[GitHub] [beam] Abacn commented on a diff in pull request #28122: fix: fix a race condition in BigtableService cache

["Abacn (via GitHub)" <gi...@apache.org>]

Abacn commented on code in PR #28122:
URL: https://github.com/apache/beam/pull/28122#discussion_r1303305418


##########
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigtable/BigtableServiceFactory.java:
##########
@@ -75,15 +76,15 @@ static BigtableServiceEntry create(ConfigId configId, BigtableService service) {
 
     @Override
     public void close() {
-      int refCount =
-          refCounts.getOrDefault(getConfigId().id(), new AtomicInteger(0)).decrementAndGet();
-      if (refCount < 0) {
-        LOG.error(
-            "close() Ref count is < 0, configId=" + getConfigId().id() + " refCount=" + refCount);
-      }
-      LOG.debug("close() for config id " + getConfigId().id() + ", ref count is " + refCount);
-      if (refCount == 0) {
-        synchronized (lock) {
+      synchronized (lock) {
+        int refCount =
+            refCounts.getOrDefault(getConfigId().id(), new AtomicInteger(0)).decrementAndGet();
+        if (refCount < 0) {
+          LOG.error(
+              "close() Ref count is < 0, configId=" + getConfigId().id() + " refCount=" + refCount);
+        }
+        LOG.debug("close() for config id " + getConfigId().id() + ", ref count is " + refCount);
+        if (refCount == 0) {

Review Comment:
   concurrent programming can be tricky. It makes sense to me that move the lock here could resolve the race condition. However, is there any harm if make the entire close() function synchronized?



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