refactor: Add EndpointContext

gax-java/gax/src/main/java/com/google/api/gax/rpc/ClientContext.java

@@ -37,7 +37,6 @@
 import com.google.api.gax.core.ExecutorAsBackgroundResource;
 import com.google.api.gax.core.ExecutorProvider;
 import com.google.api.gax.rpc.internal.QuotaProjectIdHidingCredentials;
-import com.google.api.gax.rpc.mtls.MtlsProvider;
 import com.google.api.gax.tracing.ApiTracerFactory;
 import com.google.api.gax.tracing.BaseApiTracerFactory;
 import com.google.auth.Credentials;
@@ -143,29 +142,6 @@ public static ClientContext create(ClientSettings settings) throws IOException {
     return create(settings.getStubSettings());
   }
 
-  /** Returns the endpoint that should be used. See https://google.aip.dev/auth/4114. */
-  static String getEndpoint(
-      String endpoint,
-      String mtlsEndpoint,
-      boolean switchToMtlsEndpointAllowed,
-      MtlsProvider mtlsProvider)
-      throws IOException {
-    if (switchToMtlsEndpointAllowed) {
-      switch (mtlsProvider.getMtlsEndpointUsagePolicy()) {
-        case ALWAYS:
-          return mtlsEndpoint;
-        case NEVER:
-          return endpoint;
-        default:
-          if (mtlsProvider.useMtlsClientCertificate() && mtlsProvider.getKeyStore() != null) {
-            return mtlsEndpoint;
-          }
-          return endpoint;
-      }
-    }
-    return endpoint;
-  }
-
   /**
    * Instantiates the executor, credentials, and transport context based on the given client
    * settings.
@@ -224,12 +200,13 @@ public static ClientContext create(StubSettings settings) throws IOException {
     if (transportChannelProvider.needsCredentials() && credentials != null) {
       transportChannelProvider = transportChannelProvider.withCredentials(credentials);
     }
-    String endpoint =
-        getEndpoint(
-            settings.getEndpoint(),
-            settings.getMtlsEndpoint(),
-            settings.getSwitchToMtlsEndpointAllowed(),
-            new MtlsProvider());
+    EndpointContext endpointContext =
+        EndpointContext.newBuilder()
+            .setClientSettingsEndpoint(settings.getEndpoint())
+            .setMtlsEndpoint(settings.getMtlsEndpoint())
+            .setSwitchToMtlsEndpointAllowed(settings.getSwitchToMtlsEndpointAllowed())
+            .build();
+    String endpoint = endpointContext.getResolvedEndpoint();
     if (transportChannelProvider.needsEndpoint()) {
       transportChannelProvider = transportChannelProvider.withEndpoint(endpoint);
     }

gax-java/gax/src/main/java/com/google/api/gax/rpc/EndpointContext.java

@@ -0,0 +1,128 @@
+/*
+ * Copyright 2023 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package com.google.api.gax.rpc;
+
+import com.google.api.core.InternalApi;
+import com.google.api.gax.rpc.mtls.MtlsProvider;
+import com.google.auto.value.AutoValue;
+import com.google.common.annotations.VisibleForTesting;
+import java.io.IOException;
+import javax.annotation.Nullable;
+
+/** Contains the fields required to resolve the endpoint */
+@InternalApi
+@AutoValue
+public abstract class EndpointContext {
+  /**
+   * ClientSettingsEndpoint is the endpoint value set via the ClientSettings/StubSettings classes.
+   */
+  @Nullable
+  public abstract String clientSettingsEndpoint();
+
+  @Nullable
+  public abstract String mtlsEndpoint();
+
+  public abstract boolean switchToMtlsEndpointAllowed();
+
+  @Nullable
+  public abstract MtlsProvider mtlsProvider();
+
+  public abstract Builder toBuilder();
+
+  private String resolvedEndpoint;
+
+  public static Builder newBuilder() {
+    return new AutoValue_EndpointContext.Builder().setSwitchToMtlsEndpointAllowed(false);
+  }
+
+  @VisibleForTesting
+  void determineEndpoint() throws IOException {
+    MtlsProvider mtlsProvider = mtlsProvider() == null ? new MtlsProvider() : mtlsProvider();
+    resolvedEndpoint =
+        mtlsEndpointResolver(
+            clientSettingsEndpoint(), mtlsEndpoint(), switchToMtlsEndpointAllowed(), mtlsProvider);
+  }
+
+  // This takes in parameters because determineEndpoint()'s logic will be updated
+  // to pass custom values in.
+  // Follows https://google.aip.dev/auth/4114 for resolving the endpoint
+  @VisibleForTesting
+  String mtlsEndpointResolver(
+      String endpoint,
+      String mtlsEndpoint,
+      boolean switchToMtlsEndpointAllowed,
+      MtlsProvider mtlsProvider)
+      throws IOException {
+    if (switchToMtlsEndpointAllowed && mtlsProvider != null) {
+      switch (mtlsProvider.getMtlsEndpointUsagePolicy()) {
+        case ALWAYS:
+          return mtlsEndpoint;
+        case NEVER:
+          return endpoint;
+        default:
+          if (mtlsProvider.useMtlsClientCertificate() && mtlsProvider.getKeyStore() != null) {
+            return mtlsEndpoint;
+          }
+          return endpoint;
+      }
+    }
+    return endpoint;
+  }
+
+  /**
+   * The resolved endpoint is the computed endpoint after accounting for the custom endpoints and
+   * mTLS configurations.
+   */
+  public String getResolvedEndpoint() {
+    return resolvedEndpoint;
+  }
+
+  @AutoValue.Builder
+  public abstract static class Builder {
+    /**
+     * ClientSettingsEndpoint is the endpoint value set via the ClientSettings/StubSettings classes.
+     */
+    public abstract Builder setClientSettingsEndpoint(String clientSettingsEndpoint);
+
+    public abstract Builder setMtlsEndpoint(String mtlsEndpoint);
+
+    public abstract Builder setSwitchToMtlsEndpointAllowed(boolean switchToMtlsEndpointAllowed);
+
+    public abstract Builder setMtlsProvider(MtlsProvider mtlsProvider);
+
+    abstract EndpointContext autoBuild();
+
+    public EndpointContext build() throws IOException {
+      EndpointContext endpointContext = autoBuild();
+      endpointContext.determineEndpoint();
+      return endpointContext;
+    }
+  }
+}

gax-java/gax/src/test/java/com/google/api/gax/rpc/ClientContextTest.java

@@ -36,7 +36,6 @@
 import static org.junit.Assert.assertNotSame;
 import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 
@@ -47,11 +46,8 @@
 import com.google.api.gax.core.FixedCredentialsProvider;
 import com.google.api.gax.core.FixedExecutorProvider;
 import com.google.api.gax.core.NoCredentialsProvider;
-import com.google.api.gax.rpc.mtls.MtlsProvider;
-import com.google.api.gax.rpc.mtls.MtlsProvider.MtlsEndpointUsagePolicy;
 import com.google.api.gax.rpc.testing.FakeChannel;
 import com.google.api.gax.rpc.testing.FakeClientSettings;
-import com.google.api.gax.rpc.testing.FakeMtlsProvider;
 import com.google.api.gax.rpc.testing.FakeStubSettings;
 import com.google.api.gax.rpc.testing.FakeTransportChannel;
 import com.google.auth.Credentials;
@@ -636,93 +632,6 @@ public void testUserAgentConcat() throws Exception {
   private static String endpoint = "https://foo.googleapis.com";
   private static String mtlsEndpoint = "https://foo.mtls.googleapis.com";
 
-  @Test
-  public void testAutoUseMtlsEndpoint() throws IOException {
-    // Test the case client certificate exists and mTLS endpoint is selected.
-    boolean switchToMtlsEndpointAllowed = true;
-    MtlsProvider provider =
-        new FakeMtlsProvider(
-            true,
-            MtlsEndpointUsagePolicy.AUTO,
-            FakeMtlsProvider.createTestMtlsKeyStore(),
-            "",
-            false);
-    String endpointSelected =
-        ClientContext.getEndpoint(endpoint, mtlsEndpoint, switchToMtlsEndpointAllowed, provider);
-    assertEquals(mtlsEndpoint, endpointSelected);
-  }
-
-  @Test
-  public void testEndpointNotOverridable() throws IOException {
-    // Test the case that switching to mTLS endpoint is not allowed so the original endpoint is
-    // selected.
-    boolean switchToMtlsEndpointAllowed = false;
-    MtlsProvider provider =
-        new FakeMtlsProvider(
-            true,
-            MtlsEndpointUsagePolicy.AUTO,
-            FakeMtlsProvider.createTestMtlsKeyStore(),
-            "",
-            false);
-    String endpointSelected =
-        ClientContext.getEndpoint(endpoint, mtlsEndpoint, switchToMtlsEndpointAllowed, provider);
-    assertEquals(endpoint, endpointSelected);
-  }
-
-  @Test
-  public void testNoClientCertificate() throws IOException {
-    // Test the case that client certificates doesn't exists so the original endpoint is selected.
-    boolean switchToMtlsEndpointAllowed = true;
-    MtlsProvider provider =
-        new FakeMtlsProvider(true, MtlsEndpointUsagePolicy.AUTO, null, "", false);
-    String endpointSelected =
-        ClientContext.getEndpoint(endpoint, mtlsEndpoint, switchToMtlsEndpointAllowed, provider);
-    assertEquals(endpoint, endpointSelected);
-  }
-
-  @Test
-  public void testAlwaysUseMtlsEndpoint() throws IOException {
-    // Test the case that mTLS endpoint is always used.
-    boolean switchToMtlsEndpointAllowed = true;
-    MtlsProvider provider =
-        new FakeMtlsProvider(false, MtlsEndpointUsagePolicy.ALWAYS, null, "", false);
-    String endpointSelected =
-        ClientContext.getEndpoint(endpoint, mtlsEndpoint, switchToMtlsEndpointAllowed, provider);
-    assertEquals(mtlsEndpoint, endpointSelected);
-  }
-
-  @Test
-  public void testNeverUseMtlsEndpoint() throws IOException {
-    // Test the case that mTLS endpoint is never used.
-    boolean switchToMtlsEndpointAllowed = true;
-    MtlsProvider provider =
-        new FakeMtlsProvider(
-            true,
-            MtlsEndpointUsagePolicy.NEVER,
-            FakeMtlsProvider.createTestMtlsKeyStore(),
-            "",
-            false);
-    String endpointSelected =
-        ClientContext.getEndpoint(endpoint, mtlsEndpoint, switchToMtlsEndpointAllowed, provider);
-    assertEquals(endpoint, endpointSelected);
-  }
-
-  @Test
-  public void testGetKeyStoreThrows() throws IOException {
-    // Test the case that getKeyStore throws exceptions.
-    try {
-      boolean switchToMtlsEndpointAllowed = true;
-      MtlsProvider provider =
-          new FakeMtlsProvider(true, MtlsEndpointUsagePolicy.AUTO, null, "", true);
-      ClientContext.getEndpoint(endpoint, mtlsEndpoint, switchToMtlsEndpointAllowed, provider);
-      fail("should throw an exception");
-    } catch (IOException e) {
-      assertTrue(
-          "expected getKeyStore to throw an exception",
-          e.getMessage().contains("getKeyStore throws exception"));
-    }
-  }
-
   @Test
   public void testSwitchToMtlsEndpointAllowed() throws IOException {
     StubSettings settings = new FakeStubSettings.Builder().setEndpoint(endpoint).build();