akalash commented on a change in pull request #17946:
URL: https://github.com/apache/flink/pull/17946#discussion_r760299634
##########
File path:
flink-runtime/src/main/java/org/apache/flink/runtime/checkpoint/ExecutionAttemptMappingProvider.java
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@@ -38,32 +38,34 @@
private final List<ExecutionVertex> tasks;
/** The cached mapping, which would only be updated on miss. */
- private final LinkedHashMap<ExecutionAttemptID, ExecutionVertex>
cachedTasksById;
+ private volatile Map<ExecutionAttemptID, ExecutionVertex> cachedTasksById;
public ExecutionAttemptMappingProvider(Iterable<ExecutionVertex>
tasksIterable) {
this.tasks = new ArrayList<>();
tasksIterable.forEach(this.tasks::add);
- this.cachedTasksById =
- new LinkedHashMap<ExecutionAttemptID,
ExecutionVertex>(tasks.size()) {
-
- @Override
- protected boolean removeEldestEntry(
- Map.Entry<ExecutionAttemptID, ExecutionVertex>
eldest) {
- return size() > tasks.size();
- }
- };
+ this.cachedTasksById = new ConcurrentHashMap<>(tasks.size());
}
public Optional<ExecutionVertex> getVertex(ExecutionAttemptID id) {
- if (!cachedTasksById.containsKey(id)) {
- cachedTasksById.putAll(getCurrentAttemptMappings());
- if (!cachedTasksById.containsKey(id)) {
- // the task probably gone after a restart
- cachedTasksById.put(id, null);
+ ExecutionVertex vertex = cachedTasksById.get(id);
+ if (vertex != null) {
+ return Optional.of(vertex);
+ }
+
+ return updateAndGet(id);
+ }
+
+ private Optional<ExecutionVertex> updateAndGet(ExecutionAttemptID id) {
+ synchronized (tasks) {
Review comment:
Synchronization on `this` is always dangerous since it can lead to
deadlock if somebody decides to synchronize on this object outside. So in my
case, I can create the new private lock object or I can use some other private
variable in this class. I decided to choose the second option because actually,
it looks pretty reasonable for me - synchronization on tasks shows that only
one thread can have access to tasks which is true.
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