ActiveMQ集群、负载均衡、消息回流

集群配置

官方文档

http://activemq.apache.org/clustering

主备集群

http://activemq.apache.org/masterslave.html

Master Slave Type	Requirements	Pros	Cons
Shared File System Master Slave	A shared file system such as a SAN	Run as many slaves as required. Automatic recovery of old masters	Requires shared file system
JDBC Master Slave	A Shared database	Run as many slaves as required. Automatic recovery of old masters	Requires a shared database. Also relatively slow as it cannot use the high performance journal
Replicated LevelDB Store	ZooKeeper Server	Run as many slaves as required. Automatic recovery of old masters. Very fast.	Requires a ZooKeeper server.

Shared File System Master Slave

基于共享存储的Master-Slave；多个broker共用同一数据源，谁拿到锁谁就是master,其他处于待启动状态，如果master挂掉了，某个抢到文件锁的slave变成master

JDBC Master Slave

基于JDBC的Master-Slave:使用同一个数据库，拿到LOCK表的写锁的broker成为master.

性能较低，不能使用高性能日志

Replicated LeveDB Store

基于zookeeper复制LeveDB存储的Master-Slave机制

配置步骤

1. 修改broker名称
2. 修改数据源
   1. 如果使用kahadb，配置相同路径
   2. 如果使用mysql 使用同一数据源（同一数据库和表）

尝试

http://activemq.apache.org/failover-transport-reference.html

failover 故障转移协议

断线重连机制是ActiveMQ的高可用性具体体现之一。ActiveMQ提供failover机制去实现断线重连的高可用性，可以使得连接断开之后，不断的重试连接到一个或多个brokerURL。

默认情况下，如果client与broker直接的connection断开，则client会新起一个线程，不断的从url参数中获取一个url来重试连接。

配置语法

		ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory(
				"admin",
				"admin",
				"failover:(nio://localhost:5671,nio://localhost:5672)"
				);

可配置选项

Transport Options

Option Name	Default Value	Description
backup	false	Initialize and hold a second transport connection - to enable fast failover.
initialReconnectDelay	10	The delay (in ms) before the first reconnect attempt.
maxCacheSize	131072	Size in bytes for the cache of tracked messages. Applicable only if trackMessages is true.
maxReconnectAttempts	-1 | 0	From ActiveMQ 5.6: default is -1, retry forever. 0 means disables re-connection, e.g: just try to connect once. Before ActiveMQ 5.6: default is 0, retry forever. All ActiveMQ versions: a value >0 denotes the maximum number of reconnect attempts before an error is sent back to the client.
maxReconnectDelay	30000	The maximum delay (in ms) between the second and subsequent reconnect attempts.
nest