Add QuotaHandler to GCP proxy

The quota handler terminates connections when quota is exceeded.

The next CL will add instrumentation for quota related metrics.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=185042675

javatests/google/registry/proxy/handler/WhoisQuotaHandlerTest.java

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+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// 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 google.registry.proxy.handler;
+
+import static com.google.common.truth.Truth.assertThat;
+import static google.registry.proxy.handler.ProxyProtocolHandler.REMOTE_ADDRESS_KEY;
+import static google.registry.testing.JUnitBackports.expectThrows;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.when;
+
+import google.registry.proxy.handler.QuotaHandler.OverQuotaException;
+import google.registry.proxy.handler.QuotaHandler.WhoisQuotaHandler;
+import google.registry.proxy.quota.QuotaManager;
+import google.registry.proxy.quota.QuotaManager.QuotaRequest;
+import google.registry.proxy.quota.QuotaManager.QuotaResponse;
+import io.netty.channel.ChannelFuture;
+import io.netty.channel.embedded.EmbeddedChannel;
+import org.joda.time.DateTime;
+import org.joda.time.DateTimeZone;
+import org.joda.time.Duration;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Unit tests for {@link WhoisQuotaHandler} */
+@RunWith(JUnit4.class)
+public class WhoisQuotaHandlerTest {
+
+  private final QuotaManager quotaManager = mock(QuotaManager.class);
+  private final WhoisQuotaHandler handler = new WhoisQuotaHandler(quotaManager);
+  private final EmbeddedChannel channel = new EmbeddedChannel(handler);
+  private final DateTime now = DateTime.now(DateTimeZone.UTC);
+  private final String remoteAddress = "127.0.0.1";
+  private final Object message = new Object();
+
+  @Before
+  public void setUp() {
+    channel.attr(REMOTE_ADDRESS_KEY).set(remoteAddress);
+  }
+
+  @Test
+  public void testSuccess_quotaGranted() {
+    when(quotaManager.acquireQuota(QuotaRequest.create(remoteAddress)))
+        .thenReturn(QuotaResponse.create(true, remoteAddress, now));
+
+    // First read, acquire quota.
+    assertThat(channel.writeInbound(message)).isTrue();
+    assertThat((Object) channel.readInbound()).isEqualTo(message);
+    assertThat(channel.isActive()).isTrue();
+    verify(quotaManager).acquireQuota(QuotaRequest.create(remoteAddress));
+
+    // Second read, should not acquire quota again.
+    assertThat(channel.writeInbound(message)).isTrue();
+    assertThat((Object) channel.readInbound()).isEqualTo(message);
+
+    // Channel closed, release quota.
+    ChannelFuture unusedFuture = channel.close();
+    verifyNoMoreInteractions(quotaManager);
+  }
+
+  @Test
+  public void testFailure_quotaNotGranted() {
+    when(quotaManager.acquireQuota(QuotaRequest.create(remoteAddress)))
+        .thenReturn(QuotaResponse.create(false, remoteAddress, now));
+    OverQuotaException e =
+        expectThrows(OverQuotaException.class, () -> channel.writeInbound(message));
+    assertThat(e).hasMessageThat().contains("none");
+  }
+
+  @Test
+  public void testSuccess_twoChannels_twoUserIds() {
+    // Set up another user.
+    final WhoisQuotaHandler otherHandler = new WhoisQuotaHandler(quotaManager);
+    final EmbeddedChannel otherChannel = new EmbeddedChannel(otherHandler);
+    final String otherRemoteAddress = "192.168.0.1";
+    otherChannel.attr(REMOTE_ADDRESS_KEY).set(otherRemoteAddress);
+    final DateTime later = now.plus(Duration.standardSeconds(1));
+
+    when(quotaManager.acquireQuota(QuotaRequest.create(remoteAddress)))
+        .thenReturn(QuotaResponse.create(true, remoteAddress, now));
+    when(quotaManager.acquireQuota(QuotaRequest.create(otherRemoteAddress)))
+        .thenReturn(QuotaResponse.create(false, otherRemoteAddress, later));
+
+    // Allows the first user.
+    assertThat(channel.writeInbound(message)).isTrue();
+    assertThat((Object) channel.readInbound()).isEqualTo(message);
+    assertThat(channel.isActive()).isTrue();
+
+    // Blocks the second user.
+    OverQuotaException e =
+        expectThrows(OverQuotaException.class, () -> otherChannel.writeInbound(message));
+    assertThat(e).hasMessageThat().contains("none");
+  }
+
+  @Test
+  public void testSuccess_oneUser_rateLimited() {
+    // Set up another channel for the same user.
+    final WhoisQuotaHandler otherHandler = new WhoisQuotaHandler(quotaManager);
+    final EmbeddedChannel otherChannel = new EmbeddedChannel(otherHandler);
+    otherChannel.attr(REMOTE_ADDRESS_KEY).set(remoteAddress);
+    final DateTime later = now.plus(Duration.standardSeconds(1));
+
+    // Set up the third channel for the same user
+    final WhoisQuotaHandler thirdHandler = new WhoisQuotaHandler(quotaManager);
+    final EmbeddedChannel thirdChannel = new EmbeddedChannel(thirdHandler);
+    thirdChannel.attr(REMOTE_ADDRESS_KEY).set(remoteAddress);
+    final DateTime evenLater = now.plus(Duration.standardSeconds(60));
+
+    when(quotaManager.acquireQuota(QuotaRequest.create(remoteAddress)))
+        .thenReturn(QuotaResponse.create(true, remoteAddress, now))
+        // Throttles the second connection.
+        .thenReturn(QuotaResponse.create(false, remoteAddress, later))
+        // Allows the third connection because token refilled.
+        .thenReturn(QuotaResponse.create(true, remoteAddress, evenLater));
+
+    // Allows the first channel.
+    assertThat(channel.writeInbound(message)).isTrue();
+    assertThat((Object) channel.readInbound()).isEqualTo(message);
+    assertThat(channel.isActive()).isTrue();
+
+    // Blocks the second channel.
+    OverQuotaException e =
+        expectThrows(OverQuotaException.class, () -> otherChannel.writeInbound(message));
+    assertThat(e).hasMessageThat().contains("none");
+
+    // Allows the third channel.
+    assertThat(thirdChannel.writeInbound(message)).isTrue();
+    assertThat((Object) thirdChannel.readInbound()).isEqualTo(message);
+    assertThat(thirdChannel.isActive()).isTrue();
+  }
+}