/**
* 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.s4.core;
import java.nio.ByteBuffer;
import java.util.Map;
import org.apache.s4.base.Event;
import org.apache.s4.base.Listener;
import org.apache.s4.base.Receiver;
import org.apache.s4.base.SerializerDeserializer;
import org.apache.s4.core.util.S4Metrics;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.google.common.collect.MapMaker;
import com.google.inject.Inject;
import com.google.inject.Singleton;
/**
* The {@link ReceiverImpl} and its counterpart {@link SenderImpl} are the top level classes of the communication layer.
* <p>
* {@link ReceiverImpl} is responsible for receiving an event to a {@link ProcessingElement} instance using a hashKey.
* <p>
* A Listener implementation receives data from the network and passes an event as a byte array to the
* {@link ReceiverImpl}. The byte array is deserialized and converted into an {@link Event}. Finally the event is passed
* to the matching streams.
* </p>
* There is a single {@link ReceiverImpl} instance per node.
*
* Details on how the cluster is partitioned and how events are serialized and transmitted to its destination are hidden
* from the application developer. </p>
*/
@Singleton
public class ReceiverImpl implements Receiver {
private static final Logger logger = LoggerFactory.getLogger(ReceiverImpl.class);
final private Listener listener;
final private SerializerDeserializer serDeser;
private final Map<String, Stream<? extends Event>> streams;
@Inject
S4Metrics metrics;
@Inject
public ReceiverImpl(Listener listener, SerializerDeserializer serDeser) {
this.listener = listener;
this.serDeser = serDeser;
streams = new MapMaker().makeMap();
}
@Override
public int getPartitionId() {
return listener.getPartitionId();
}
/** Save stream keyed by app id and stream id. */
void addStream(Stream<? extends Event> stream) {
streams.put(stream.getName(), stream);
}
/** Remove stream when it is no longer needed. */
void removeStream(Stream<? extends Event> stream) {
streams.remove(stream.getName());
}
@Override
public void receive(ByteBuffer message) {
metrics.receivedEventFromCommLayer(message.array().length);
Event event = (Event) serDeser.deserialize(message);
String streamId = event.getStreamId();
/*
* Match streamId in event to the target stream and pass the event to the target stream. TODO: make this more
* efficient for the case in which we send the same event to multiple PEs.
*/
try {
streams.get(streamId).receiveEvent(event);
} catch (NullPointerException e) {
logger.error("Could not find target stream for event with streamId={}", streamId);
}
}
}