showuon commented on code in PR #15732:
URL: https://github.com/apache/kafka/pull/15732#discussion_r1570596642
##########
metadata/src/main/java/org/apache/kafka/metadata/migration/KRaftMigrationDriver.java:
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@@ -391,13 +391,16 @@ void enqueueMetadataChangeEvent(
// Events handled by Migration Driver.
abstract class MigrationEvent implements EventQueue.Event {
+ // Use no-op handler by default because the retryHandler will be
overridden if needed
+ public void retryHandler() { }
@SuppressWarnings("ThrowableNotThrown")
@Override
public void handleException(Throwable e) {
if (e instanceof MigrationClientAuthException) {
KRaftMigrationDriver.this.faultHandler.handleFault("Encountered ZooKeeper
authentication in " + this, e);
} else if (e instanceof MigrationClientException) {
log.info(String.format("Encountered ZooKeeper error during
event %s. Will retry.", this), e.getCause());
+ retryHandler();
Review Comment:
@chia7712 , I take your suggestion to add `RecoverMigrationStateFromZKEvent`
so that we don't need to worry about retry anymore. I was checking if this
change will cause any side effect, and here is my finding:
1. `recoverMigrationStateFromZK` is expected to run before the driver starts
the state machine.
2. In the `recoverMigrationStateFromZK`, we'll do these things:
a. create a ZNode for migration and initial migration state
b. install this class as a metadata publisher
c. transition to INACTIVE state
3. If this `recoverMigrationStateFromZK` is keep failing, the log will keep
outputting errors and keep retrying. Once it succeeds, the metadata publisher
will be installed and the `onControllerChange` and `onMetadataUpdate` will be
triggered to start the process. That means, if we change
`recoverMigrationStateFromZK` into an event, it won't affect anything because
what we need to do at this state is just waiting for the (a)(b)(c) operation
completes.
So, I'm +1 with this suggestion. Thank you.
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