[GitHub] [zookeeper] tisonkun commented on a diff in pull request #2064: ZOOKEEPER-4743: Jump from 2 to 0 when zookeeper dataVersion incre

[via GitHub]

tisonkun commented on code in PR #2064:
URL: https://github.com/apache/zookeeper/pull/2064#discussion_r1330458351


##########
zookeeper-server/src/main/java/org/apache/zookeeper/server/PrepRequestProcessor.java:
##########
@@ -735,10 +735,18 @@ private String getParentPathAndValidate(String path) 
throws BadArgumentsExceptio
     }
 
     private static int checkAndIncVersion(int currentVersion, int 
expectedVersion, String path) throws KeeperException.BadVersionException {
-        if (expectedVersion != -1 && expectedVersion != currentVersion) {
-            throw new KeeperException.BadVersionException(path);
+       if (expectedVersion != -1) {
+            if (expectedVersion != currentVersion) {
+                throw new KeeperException.BadVersionException(path);
+            }
+            if (expectedVersion == -2) {
+                return 0;
+            } else {
+                return currentVersion + 1;
+            }
+        } else {
+            return currentVersion + 1;

Review Comment:
   @kezhuw Perhaps we can directly align the proposed `checkAndIncVersion`?
   
   I'd suggest:
   
   ```java
       private static int checkAndIncVersion(int currentVersion, int 
expectedVersion, String path) throws KeeperException.BadVersionException {
           if (expectedVersion != -1 && expectedVersion != currentVersion) {
               throw new KeeperException.BadVersionException(path);
           }
   
           // Skip increase the data version to -1 by jumping from -2 to 0. 
Otherwise, the client will
           // receive a new data version -1. Now if the client wants to check 
the data version, it can
           // only pass -1 as the next expected version, but -1 as the expected 
version means do not
           // check the data version. So the client is unable to express the 
expected manner.
           return currentVersion != -2 ? currentVersion + 1 : 0;
       }
   ```



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