Gracefully shutdown example servers (#6512)

api/src/main/java/io/grpc/Server.java

@@ -107,6 +107,10 @@ public abstract class Server {
    * After this call returns, this server has released the listening socket(s) and may be reused by
    * another server.
    *
+   * <p>Note that this method will not wait for preexisting calls to finish before returning.
+   * {@link #awaitTermination()} or {@link #awaitTermination(long, TimeUnit)} needs to be called to
+   * wait for existing calls to finish.
+   *
    * @return {@code this} object
    * @since 1.0.0
    */

examples/src/main/java/io/grpc/examples/advanced/HelloJsonServer.java

@@ -28,6 +28,7 @@ import io.grpc.examples.helloworld.HelloRequest;
 import io.grpc.stub.ServerCalls.UnaryMethod;
 import io.grpc.stub.StreamObserver;
 import java.io.IOException;
+import java.util.concurrent.TimeUnit;
 import java.util.logging.Logger;
 
 /**
@@ -59,15 +60,19 @@ public class HelloJsonServer {
       public void run() {
         // Use stderr here since the logger may have been reset by its JVM shutdown hook.
         System.err.println("*** shutting down gRPC server since JVM is shutting down");
-        HelloJsonServer.this.stop();
+        try {
+          HelloJsonServer.this.stop();
+        } catch (InterruptedException e) {
+          e.printStackTrace(System.err);
+        }
         System.err.println("*** server shut down");
       }
     });
   }
 
-  private void stop() {
+  private void stop() throws InterruptedException {
     if (server != null) {
-      server.shutdown();
+      server.shutdown().awaitTermination(30, TimeUnit.SECONDS);
     }
   }
 

examples/src/main/java/io/grpc/examples/experimental/CompressingHelloWorldServerAllMethods.java

@@ -17,6 +17,7 @@
 package io.grpc.examples.experimental;
 
 import java.io.IOException;
+import java.util.concurrent.TimeUnit;
 import java.util.logging.Logger;
 
 import io.grpc.Metadata;
@@ -33,7 +34,7 @@ import io.grpc.stub.StreamObserver;
 
 /**
  * Server that manages startup/shutdown of a {@code Greeter} server
- * with an interceptor to enable compression for all responses. 
+ * with an interceptor to enable compression for all responses.
  */
 public class CompressingHelloWorldServerAllMethods {
   private static final Logger logger = Logger.getLogger(CompressingHelloWorldServerAllMethods.class.getName());
@@ -62,15 +63,19 @@ public class CompressingHelloWorldServerAllMethods {
       public void run() {
         // Use stderr here since the logger may have been reset by its JVM shutdown hook.
         System.err.println("*** shutting down gRPC server since JVM is shutting down");
-        CompressingHelloWorldServerAllMethods.this.stop();
+        try {
+          CompressingHelloWorldServerAllMethods.this.stop();
+        } catch (InterruptedException e) {
+          e.printStackTrace(System.err);
+        }
         System.err.println("*** server shut down");
       }
     });
   }
 
-  private void stop() {
+  private void stop() throws InterruptedException {
     if (server != null) {
-      server.shutdown();
+      server.shutdown().awaitTermination(30, TimeUnit.SECONDS);
     }
   }
 

examples/src/main/java/io/grpc/examples/experimental/CompressingHelloWorldServerPerMethod.java

@@ -17,6 +17,7 @@
 package io.grpc.examples.experimental;
 
 import java.io.IOException;
+import java.util.concurrent.TimeUnit;
 import java.util.logging.Logger;
 
 import io.grpc.Server;
@@ -49,15 +50,19 @@ public class CompressingHelloWorldServerPerMethod {
       public void run() {
         // Use stderr here since the logger may have been reset by its JVM shutdown hook.
         System.err.println("*** shutting down gRPC server since JVM is shutting down");
-        CompressingHelloWorldServerPerMethod.this.stop();
+        try {
+          CompressingHelloWorldServerPerMethod.this.stop();
+        } catch (InterruptedException e) {
+          e.printStackTrace(System.err);
+        }
         System.err.println("*** server shut down");
       }
     });
   }
 
-  private void stop() {
+  private void stop() throws InterruptedException {
     if (server != null) {
-      server.shutdown();
+      server.shutdown().awaitTermination(30, TimeUnit.SECONDS);
     }
   }
 

examples/src/main/java/io/grpc/examples/header/CustomHeaderServer.java

@@ -24,6 +24,7 @@ import io.grpc.examples.helloworld.HelloReply;
 import io.grpc.examples.helloworld.HelloRequest;
 import io.grpc.stub.StreamObserver;
 import java.io.IOException;
+import java.util.concurrent.TimeUnit;
 import java.util.logging.Logger;
 
 /**
@@ -48,15 +49,19 @@ public class CustomHeaderServer {
       public void run() {
         // Use stderr here since the logger may have been reset by its JVM shutdown hook.
         System.err.println("*** shutting down gRPC server since JVM is shutting down");
-        CustomHeaderServer.this.stop();
+        try {
+          CustomHeaderServer.this.stop();
+        } catch (InterruptedException e) {
+          e.printStackTrace(System.err);
+        }
         System.err.println("*** server shut down");
       }
     });
   }
 
-  private void stop() {
+  private void stop() throws InterruptedException {
     if (server != null) {
-      server.shutdown();
+      server.shutdown().awaitTermination(30, TimeUnit.SECONDS);
     }
   }
 

examples/src/main/java/io/grpc/examples/hedging/HedgingHelloWorldServer.java

@@ -29,6 +29,7 @@ import io.grpc.examples.helloworld.HelloRequest;
 import io.grpc.stub.StreamObserver;
 import java.io.IOException;
 import java.util.Random;
+import java.util.concurrent.TimeUnit;
 import java.util.logging.Logger;
 
 /**
@@ -53,15 +54,19 @@ public class HedgingHelloWorldServer {
       public void run() {
         // Use stderr here since the logger may have been reset by its JVM shutdown hook.
         System.err.println("*** shutting down gRPC server since JVM is shutting down");
-        HedgingHelloWorldServer.this.stop();
+        try {
+          HedgingHelloWorldServer.this.stop();
+        } catch (InterruptedException e) {
+          e.printStackTrace(System.err);
+        }
         System.err.println("*** server shut down");
       }
     });
   }
 
-  private void stop() {
+  private void stop() throws InterruptedException {
     if (server != null) {
-      server.shutdown();
+      server.shutdown().awaitTermination(30, TimeUnit.SECONDS);
     }
   }
 

examples/src/main/java/io/grpc/examples/helloworld/HelloWorldServer.java

@@ -20,6 +20,7 @@ import io.grpc.Server;
 import io.grpc.ServerBuilder;
 import io.grpc.stub.StreamObserver;
 import java.io.IOException;
+import java.util.concurrent.TimeUnit;
 import java.util.logging.Logger;
 
 /**
@@ -43,15 +44,19 @@ public class HelloWorldServer {
       public void run() {
         // Use stderr here since the logger may have been reset by its JVM shutdown hook.
         System.err.println("*** shutting down gRPC server since JVM is shutting down");
-        HelloWorldServer.this.stop();
+        try {
+          HelloWorldServer.this.stop();
+        } catch (InterruptedException e) {
+          e.printStackTrace(System.err);
+        }
         System.err.println("*** server shut down");
       }
     });
   }
 
-  private void stop() {
+  private void stop() throws InterruptedException {
     if (server != null) {
-      server.shutdown();
+      server.shutdown().awaitTermination(30, TimeUnit.SECONDS);
     }
   }
 

examples/src/main/java/io/grpc/examples/manualflowcontrol/ManualFlowControlServer.java

@@ -23,6 +23,7 @@ import io.grpc.stub.ServerCallStreamObserver;
 import io.grpc.stub.StreamObserver;
 
 import java.io.IOException;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.logging.Logger;
 
@@ -135,8 +136,13 @@ public class ManualFlowControlServer {
     Runtime.getRuntime().addShutdownHook(new Thread() {
       @Override
       public void run() {
-        logger.info("Shutting down");
-        server.shutdown();
+        // Use stderr here since the logger may have been reset by its JVM shutdown hook.
+        System.err.println("Shutting down");
+        try {
+          server.shutdown().awaitTermination(30, TimeUnit.SECONDS);
+        } catch (InterruptedException e) {
+          e.printStackTrace(System.err);
+        }
       }
     });
     server.awaitTermination();

examples/src/main/java/io/grpc/examples/routeguide/RouteGuideServer.java

@@ -36,6 +36,7 @@ import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.TimeUnit;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -73,16 +74,20 @@ public class RouteGuideServer {
       public void run() {
         // Use stderr here since the logger may have been reset by its JVM shutdown hook.
         System.err.println("*** shutting down gRPC server since JVM is shutting down");
-        RouteGuideServer.this.stop();
+        try {
+          RouteGuideServer.this.stop();
+        } catch (InterruptedException e) {
+          e.printStackTrace(System.err);
+        }
         System.err.println("*** server shut down");
       }
     });
   }
 
   /** Stop serving requests and shutdown resources. */
-  public void stop() {
+  public void stop() throws InterruptedException {
     if (server != null) {
-      server.shutdown();
+      server.shutdown().awaitTermination(30, TimeUnit.SECONDS);
     }
   }
 

examples/src/test/java/io/grpc/examples/routeguide/RouteGuideServerTest.java

@@ -86,7 +86,11 @@ public class RouteGuideServerTest {
 
   @After
   public void tearDown() {
-    server.stop();
+    try {
+      server.stop();
+    } catch (InterruptedException e) {
+      e.printStackTrace();
+    }
   }
 
   @Test