Update PlatformSpecific to only detect App Engine Standard Environment

hystrix-contrib/hystrix-metrics-event-stream/src/main/java/com/netflix/hystrix/contrib/metrics/eventstream/HystrixMetricsPoller.java

@@ -80,7 +80,7 @@ public HystrixMetricsPoller(MetricsAsJsonPollerListener listener, int delay) {
         this.listener = listener;
 
         ThreadFactory threadFactory = null;
-        if (!PlatformSpecific.isAppEngine()) {
+        if (!PlatformSpecific.isAppEngineStandardEnvironment()) {
             threadFactory = new MetricsPollerThreadFactory();
         } else {
             threadFactory = PlatformSpecific.getAppEngineThreadFactory();

hystrix-core/src/main/java/com/netflix/hystrix/strategy/concurrency/HystrixConcurrencyStrategy.java

@@ -72,7 +72,7 @@ public abstract class HystrixConcurrencyStrategy {
      */
     public ThreadPoolExecutor getThreadPool(final HystrixThreadPoolKey threadPoolKey, HystrixProperty<Integer> corePoolSize, HystrixProperty<Integer> maximumPoolSize, HystrixProperty<Integer> keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {
         ThreadFactory threadFactory = null;
-        if (!PlatformSpecific.isAppEngine()) {
+        if (!PlatformSpecific.isAppEngineStandardEnvironment()) {
             threadFactory = new ThreadFactory() {
                 protected final AtomicInteger threadNumber = new AtomicInteger(0);
 

hystrix-core/src/main/java/com/netflix/hystrix/util/HystrixTimer.java

@@ -153,7 +153,7 @@ public void initialize() {
             int coreSize = propertiesStrategy.getTimerThreadPoolProperties().getCorePoolSize().get();
 
             ThreadFactory threadFactory = null;
-            if (!PlatformSpecific.isAppEngine()) {
+            if (!PlatformSpecific.isAppEngineStandardEnvironment()) {
                 threadFactory = new ThreadFactory() {
                     final AtomicInteger counter = new AtomicInteger();
 

hystrix-core/src/main/java/com/netflix/hystrix/util/PlatformSpecific.java

@@ -19,26 +19,31 @@
 import java.util.concurrent.ThreadFactory;
 
 public class PlatformSpecific {
-    private final boolean isAppEngine;
+    private final boolean isAppEngineStandardEnvironment;
 
     private static PlatformSpecific INSTANCE = new PlatformSpecific();
 
     private PlatformSpecific() {
-        isAppEngine = determineAppEngineReflectively();
+        isAppEngineStandardEnvironment = determineAppEngineReflectively();
     }
 
-    public static boolean isAppEngine() {
-        return INSTANCE.isAppEngine;
+    public static boolean isAppEngineStandardEnvironment() {
+        return INSTANCE.isAppEngineStandardEnvironment;
     }
 
     /*
      * This detection mechanism is from Guava - specifically
      * http://docs.guava-libraries.googlecode.com/git/javadoc/src-html/com/google/common/util/concurrent/MoreExecutors.html#line.766
+     * Added GAE_LONG_APP_ID check to detect only AppEngine Standard Environment
      */
     private static boolean determineAppEngineReflectively() {
         if (System.getProperty("com.google.appengine.runtime.environment") == null) {
             return false;
         }
+        // GAE_LONG_APP_ID is only set in the GAE Flexible Environment, where we want standard threading
+        if (System.getenv("GAE_LONG_APP_ID") != null) {
+            return false;
+        }
         try {
             // If the current environment is null, we're not inside AppEngine.
             return Class.forName("com.google.apphosting.api.ApiProxy")