[GitHub] [pulsar] michaeljmarshall commented on a change in pull request #12123: Fix the potential race condition in the BlobStore readhandler

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

michaeljmarshall commented on a change in pull request #12123:
URL: https://github.com/apache/pulsar/pull/12123#discussion_r713583729



##########
File path: tiered-storage/jcloud/src/main/java/org/apache/bookkeeper/mledger/offload/jcloud/impl/BlobStoreBackedReadHandleImpl.java
##########
@@ -54,6 +56,15 @@
     private final DataInputStream dataStream;
     private final ExecutorService executor;
 
+    enum State {
+        Opened,
+        Closed
+    }
+
+    private AtomicReferenceFieldUpdater<BlobStoreBackedReadHandleImpl, State> STATE_UPDATER = AtomicReferenceFieldUpdater
+        .newUpdater(BlobStoreBackedReadHandleImpl.class, State.class, "state");
+    private volatile State state = null;

Review comment:
       I'm not sure that we need these concurrency controls. The `executor` in this class is a single thread. Therefore, a local `state` variable should be sufficient as long as we only update the variable from within the `executor`'s thread.

##########
File path: tiered-storage/jcloud/src/main/java/org/apache/bookkeeper/mledger/offload/jcloud/impl/BlobStoreBackedReadHandleImpl.java
##########
@@ -105,6 +118,11 @@ public LedgerMetadata getLedgerMetadata() {
                 long nextExpectedId = firstEntry;
                 try {
                     while (entriesToRead > 0) {
+                        State state = STATE_UPDATER.get(this);
+                        if (state == State.Closed) {
+                            log.warn("Reading a closed read handler. Ledger ID: {}, Read range: {}-{}", ledgerId, firstEntry, lastEntry);
+                            throw new BKException.BKUnexpectedConditionException();

Review comment:
       Should this complete the `promise` exceptionally?




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