Add GRACEFUL_DISCONNECT event support (CEP-59)

src/main/java/com/datastax/oss/protocol/internal/ProtocolConstants.java

@@ -148,6 +148,7 @@ public static class EventType {
     public static final String TOPOLOGY_CHANGE = "TOPOLOGY_CHANGE";
     public static final String STATUS_CHANGE = "STATUS_CHANGE";
     public static final String SCHEMA_CHANGE = "SCHEMA_CHANGE";
+    public static final String GRACEFUL_DISCONNECT = "GRACEFUL_DISCONNECT";
   }
 
   public static class SchemaChangeType {

src/main/java/com/datastax/oss/protocol/internal/response/Event.java

@@ -20,6 +20,7 @@
 import com.datastax.oss.protocol.internal.PrimitiveSizes;
 import com.datastax.oss.protocol.internal.ProtocolConstants;
 import com.datastax.oss.protocol.internal.ProtocolErrors;
+import com.datastax.oss.protocol.internal.response.event.GracefulDisconnectEvent;
 import com.datastax.oss.protocol.internal.response.event.SchemaChangeEvent;
 import com.datastax.oss.protocol.internal.response.event.StatusChangeEvent;
 import com.datastax.oss.protocol.internal.response.event.TopologyChangeEvent;
@@ -54,7 +55,8 @@ public Codec(int protocolVersion) {
           protocolVersion,
           new TopologyChangeEvent.SubCodec(protocolVersion),
           new StatusChangeEvent.SubCodec(protocolVersion),
-          new SchemaChangeEvent.SubCodec(protocolVersion));
+          new SchemaChangeEvent.SubCodec(protocolVersion),
+          new GracefulDisconnectEvent.SubCodec(protocolVersion));
     }
 
     @Override

src/main/java/com/datastax/oss/protocol/internal/response/event/GracefulDisconnectEvent.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright DataStax, Inc.
+ *
+ * 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 com.datastax.oss.protocol.internal.response.event;
+
+import com.datastax.oss.protocol.internal.Message;
+import com.datastax.oss.protocol.internal.PrimitiveCodec;
+import com.datastax.oss.protocol.internal.ProtocolConstants;
+import com.datastax.oss.protocol.internal.response.Event;
+
+public class GracefulDisconnectEvent extends Event {
+  public GracefulDisconnectEvent() {
+    super(ProtocolConstants.EventType.GRACEFUL_DISCONNECT);
+  }
+
+  @Override
+  public String toString() {
+    return "EVENT GRACEFUL_DISCONNECT";
+  }
+
+  public static class SubCodec extends Event.SubCodec {
+
+    public SubCodec(int protocolVersion) {
+      super(ProtocolConstants.EventType.GRACEFUL_DISCONNECT, protocolVersion);
+    }
+
+    @Override
+    public <B> void encode(B dest, Message message, PrimitiveCodec<B> encoder) {
+      // no-op: the event has no body, the type string is enough
+    }
+
+    @Override
+    public int encodedSize(Message message) {
+      return 0;
+    }
+
+    @Override
+    public <B> Message decode(B source, PrimitiveCodec<B> decoder) {
+      return new GracefulDisconnectEvent();
+    }
+  }
+}

src/test/java/com/datastax/oss/protocol/internal/response/event/GracefulDisconnectEventTest.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright DataStax, Inc.
+ *
+ * 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 com.datastax.oss.protocol.internal.response.event;
+
+import static com.datastax.oss.protocol.internal.Assertions.assertThat;
+
+import com.datastax.oss.protocol.internal.Message;
+import com.datastax.oss.protocol.internal.MessageTestBase;
+import com.datastax.oss.protocol.internal.PrimitiveSizes;
+import com.datastax.oss.protocol.internal.ProtocolConstants;
+import com.datastax.oss.protocol.internal.TestDataProviders;
+import com.datastax.oss.protocol.internal.binary.MockBinaryString;
+import com.datastax.oss.protocol.internal.response.Event;
+import com.tngtech.java.junit.dataprovider.DataProviderRunner;
+import com.tngtech.java.junit.dataprovider.UseDataProvider;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+@RunWith(DataProviderRunner.class)
+public class GracefulDisconnectEventTest extends MessageTestBase<GracefulDisconnectEvent> {
+
+  public GracefulDisconnectEventTest() {
+    super(GracefulDisconnectEvent.class);
+  }
+
+  @Override
+  protected Message.Codec newCodec(int protocolVersion) {
+    return new Event.Codec(protocolVersion);
+  }
+
+  @Test
+  @UseDataProvider(location = TestDataProviders.class, value = "protocolV5OrAbove")
+  public void should_encode_and_decode(int protocolVersion) {
+    GracefulDisconnectEvent initial = new GracefulDisconnectEvent();
+
+    MockBinaryString encoded = encode(initial, protocolVersion);
+
+    assertThat(encoded)
+        .isEqualTo(new MockBinaryString().string(ProtocolConstants.EventType.GRACEFUL_DISCONNECT));
+    assertThat(encodedSize(initial, protocolVersion))
+        .isEqualTo(PrimitiveSizes.SHORT + ProtocolConstants.EventType.GRACEFUL_DISCONNECT.length());
+
+    GracefulDisconnectEvent decoded = decode(encoded, protocolVersion);
+
+    assertThat(decoded.type).isEqualTo(ProtocolConstants.EventType.GRACEFUL_DISCONNECT);
+  }
+}