Fix for AsyncHttpClient#192.

Author: rlubke

api/src/main/java/org/asynchttpclient/AsyncHttpClientConfig.java

@@ -106,6 +106,7 @@ public class AsyncHttpClientConfig {
     protected boolean allowSslConnectionPool;
     protected boolean useRawUrl;
     protected boolean removeQueryParamOnRedirect;
+    protected boolean managedApplicationThreadPool;
     protected HostnameVerifier hostnameVerifier;
     protected int ioThreadMultiplier;
     protected boolean strict302Handling;
@@ -190,6 +191,7 @@ private AsyncHttpClientConfig(int maxTotalConnections,
         this.useRelativeURIsWithSSLProxies = useRelativeURIsWithSSLProxies;
 
         if (applicationThreadPool == null) {
+            managedApplicationThreadPool = true;
             this.applicationThreadPool = Executors.newCachedThreadPool();
         } else {
             this.applicationThreadPool = applicationThreadPool;
@@ -342,6 +344,19 @@ public ExecutorService executorService() {
         return applicationThreadPool;
     }
 
+    /**
+     * @return <code>true</code> if this <code>AsyncHttpClientConfig</code> instance created the
+     *  {@link ExecutorService} returned by {@link #executorService()}, otherwise returns <code>false</code>.
+     *  The return from this method is typically used by the various provider implementations to determine
+     *  if it should shutdown the {@link ExecutorService} when the {@link AsyncHttpClient} is closed.  Developers
+     *  should take care and not share managed {@link ExecutorService} instances between client instances.
+     *
+     * @since 2.2.0
+     */
+    public boolean isManagedExecutorService() {
+        return managedApplicationThreadPool;
+    }
+
     /**
      * An instance of {@link ProxyServer} used by an {@link AsyncHttpClient}
      *

providers/grizzly/src/main/java/org/asynchttpclient/providers/grizzly/GrizzlyAsyncHttpProvider.java

@@ -183,9 +183,13 @@ public void close() {
         try {
             connectionManager.destroy();
             clientTransport.stop();
-            final ExecutorService service = clientConfig.executorService();
-            if (service != null) {
-                service.shutdown();
+            if (clientConfig.isManagedExecutorService()) {
+                final ExecutorService service = clientConfig.executorService();
+                // service may be null due to a custom configuration that
+                // leverages Grizzly's SameThreadIOStrategy.
+                if (service != null) {
+                    service.shutdown();
+                }
             }
             if (timeoutExecutor != null) {
                 timeoutExecutor.stop();

providers/netty/src/main/java/org/asynchttpclient/providers/netty/NettyAsyncHttpProvider.java

@@ -828,7 +828,9 @@ public void close() {
                 }
             }
 
-            config.executorService().shutdown();
+            if (config.isManagedExecutorService()) {
+                config.executorService().shutdown();
+            }
             config.reaper().shutdown();
             if (this.allowReleaseSocketChannelFactory) {
                 socketChannelFactory.releaseExternalResources();