[GitHub] [hadoop] ayushtkn commented on a change in pull request #3976: HDFS-16452. msync RPC should send to acitve namenode directly

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

ayushtkn commented on a change in pull request #3976:
URL: https://github.com/apache/hadoop/pull/3976#discussion_r804141267



##########
File path: hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/ObserverReadProxyProvider.java
##########
@@ -368,6 +368,21 @@ private boolean shouldFindObserver() {
     return true;
   }
 
+  private void confirmActiveToMsync() throws IOException {
+    ClientProtocol activeProxy = (ClientProtocol) getCurrentProxy().proxy;
+    for (int i = 0; i < nameNodeProxies.size(); i++) {
+      NNProxyInfo<T> current = getCurrentProxy();
+      HAServiceState currState = current.getCachedState();
+      if (currState == HAServiceState.ACTIVE) {
+        activeProxy = getProxyAsClientProtocol(current.proxy);
+        LOG.info("active proxy is choosed :{}", current);
+        break;
+      } else {
+        changeProxy(current);

Review comment:
       hmm, the current proxy in observer proxy provider in general should be pointing to Observer namenode, you seems to change  the current proxy itself to active here? What would happen to subsequent calls, will they go to active or the concurrent calls

##########
File path: hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/ObserverReadProxyProvider.java
##########
@@ -342,7 +342,7 @@ private synchronized void initializeMsync() throws IOException {
     if (msynced) {
       return; // No need for an msync
     }
-    getProxyAsClientProtocol(failoverProxy.getProxy().proxy).msync();

Review comment:
       what does failoverProxy.getProxy().proxy points to?
   the same logic seems to be used for invocation as well
   ```
         // Either all observers have failed, observer reads are disabled,
         // or this is a write request. In any case, forward the request to
         // the active NameNode.
         LOG.debug("Using failoverProxy to service {}", method.getName());
         ProxyInfo<T> activeProxy = failoverProxy.getProxy();
         try {
           retVal = method.invoke(activeProxy.proxy, args);
         } catch (InvocationTargetException e) {
           // This exception will be handled by higher layers
           throw e.getCause();
         }
   ```




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