The events oninvoke, onreturn, and onthrow will be triggered before a call, after a call, and when an exception occurs, respectively. You can configure which class and method to notify when these events happen.
Before calling the service method, we can log the start time, after the call, calculate the total time consumed, and in case of exceptions, we can trigger alerts or print error logs, or log request and response logs before and after the service call.
Reference Case dubbo-samples-notify
interface IDemoService {
public Person get(int id);
}
class NormalDemoService implements IDemoService {
public Person get(int id) {
return new Person(id, "charles`son", 4);
}
}
<dubbo:application name="rpc-callback-demo" />
<dubbo:registry address="zookeeper://127.0.0.1:2181"/>
<bean id="demoService" class="org.apache.dubbo.callback.implicit.NormalDemoService" />
<dubbo:service interface="org.apache.dubbo.callback.implicit.IDemoService" ref="demoService" version="1.0.0" group="cn"/>
interface Notify {
public void onreturn(Person msg, Integer id);
public void onthrow(Throwable ex, Integer id);
}
class NotifyImpl implements Notify {
public Map<Integer, Person> ret = new HashMap<Integer, Person>();
public Map<Integer, Throwable> errors = new HashMap<Integer, Throwable>();
public void onreturn(Person msg, Integer id) {
System.out.println("onreturn:" + msg);
ret.put(id, msg);
}
public void onthrow(Throwable ex, Integer id) {
errors.put(id, ex);
}
}
The following combinations exist:
async=true onreturn="xxx"async=false onreturn="xxx"async=trueasync=falsecallback and async functionalities are orthogonally decomposed, where async=true indicates whether the result returns immediately, and async=false is default, while onreturn indicates whether a callback is needed.
<bean id ="demoCallback" class = "org.apache.dubbo.callback.implicit.NotifyImpl" />
<dubbo:reference id="demoService" interface="org.apache.dubbo.callback.implicit.IDemoService" version="1.0.0" group="cn" >
<dubbo:method name="get" async="true" onreturn = "demoCallback.onreturn" onthrow="demoCallback.onthrow" />
</dubbo:reference>
IDemoService demoService = (IDemoService) context.getBean("demoService");
NotifyImpl notify = (NotifyImpl) context.getBean("demoCallback");
int requestId = 2;
Person ret = demoService.get(requestId);
Assert.assertEquals(null, ret);
//for Test：used to indicate that callback is called normally, the specific implementation is left to the business.
for (int i = 0; i < 10; i++) {
if (!notify.ret.containsKey(requestId)) {
Thread.sleep(200);
} else {
break;
}
}
Assert.assertEquals(requestId, notify.ret.get(requestId).getId());