下载 activemq 压缩包解压后,conf 目录下有各种示例配置文件,红线标出的是静态发现和动态发现的配置。
1. 静态配置
启动3个 broker,端口分别为61616,61618,61620,配置如下:
<networkConnectors></networkConnectors>
<transportConnectors>
<transportConnector name="openwire" uri="tcp://localhost:61616"/>
</transportConnectors>
<networkConnectors>
<networkConnector uri="static:(tcp://localhost:61616)" duplex="true"/>
</networkConnectors>
<transportConnectors>
<transportConnector name="openwire" uri="tcp://localhost:61618"/>
</transportConnectors>
<networkConnectors>
<networkConnector uri="static:(tcp://localhost:61616,tcp://localhost:61618)" duplex="true"/>
</networkConnectors>
<transportConnectors>
<transportConnector name="openwire" uri="tcp://localhost:61620"/>
</transportConnectors>
3个 broker 组成了一张网,当 producer 发送消息给 broker:61616 后,broker:61618 的消费者可以收到该消息。消息从 broker:61616 流动到 broker:61618,底层原理是 broker:61618 是 broker:61616 的一个消费者。
2. 动态配置
同样地, 启动3个 broker,端口分别为61616,61618,61620,配置如下:
<networkConnectors>
<networkConnector uri="multicast://default"/>
</networkConnectors>
<transportConnector name="openwire" uri="tcp://0.0.0.0:61616" discoveryUri="multicast://default" />
</transportConnectors>
<networkConnectors>
<networkConnector uri="multicast://default"/>
</networkConnectors>
<transportConnectors>
<transportConnector name="openwire" uri="tcp://0.0.0.0:61618" discoveryUri="multicast://default" />
</transportConnectors>
<networkConnectors>
<networkConnector uri="multicast://default"/>
</networkConnectors>
<transportConnectors>
<transportConnector name="openwire" uri="tcp://0.0.0.0:61620" discoveryUri="multicast://default" />
</transportConnectors>
使用多播协议,把 3 个 broker 动态地组成了一张网。
// 省略其他代码
public class MulticastDiscoveryAgent implements DiscoveryAgent, Runnable { public static final String DEFAULT_DISCOVERY_URI_STRING = "multicast://239.255.2.3:6155";
public static final String DEFAULT_HOST_STR = "default";
public static final String DEFAULT_HOST_IP = System.getProperty("activemq.partition.discovery", "239.255.2.3");
public static final int DEFAULT_PORT = 6155; private static final Logger LOG = LoggerFactory.getLogger(MulticastDiscoveryAgent.class);
private static final String TYPE_SUFFIX = "ActiveMQ-4.";
private static final String ALIVE = "alive.";
private static final String DEAD = "dead.";
private static final String DELIMITER = "%";
private static final int BUFF_SIZE = 8192;
private static final int DEFAULT_IDLE_TIME = 500;
private static final int HEARTBEAT_MISS_BEFORE_DEATH = 10; public void run() {
byte[] buf = new byte[BUFF_SIZE];
DatagramPacket packet = new DatagramPacket(buf, 0, buf.length);
while (started.get()) {
// 发送多播数据
doTimeKeepingServices();
try {
// 接收多播数据
mcast.receive(packet);
if (packet.getLength() > 0) {
String str = new String(packet.getData(), packet.getOffset(), packet.getLength());
processData(str);
}
} catch (SocketTimeoutException se) {
// ignore
} catch (IOException e) {
if (started.get()) {
LOG.error("failed to process packet: " + e);
}
}
}
}
}
3. broker 集群的原理
如上图,61616和61618组成集群,当61618加入一个consumer时,61618向61616发送一条ConsumerInfo消息,这样61618就成为了61616的consumer。
ConsumerInfo 示例:
ConsumerInfo {
commandId = 4,
responseRequired = false,
consumerId = dynamic-broker1->dynamic-broker2-1872-1524494145961-2:1:1:1,
destination = queue://TEST.BAT,
prefetchSize = 1,
maximumPendingMessageLimit = 0,
browser = false,
dispatchAsync = true,
selector = null,
clientId = ID:USER-20140617MT-1882-1524494166015-0:1,
subscriptionName = null,
noLocal = false,
exclusive = true,
retroactive = false,
priority = -5,
brokerPath = [ID:USER-20140617MT-1877-1524494148767-0:1],
optimizedAcknowledge = false,
noRangeAcks = false,
additionalPredicate = org.apache.activemq.command.NetworkBridgeFilter@413249b
}