[fix][broker] Remove blocking calls from internalGetPartitionedStats

[nodece]

Motivation

The metadata-store thread is blocked in the Pulsar 3.0.x:

"metadata-store-11-1" #18 prio=5 os_prio=0 cpu=191.70ms elapsed=92.64s tid=0x00007fe149887e80 nid=0x3f39b waiting on condition  [0x00007fdedd3fd000]
   java.lang.Thread.State: TIMED_WAITING (parking)
	at jdk.internal.misc.Unsafe.park([email protected]/Native Method)
	- parking to wait for  <0x00001000270a2020> (a java.util.concurrent.CompletableFuture$Signaller)
	at java.util.concurrent.locks.LockSupport.parkNanos([email protected]/LockSupport.java:252)
	at java.util.concurrent.CompletableFuture$Signaller.block([email protected]/CompletableFuture.java:1866)
	at java.util.concurrent.ForkJoinPool.unmanagedBlock([email protected]/ForkJoinPool.java:3463)
	at java.util.concurrent.ForkJoinPool.managedBlock([email protected]/ForkJoinPool.java:3434)
	at java.util.concurrent.CompletableFuture.timedGet([email protected]/CompletableFuture.java:1939)
	at java.util.concurrent.CompletableFuture.get([email protected]/CompletableFuture.java:2095)
	at org.apache.pulsar.broker.resources.BaseResources.exists(BaseResources.java:183)
	at org.apache.pulsar.broker.resources.NamespaceResources$PartitionedTopicResources.partitionedTopicExists(NamespaceResources.java:302)
	at org.apache.pulsar.broker.admin.impl.PersistentTopicsBase.lambda$internalGetPartitionedStats$173(PersistentTopicsBase.java:1579)
	at org.apache.pulsar.broker.admin.impl.PersistentTopicsBase$$Lambda$687/0x0000000801261160.apply(Unknown Source)
	at java.util.concurrent.CompletableFuture.uniHandle([email protected]/CompletableFuture.java:934)
	at java.util.concurrent.CompletableFuture.uniHandleStage([email protected]/CompletableFuture.java:950)
	at java.util.concurrent.CompletableFuture.handle([email protected]/CompletableFuture.java:2340)
	at org.apache.pulsar.broker.admin.impl.PersistentTopicsBase.lambda$internalGetPartitionedStats$174(PersistentTopicsBase.java:1560)
	at org.apache.pulsar.broker.admin.impl.PersistentTopicsBase$$Lambda$674/0x00000008012561a0.accept(Unknown Source)

Modifications

Remove blocking calls.

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete