[KAFKA-7620] ConfigProvider is broken for KafkaConnect when TTL is not null

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.0, 2.0.1
• Fix Version/s: 2.2.0, 2.1.1, 2.0.2
• Component/s: connect
• Assignee: Robert Yokota
• Reporter: Ye Ji
• Created: 13/Nov/18 05:08
• Updated: 28/Nov/18 06:03
• Resolved: 28/Nov/18 06:02

Description

If the ConfigData returned by ConfigProvider.get implementations has non-null and non-negative ttl, it will trigger infinite recursion, here is an excerpt of the stack trace:

at org.apache.kafka.connect.runtime.WorkerConfigTransformer.scheduleReload(WorkerConfigTransformer.java:62)
	at org.apache.kafka.connect.runtime.WorkerConfigTransformer.scheduleReload(WorkerConfigTransformer.java:56)
	at org.apache.kafka.connect.runtime.WorkerConfigTransformer.transform(WorkerConfigTransformer.java:49)
	at org.apache.kafka.connect.runtime.distributed.ClusterConfigState.connectorConfig(ClusterConfigState.java:121)
	at org.apache.kafka.connect.runtime.distributed.DistributedHerder.connectorConfigReloadAction(DistributedHerder.java:648)
	at org.apache.kafka.connect.runtime.WorkerConfigTransformer.scheduleReload(WorkerConfigTransformer.java:62)
	at org.apache.kafka.connect.runtime.WorkerConfigTransformer.scheduleReload(WorkerConfigTransformer.java:56)
	at org.apache.kafka.connect.runtime.WorkerConfigTransformer.transform(WorkerConfigTransformer.java:49)

Basically,
1) if a non-null ttl is returned from the config provider, connect runtime will try to schedule a reload in the future,
2) scheduleReload function reads the config again to see if it is a restart or not, by calling org.apache.kafka.connect.runtime.WorkerConfigTransformer.transform to transform the config
3) the transform function calls config provider, and gets a non-null ttl, causing scheduleReload being called, we are back to step 1.

To reproduce, simply fork the provided FileConfigProvider, and add a non-negative ttl to the ConfigData returned by the get functions.

Issue Links

• links to: GitHub Pull Request #5914