/**
* 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.flume.channel;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;
import org.apache.flume.Channel;
import org.apache.flume.ChannelException;
import org.apache.flume.Context;
import org.apache.flume.Event;
import org.apache.flume.Transaction;
import com.google.common.base.Preconditions;
/**
* <p>
* A capacity-capped {@link Channel} implementation that supports in-memory
* buffering and delivery of events.
* </p>
* <p>
* This channel is appropriate for
* <q>best effort</q> delivery of events where high throughput is favored over
* data durability. To be clear, <b>this channel offers absolutely no guarantee
* of event delivery</b> in the face of (any) component failure.
* </p>
* <p>
* TODO: Discuss guarantees, corner cases re: potential data loss (e.g. consumer
* begins a tx, takes events, and gets SIGKILL before rollback).
* </p>
* <p>
* <b>Configuration options</b>
* </p>
* <table>
* <tr>
* <th>Parameter</th>
* <th>Description</th>
* <th>Unit / Type</th>
* <th>Default</th>
* </tr>
* <tr>
* <td><tt>capacity</tt></td>
* <td>The in-memory capacity of this channel. Store up to <tt>capacity</tt>
* events before refusing new events.</td>
* <td>events / int</td>
* <td>50</td>
* </tr>
* <tr>
* <td><tt>keep-alive</tt></td>
* <td>The amount of time (seconds) to wait for an event before returning
* <tt>null</tt> on {@link #take()}.</td>
* <td>seconds / int</td>
* <td>3</td>
* </tr>
* </table>
* <p>
* <b>Metrics</b>
* </p>
* <p>
* TODO
* </p>
*/
public class PseudoTxnMemoryChannel extends AbstractChannel {
private static final Integer defaultCapacity = 50;
private static final Integer defaultKeepAlive = 3;
private BlockingQueue<Event> queue;
private Integer keepAlive;
@Override
public void configure(Context context) {
Integer capacity = context.getInteger("capacity");
keepAlive = context.getInteger("keep-alive");
if (capacity == null) {
capacity = defaultCapacity;
}
if (keepAlive == null) {
keepAlive = defaultKeepAlive;
}
queue = new ArrayBlockingQueue<Event>(capacity);
}
@Override
public void put(Event event) {
Preconditions.checkState(queue != null,
"No queue defined (Did you forget to configure me?");
try {
queue.put(event);
} catch (InterruptedException ex) {
throw new ChannelException("Failed to put(" + event + ")", ex);
}
}
@Override
public Event take() {
Preconditions.checkState(queue != null,
"No queue defined (Did you forget to configure me?");
try {
return queue.poll(keepAlive, TimeUnit.SECONDS);
} catch (InterruptedException ex) {
throw new ChannelException("Failed to take()", ex);
}
}
@Override
public Transaction getTransaction() {
return NoOpTransaction.sharedInstance();
}
/**
* <p>
* A no-op transaction implementation that does nothing at all.
* </p>
*/
public static class NoOpTransaction implements Transaction {
private static NoOpTransaction sharedInstance;
public static Transaction sharedInstance() {
if (sharedInstance == null) {
sharedInstance = new NoOpTransaction();
}
return sharedInstance;
}
@Override
public void begin() {
}
@Override
public void commit() {
}
@Override
public void rollback() {
}
@Override
public void close() {
}
}
}