[improve][broker] Use shrink map for message redelivery.

[Technoboy-]

Motivation

Sometimes the messages sent to consumers are delayed over 100ms and we find that the CPU is wasted on :

"BookKeeperClientWorker-OrderedExecutor-4-0" #64 prio=5 os_prio=0 cpu=2447920216.81ms elapsed=3636758.63s tid=0x00007f48bdc07290 nid=0xae runnable  [0x00007f47ee2e2000]
   java.lang.Thread.State: RUNNABLE
	at org.apache.bookkeeper.util.collections.ConcurrentLongLongPairHashMap.forEach(ConcurrentLongLongPairHashMap.java:197)
	at org.apache.pulsar.broker.service.persistent.MessageRedeliveryController.containsStickyKeyHashes(MessageRedeliveryController.java:97)
	at org.apache.pulsar.broker.service.persistent.PersistentStickyKeyDispatcherMultipleConsumers.getRestrictedMaxEntriesForConsumer(PersistentStickyKeyDispatcherMultipleConsumers.java:335)
	at org.apache.pulsar.broker.service.persistent.PersistentStickyKeyDispatcherMultipleConsumers.sendMessagesToConsumers(PersistentStickyKeyDispatcherMultipleConsumers.java:232)
	at org.apache.pulsar.broker.service.persistent.PersistentDispatcherMultipleConsumers.readEntriesComplete(PersistentDispatcherMultipleConsumers.java:480)
	- locked <0x0000100117401718> (a org.apache.pulsar.broker.service.persistent.PersistentStickyKeyDispatcherMultipleConsumers)
	at org.apache.bookkeeper.mledger.impl.OpReadEntry.lambda$checkReadCompletion$2(OpReadEntry.java:156)

Then we find there are many empty datas in the map from dump :

As #14515 has introduced shrink map, it's better to use it to avoid iterator the empty data.

Documentation

• no-need-doc

[codelipenghui]

I have added release labels, it's a serious problem that will cause the thread BookKeeperClientWorker-OrderedExecutor to 100% CPU usage.