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This article mainly introduces "what is the role of dubbo's FailbackClusterInvoker". In daily operation, I believe many people have doubts about the role of dubbo's FailbackClusterInvoker. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful to answer the questions of "what is the role of dubbo's FailbackClusterInvoker?" Next, please follow the editor to study!

Order

This paper mainly studies the FailbackClusterInvoker of dubbo.

FailbackClusterInvoker

Dubbo-2.7.3/dubbo-cluster/src/main/java/org/apache/dubbo/rpc/cluster/support/FailbackClusterInvoker.java

Public class FailbackClusterInvoker extends AbstractClusterInvoker {private static final Logger logger = LoggerFactory.getLogger (FailbackClusterInvoker.class); private static final long RETRY_FAILED_PERIOD = 5; private final int retries; private final int failbackTasks; private volatile Timer failTimer; public FailbackClusterInvoker (Directory directory) {super (directory); int retriesConfig = getUrl (). GetParameter (RETRIES_KEY, DEFAULT_FAILBACK_TIMES) If (retriesConfig = retries) {logger.error ("Failed retry times exceed threshold (" + retries + "), We have to abandon, invocation- >" + invocation);} else {rePut (timeout) } private void rePut (Timeout timeout) {if (timeout = = null) {return;} Timer timer = timeout.timer (); if (timer.isStop () | | timeout.isCancelled ()) {return } timer.newTimeout (timeout.task (), tick, TimeUnit.SECONDS);}}

The constructor of FailbackClusterInvoker initializes retriesConfig and the failbackTasksConfig;doInvoke method executes the addFailed method when catch to Throwable, which registers a RetryTimerTask,delay with HashedWheelTimer for 5 seconds; the run method of RetryTimerTask first selects a retryInvoker through the select method, then retries, increments retryTimes when catch to Throwable, executes the rePut method when the limit is not exceeded, and re-registers RetryTimerTask

FailbackClusterInvokerTest

Dubbo-2.7.3/dubbo-cluster/src/test/java/org/apache/dubbo/rpc/cluster/support/FailbackClusterInvokerTest.java

@ TestMethodOrder (MethodOrderer.OrderAnnotation.class) public class FailbackClusterInvokerTest {List invokers = new ArrayList (); URL url = URL.valueOf ("test://test:11/test?retries=2&failbacktasks=2"); Invoker invoker = mock (Invoker.class); RpcInvocation invocation = new RpcInvocation (); Directory dic; Result result = new AppResponse () / * * @ throws java.lang.Exception * / @ BeforeEach public void setUp () throws Exception {dic = mock (Directory.class); given (dic.getUrl ()) .willReturn (url); given (dic.list (invocation)) .willReturn (invokers); given (dic.getInterface ()) .willReturn (FailbackClusterInvokerTest.class); invocation.setMethodName ("method1"); invokers.add (invoker) } @ AfterEach public void tearDown () {dic = null; invocation = new RpcInvocation (); invokers.clear ();} private void resetInvokerToException () {given (invoker.invoke (invocation)) .willThrow (new RuntimeException ()); given (invoker.getUrl ()) .willReturn (url); given (invoker.getInterface ()) .willReturn (FailbackClusterInvokerTest.class) } private void resetInvokerToNoException () {given (invoker.invoke (invocation)) .willReturn (result); given (invoker.getUrl ()) .willReturn (url); given (invoker.getInterface ()) .willReturn (FailbackClusterInvokerTest.class);} @ Test @ Order (1) public void testInvokeException () {resetInvokerToException (); FailbackClusterInvoker invoker = new FailbackClusterInvoker (dic); invoker.invoke (invocation) Assertions.assertNull (RpcContext.getContext (). GetInvoker ()); DubboAppender.clear ();} @ Test @ Order (2) public void testInvokeNoException () {resetInvokerToNoException (); FailbackClusterInvoker invoker = new FailbackClusterInvoker (dic); Result ret = invoker.invoke (invocation); Assertions.assertSame (result, ret) @ Test @ Order (3) public void testNoInvoke () {dic = mock (Directory.class); given (dic.getUrl ()) .willReturn (url); given (dic.list (invocation)) .willReturn (null); given (dic.getInterface ()) .willReturn (FailbackClusterInvokerTest.class); invocation.setMethodName ("method1"); invokers.add (invoker); resetInvokerToNoException () FailbackClusterInvoker invoker = new FailbackClusterInvoker (dic); LogUtil.start (); DubboAppender.clear (); invoker.invoke (invocation); assertEquals (1, LogUtil.findMessage ("Failback to invoke")); LogUtil.stop ();} @ Disabled @ Test @ Order (4) public void testARetryFailed () throws Exception {/ / Test retries and resetInvokerToException () FailbackClusterInvoker invoker = new FailbackClusterInvoker (dic); LogUtil.start (); DubboAppender.clear (); invoker.invoke (invocation); Assertions.assertNull (RpcContext.getContext (). GetInvoker ()); / / invoker.retryFailed () / / when retry the invoker which get from failed map already is not the mocked invoker,so / / Ensure that the main thread is online CountDownLatch countDown = new CountDownLatch (1); countDown.await (15000L, TimeUnit.MILLISECONDS); LogUtil.stop (); Assertions.assertEquals (4, LogUtil.findMessage (Level.ERROR, "Failed retry to invoke method"), "must have four error message") Assertions.assertEquals (2, LogUtil.findMessage (Level.ERROR, "Failed retry times exceed threshold"), "must have two error message"); Assertions.assertEquals (1, LogUtil.findMessage (Level.ERROR, "Failback background works error"), "must have one error message"); / / it can be invoke successfully}}

Here we use mockito to mock resetInvokerToException and resetInvokerToNoException.

Summary

The constructor of FailbackClusterInvoker initializes retriesConfig and the failbackTasksConfig;doInvoke method executes the addFailed method when catch to Throwable, which registers a RetryTimerTask,delay with HashedWheelTimer for 5 seconds; the run method of RetryTimerTask first selects a retryInvoker through the select method, then retries, increments retryTimes when catch to Throwable, executes the rePut method when the limit is not exceeded, and re-registers RetryTimerTask

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