Configure to use less memory for short-lived CLI tools #431
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merlimat
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hangc0276
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May 26, 2021
Fix apache#431 ### Motivation When multi consumers poll the same topic for the same position at the same time, it may trigger KafkaTopicConsumerManager#consumers concurrentHashMap deadlock and block the following read/write operation related to the same topic. ### Deadlock Parse deadlock stack ``` "bookkeeper-ml-workers-OrderedExecutor-0-0" apache#141 prio=5 os_prio=0 tid=0x00007f4866042000 nid=0x1013 waiting on condition [0x00007f47c9ad6000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x00000000865b0b58> (a org.apache.pulsar.common.util.collections.ConcurrentLongHashMap$Section) at java.util.concurrent.locks.StampedLock.acquireWrite(StampedLock.java:1119) at java.util.concurrent.locks.StampedLock.writeLock(StampedLock.java:354) at org.apache.pulsar.common.util.collections.ConcurrentLongHashMap$Section.put(ConcurrentLongHashMap.java:272) at org.apache.pulsar.common.util.collections.ConcurrentLongHashMap.putIfAbsent(ConcurrentLongHashMap.java:129) at io.streamnative.pulsar.handlers.kop.KafkaTopicConsumerManager.add(KafkaTopicConsumerManager.java:258) at io.streamnative.pulsar.handlers.kop.MessageFetchContext.lambda$null$10(MessageFetchContext.java:342) at io.streamnative.pulsar.handlers.kop.MessageFetchContext$$Lambda$1021/1882277105.accept(Unknown Source) at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:656) at java.util.concurrent.CompletableFuture.uniAcceptStage(CompletableFuture.java:669) at java.util.concurrent.CompletableFuture.thenAccept(CompletableFuture.java:1997) at io.streamnative.pulsar.handlers.kop.MessageFetchContext.lambda$null$12(MessageFetchContext.java:337) at io.streamnative.pulsar.handlers.kop.MessageFetchContext$$Lambda$1020/843113083.accept(Unknown Source) at java.util.concurrent.ConcurrentHashMap$EntrySetView.forEach(ConcurrentHashMap.java:4795) at io.streamnative.pulsar.handlers.kop.MessageFetchContext.lambda$readMessagesInternal$13(MessageFetchContext.java:328) at io.streamnative.pulsar.handlers.kop.MessageFetchContext$$Lambda$1015/1232352552.accept(Unknown Source) at java.util.concurrent.CompletableFuture.uniWhenComplete(CompletableFuture.java:760) at java.util.concurrent.CompletableFuture$UniWhenComplete.tryFire(CompletableFuture.java:736) at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474) at java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:1962) at io.streamnative.pulsar.handlers.kop.MessageFetchContext$2.readEntriesComplete(MessageFetchContext.java:479) at org.apache.bookkeeper.mledger.impl.OpReadEntry.lambda$checkReadCompletion$2(OpReadEntry.java:156) at org.apache.bookkeeper.mledger.impl.OpReadEntry$$Lambda$845/165410888.run(Unknown Source) at org.apache.bookkeeper.mledger.util.SafeRun$1.safeRun(SafeRun.java:36) at org.apache.bookkeeper.common.util.SafeRunnable.run(SafeRunnable.java:36) at org.apache.bookkeeper.common.util.OrderedExecutor$TimedRunnable.run(OrderedExecutor.java:204) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) at java.lang.Thread.run(Thread.java:748) ``` The deadlock happens as the following picture.  When Consumer C1 send poll request with `offset = 500`, KOP dispatch Thread A to fetch data from bookkeeper, and then Consuemr C2 also send poll request with `offset = 500` and KOP dispatch Thread B to fetch data. In `t0` timeStamp, thread A fetch data completed and do callback operation. KOP will **own thread C** to fetch data from BookKeeper. In `t1` timeStamp, thread B call `consumers.computeIfAbsent` with `key = 500` to get related cursor. In concurrentHashMap implementation, `computeIfAbsent` method will **hold the section write lock of `key = 500`** and do computation operation. In `t2` timeStamp, thread C fetch data completed and call `consumers.putIfAbsent` with `key = 500` in callback operation. It will try to **acquire the section write lock of `key = 500`** in concurrentHashMap. Howere the section write lock of `key = 500` has been hold by Thread B in `t1` timeStamp, thread C will stay to wait for write lock. In `t3` timeStamp, thread B call `getPositionForOffset` in `computeIfAbsent` operation. `getPositionForOffset` need to acquire thread C to read entry from BookKeeper. However thread C has been own in t0 timeStamp, thus, thread B will hold section write lock of `key = 500` in concurrentHashMap to wait for thread C. Dead lock happens. ### Modification 1. Move `getPositionForOffset` out of concurrentHashMap section write lock. 2. Add test to simulate the above multi consumers poll the same topic for the same offset at the same time situation.
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Motivation
Existing tools like
pulsar-adminandpulsar-clientshould use less memory to have shorter startup times.