/*
 * Copyright 2015-present Open Networking Foundation
 *
 * 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 org.onlab.util;

import org.onlab.metrics.MetricsService;

import java.util.Timer;
import java.util.concurrent.ExecutorService;

import static com.google.common.base.Preconditions.checkArgument;
import static java.util.concurrent.Executors.newFixedThreadPool;
import static java.util.concurrent.Executors.newSingleThreadExecutor;
import static org.onlab.util.Tools.groupedThreads;

/**
 * Utility for managing a set of shared execution resources, such as a timer,
 * single thread executor and thread pool executor for use by various parts of
 * the platform or by applications.
 * <p>
 * Whenever possible, use of these shared resources is encouraged over creating
 * separate ones.
 * </p>
 */
public final class SharedExecutors {

    public static final int DEFAULT_POOL_SIZE = 30;

    private static SharedExecutorService singleThreadExecutor;
    private static SharedExecutorService poolThreadExecutor;

    private static SharedTimer sharedTimer;

    // Ban public construction
    private SharedExecutors() {
    }

    /**
     * Returns the shared single thread executor.
     *
     * @return shared single thread executor
     */
    public static ExecutorService getSingleThreadExecutor() {
        setup();
        return singleThreadExecutor;
    }

    /**
     * Returns the shared thread pool executor.
     *
     * @return shared executor pool
     */
    public static ExecutorService getPoolThreadExecutor() {
        setup();
        return poolThreadExecutor;
    }

    /**
     * Returns the shared timer.
     *
     * @return shared timer
     */
    public static Timer getTimer() {
        setup();
        return sharedTimer;
    }

    /**
     * Sets the shared thread pool size.
     *
     * @param poolSize new pool size
     */
    public static void setPoolSize(int poolSize) {
        checkArgument(poolSize > 0, "Shared pool size size must be greater than 0");
        poolThreadExecutor.setBackingExecutor(
                newFixedThreadPool(poolSize, groupedThreads("onos/shared",
                                                            "onos-pool-executor-%d")));
    }

    /**
     * Enables or disables calculation of the pool performance metrics. If
     * the metrics service is not null metric collection will be enabled;
     * otherwise it will be disabled.
     *
     * @param metricsService optional metric service
     */
    public static void setMetricsService(MetricsService metricsService) {
        poolThreadExecutor.setMetricsService(metricsService);
    }

    /**
     * Shuts down all shared timers and executors and therefore should be
     * called only by the framework.
     */
    public static void shutdown() {
        sharedTimer.shutdown();
        singleThreadExecutor.backingExecutor().shutdown();
        poolThreadExecutor.backingExecutor().shutdown();
        sharedTimer = null;
        singleThreadExecutor = null;
        poolThreadExecutor = null;
    }

    private static synchronized void setup() {
        if (sharedTimer == null) {
            sharedTimer = new SharedTimer();

            singleThreadExecutor =
                new SharedExecutorService(
                    newSingleThreadExecutor(groupedThreads("onos/shared",
                        "onos-single-executor")));

            poolThreadExecutor =
                new SharedExecutorService(
                    newFixedThreadPool(DEFAULT_POOL_SIZE,
                        groupedThreads("onos/shared",
                            "onos-pool-executor-%d")));
        }
    }

    // Timer extension which does not allow outside cancel method.
    private static class SharedTimer extends Timer {

        public SharedTimer() {
            super("onos-shared-timer");
        }

        @Override
        public void cancel() {
            throw new UnsupportedOperationException("Cancel of shared timer is not allowed");
        }

        private void shutdown() {
            super.cancel();
        }
    }

}

@@ -1575,16 +1575,82 @@
 edTimer;
+%0A    private static final Object SHARED_TIMER_LOCK = new Object();
 %0A%0A    //
@@ -3368,32 +3368,79 @@
 id shutdown() %7B%0A
+        synchronized (SHARED_TIMER_LOCK) %7B%0A    
         sharedTi
@@ -3455,32 +3455,36 @@
 down();%0A        
+    
 singleThreadExec
@@ -3518,32 +3518,36 @@
 down();%0A        
+  
+  
 poolThreadExecut
@@ -3571,32 +3571,36 @@
 r().shutdown();%0A
+    
         sharedTi
@@ -3611,32 +3611,36 @@
 = null;%0A        
+    
 singleThreadExec
@@ -3652,32 +3652,36 @@
 = null;%0A        
+  
+  
 poolThreadExecut
@@ -3687,24 +3687,34 @@
 tor = null;%0A
+        %7D%0A
     %7D%0A%0A    p
@@ -3731,32 +3731,62 @@
 tic 
-synchronized void setup(
+void setup() %7B%0A        synchronized (SHARED_TIMER_LOCK
 ) %7B%0A
@@ -3793,16 +3793,20 @@
         
+ 
+   
 if (shar
@@ -3820,24 +3820,28 @@
  == null) %7B%0A
+    
             
@@ -3870,24 +3870,28 @@
 edTimer();%0A%0A
+    
             
@@ -3921,32 +3921,36 @@
                 
+    
 new SharedExecut
@@ -3952,32 +3952,36 @@
 xecutorService(%0A
+    
                 
@@ -4030,32 +4030,36 @@
 (%22onos/shared%22,%0A
+    
                 
@@ -4098,32 +4098,36 @@
 );%0A%0A            
+    
 poolThreadExecut
@@ -4123,32 +4123,36 @@
 hreadExecutor =%0A
+    
                 
@@ -4190,32 +4190,36 @@
                 
+   
+ 
 newFixedThreadPo
@@ -4240,16 +4240,20 @@
 L_SIZE,%0A
+    
         
@@ -4318,32 +4318,36 @@
                 
+    
 %22onos-pool-execu
@@ -4354,24 +4354,38 @@
 tor-%25d%22)));%0A
+            %7D%0A
         %7D%0A  

Fix Sonar complaints about synchronization