MINOR : lower Metadata info log to debug for topic ID change

[nicolasguyomar]

Hi team,

Minor suggestion to lower that new log to DEBUG as we used not to have any INFO log in this class and it looks like something has changed when you start a client while it's just the first metadata response result which is triggering the log with a somehow worrisome change from null to an actual topicID, as if something was not OK before, because null, and now it's good

Let me know what you think

Thank you

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[jolshan]

something has changed when you start a client while it's just the first metadata response result which is triggering the log with a somehow worrisome change from null to an actual topicID, as if something was not OK before, because null, and now it's good

Can you clarify this point? Are you seeing this log on startup? This message should only be logged when the ID was not null.

[nicolasguyomar]

Hello @jolshan

Yes you will see the log on any consumer/producer startup

[jolshan]

I'm not sure I follow why this happens though -- can you share an example of one of the logs?

[nicolasguyomar]

Hello @jolshan , this is a Confluent Bundle 7.2.0 console producer output, producing a "test" message in topic "nicolas"

You'll see that upon receiving the first Metadata response, we log the message that I would like to "hide", but you're probably right we should not log it at all

[2022-07-19 15:35:41,214] INFO [Producer clientId=console-producer] Resetting the last seen epoch of partition nicolas-0 to 0 since the associated topicId changed from null to 7OdYyViuRY2XmggNWuP_Vg (org.apache.kafka.clients.Metadata)

./kafka-console-producer --bootstrap-server=localhost:9092 --topic nicolas
[2022-07-19 15:35:30,945] INFO Registered kafka:type=kafka.Log4jController MBean (kafka.utils.Log4jControllerRegistration$)
[2022-07-19 15:35:31,012] INFO ProducerConfig values: 
	xxxx
 (org.apache.kafka.clients.producer.ProducerConfig)
[2022-07-19 15:35:31,037] INFO [Producer clientId=console-producer] Instantiated an idempotent producer. (org.apache.kafka.clients.producer.KafkaProducer)
[2022-07-19 15:35:31,129] INFO Successfully logged in. (org.apache.kafka.common.security.authenticator.AbstractLogin)
[2022-07-19 15:35:31,227] WARN The configuration 'sasl.mechanisms' was supplied but isn't a known config. (org.apache.kafka.clients.producer.ProducerConfig)
[2022-07-19 15:35:31,227] WARN The configuration 'schema.registry.url' was supplied but isn't a known config. (org.apache.kafka.clients.producer.ProducerConfig)
[2022-07-19 15:35:31,227] WARN The configuration 'schema.registry.basic.auth.credentials.source' was supplied but isn't a known config. (org.apache.kafka.clients.producer.ProducerConfig)
[2022-07-19 15:35:31,227] WARN The configuration 'sasl.username' was supplied but isn't a known config. (org.apache.kafka.clients.producer.ProducerConfig)
[2022-07-19 15:35:31,227] WARN The configuration 'schema.registry.basic.auth.user.info' was supplied but isn't a known config. (org.apache.kafka.clients.producer.ProducerConfig)
[2022-07-19 15:35:31,227] WARN The configuration 'sasl.password' was supplied but isn't a known config. (org.apache.kafka.clients.producer.ProducerConfig)
[2022-07-19 15:35:31,230] INFO Kafka version: 7.2.0-ce (org.apache.kafka.common.utils.AppInfoParser)
[2022-07-19 15:35:31,230] INFO Kafka commitId: 510078ca78367bd2542eaca9d26ebd22c5ca95cc (org.apache.kafka.common.utils.AppInfoParser)
[2022-07-19 15:35:31,230] INFO Kafka startTimeMs: 1658237731227 (org.apache.kafka.common.utils.AppInfoParser)
>[2022-07-19 15:35:32,290] INFO [Producer clientId=console-producer] Cluster ID: lkc-xrrwg (org.apache.kafka.clients.Metadata)
[2022-07-19 15:35:32,293] INFO [Producer clientId=console-producer] ProducerId set to 11385814 with epoch 0 (org.apache.kafka.clients.producer.internals.TransactionManager)
test
[2022-07-19 15:35:41,214] INFO [Producer clientId=console-producer] Resetting the last seen epoch of partition nicolas-0 to 0 since the associated topicId changed from null to 7OdYyViuRY2XmggNWuP_Vg (org.apache.kafka.clients.Metadata)
>^C[2022-07-19 15:35:55,532] INFO [Producer clientId=console-producer] Closing the Kafka producer with timeoutMillis = 9223372036854775807 ms. (org.apache.kafka.clients.producer.KafkaProducer)
[2022-07-19 15:35:55,557] INFO Metrics scheduler closed (org.apache.kafka.common.metrics.Metrics)
[2022-07-19 15:35:55,557] INFO Closing reporter org.apache.kafka.common.metrics.JmxReporter (org.apache.kafka.common.metrics.Metrics)
[2022-07-19 15:35:55,557] INFO Metrics reporters closed (org.apache.kafka.common.metrics.Metrics)
[2022-07-19 15:35:55,558] INFO App info kafka.producer for console-producer unregistered (org.apache.kafka.common.utils.AppInfoParser)

[jolshan]

Ah looks like the issue is that the oldID is null (not the new ID).

As described by this comment:

    // If the new topic ID is valid and different from the last seen topic ID, update the metadata.
    // Between the time that a topic is deleted and re-created, the client may lose track of the
   // corresponding topicId (i.e. `oldTopicId` will be null). In this case, when we discover the new
   // topicId, we allow the corresponding leader epoch to override the last seen value.

So based on this comment, we do want to override the epoch. Just curious why this one extra log message was causing issues. I suppose one thing we can do is check if this is the first metadata response/ if the epochs are equal, but not sure how much this helps.

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