gabriellefu commented on code in PR #23184:
URL: https://github.com/apache/kafka/pull/23184#discussion_r3897569518
##########
streams/src/main/java/org/apache/kafka/streams/state/internals/StoreQueryUtils.java:
##########
@@ -128,29 +128,35 @@ public static <R> QueryResult<R> handleBasicQueries(
final QueryResult<R> result;
final QueryHandler<?> handler =
QUERY_HANDLER_MAP.get(query.getClass());
- synchronized (position) {
- if (handler == null) {
- result = QueryResult.forUnknownQueryType(query, store);
- } else if (context == null || !isPermitted(position,
positionBound, context.taskId().partition())) {
- result = QueryResult.notUpToBound(
- position,
- positionBound,
- context == null ? null : context.taskId().partition()
- );
- } else {
- result = ((QueryHandler<R>) handler).apply(
- query,
- positionBound,
- config,
- store
- );
- }
- if (config.isCollectExecutionInfo()) {
- result.addExecutionInfo(
- "Handled in " + store.getClass() + " in " +
(System.nanoTime() - start) + "ns"
- );
+ // Take the store monitor before the position lock, matching the write
paths, so a
+ // concurrent put/query cannot deadlock (KAFKA-19629). Callers must
not hold the
+ // position lock when calling in, unless nothing else locks their
store monitor
Review Comment:
sounds good, i'll add it accordingly
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