[GitHub] [incubator-doris] caiconghui commented on a change in pull request #6513: [Optimize][Clone] Take version count into consideration when choosing src replica for clone task

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

caiconghui commented on a change in pull request #6513:
URL: https://github.com/apache/incubator-doris/pull/6513#discussion_r698136571



##########
File path: fe/fe-core/src/main/java/org/apache/doris/clone/TabletSchedCtx.java
##########
@@ -499,10 +501,26 @@ public void chooseSrcReplica(Map<Long, PathSlot> backendsWorkingSlots) throws Sc
             
             long srcPathHash = slot.takeSlot(srcReplica.getPathHash());
             if (srcPathHash != -1) {
-                setSrc(srcReplica);
-                return;
+                if (!findSrcReplica) {
+                    // version count is set by report process, so it may not be set yet and default value is -1.
+                    // so we need to check it.
+                    minVersionCount = srcReplica.getVersionCount() == -1 ? Long.MAX_VALUE : srcReplica.getVersionCount();
+                    setSrc(srcReplica);
+                    findSrcReplica = true;
+                } else {
+                    long curVerCount = srcReplica.getVersionCount() == -1 ? Long.MAX_VALUE : srcReplica.getVersionCount();
+                    if (curVerCount < minVersionCount) {
+                        minVersionCount = curVerCount;
+                        setSrc(srcReplica);
+                        findSrcReplica = true;
+                    }
+                }
             }
         }
+
+        if (findSrcReplica) {

Review comment:
       ```suggestion
           if (!findSrcReplica) {
                throw new SchedException(Status.SCHEDULE_FAILED, "unable to find source slot");
           }
   
          
   ```




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