Synchronize the calls subscription observer (underlying `ServerCallIm…

…pl` isn't thread-safe). Allow to set the `Executor` for `GrpcContainer`. Bump the library version to `1.7.5`.
SpineEventEngine · Jul 26, 2021 · 0908adf · 0908adf
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diff --git a/license-report.md b/license-report.md
@@ -1,6 +1,6 @@
 
 
-# Dependencies of `io.spine:spine-client:1.7.1`
+# Dependencies of `io.spine:spine-client:1.7.5`
 
 ## Runtime
 1. **Group:** com.google.android **Name:** annotations **Version:** 4.1.1.4
@@ -399,12 +399,12 @@
  The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
 
-This report was generated on **Fri Jan 08 14:16:21 EET 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
+This report was generated on **Mon Jul 26 22:39:51 EEST 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine:spine-core:1.7.1`
+# Dependencies of `io.spine:spine-core:1.7.5`
 
 ## Runtime
 1. **Group:** com.google.code.findbugs **Name:** jsr305 **Version:** 3.0.2
@@ -763,12 +763,12 @@ This report was generated on **Fri Jan 08 14:16:21 EET 2021** using [Gradle-Lice
  The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
 
-This report was generated on **Fri Jan 08 14:16:22 EET 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
+This report was generated on **Mon Jul 26 22:39:51 EEST 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:spine-model-assembler:1.7.1`
+# Dependencies of `io.spine.tools:spine-model-assembler:1.7.5`
 
 ## Runtime
 1. **Group:** com.google.android **Name:** annotations **Version:** 4.1.1.4
@@ -1162,12 +1162,12 @@ This report was generated on **Fri Jan 08 14:16:22 EET 2021** using [Gradle-Lice
  The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
 
-This report was generated on **Fri Jan 08 14:16:22 EET 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
+This report was generated on **Mon Jul 26 22:39:51 EEST 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:spine-model-verifier:1.7.1`
+# Dependencies of `io.spine.tools:spine-model-verifier:1.7.5`
 
 ## Runtime
 1. **Group:** com.google.android **Name:** annotations **Version:** 4.1.1.4
@@ -1627,12 +1627,12 @@ This report was generated on **Fri Jan 08 14:16:22 EET 2021** using [Gradle-Lice
  The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
 
-This report was generated on **Fri Jan 08 14:16:23 EET 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
+This report was generated on **Mon Jul 26 22:39:52 EEST 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine:spine-server:1.7.1`
+# Dependencies of `io.spine:spine-server:1.7.5`
 
 ## Runtime
 1. **Group:** com.google.android **Name:** annotations **Version:** 4.1.1.4
@@ -2039,12 +2039,12 @@ This report was generated on **Fri Jan 08 14:16:23 EET 2021** using [Gradle-Lice
  The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
 
-This report was generated on **Fri Jan 08 14:16:23 EET 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
+This report was generated on **Mon Jul 26 22:39:52 EEST 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine:spine-testutil-client:1.7.1`
+# Dependencies of `io.spine:spine-testutil-client:1.7.5`
 
 ## Runtime
 1. **Group:** com.google.android **Name:** annotations **Version:** 4.1.1.4
@@ -2493,12 +2493,12 @@ This report was generated on **Fri Jan 08 14:16:23 EET 2021** using [Gradle-Lice
  The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
 
-This report was generated on **Fri Jan 08 14:16:25 EET 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
+This report was generated on **Mon Jul 26 22:39:54 EEST 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine:spine-testutil-core:1.7.1`
+# Dependencies of `io.spine:spine-testutil-core:1.7.5`
 
 ## Runtime
 1. **Group:** com.google.android **Name:** annotations **Version:** 4.1.1.4
@@ -2947,12 +2947,12 @@ This report was generated on **Fri Jan 08 14:16:25 EET 2021** using [Gradle-Lice
  The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
 
-This report was generated on **Fri Jan 08 14:16:26 EET 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
+This report was generated on **Mon Jul 26 22:39:55 EEST 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine:spine-testutil-server:1.7.1`
+# Dependencies of `io.spine:spine-testutil-server:1.7.5`
 
 ## Runtime
 1. **Group:** com.google.android **Name:** annotations **Version:** 4.1.1.4
@@ -3445,4 +3445,4 @@ This report was generated on **Fri Jan 08 14:16:26 EET 2021** using [Gradle-Lice
  The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
 
-This report was generated on **Fri Jan 08 14:16:30 EET 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
+This report was generated on **Mon Jul 26 22:39:57 EEST 2021** using [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
diff --git a/pom.xml b/pom.xml
@@ -12,7 +12,7 @@ all modules and does not describe the project structure per-subproject.
 
 <groupId>io.spine</groupId>
 <artifactId>spine-core-java</artifactId>
-<version>1.7.1</version>
+<version>1.7.5</version>
 
 <inceptionYear>2015</inceptionYear>
 

diff --git a/server/src/main/java/io/spine/server/GrpcContainer.java b/server/src/main/java/io/spine/server/GrpcContainer.java
@@ -42,10 +42,12 @@
 import java.io.IOException;
 import java.util.Optional;
 import java.util.Set;
+import java.util.concurrent.Executor;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.Preconditions.checkState;
 import static java.lang.String.format;
+import static java.util.Objects.requireNonNull;
 
 /**
  * Wrapping container for gRPC server.
@@ -54,6 +56,7 @@
  *
  * <p>Uses {@link ServerServiceDefinition}s of each service.
  */
+@SuppressWarnings("ClassWithTooManyMethods")    /* Extensive configuration. */
 public final class GrpcContainer {
 
     private static final String SERVER_NOT_STARTED_MSG =
@@ -128,15 +131,41 @@ public Optional<String> serverName() {
     /**
      * Starts the service.
      *
+     * <p>A gRPC-default executor is used for the server routines. I.e., in-process gRPC server
+     * is going to run on top of a {@linkplain ServerBuilder#directExecutor() direct executor},
+     * and a server exposed at a port will run on top of a shared cached thread pool.
+     *
+     * <p>See the {@link ServerBuilder} Javadocs corresponding to the current gRPC version
+     * for more details.
+     *
      * @throws IOException
      *         if unable to bind
      */
     public void start() throws IOException {
-        checkState(grpcServer == null, "gRPC server is started already.");
-        grpcServer = createGrpcServer();
+        checkNotStarted();
+        grpcServer = createGrpcServer(/* ...with a gRPC-default executor. */ null);
+        grpcServer.start();
+    }
+
+    /**
+     * Starts the service on top of the given {@code Executor}.
+     *
+     * @param executor
+     *         an executor to use for gRPC server
+     * @throws IOException
+     *         if unable to bind
+     */
+    public void start(Executor executor) throws IOException {
+        checkNotStarted();
+        checkNotNull(executor, "Executor must not be `null`.");
+        grpcServer = createGrpcServer(executor);
         grpcServer.start();
     }
 
+    private void checkNotStarted() {
+        checkState(grpcServer == null, "gRPC server is started already.");
+    }
+
     /**
      * Returns {@code true} if the server is shut down or was not started at all,
      * {@code false} otherwise.
@@ -238,30 +267,64 @@ public void addShutdownHook() {
                .addShutdownHook(new Thread(shutdownCallback()));
     }
 
-    private Server createGrpcServer() {
+    /**
+     * Creates a gRPC server which uses a specified executor.
+     *
+     * <p>If {@code null} is passed, a default behavior of the gRPC {@link ServerBuilder}
+     * is applied.
+     *
+     * @param executor
+     *         executor to use for the gRPC server
+     */
+    private Server createGrpcServer(@Nullable Executor executor) {
         if (injectedServer != null) {
             return injectedServer;
         }
-        ServerBuilder builder = createServerBuilder();
+        ServerBuilder<?> builder = createServerBuilder(executor);
         for (ServerServiceDefinition service : services) {
             builder.addService(service);
         }
         return builder.build();
     }
 
-    private ServerBuilder createServerBuilder() {
-        ServerBuilder result =
+    /**
+     * Creates a builder of the gRPC server with the provided executor.
+     *
+     * <p>If {@code null} is passed, a default behavior of the gRPC {@link ServerBuilder}
+     * is applied.
+     *
+     * @param executor
+     *         executor to configure for the created builder
+     */
+    private ServerBuilder<?> createServerBuilder(@Nullable Executor executor) {
+        ServerBuilder<?> result =
                 serverName == null
-                ? ServerBuilder.forPort(checkNotNull(port))
-                : InProcessServerBuilder.forName(serverName)
-                                        .directExecutor();
+                ? builderAtPort(requireNonNull(port), executor)
+                : inProcessBuilder(serverName, executor);
         return result;
     }
 
+    private static ServerBuilder<?> inProcessBuilder(String name, @Nullable Executor executor) {
+        InProcessServerBuilder builder = InProcessServerBuilder.forName(name);
+        builder = executor == null
+                  ? builder.directExecutor()
+                  : builder.executor(executor);
+        return builder;
+    }
+
+    private static ServerBuilder<?> builderAtPort(Integer port, @Nullable Executor executor) {
+        ServerBuilder<?> builder = ServerBuilder.forPort(port);
+        builder = executor == null
+                  ? builder
+                  : builder.executor(executor);
+        return builder;
+    }
+
     /**
      * Injects a server to this container.
      *
-     * <p>All calls to {@link #createGrpcServer()} will resolve to the given server instance.
+     * <p>All calls to {@link #createGrpcServer(Executor)} will resolve to the given server
+     * instance.
      *
      * <p>A test-only method.
      */
@@ -356,6 +419,7 @@ public Builder removeService(ServerServiceDefinition service) {
 
         /**
          * Obtains the services already added to the builder.
+         *
          * @deprecated please use {@link #services()}.
          */
         @Deprecated

diff --git a/server/src/main/java/io/spine/server/stand/SubscriptionCallback.java b/server/src/main/java/io/spine/server/stand/SubscriptionCallback.java
@@ -47,8 +47,10 @@ public interface SubscriptionCallback extends Consumer<SubscriptionUpdate> {
      */
     static SubscriptionCallback forwardingTo(StreamObserver<SubscriptionUpdate> observer) {
         return update -> {
-            checkNotNull(update);
-            observer.onNext(update);
+            synchronized (observer) {
+                checkNotNull(update);
+                observer.onNext(update);
+            }
         };
     }
 }
diff --git a/server/src/test/java/io/spine/server/GrpcContainerTest.java b/server/src/test/java/io/spine/server/GrpcContainerTest.java
@@ -42,14 +42,15 @@
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.common.truth.Truth8.assertThat;
 import static io.spine.testing.TestValues.randomString;
+import static java.util.concurrent.Executors.newSingleThreadExecutor;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
 
-@DisplayName("GrpcContainer should")
+@DisplayName("`GrpcContainer` should")
 class GrpcContainerTest {
 
     private GrpcContainer grpcContainer;
@@ -99,6 +100,15 @@ void startServer() throws IOException {
                 .isNotNull();
     }
 
+    @Test
+    @DisplayName("start server with the given `Executor`")
+    void startServerWithExecutor() throws IOException {
+        grpcContainer.start(newSingleThreadExecutor());
+
+        assertThat(grpcContainer.grpcServer())
+                .isNotNull();
+    }
+
     @Test
     @DisplayName("shutdown server")
     void shutdownItself() throws IOException {

diff --git a/version.gradle.kts b/version.gradle.kts
@@ -34,7 +34,7 @@
 /**
  * Version of this library.
  */
-val coreJava = "1.7.4"
+val coreJava = "1.7.5"
 
 /**
  * Versions of the Spine libraries that `core-java` depends on.