[KAFKA-9267] ZkSecurityMigrator should not create /controller node - ASF JIRA

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Details

Type: Bug
Status: Resolved
Priority: Major
Resolution: Fixed
Affects Version/s: None
Fix Version/s: 2.5.0
Component/s: admin
Labels:
None

Flags:

Patch, Important

Description

As we can see in these source codes – ZkSecurityMigrator.scala#L226

ZkSecurityMigrator checks and sets acl recursively for each path in SecureRootPaths. And /controller is also in SecureRootPaths.

As we can predicted, zkClient.makeSurePersistentPathExists() will create /controller node if /controller is not existed.

/controller is a EPHEMERAL node for controller election, but makeSurePersistentPathExists() will create a PERSISTENT node with null data.

If that happens, null data will cause a NPE, and the controller cannot be elected, kafka cluster will be unavailable .
In addition, a PERSISTENT node doesn't disappear automatically, we have to delete it manually to fix the problem.

PERSISTENT /controller node with null data in zk:

[zk: localhost:2181(CONNECTED) 16] get /kafka/controller
null
cZxid = 0x1100002284
ctime = Tue Dec 03 18:37:26 CST 2019
mZxid = 0x1100002284
mtime = Tue Dec 03 18:37:26 CST 2019
pZxid = 0x1100002284
cversion = 0
dataVersion = 0
aclVersion = 1
ephemeralOwner = 0x0
dataLength = 0
numChildren = 0

Normal /controller node in zk:

[zk: localhost:2181(CONNECTED) 21] get /kafka/controller
{"version":1,"brokerid":1001,"timestamp":"1575370170528"}
cZxid = 0x11000023e1
ctime = Tue Dec 03 18:49:30 CST 2019
mZxid = 0x11000023e1
mtime = Tue Dec 03 18:49:30 CST 2019
pZxid = 0x11000023e1
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x16ecb572df50021
dataLength = 57
numChildren = 0

NPE in controller.log :

[2019-11-21 15:02:41,276] INFO [ControllerEventThread controllerId=1002] Starting (kafka.controller.ControllerEventManager$ControllerEventThread)
[2019-11-21 15:02:41,282] ERROR [ControllerEventThread controllerId=1002] Error processing event Startup (kafka.controller.ControllerEventManager$ControllerEventThread)
java.lang.NullPointerException
 at com.fasterxml.jackson.core.JsonFactory.createParser(JsonFactory.java:857)
 at com.fasterxml.jackson.databind.ObjectMapper.readTree(ObjectMapper.java:2572)
 at kafka.utils.Json$.parseBytes(Json.scala:62)
 at kafka.zk.ControllerZNode$.decode(ZkData.scala:56)
 at kafka.zk.KafkaZkClient.getControllerId(KafkaZkClient.scala:902)
 at kafka.controller.KafkaController.kafka$controller$KafkaController$$elect(KafkaController.scala:1199)
 at kafka.controller.KafkaController$Startup$.process(KafkaController.scala:1148)
 at kafka.controller.ControllerEventManager$ControllerEventThread$$anonfun$doWork$1.apply$mcV$sp(ControllerEventManager.scala:86)
 at kafka.controller.ControllerEventManager$ControllerEventThread$$anonfun$doWork$1.apply(ControllerEventManager.scala:86)
 at kafka.controller.ControllerEventManager$ControllerEventThread$$anonfun$doWork$1.apply(ControllerEventManager.scala:86)
 at kafka.metrics.KafkaTimer.time(KafkaTimer.scala:31)
 at kafka.controller.ControllerEventManager$ControllerEventThread.doWork(ControllerEventManager.scala:85)
 at kafka.utils.ShutdownableThread.run(ShutdownableThread.scala:82)

So, I submit a PR that ZkSecurityMigrator will not handle /controller node when /controller is not existed.

This bug seems to affect all versions, please review and merge the PR as soon as possible.

Thanks!