ActiveMQ集群

1 Master Slave

https://activemq.apache.org/masterslave
一个单一的MQ实例，如果机器故障了，系统就不可用了。
ActiveMQ提供了主从集群机制来实现高可用。

• 多个Broker实例共享存储
• 多个Broker通过抢独占锁来成为Master
• Master节点对外提供服务，Slave节点暂停等待独占锁
• Master节点故障，非持久化消息将丢失，所以一般要用持久化消息。
• 客户端以多Broker故障恢复方式进行连接

failover:(tcp://broker1:61616,tcp://broker2:61616,tcp://broker3:61616)

failover详细说明：http://activemq.apache.org/failover-transport-reference.html
Broke1 Master 故障

Broke1 重启

ActiveMQ中支持如下两种Master Slave实现方式：

• Shared File System Master Slave 独占锁 是共享存储目录下的lock文件 https://activemq.apache.org/shared-file-system-master-slave
• JDBC Master Slave 独占锁为 activemq_lock表记录 https://activemq.apache.org/jdbc-master-slave

2 分布式队列和主题

2.1 Networks of Brokers
https://activemq.apache.org/networks-of-brokers From 1.1 onwards of ActiveMQ supports networks of brokers which allows us to support distributed queues and topics across a network of brokers. This allows a client to connect to any broker in the network - and fail over to another broker if there is a failure - providing from the clients perspective a HA cluster of brokers.

原理说明：

• 独立的Broker彼此相连；
• 客户端采用Failover方式连接任意一个Broker；
• 客户端生产的消息发送到它连接的broker，并存储在该broker上；
• 消费者客户端可以连接任意Broker来消费目标的消息。
  https://activemq.apache.org/how-do-distributed-queues-work
  Distributed Queues in Store/Forward When we publish a message on a queue, it is stored in the persistent store of the broker that the publisher is communicating. Then if that broker is configured to store/foward to other brokers and clients, the broker will send it to one of these clients (which could be a node or a broker depending on the dispatch algorithm). This dispatch algorithm continues until the message is finally dispatched and consumed by a client.
  At any point in time the message will only exist in one broker’s store until its consumed. Note that messages are only distributed onto other brokers if there is a consumer on those brokers. e.g. if we had broker A, B, C and a publisher on a queue on A. If we have consumers on the queue on A and B then messages for the queue will be spread across both brokers A and B; some messages going to B, some being consumed on A, none going to C. If a consumer on the queue starts on C, then messages will flow there too. If the consumer stops then no more messages will be dispatched to C.
  配置：
  静态IP配置方式：

 <broker brokerName="receiver" persistent="false" useJmx="false">      
<networkConnectors>
      <!-- 配置要网络连接的其他Broker -->
      <networkConnector uri="static: (tcp://host1:61616,tcp://host2:61616,tcp://..)"/>    </networkConnectors>
    ...
  </broker>

There are some useful properties you can set on a static network connector for retries: 一些有用 的重试参数：

multicast 动态发现方式：

<networkConnectors>
   <networkConnector uri="multicast://default"/>
 </networkConnectors>

所有broker开启multicast：

<!-- transportConnector 中通过属性discoveryUri="multicast://default" 开启mulcast -> 
<transportConnector name="openwire" uri="tcp://0.0.0.0:61616? maximumConnections=1000&amp;wireFormat.maxFrameSize=104857600" discoveryUri="multicast://default">
    <publishedAddressPolicy>
        <!--并添加publishedAddressPolicy 发布地址时发布IP，防止主机名不可访问的情况 -->
        <publishedAddressPolicy publishedHostStrategy="IPADDRESS" />   
 </publishedAddressPolicy>
 </transportConnector>

客户端连接：

failover:(tcp://broker1:61616,tcp://broker2:61616,tcp://broker3:61616)

【注意】如果要实际使用，请详细了解networkConnector的配置属性：
https://activemq.apache.org/networks-of-brokers
Broker网络连接的不足：缺乏高可用

2.2 Networks + Master-Slave

networkConnectors 配置：

<networkConnectors>
   <networkConnector uri="masterslave:(tcp://other-cluster-1master:61616,tcp://cluster-1-slave:61616)" />
    <networkConnector uri="masterslave:(tcp://other-cluster-2master:61616,tcp://cluster-2-slave:61616)" />
    ……… 
</networkConnectors>

客户端连接：

failover:(tcp://broker1:61616,tcp://broker2:61616,tcp://broker3:61616,...)? randomize=true

可用配置参数请从官网文档详细了解：
https://activemq.apache.org/networks-of-brokers http://activemq.apache.org/failover-transport-reference.html