KAFKA-14247: Define event handler interface and events

clients/src/main/java/org/apache/kafka/clients/consumer/internals/DefaultEventHandler.java

@@ -0,0 +1,44 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.kafka.clients.consumer.internals;
+
+import org.apache.kafka.clients.consumer.internals.events.ConsumerRequestEvent;
+import org.apache.kafka.clients.consumer.internals.events.ConsumerResponseEvent;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+
+public class DefaultEventHandler implements EventHandler<ConsumerRequestEvent, ConsumerResponseEvent> {
+    private BlockingQueue<ConsumerRequestEvent> consumerRequestEvents;
+    private BlockingQueue<ConsumerResponseEvent> consumerResponseEvents;
+
+    public DefaultEventHandler() {
+        this.consumerRequestEvents = new LinkedBlockingQueue<>();
+        this.consumerResponseEvents = new LinkedBlockingQueue<>();
+        // TODO: a concreted implementation of how requests are being consumed, and how responses are being produced.
+    }
+
+    @Override
+    public ConsumerResponseEvent poll() {
+        return consumerResponseEvents.poll();
+    }
+
+    @Override
+    public boolean add(ConsumerRequestEvent event) {
+        return consumerRequestEvents.add(event);
+    }
+}

clients/src/main/java/org/apache/kafka/clients/consumer/internals/EventHandler.java

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.kafka.clients.consumer.internals;
+
+/**
+ * The EventHandler interfaces the client and handler implementation.  The client should add an event for consumption,
+ * and try to poll for the responses.  Here, one could poll a response with type K, and add a request with type T.
+ * @param <T> Event request type
+ * @param <K> Event response type
+ */
+public interface EventHandler<T, K> {
+    public K poll();
+    public boolean add(T event);
+}

clients/src/main/java/org/apache/kafka/clients/consumer/internals/events/ConsumerRequestEvent.java

@@ -0,0 +1,20 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.kafka.clients.consumer.internals.events;
+
+abstract public class ConsumerRequestEvent {
+}

clients/src/main/java/org/apache/kafka/clients/consumer/internals/events/ConsumerResponseEvent.java

@@ -0,0 +1,20 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.kafka.clients.consumer.internals.events;
+
+abstract public class ConsumerResponseEvent {
+}