azkaban-aplcache

diff --git a/azkaban-common/src/main/java/azkaban/trigger/TriggerManager.java b/azkaban-common/src/main/java/azkaban/trigger/TriggerManager.java
index 44ad6ca..0538e6e 100644
--- a/azkaban-common/src/main/java/azkaban/trigger/TriggerManager.java
+++ b/azkaban-common/src/main/java/azkaban/trigger/TriggerManager.java
@@ -26,6 +26,7 @@ import azkaban.executor.ExecutableFlow;
 import azkaban.executor.ExecutorManager;
 import azkaban.utils.Props;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.HashMap;
@@ -38,6 +39,7 @@ import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.PriorityBlockingQueue;
 import org.apache.log4j.Logger;
 
+@Singleton
 public class TriggerManager extends EventHandler implements
     TriggerManagerAdapter {
   public static final long DEFAULT_SCANNER_INTERVAL_MS = 60000;

diff --git a/azkaban-web-server/src/test/java/azkaban/webapp/AzkabanWebServerTest.java b/azkaban-web-server/src/test/java/azkaban/webapp/AzkabanWebServerTest.java
index 14b2f0b..4f17833 100644
--- a/azkaban-web-server/src/test/java/azkaban/webapp/AzkabanWebServerTest.java
+++ b/azkaban-web-server/src/test/java/azkaban/webapp/AzkabanWebServerTest.java
@@ -22,12 +22,14 @@ import static azkaban.executor.ExecutorManager.AZKABAN_USE_MULTIPLE_EXECUTORS;
 import static java.util.Objects.requireNonNull;
 import static org.apache.commons.io.FileUtils.deleteQuietly;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
 
 import azkaban.AzkabanCommonModule;
 import azkaban.database.AzkabanDatabaseSetup;
 import azkaban.database.AzkabanDatabaseUpdater;
 import azkaban.executor.Executor;
 import azkaban.executor.ExecutorLoader;
+import azkaban.trigger.TriggerManager;
 import azkaban.utils.Props;
 import com.google.inject.Guice;
 import com.google.inject.Injector;
@@ -111,6 +113,11 @@ public class AzkabanWebServerTest {
     executorLoader.updateExecutor(executor);
 
     assertNotNull(injector.getInstance(AzkabanWebServer.class));
+
+    //Test if triggermanager is singletonly guiced. If not, the below test will fail.
+    final TriggerManager triggerManager1 = requireNonNull(injector.getInstance(TriggerManager.class));
+    final TriggerManager triggerManager2 = requireNonNull(injector.getInstance(TriggerManager.class));
+    assertTrue(triggerManager1 == triggerManager2);
     SERVICE_PROVIDER.unsetInjector();
   }
 }