BewareMyPower commented on code in PR #23049:
URL: https://github.com/apache/pulsar/pull/23049#discussion_r1682295880
##########
pulsar-broker/src/main/java/org/apache/pulsar/broker/namespace/NamespaceService.java:
##########
@@ -1509,6 +1514,31 @@ public CompletableFuture<List<String>>
getListOfTopics(NamespaceName namespaceNa
}
}
+ public CompletableFuture<List<String>> getListOfUserTopics(NamespaceName
namespaceName, Mode mode) {
+ String key = String.format("%s://%s", mode, namespaceName);
+ CompletableFuture<List<String>> queryRes =
+ inProgressQueryUserTopics.computeIfAbsent(key, k -> {
+ CompletableFuture<List<String>> res = new CompletableFuture<>();
+ // Switch thread to avoid blocking other threads who are calling
the current method.
+ pulsar.getExecutor().execute(() -> {
+ getListOfTopics(namespaceName, mode).thenApply(list -> {
+ return TopicList.filterSystemTopic(list);
+ }).whenComplete((topics, ex) -> {
+ if (ex != null) {
+ res.completeExceptionally(ex);
+ } else {
+ res.complete(topics);
+ }
+ });
+ });
+ return res;
+ });
+ queryRes.whenComplete((ignore, ex) -> {
Review Comment:
The existing code looks like:
```java
static class Cache {
private final Map<Integer, CompletableFuture<Integer>> futures = new
ConcurrentHashMap<>();
public CompletableFuture<Integer> run(int x) {
final var future = futures.computeIfAbsent(x, __ -> new
CompletableFuture<>());
future.whenComplete((__, ___) -> {
System.out.println("Remove " + x);
futures.remove(x, future);
});
return future;
}
}
```
Given the following code:
```
final var cache = new Cache();
cache.run(1);
cache.run(1);
cache.run(1);
cache.run(1).complete(100);
```
Outputs:
```
Remove 1
Remove 1
Remove 1
Remove 1
```
The fix:
```java
public CompletableFuture<Integer> run(int x) {
final var inserted = new MutableBoolean(false);
final var future = futures.computeIfAbsent(x, __ -> {
inserted.setTrue();
return new CompletableFuture<>();
});
if (inserted.isTrue()) {
future.whenComplete((__, ___) -> {
System.out.println("Remove " + x);
futures.remove(x, future);
});
}
return future;
}
```
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