Enable use of InProcessTransport outside of InProcessServer

This allows an InProcessTransport instance to be created via a new
internal accessor class InternalInProcess. We effectively just expose a
method to create an InProcessTransport with a existing ServerListener
instance.

This will be used for in-process channels to an under-development
on-device server.

core/src/main/java/io/grpc/inprocess/InProcessTransport.java

@@ -21,6 +21,7 @@ import static io.grpc.internal.GrpcUtil.TIMEOUT_KEY;
 import static java.lang.Math.max;
 
 import com.google.common.base.MoreObjects;
+import com.google.common.base.Optional;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.SettableFuture;
 import io.grpc.Attributes;
@@ -48,6 +49,7 @@ import io.grpc.internal.InsightBuilder;
 import io.grpc.internal.ManagedClientTransport;
 import io.grpc.internal.NoopClientStream;
 import io.grpc.internal.ObjectPool;
+import io.grpc.internal.ServerListener;
 import io.grpc.internal.ServerStream;
 import io.grpc.internal.ServerStreamListener;
 import io.grpc.internal.ServerTransport;
@@ -79,6 +81,7 @@ final class InProcessTransport implements ServerTransport, ConnectionClientTrans
   private final int clientMaxInboundMetadataSize;
   private final String authority;
   private final String userAgent;
+  private final Optional<ServerListener> optionalServerListener;
   private int serverMaxInboundMetadataSize;
   private ObjectPool<ScheduledExecutorService> serverSchedulerPool;
   private ScheduledExecutorService serverScheduler;
@@ -111,9 +114,8 @@ final class InProcessTransport implements ServerTransport, ConnectionClientTrans
         }
       };
 
-  public InProcessTransport(
-      String name, int maxInboundMetadataSize, String authority, String userAgent,
-      Attributes eagAttrs) {
+  private InProcessTransport(String name, int maxInboundMetadataSize, String authority,
+      String userAgent, Attributes eagAttrs, Optional<ServerListener> optionalServerListener) {
     this.name = name;
     this.clientMaxInboundMetadataSize = maxInboundMetadataSize;
     this.authority = authority;
@@ -125,21 +127,45 @@ final class InProcessTransport implements ServerTransport, ConnectionClientTrans
         .set(Grpc.TRANSPORT_ATTR_REMOTE_ADDR, new InProcessSocketAddress(name))
         .set(Grpc.TRANSPORT_ATTR_LOCAL_ADDR, new InProcessSocketAddress(name))
         .build();
+    this.optionalServerListener = optionalServerListener;
     logId = InternalLogId.allocate(getClass(), name);
   }
 
+  public InProcessTransport(
+      String name, int maxInboundMetadataSize, String authority, String userAgent,
+      Attributes eagAttrs) {
+    this(name, maxInboundMetadataSize, authority, userAgent, eagAttrs,
+        Optional.<ServerListener>absent());
+  }
+
+  InProcessTransport(
+      String name, int maxInboundMetadataSize, String authority, String userAgent,
+      Attributes eagAttrs, ObjectPool<ScheduledExecutorService> serverSchedulerPool,
+      List<ServerStreamTracer.Factory> serverStreamTracerFactories,
+      ServerListener serverListener) {
+    this(name, maxInboundMetadataSize, authority, userAgent, eagAttrs, Optional.of(serverListener));
+    this.serverMaxInboundMetadataSize = maxInboundMetadataSize;
+    this.serverSchedulerPool = serverSchedulerPool;
+    this.serverStreamTracerFactories = serverStreamTracerFactories;
+  }
+
   @CheckReturnValue
   @Override
   public synchronized Runnable start(ManagedClientTransport.Listener listener) {
     this.clientTransportListener = listener;
-    InProcessServer server = InProcessServer.findServer(name);
-    if (server != null) {
-      serverMaxInboundMetadataSize = server.getMaxInboundMetadataSize();
-      serverSchedulerPool = server.getScheduledExecutorServicePool();
+    if (optionalServerListener.isPresent()) {
       serverScheduler = serverSchedulerPool.getObject();
-      serverStreamTracerFactories = server.getStreamTracerFactories();
-      // Must be semi-initialized; past this point, can begin receiving requests
-      serverTransportListener = server.register(this);
+      serverTransportListener = optionalServerListener.get().transportCreated(this);
+    } else {
+      InProcessServer server = InProcessServer.findServer(name);
+      if (server != null) {
+        serverMaxInboundMetadataSize = server.getMaxInboundMetadataSize();
+        serverSchedulerPool = server.getScheduledExecutorServicePool();
+        serverScheduler = serverSchedulerPool.getObject();
+        serverStreamTracerFactories = server.getStreamTracerFactories();
+        // Must be semi-initialized; past this point, can begin receiving requests
+        serverTransportListener = server.register(this);
+      }
     }
     if (serverTransportListener == null) {
       shutdownStatus = Status.UNAVAILABLE.withDescription("Could not find server: " + name);

core/src/main/java/io/grpc/inprocess/InternalInProcess.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2020 The gRPC Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.inprocess;
+
+import io.grpc.Attributes;
+import io.grpc.Internal;
+import io.grpc.ServerStreamTracer;
+import io.grpc.internal.ConnectionClientTransport;
+import io.grpc.internal.ObjectPool;
+import io.grpc.internal.ServerListener;
+import java.util.List;
+import java.util.concurrent.ScheduledExecutorService;
+
+/**
+ * Internal {@link InProcessTransport} accessor.
+ *
+ * <p>This is intended for use by io.grpc.internal, and the specifically
+ * supported transport packages.
+ */
+@Internal
+public final class InternalInProcess {
+
+  private InternalInProcess() {}
+
+  /**
+   * Creates a new InProcessTransport.
+   *
+   * <p>When started, the transport will be registered with the given
+   * {@link ServerListener}.
+   */
+  @Internal
+  public static ConnectionClientTransport createInProcessTransport(
+      String name,
+      int maxInboundMetadataSize,
+      String authority,
+      String userAgent,
+      Attributes eagAttrs,
+      ObjectPool<ScheduledExecutorService> serverSchedulerPool,
+      List<ServerStreamTracer.Factory> serverStreamTracerFactories,
+      ServerListener serverListener) {
+    return new InProcessTransport(
+        name,
+        maxInboundMetadataSize,
+        authority,
+        userAgent,
+        eagAttrs,
+        serverSchedulerPool,
+        serverStreamTracerFactories,
+        serverListener);
+  }
+}

core/src/test/java/io/grpc/inprocess/StandaloneInProcessTransportTest.java

@@ -0,0 +1,159 @@
+/*
+ * Copyright 2020 The gRPC Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.inprocess;
+
+import com.google.common.collect.ImmutableList;
+import io.grpc.InternalChannelz.SocketStats;
+import io.grpc.InternalInstrumented;
+import io.grpc.ServerStreamTracer;
+import io.grpc.internal.AbstractTransportTest;
+import io.grpc.internal.GrpcUtil;
+import io.grpc.internal.InternalServer;
+import io.grpc.internal.ManagedClientTransport;
+import io.grpc.internal.ObjectPool;
+import io.grpc.internal.ServerListener;
+import io.grpc.internal.ServerTransport;
+import io.grpc.internal.ServerTransportListener;
+import io.grpc.internal.SharedResourcePool;
+import java.io.IOException;
+import java.net.SocketAddress;
+import java.util.List;
+import java.util.concurrent.ScheduledExecutorService;
+import javax.annotation.Nullable;
+import org.junit.Ignore;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Unit tests for {@link InProcessTransport} when used with a separate {@link InternalServer}. */
+@RunWith(JUnit4.class)
+public final class StandaloneInProcessTransportTest extends AbstractTransportTest {
+  private static final String TRANSPORT_NAME = "perfect-for-testing";
+  private static final String AUTHORITY = "a-testing-authority";
+  private static final String USER_AGENT = "a-testing-user-agent";
+
+  private final ObjectPool<ScheduledExecutorService> schedulerPool =
+      SharedResourcePool.forResource(GrpcUtil.TIMER_SERVICE);
+
+  private TestServer currentServer;
+
+  @Override
+  protected List<? extends InternalServer> newServer(
+      List<ServerStreamTracer.Factory> streamTracerFactories) {
+    return ImmutableList.of(new TestServer(streamTracerFactories));
+  }
+
+  @Override
+  protected List<? extends InternalServer> newServer(
+      int port, List<ServerStreamTracer.Factory> streamTracerFactories) {
+    return newServer(streamTracerFactories);
+  }
+
+  @Override
+  protected String testAuthority(InternalServer server) {
+    return AUTHORITY;
+  }
+
+  @Override
+  protected ManagedClientTransport newClientTransport(InternalServer server) {
+    TestServer testServer = (TestServer) server;
+    return InternalInProcess.createInProcessTransport(
+        TRANSPORT_NAME,
+        GrpcUtil.DEFAULT_MAX_HEADER_LIST_SIZE,
+        testAuthority(server),
+        USER_AGENT,
+        eagAttrs(),
+        schedulerPool,
+        testServer.streamTracerFactories,
+        testServer.serverListener);
+  }
+
+  @Override
+  protected boolean sizesReported() {
+    // TODO(zhangkun83): InProcessTransport doesn't record metrics for now
+    // (https://github.com/grpc/grpc-java/issues/2284)
+    return false;
+  }
+
+  @Test
+  @Ignore
+  @Override
+  public void socketStats() throws Exception {
+    // test does not apply to in-process
+  }
+
+  /** An internalserver just for this test. */
+  private final class TestServer implements InternalServer {
+
+    final List<ServerStreamTracer.Factory> streamTracerFactories;
+    ServerListener serverListener;
+
+    TestServer(List<ServerStreamTracer.Factory> streamTracerFactories) {
+      this.streamTracerFactories = streamTracerFactories;
+    }
+
+    @Override
+    public void start(ServerListener serverListener) throws IOException {
+      if (currentServer != null) {
+        throw new IOException("Server already present");
+      }
+      currentServer = this;
+      this.serverListener = new ServerListenerWrapper(serverListener);
+    }
+
+    @Override
+    public void shutdown() {
+      currentServer = null;
+      serverListener.serverShutdown();
+    }
+
+    @Override
+    public SocketAddress getListenSocketAddress() {
+      return new SocketAddress() {};
+    }
+
+    @Override
+    @Nullable
+    public InternalInstrumented<SocketStats> getListenSocketStats() {
+      return null;
+    }
+  }
+
+  /** Wraps the server listener to ensure we don't accept new transports after shutdown. */
+  private static final class ServerListenerWrapper implements ServerListener {
+    private final ServerListener delegateListener;
+    private boolean shutdown;
+
+    ServerListenerWrapper(ServerListener delegateListener) {
+      this.delegateListener = delegateListener;
+    }
+
+    @Override
+    public ServerTransportListener transportCreated(ServerTransport transport) {
+      if (shutdown) {
+        return null;
+      }
+      return delegateListener.transportCreated(transport);
+    }
+
+    @Override
+    public void serverShutdown() {
+      shutdown = true;
+      delegateListener.serverShutdown();
+    }
+  }
+}