[GitHub] [kafka] vvcephei commented on a change in pull request #8987: KAFKA-10221: Backport fix for KAFKA-9603 to 2.5

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vvcephei commented on a change in pull request #8987:
URL: https://github.com/apache/kafka/pull/8987#discussion_r450961919



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File path: streams/src/main/java/org/apache/kafka/streams/state/internals/AbstractRocksDBSegmentedBytesStore.java
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@@ -251,7 +252,7 @@ void restoreAllInternal(final Collection<KeyValue<byte[], byte[]>> records) {
                 // This handles the case that state store is moved to a new client and does not
                 // have the local RocksDB instance for the segment. In this case, toggleDBForBulkLoading
                 // will only close the database and open it again with bulk loading enabled.
-                if (!bulkLoadSegments.contains(segment)) {
+                if (!bulkLoadSegments.contains(segment) && context instanceof ProcessorContextImpl) {

Review comment:
       Woah, this is subtle. IIUC, the fix works by asserting that we should only enable bulk loading if the provided context is a ProcessorContextImpl, which is the kind of context that is only provided when adding the store to an active task.
   
   This seems correct to me, and although it's very subtle, it also seems ok as a patch for an older codebase that won't need to be maintained much. But maybe we can have a comment, or an internal method for the check, like 
   
   ```suggestion
                   if (!bulkLoadSegments.contains(segment) && isStoreForActiveTask(context)) {
   ```
   
   so that it'll be more obvious what's going on here?




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