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Posted to dev@kafka.apache.org by "Steven Schlansker (JIRA)" <ji...@apache.org> on 2016/06/30 18:03:10 UTC
[jira] [Created] (KAFKA-3921) Periodic refresh of metadata causes
spurious log messages
Steven Schlansker created KAFKA-3921:
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Summary: Periodic refresh of metadata causes spurious log messages
Key: KAFKA-3921
URL: https://issues.apache.org/jira/browse/KAFKA-3921
Project: Kafka
Issue Type: Improvement
Components: clients
Affects Versions: 0.9.0.1
Reporter: Steven Schlansker
Kafka cluster metadata has a configurable expiry period. (I don't understand why this is -- cluster updates can happen at any time, and we have to pick those up quicker than every 10 minutes? But this ticket isn't about that.)
When this interval expires, the ClientUtils class spins up a SyncProducer, which sends a special message to retrieve metadata. The producer is then closed immediately after processing this message.
This causes the SyncProducer to log both a connection open and close at INFO level:
{code}
2016-06-30T17:50:19.408Z INFO <> [ProducerSendThread-central-buzzsaw-1-myhost] kafka.client.ClientUtils$ - Fetching metadata from broker BrokerEndPoint(2,broker-3.mycorp.com,9092) with correlation id 17188 for 1 topic(s) Set(logstash)
2016-06-30T17:50:19.410Z INFO <> [ProducerSendThread-central-buzzsaw-1-myhost] kafka.producer.SyncProducer - Connected to broker-3.mycorp.com:9092 for producing
2016-06-30T17:50:19.411Z INFO <> [ProducerSendThread-central-buzzsaw-1-myhost] kafka.producer.SyncProducer - Disconnecting from broker-3.mycorp.com:9092
2016-06-30T17:50:19.411Z INFO <> [ProducerSendThread-central-buzzsaw-1-myhost] kafka.producer.SyncProducer - Disconnecting from broker-14.mycorp.com:9092
2016-06-30T17:50:19.411Z INFO <> [ProducerSendThread-central-buzzsaw-1-myhost] kafka.producer.SyncProducer - Disconnecting from broker-logkafka-13.mycorp.com:9092
2016-06-30T17:50:19.411Z INFO <> [ProducerSendThread-central-buzzsaw-1-myhost] kafka.producer.SyncProducer - Disconnecting from broker-12.mycorp.com:9092
2016-06-30T17:50:19.413Z INFO <> [ProducerSendThread-central-buzzsaw-1-myhost] kafka.producer.SyncProducer - Connected to broker-12.mycorp.com:9092 for producing
{code}
When you are reading the logs, this appears periodically. We've had more than one administrator then think that the cluster is unhealthy, and client connections are getting dropped -- it's disconnecting from the broker so frequently! What is wrong??? But in reality, it is just this harmless / expected metadata update.
Can we tweak the log levels so that the periodic background refresh does not log unless something goes wrong? The log messages are misleading and easy to misinterpret. I had to read the code pretty thoroughly to convince myself that these messages are actually harmless.
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