divijvaidya opened a new pull request, #13284:
URL: https://github.com/apache/kafka/pull/13284
# Motivation
The test suite fails with the following error:
```
org.opentest4j.AssertionFailedError: Condition not met within timeout 30000.
topic A.test-topic-0 was not created on cluster B-
._~:/?#[]@!$&'()*+;="<>%{}|\^`618 in time ==> expected: <true> but was: <false>
```
Root cause of the failure is available in stdout:
```
[2023-02-17 18:56:32,308] INFO This node is a follower for A->B-
._~:/?#[]@!$&'()*+;="<>%{}|\^`618. Using existing connector configuration.
(org.apache.kafka.connect.mirror.MirrorMaker:234)
[2023-02-17 18:56:42,567] INFO Kafka MirrorMaker stopping
(org.apache.kafka.connect.mirror.MirrorMaker:202)
[2023-02-17 18:56:43,371] INFO Kafka MirrorMaker stopped.
(org.apache.kafka.connect.mirror.MirrorMaker:213)
[2023-02-17 18:56:43,371] INFO Kafka MirrorMaker stopping
(org.apache.kafka.connect.mirror.MirrorMaker:202)
[2023-02-17 18:56:44,376] INFO Kafka MirrorMaker stopped.
(org.apache.kafka.connect.mirror.MirrorMaker:213)
[2023-02-17 18:56:44,377] INFO Kafka MirrorMaker stopping
(org.apache.kafka.connect.mirror.MirrorMaker:202)
[2023-02-17 18:56:45,782] ERROR Failed to configure MirrorSourceConnector
connector for A->B- ._~:/?#[]@!$&'()*+;="<>%{}|\^`618
(org.apache.kafka.connect.mirror.MirrorMaker:236)
org.apache.kafka.connect.errors.ConnectException: Worker is shutting down
at
org.apache.kafka.connect.runtime.distributed.DistributedHerder.halt(DistributedHerder.java:766)
at
org.apache.kafka.connect.runtime.distributed.DistributedHerder.run(DistributedHerder.java:361)
at
java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at
java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at
java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
```
The test tries to assert topic replication on the second cluster but the
mirror maker nodes themselves are unavailable. They are unavailable because the
connectors fail to configure. Connectors fail to configure because the worker
is already shutting down by the time they are ready to be configured.
# Change
This highlights a gap in MirrorMaker startup sequence where it does not wait
for connectors to be configured by the herders before declaring itself as
"started". This leads to a situation where MirrorMaker claims it has started
but the herders are still in the process of configuring the connectors. During
this time, mirror maker will not perform any replication.
With this change, we add a dependency on connector configuration for the
MirrorMaker to declare itself as started.
# Rejected alternative
An alternative approach is to modify the test to wait for connectors to get
configured on all 3 MM nodes before starting the actual test i.e. before making
a call to create topic. But this alternative is artificially hiding the
problems which users of MirrorMaker may also face.
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