BewareMyPower commented on PR #23786:
URL: https://github.com/apache/pulsar/pull/23786#issuecomment-2562522075
The `pulsar-io-3-6` thread that holds the lock of `BrokerService#topics` is
blocked at:
```java
public CompletableFuture<ManagedLedgerFactory>
getManagedLedgerFactoryForTopic(TopicName topicName) {
// NOTE: it calls `getTopicPoliciesBypassSystemTopic` and tries to
acquire the lock of
//. `SystemTopicBasedTopicPoliciesService#policyCacheInitMap`
return getManagedLedgerConfig(topicName)
```
called by
```java
protected CompletableFuture<Map<String, String>>
fetchTopicPropertiesAsync(TopicName topicName) {
if (!topicName.isPartitioned()) {
return getManagedLedgerFactoryForTopic(topicName).thenCompose(
```
called by
```java
private void checkOwnershipAndCreatePersistentTopic(/* ... */) {
TopicName topicName = TopicName.get(topic);
pulsar.getNamespaceService().isServiceUnitActiveAsync(topicName)
.thenAccept(isActive -> {
if (isActive) {
CompletableFuture<Map<String, String>>
propertiesFuture;
if (properties == null) {
//Read properties from storage when loading
topic.
propertiesFuture =
fetchTopicPropertiesAsync(topicName); // HERE
```
called by
```java
protected CompletableFuture<Optional<Topic>>
loadOrCreatePersistentTopic(final String topic,
boolean createIfMissing, Map<String, String> properties,
@Nullable TopicPolicies topicPolicies) {
/* ... */
checkTopicNsOwnership(topic)
.thenRun(() -> {
final Semaphore topicLoadSemaphore =
topicLoadRequestSemaphore.get();
if (topicLoadSemaphore.tryAcquire()) {
checkOwnershipAndCreatePersistentTopic(topic,
createIfMissing, topicFuture, // HERE
properties, topicPolicies);
```
Here `checkTopicNsOwnership` and `isServiceUnitActiveAsync` futures all
completed immediately in the current thread so the callback of
`topics.computeIfAbsent` is blocked at acquiring the lock of
``SystemTopicBasedTopicPoliciesService#policyCacheInitMap`.
I think the correct fix is to move `checkTopicNsOwnership(topic).thenRun` to
`checkTopicNsOwnership(topic).thenRunAsync` (or other places in the same call)
so that the callback of `topics.computeIfAbsent` won't be blocked.
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