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Status

Current state: "Draft"

Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]

JIRA: KAFKA-17027

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

In the code base, there are different formats of metric tags like:

• "broker-id" in BrokerBlockingSender
• "BrokerId" in NodeToControllerChannelManagerImpl
• "clientId" in AbstractFetcherManager

This proposal is to unify metric tag format as lower camel case, because most of places use this format like:

• "networkProcessor" in SockerServer
• "delayedOperation" in DelayedOperation
• "clientSoftwareName" and "clientSoftwareVersion" in RequestChannel

Public Interfaces

• "broker-id" → "brokerId" in ControllerChannelManager, BrokerBlockingSender, ReplicaFetcherBlockingSend, ReplicaVerificationTool, ControllerChannelManager
• "BrokerId" → "brokerId" in NodeToControllerChannelManagerImpl
• "fetcher-id" → "fetcherId" in BrokerBlockingSender, ReplicaFetcherBlockingSend, ReplicaVerificationTool
• "client-id" → "clientId" in KafkaAdminClient, ConsumerMetrics, KafkaProducer, and ProducerMetrics
• "node-id" → "nodeId" in Selector
• "processor-node-id" → "processorNodeId" in StreamsMetricsImpl
• "record-cache-id" → "recordCacheId" in StreamsMetricsImpl

Above changes are found by following code in e2e test:

    val pattern = Pattern.compile("^[a-z]+((\\d)|([A-Z0-9][a-z0-9]+))*([A-Z])?$")
    ManagementFactory.getPlatformMBeanServer.queryNames(null, null).forEach(mbean => {
      mbean.getKeyPropertyList.forEach((key, _) => {
        val matcher = pattern.matcher(key)
        if (!matcher.find()) {
          println(mbean)
        }
      })
    })

Proposed Changes

1. Use both old and correct metric tag formats in 4.0 and log warning message for old metric tags.
2. Remove old metric tag formats after 5.0

Compatibility, Deprecation, and Migration Plan

• Before 4.x, users can keep using deprecated metric tag format.
• After 5.0, users need to update use lower camel case format.

Test Plan

The new unit test used to verify the "warning messages" about deprecated metric tag format will be added. The messages are used to encourage users to adopt the lower camel case format.

Rejected Alternatives

N/A