Move XdsChannelFactory to its own file and improve tests.

xds/src/main/java/io/grpc/xds/XdsChannelFactory.java

@@ -0,0 +1,89 @@
+/*
+ * 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.xds;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.common.annotations.VisibleForTesting;
+import io.grpc.ManagedChannel;
+import io.grpc.ManagedChannelBuilder;
+import io.grpc.alts.GoogleDefaultChannelBuilder;
+import io.grpc.xds.Bootstrapper.ChannelCreds;
+import io.grpc.xds.Bootstrapper.ServerInfo;
+import io.grpc.xds.XdsClient.XdsChannel;
+import io.grpc.xds.XdsLogger.XdsLogLevel;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Factory for creating channels to xDS severs.
+ */
+abstract class XdsChannelFactory {
+  @VisibleForTesting
+  static boolean experimentalV3SupportEnvVar = Boolean.parseBoolean(
+      System.getenv("GRPC_XDS_EXPERIMENTAL_V3_SUPPORT"));
+
+  private static final String XDS_V3_SERVER_FEATURE = "xds_v3";
+  private static final XdsChannelFactory DEFAULT_INSTANCE = new XdsChannelFactory() {
+    /**
+     * Creates a channel to the first server in the given list.
+     */
+    @Override
+    XdsChannel createChannel(List<ServerInfo> servers) throws XdsInitializationException {
+      checkArgument(!servers.isEmpty(), "No management server provided.");
+      XdsLogger logger = XdsLogger.withPrefix("xds-client-channel-factory");
+      ServerInfo serverInfo = servers.get(0);
+      String serverUri = serverInfo.getServerUri();
+      logger.log(XdsLogLevel.INFO, "Creating channel to {0}", serverUri);
+      List<ChannelCreds> channelCredsList = serverInfo.getChannelCredentials();
+      ManagedChannelBuilder<?> channelBuilder = null;
+      // Use the first supported channel credentials configuration.
+      // Currently, only "google_default" is supported.
+      for (ChannelCreds creds : channelCredsList) {
+        if (creds.getType().equals("google_default")) {
+          logger.log(XdsLogLevel.INFO, "Using channel credentials: google_default");
+          channelBuilder = GoogleDefaultChannelBuilder.forTarget(serverUri);
+          break;
+        }
+      }
+      if (channelBuilder == null) {
+        logger.log(XdsLogLevel.INFO, "Using default channel credentials");
+        channelBuilder = ManagedChannelBuilder.forTarget(serverUri);
+      }
+
+      ManagedChannel channel = channelBuilder
+          .keepAliveTime(5, TimeUnit.MINUTES)
+          .build();
+      boolean useProtocolV3 = experimentalV3SupportEnvVar
+          && serverInfo.getServerFeatures().contains(XDS_V3_SERVER_FEATURE);
+
+      return new XdsChannel(channel, useProtocolV3);
+    }
+  };
+
+  static XdsChannelFactory getInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  /**
+   * Creates a channel to one of the provided management servers.
+   *
+   * @throws XdsInitializationException if failed to create a channel with the given list of
+   *         servers.
+   */
+  abstract XdsChannel createChannel(List<ServerInfo> servers) throws XdsInitializationException;
+}

xds/src/test/java/io/grpc/xds/XdsChannelFactoryTest.java

@@ -0,0 +1,100 @@
+/*
+ * 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.xds;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.fail;
+
+import io.grpc.xds.Bootstrapper.ChannelCreds;
+import io.grpc.xds.Bootstrapper.ServerInfo;
+import io.grpc.xds.XdsClient.XdsChannel;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/**
+ * Tests for {@link XdsChannelFactory}.
+ */
+@RunWith(JUnit4.class)
+public class XdsChannelFactoryTest {
+
+  private final XdsChannelFactory channelFactory = XdsChannelFactory.getInstance();
+  private final List<XdsChannel> channels = new ArrayList<>();
+  private ServerInfo server1;  // google_default
+  private ServerInfo server2;  // plaintext, v3
+  private ServerInfo server3;  // unsupported
+
+  @Before
+  public void setUp() {
+    ChannelCreds tls = new ChannelCreds("tls", null);
+    ChannelCreds googleDefault = new ChannelCreds("google_default", null);
+    ChannelCreds insecure = new ChannelCreds("insecure", null);
+    ChannelCreds unsupported = new ChannelCreds("unsupported", null);
+    server1 = new ServerInfo("server1.com", Collections.singletonList(googleDefault),
+        Collections.<String>emptyList());
+    server2 = new ServerInfo("server2.com", Collections.singletonList(insecure),
+        Collections.singletonList("xds_v3"));
+    server3 = new ServerInfo("server4.com", Collections.singletonList(unsupported),
+        Collections.<String>emptyList());
+  }
+
+  @After
+  public void tearDown() {
+    for (XdsChannel channel : channels) {
+      channel.getManagedChannel().shutdown();
+    }
+  }
+
+  @Test
+  public void failToCreateChannel_unsupportedChannelCreds() {
+    try {
+      createChannel(server3);
+      fail("Should have thrown");
+    } catch (XdsInitializationException expected) {
+    }
+  }
+
+  @Test
+  public void defaultUseV2ProtocolL() throws XdsInitializationException {
+    XdsChannel channel = createChannel(server1);
+    assertThat(channel.isUseProtocolV3()).isFalse();
+  }
+
+  @Test
+  public void supportServerFeature_v3Protocol() throws XdsInitializationException {
+    boolean originalV3SupportEnvVar = XdsChannelFactory.experimentalV3SupportEnvVar;
+    XdsChannelFactory.experimentalV3SupportEnvVar = true;
+    try {
+      XdsChannel channel = createChannel(server2);
+      assertThat(channel.isUseProtocolV3()).isTrue();
+    } finally {
+      XdsChannelFactory.experimentalV3SupportEnvVar = originalV3SupportEnvVar;
+    }
+  }
+
+  private XdsChannel createChannel(ServerInfo... servers) throws XdsInitializationException {
+    XdsChannel channel = channelFactory.createChannel(Arrays.asList(servers));
+    channels.add(channel);
+    return channel;
+  }
+}