.google.common.util.concurrent.AbstractIdleService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Map;
import java.util.Set;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;

/**
 * Keeps track of the number of heartbeat records received from all SQL Compiler processes.
 */
public class HealthInspector extends AbstractIdleService {
    private static final Logger LOG = LoggerFactory.getLogger(HealthInspector.class);
    private ScheduledFuture monitorFuture;
    private ScheduledFuture initialTimeout;
    private final ProcessMonitor serviceFailed;
    private final Set<String> heartbeatCounter;
    private final Set<String> modelCounter;

    /**
     * Constructor for HealthInspector which ensures the liveness of the SQL Compiler processes.
     * If the class fails to detect a heartbeat from every registered process in the last two seconds then this class
     * invokes the {@link ProcessMonitor#notifyFailure(java.util.Set)} defined in the {@link ProcessMonitor} object.
     *
     * @param processMonitor The reference of the class that implements
     * {@link ProcessMonitor#notifyFailure(java.util.Set)}
     */
    public HealthInspector(ProcessMonitor processMonitor) {
        serviceFailed = processMonitor;
        Map<String, Boolean> heartbeatMap = Maps.newConcurrentMap();
        Map<String, Boolean> modelMap = Maps.newConcurrentMap();
        heartbeatCounter = Sets.newSetFromMap(heartbeatMap);
        modelCounter = Sets.newSetFromMap(modelMap);
    }

    /**
     * Registers the provided process name for health inspection.
     * This function should be invoked for every process that has to be monitored by this class.
     *
     * @param processName The unique name of the process that is being registered for monitoring
     */
    public void register(String processName) {
        modelCounter.add(processName);
    }

    /**
     * Logs the ping generated by the given process name.
     * This function should be invoked for every ping that is received.
     *
     * @param processName Name of the pinging process
     */
    public void ping(String processName) {
        heartbeatCounter.add(processName);
    }

    private boolean checkState() {
        // Check if all processes returned at least one ping since the last call. Actual expectation is 1 per second.
        if (!heartbeatCounter.containsAll(modelCounter)) {
            LOG.info("Heartbeat detection failed");
            return false;
        }
        heartbeatCounter.clear();
        return true;
    }

    /**
     * This function initiates the monitoring services that checks if a heartbeat from each registered process was
     * detected in the last 2 seconds. In case of failure, {@link ProcessMonitor#notifyFailure(java.util.Set)} of the
     * constructor's parameter object is invoked.
     */
    @Override
    protected void startUp() throws Exception {
        initialTimeout = Executors.newScheduledThreadPool(1).schedule(new Runnable() {
            @Override
            public void run() {
                if (modelCounter.size() <= 0) {
                    LOG.info("Heartbeat detection failed");
                    serviceFailed.notifyFailure(null);
                }
            }
        }, Constants.INITIALIZATION_TIMEOUT, TimeUnit.SECONDS);
        monitorFuture = Executors.newScheduledThreadPool(1).scheduleWithFixedDelay(new Runnable() {
            @Override
            public void run() {
                if (!checkState()) {
                    Set<String> missingHeartbeatRecord = Sets.newHashSet(modelCounter);
                    missingHeartbeatRecord.removeAll(heartbeatCounter);
                    serviceFailed.notifyFailure(missingHeartbeatRecord);
                }
            }
        }, 2 * Constants.HEARTBEAT_FREQUENCY, Constants.HEARTBEAT_FREQUENCY, TimeUnit.SECONDS);
    }

    /**
     * Stops the monitoring service.
     */
    @Override
    protected void shutDown() throws Exception {
        monitorFuture.cancel(true);
        modelCounter.clear();
    }
}