ActiveMQ - 容错

Failover协议

如下图所示，生产者往broker61616发送消息，消费者通过broker61618接收消息。broker61616和broker61618通过networkConnectors连接。

Consumer的代码如下：

private static final String BROKEURL = "failover:(tcp://0.0.0.0:61618,tcp://0.0.0.0:61616)";
public static void main(String[] args) {
    ConnectionFactory connectionFactory;
    Connection connection = null;
    Session session = null;
    Destination destination;
    MessageConsumer consumer = null;
    Message message;
    boolean useTransaction = false;
    try {
        // 创建一个ConnectionFactory
        connectionFactory = new ActiveMQConnectionFactory(BROKEURL);
        // 创建一个Connection
        connection = connectionFactory.createConnection();
        // 启动消息传递的连接
        connection.start();
        // 创建一个session
        session = connection.createSession(useTransaction, Session.AUTO_ACKNOWLEDGE);
        // 创建一个destination，把消息发送到test.queue
        destination = session.createQueue("test.failover");
        // 创建一个消费者
        consumer = session.createConsumer(destination);
        // 接收一个消息
        while (null != (message = consumer.receive())) {
            System.out.println("consumer receive:" + ((TextMessage) message).getText());
            Thread.sleep(1000);
        }
    } catch (JMSException e) {
        e.printStackTrace();
    } catch (InterruptedException e) {
        e.printStackTrace();
    } finally {

    }
}

Producer代码如下：

private static final String BROKEURL = "failover:(tcp://0.0.0.0:61616,tcp://0.0.0.0:61618)";

public static void main(String[] args) {
    ConnectionFactory connectionFactory;
    Connection connection = null;
    Session session = null;
    Destination destination;
    MessageProducer producer = null;
    boolean useTransaction = false;
    try {
        // 创建一个ConnectionFactory
        connectionFactory = new ActiveMQConnectionFactory(BROKEURL);
        // 创建一个Connection
        connection = connectionFactory.createConnection();
        // 启动消息传递的连接
        connection.start();
        // 创建一个session
        session = connection.createSession(useTransaction, Session.AUTO_ACKNOWLEDGE);
        // 创建一个destination，把消息发送到test.queue
        destination = session.createQueue("test.failover");
        // 创建一个生产者
        producer = session.createProducer(destination);
        for (int i = 0; i < 10; i++) {
            // 创建一个消息
            Message message = session.createTextMessage("this is test.failover:" + i);
            // 发送消息
            producer.send(message);
            System.out.println(i);
        }

    } catch (JMSException e) {
        e.printStackTrace();
    } finally {
        try {
            if (producer != null) {
                producer.close();
            }
            if (session != null) {
                session.close();
            }
            if (connection != null) {
                connection.close();
            }
        } catch (JMSException e) {
            e.printStackTrace();
        }
    }
}

启动两个ActiveMQ，61616和61618。producer往61616发送消息，consumer从61618接收数据。消息发送完后，把61618给关闭了，此时，consumer会报如下错误：

 INFO | Successfully connected to tcp://0.0.0.0:61618
consumer receive:this is test.failover:0
consumer receive:this is test.failover:1
consumer receive:this is test.failover:2
 WARN | Transport (tcp://0.0.0.0:61618) failed , attempting to automatically reconnect: {}
java.net.SocketException: Connection reset
    at java.net.SocketInputStream.read(SocketInputStream.java:210)
    at java.net.SocketInputStream.read(SocketInputStream.java:141)
    at org.apache.activemq.transport.tcp.TcpBufferedInputStream.fill(TcpBufferedInputStream.java:50)
    at org.apache.activemq.transport.tcp.TcpTransport$2.fill(TcpTransport.java:634)
    at org.apache.activemq.transport.tcp.TcpBufferedInputStream.read(TcpBufferedInputStream.java:59)
    at org.apache.activemq.transport.tcp.TcpTransport$2.read(TcpTransport.java:619)
    at java.io.DataInputStream.readInt(DataInputStream.java:387)
    at org.apache.activemq.openwire.OpenWireFormat.unmarshal(OpenWireFormat.java:268)
    at org.apache.activemq.transport.tcp.TcpTransport.readCommand(TcpTransport.java:240)
    at org.apache.activemq.transport.tcp.TcpTransport.doRun(TcpTransport.java:232)
    at org.apache.activemq.transport.tcp.TcpTransport.run(TcpTransport.java:215)
    at java.lang.Thread.run(Thread.java:748)
 INFO | Successfully reconnected to tcp://0.0.0.0:61616

61618连接不了，最后一句可以看到重新连到61616，完成故障转移。此时重启61618，61618的几个消息被继续消费：

consumer receive:this is test.failover:3
consumer receive:this is test.failover:4
consumer receive:this is test.failover:5
consumer receive:this is test.failover:6
consumer receive:this is test.failover:7
consumer receive:this is test.failover:8
consumer receive:this is test.failover:9

本来想看看destinationPolicy的replayWhenNoConsumers属性，让消息从broker61618回流到broker61616，这边没设置，已经回流。我的版本是apache-activemq-5.15.12。

配置值

属性	默认值	描述
initialReconnectDelay	10	在第一次尝试重新连接之前等待的时间长度（毫秒）
maxReconnectDelay	30000	最长重连时间间隔（毫秒）
useExponentialBackOff	true	重连时间间隔是否以指数形式增长
backOffMultiplier	2.0	递增倍数
maxReconnectAttempts	-1	自5.6版本开始，-1为默认值，代表不限重试次数，0标识从不重试（只尝试连接一次，并不重连），5.6以前的版本，0为默认值，代表不重试，如果设置大于0的数，则代表最大重试次数
startupMaxReconnectAttempts	0	初始化时的最大重试次数
randomize	true	使用随机连接，以达到负载均衡的目的
backup	false	提前初始化一个未使用的链接，以便进行快速的失败转移
trackMessages	false	设置是否缓存（故障发生时）尚未传送完成的消息，当broker一旦重新连接成功，便将这些缓存中的消息刷新到新连接的代理中，使得消息可以在broker切换前后顺利传送
maxCacheSize	127*1024bytes	当trackMessage启动时，缓存的最大字节
updateURISupported	true	设定是否可以动态修改broker uri(自5.4版本开始）