[GitHub] [dubbo] guohao commented on a diff in pull request #10691: Add dual chain support for state router, prevent update when invoke

[GitBox <gi...@apache.org>]

guohao commented on code in PR #10691:
URL: https://github.com/apache/dubbo/pull/10691#discussion_r993201655


##########
dubbo-cluster/src/main/java/org/apache/dubbo/rpc/cluster/RouterChain.java:
##########
@@ -103,264 +76,95 @@ public static <T> RouterChain<T> buildChain(Class<T> interfaceClass, URL url) {
 
         RouterSnapshotSwitcher routerSnapshotSwitcher = ScopeModelUtil.getFrameworkModel(moduleModel).getBeanFactory().getBean(RouterSnapshotSwitcher.class);
 
-        return new RouterChain<>(routers, stateRouters, shouldFailFast, routerSnapshotSwitcher);
+        return new SingleRouterChain<>(routers, stateRouters, shouldFailFast, routerSnapshotSwitcher);
     }
 
-    public RouterChain(List<Router> routers, List<StateRouter<T>> stateRouters, boolean shouldFailFast, RouterSnapshotSwitcher routerSnapshotSwitcher) {
-        initWithRouters(routers);
-
-        initWithStateRouters(stateRouters);
-
-        this.shouldFailFast = shouldFailFast;
-        this.routerSnapshotSwitcher = routerSnapshotSwitcher;
-    }
-
-    private void initWithStateRouters(List<StateRouter<T>> stateRouters) {
-        StateRouter<T> stateRouter = TailStateRouter.getInstance();
-        for (int i = stateRouters.size() - 1; i >= 0; i--) {
-            StateRouter<T> nextStateRouter = stateRouters.get(i);
-            nextStateRouter.setNextRouter(stateRouter);
-            stateRouter = nextStateRouter;
+    public RouterChain(SingleRouterChain<T>[] chains) {
+        if (chains.length != 2) {
+            throw new IllegalArgumentException("chains' size should be 2.");
         }
-        this.headStateRouter = stateRouter;
-        this.stateRouters = Collections.unmodifiableList(stateRouters);
+        this.mainChain = chains[0];
+        this.backupChain = chains[1];
+        this.currentChain = this.mainChain;
     }
 
-    /**
-     * the resident routers must being initialized before address notification.
-     * only for ut
-     */
-    public void initWithRouters(List<Router> builtinRouters) {
-        this.builtinRouters = builtinRouters;
-        this.routers = new LinkedList<>(builtinRouters);
+    public List<Invoker<T>> route(URL url, BitList<Invoker<T>> availableInvokers, Invocation invocation) {
+        return currentChain.route(url, availableInvokers, invocation);
     }
 
     /**
-     * If we use route:// protocol in version before 2.7.0, each URL will generate a Router instance, so we should
-     * keep the routers up to date, that is, each time router URLs changes, we should update the routers list, only
-     * keep the builtinRouters which are available all the time and the latest notified routers which are generated
-     * from URLs.
-     *
-     * @param routers routers from 'router://' rules in 2.6.x or before.
+     * Notify router chain of the initial addresses from registry at the first time.
+     * Notify whenever addresses in registry change.
      */
-    public void addRouters(List<Router> routers) {
-        List<Router> newRouters = new LinkedList<>();
-        newRouters.addAll(builtinRouters);
-        newRouters.addAll(routers);
-        CollectionUtils.sort(newRouters);
-        this.routers = newRouters;
-    }
-
-    public List<Router> getRouters() {
-        return routers;
-    }
-
-    public StateRouter<T> getHeadStateRouter() {
-        return headStateRouter;
-    }
-
-    public List<Invoker<T>> route(URL url, BitList<Invoker<T>> availableInvokers, Invocation invocation) {
-        if (RpcContext.getServiceContext().isNeedPrintRouterSnapshot()) {
-            return routeAndPrint(url, availableInvokers, invocation);
-        } else {
-            return simpleRoute(url, availableInvokers, invocation);
-        }
-    }
+    public synchronized void setInvokers(BitList<Invoker<T>> invokers) {
+        // 1. switch
+        currentChain = backupChain;
 
-    public List<Invoker<T>> routeAndPrint(URL url, BitList<Invoker<T>> availableInvokers, Invocation invocation) {
-        RouterSnapshotNode<T> snapshot = buildRouterSnapshot(url, availableInvokers, invocation);
-        logRouterSnapshot(url, invocation, snapshot);
-        return snapshot.getChainOutputInvokers();
-    }
-
-    public List<Invoker<T>> simpleRoute(URL url, BitList<Invoker<T>> availableInvokers, Invocation invocation) {
-        BitList<Invoker<T>> resultInvokers = availableInvokers.clone();
+        // 2. wait
+        waitChain(mainChain);
 
-        // 1. route state router
-        resultInvokers = headStateRouter.route(resultInvokers, url, invocation, false, null);
-        if (resultInvokers.isEmpty() && (shouldFailFast || routers.isEmpty())) {
-            printRouterSnapshot(url, availableInvokers, invocation);
-            return BitList.emptyList();
-        }
+        // 3. notify
+        mainChain.setInvokers(invokers);
 
-        if (routers.isEmpty()) {
-            return resultInvokers;
-        }
-        List<Invoker<T>> commonRouterResult = resultInvokers.cloneToArrayList();
-        // 2. route common router
-        for (Router router : routers) {
-            // Copy resultInvokers to a arrayList. BitList not support
-            RouterResult<Invoker<T>> routeResult = router.route(commonRouterResult, url, invocation, false);
-            commonRouterResult = routeResult.getResult();
-            if (CollectionUtils.isEmpty(commonRouterResult) && shouldFailFast) {
-                printRouterSnapshot(url, availableInvokers, invocation);
-                return BitList.emptyList();
-            }
-
-            // stop continue routing
-            if (!routeResult.isNeedContinueRoute()) {
-                return commonRouterResult;
-            }
-        }
+        // 4. switch back
+        currentChain = mainChain;
 
-        if (commonRouterResult.isEmpty()) {
-            printRouterSnapshot(url, availableInvokers, invocation);
-            return BitList.emptyList();
-        }
+        // 5. wait
+        waitChain(backupChain);
 
-        return commonRouterResult;
+        // 6. notify
+        backupChain.setInvokers(invokers);
     }
 
-    /**
-     * store each router's input and output, log out if empty
-     */
-    private void printRouterSnapshot(URL url, BitList<Invoker<T>> availableInvokers, Invocation invocation) {
-        if (logger.isWarnEnabled()) {
-            logRouterSnapshot(url, invocation, buildRouterSnapshot(url, availableInvokers, invocation));
+    private void waitChain(SingleRouterChain<T> oldChain) {
+        try {
+            Thread.sleep(1);

Review Comment:
   No need to wait if concurrency == 0



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