Fixed ThreadPool keeping standalone application alive

CHANGELOG.md

@@ -1,10 +1,13 @@
 # CHANGELOG
 
+# Version 2.1.2
+- Fix [#662](https://github.com/Microsoft/ApplicationInsights-Java/issues/662). Updated thread pool to properly shutdown all threads.
+
 # Version 2.1.1
 - Introducing support for SpringBoot via Application-Insights-SpringBoot-Starter [#646](https://github.com/Microsoft/ApplicationInsights-Java/pull/646). This is currently in beta.
 - In order to add support for SpringBoot starter some fields in core SDK are made public.
 - Introduced public constructor in `InProcessTelemetryChannel.java` class.
-- Introduced a public method `getActiveWithoutInitializingConfig()` in `TelemetryConfiguration.java` class.  
+- Introduced a public method `getActiveWithoutInitializingConfig()` in `TelemetryConfiguration.java` class. 
 
 # Version 2.1.0
 - Introduced Heartbeat feature which sends periodic heartbeats with basic information about application and runtime to Application Insights.

core/src/main/java/com/microsoft/applicationinsights/internal/channel/common/ApacheSender43.java

@@ -24,12 +24,15 @@
 import java.io.IOException;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.LinkedBlockingDeque;
+import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
 
 import com.microsoft.applicationinsights.internal.logger.InternalLogger;
 
 import com.microsoft.applicationinsights.internal.shutdown.SDKShutdownActivity;
+import com.microsoft.applicationinsights.internal.util.ThreadPoolUtils;
 import org.apache.http.HttpResponse;
 import org.apache.http.client.HttpClient;
 import org.apache.http.client.config.RequestConfig;
@@ -46,7 +49,9 @@ final class ApacheSender43 implements ApacheSender {
 
     private final AtomicReference<CloseableHttpClient> httpClientRef = new AtomicReference<>();
     private volatile boolean isClientInitialized = false;
-    private final ExecutorService initializer = Executors.newSingleThreadExecutor();
+    private final ExecutorService initializer = new ThreadPoolExecutor(0, 1, 2, TimeUnit.SECONDS, new LinkedBlockingDeque<Runnable>(),
+            ThreadPoolUtils.createNamedDaemonThreadFactory(ApacheSender43.class.getSimpleName()+"_initializer"));
+
     public ApacheSender43() {
         initializer.execute(new Runnable() {
 

core/src/main/java/com/microsoft/applicationinsights/internal/shutdown/SDKShutdownActivity.java

@@ -200,7 +200,9 @@ private SDKShutdownAction getShutdownAction() {
                 if (shutdownAction == null) {
                     try {
                         shutdownAction = new SDKShutdownAction();
-                        Runtime.getRuntime().addShutdownHook(new Thread(shutdownAction, SDKShutdownActivity.class.getSimpleName()));
+                        Thread t = new Thread(shutdownAction, SDKShutdownActivity.class.getSimpleName());
+                        t.setDaemon(true);
+                        Runtime.getRuntime().addShutdownHook(t);
                     } catch (Exception e) {
                         InternalLogger.INSTANCE.error("Error while adding shutdown hook in getShutDownThread call");
                         InternalLogger.INSTANCE.trace("Stack trace generated is %s", ExceptionUtils.getStackTrace(e));