我编写了一个简单的程序来了解snmp4j异步请求/响应的工作原理:
TransportMapping transport = new DefaultUdpTransportMapping();
Snmp snmp = new Snmp(transport);
transport.listen();
Address targetAddress = GenericAddress.parse("udp:192.168.1.116/161");
CommunityTarget target = new CommunityTarget();
target.setAddress(targetAddress);
target.setCommunity(new OctetString("nid"));
target.setRetries(0);
target.setTimeout(30000);
target.setVersion(SnmpConstants.version2c);
ResponseListener listener = new ResponseListener() {
@Override
public void onResponse(ResponseEvent event) {
((Snmp) event.getSource()).cancel(event.getRequest(), this);
System.out.println("Received response PDU is: " + event.getResponse());
System.out.println("response listener thread id: " + Thread.currentThread().getId());
System.out.println("**********************************");
try {
Thread.sleep(5000);
} catch (InterruptedException ex) {
Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
}
}
};
System.out.println("main thread id: " + Thread.currentThread().getId());
for (int i = 0; i < 10; i++) {
PDU pdu1 = new PDU();
pdu1.add(new VariableBinding(new OID("1.3.6.1.4.1.22420.2.5.3.1.1.1")));
pdu1.add(new VariableBinding(new OID("1.3.6.1.4.1.22420.2.5.3.1.1.2")));
pdu1.setType(PDU.GET);
snmp.send(pdu1, target, null, listener);
}
Thread.sleep(100000);
示例输出如下:
main thread id: 1
Received response PDU is: RESPONSE[requestID=205585942, errorStatus=Success(0), errorIndex=0, VBS[1.3.6.1.4.1.22420.2.5.3.1.1.1 = 1; 1.3.6.1.4.1.22420.2.5.3.1.1.2 = 2]]
response listener thread id: 8
**********************************
Received response PDU is: RESPONSE[requestID=205585943, errorStatus=Success(0), errorIndex=0, VBS[1.3.6.1.4.1.22420.2.5.3.1.1.1 = 1; 1.3.6.1.4.1.22420.2.5.3.1.1.2 = 2]]
response listener thread id: 8
**********************************
Received response PDU is: RESPONSE[requestID=205585944, errorStatus=Success(0), errorIndex=0, VBS[1.3.6.1.4.1.22420.2.5.3.1.1.1 = 1; 1.3.6.1.4.1.22420.2.5.3.1.1.2 = 2]]
response listener thread id: 8
**********************************
Received response PDU is: RESPONSE[requestID=205585945, errorStatus=Success(0), errorIndex=0, VBS[1.3.6.1.4.1.22420.2.5.3.1.1.1 = 1; 1.3.6.1.4.1.22420.2.5.3.1.1.2 = 2]]
response listener thread id: 8
**********************************
Received response PDU is: RESPONSE[requestID=205585946, errorStatus=Success(0), errorIndex=0, VBS[1.3.6.1.4.1.22420.2.5.3.1.1.1 = 1; 1.3.6.1.4.1.22420.2.5.3.1.1.2 = 2]]
response listener thread id: 8
**********************************
Received response PDU is: RESPONSE[requestID=205585947, errorStatus=Success(0), errorIndex=0, VBS[1.3.6.1.4.1.22420.2.5.3.1.1.1 = 1; 1.3.6.1.4.1.22420.2.5.3.1.1.2 = 2]]
response listener thread id: 8
**********************************
Received response PDU is: null
response listener thread id: 9
**********************************
Received response PDU is: RESPONSE[requestID=205585948, errorStatus=Success(0), errorIndex=0, VBS[1.3.6.1.4.1.22420.2.5.3.1.1.1 = 1; 1.3.6.1.4.1.22420.2.5.3.1.1.2 = 2]]
response listener thread id: 8
**********************************
Received response PDU is: null
response listener thread id: 9
**********************************
Received response PDU is: RESPONSE[requestID=205585950, errorStatus=Success(0), errorIndex=0, VBS[1.3.6.1.4.1.22420.2.5.3.1.1.1 = 1; 1.3.6.1.4.1.22420.2.5.3.1.1.2 = 2]]
response listener thread id: 8
**********************************
输出显示多个线程ID。这意味着并行处理响应数据包。我对吗?线程ID为9的两个响应返回null
。有什么理由吗?在使用同步模型时,我无法得到它。这是因为Thread.sleep
在ResponseListener
内。因此,如果我无法在ResponseListener
内阻止工作,并且我想并行处理响应,我需要添加ExecuterService
?
答案 0 :(得分:4)
SNMP4j在内部使用线程池来处理消息。 ResponseListener
s onResponse()
是从那些线程中调用的,您的线程ID是您正在查看的。与同步模式不同,它是在您自己的线程中执行的。
null
返回值表示它在超时时间内完成。是的,我猜它是因为你在ResponseListener
中睡了5秒钟,这阻止了一个消息接收线程。
对于ExecutorService
,将处理负载从SNMP4j消息线程移到您自己的代码中是个好主意,您可以在其中控制队列等。或者您可以使用synchronized {{ 1}}和一个计数List
,它会唤醒一个线程来处理收到的消息。