[KAFKA-12326] MM2 fails to start to due missing required configuration "bootstrap.servers"

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 2.5.2, 2.8.0, 2.7.1, 2.6.2
• Fix Version/s: 2.5.2, 2.8.0, 2.7.1, 2.6.2
• Assignee: Randall Hauch
• Reporter: David Jacot
• Reviewer: Konstantine Karantasis
• Created: 12/Feb/21 16:10
• Updated: 14/Feb/21 03:34
• Resolved: 12/Feb/21 23:40

Description

I just tried to mirror a topic with MM2 between two clusters with a really simple configuration. Basically, the one provided in the repo with the correct `bootstrap.servers`.

MM2 fails with the following error:

[2021-02-12 17:05:50,389] ERROR [Worker clientId=connect-1, groupId=B-mm2] Uncaught exception in herder work thread, exiting:  (org.apache.kafka.connect.runtime.distributed.DistributedHerder:324)
org.apache.kafka.common.config.ConfigException: Missing required configuration "bootstrap.servers" which has no default value.
	at org.apache.kafka.common.config.ConfigDef.parseValue(ConfigDef.java:493)
	at org.apache.kafka.common.config.ConfigDef.parse(ConfigDef.java:483)
	at org.apache.kafka.common.config.AbstractConfig.<init>(AbstractConfig.java:108)
	at org.apache.kafka.common.config.AbstractConfig.<init>(AbstractConfig.java:142)
	at org.apache.kafka.clients.admin.AdminClientConfig.<init>(AdminClientConfig.java:233)
	at org.apache.kafka.clients.admin.Admin.create(Admin.java:145)
	at org.apache.kafka.connect.util.TopicAdmin.<init>(TopicAdmin.java:277)
	at org.apache.kafka.connect.util.SharedTopicAdmin.createAdmin(SharedTopicAdmin.java:143)
	at java.util.concurrent.atomic.AtomicReference.updateAndGet(AtomicReference.java:179)
	at org.apache.kafka.connect.util.SharedTopicAdmin.topicAdmin(SharedTopicAdmin.java:82)
	at org.apache.kafka.connect.util.SharedTopicAdmin.get(SharedTopicAdmin.java:72)
	at org.apache.kafka.connect.util.SharedTopicAdmin.get(SharedTopicAdmin.java:44)
	at org.apache.kafka.connect.util.KafkaBasedLog.start(KafkaBasedLog.java:163)
	at org.apache.kafka.connect.storage.KafkaOffsetBackingStore.start(KafkaOffsetBackingStore.java:136)
	at org.apache.kafka.connect.runtime.Worker.start(Worker.java:197)
	at org.apache.kafka.connect.runtime.AbstractHerder.startServices(AbstractHerder.java:128)
	at org.apache.kafka.connect.runtime.distributed.DistributedHerder.run(DistributedHerder.java:310)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

It seems that a regression was introduced by https://github.com/apache/kafka/commit/982ea2f6a471c217c7400a725c9504d9d8348d02. MM2 starts when the commit is reverted.

Issue Links

• is caused by: KAFKA-10021 When reading to the end of the config log, check if fetch.max.wait.ms is greater than worker.sync.timeout.ms
• links to: GitHub Pull Request #10122