lhotari commented on code in PR #17254:
URL: https://github.com/apache/pulsar/pull/17254#discussion_r954460316
##########
pulsar-broker/src/main/java/org/apache/pulsar/broker/namespace/NamespaceService.java:
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@@ -644,6 +646,25 @@ private CompletableFuture<Optional<CandidateBrokerResult>>
getCandidateBrokerRes
}
+ private CompletableFuture<Optional<LeaderBroker>>
getOrWaitForLeader(AtomicInteger retries) {
+ return pulsar.getLeaderElectionService().readCurrentLeader()
+ .handle((leaderBroker, t) -> {
+ CompletableFuture<Optional<LeaderBroker>> retval;
+ if ((t != null || !leaderBroker.isPresent()) &&
retries.getAndIncrement() < 3) {
+ // retry after a delay of 5 seconds
+ retval =
+ CompletableFuture.supplyAsync(() -> null,
+
CompletableFuture.delayedExecutor(5, SECONDS))
+ .thenCompose(__ ->
getOrWaitForLeader(retries));
+ } else {
+ retval = CompletableFuture.completedFuture(
+ leaderBroker != null ? leaderBroker :
Optional.empty());
+ }
+ return retval;
+ })
+ .thenCompose(Function.identity());
Review Comment:
when using `.handle` that returns a CompletableFuture, it's necessary to
"flatten" it with `.thenCompose(Function.identity())`.
This is a known gap in CompletableFuture API that there is no
`handleCompose` method directly. (an [stackoverflow answer explaining
details](https://stackoverflow.com/a/60602429), contains links to other
answers) . Java 12+ contains `.exceptionallyCompose`, but no `.handleCompose`
which is unfortunate.
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