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Status

Current state:   [One of "Under Discussion", "Accepted", "Rejected"]

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

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

Motivation

Describe the problems you are trying to solve.

Public Interfaces

Briefly list any new interfaces that will be introduced as part of this proposal or any existing interfaces that will be removed or changed. The purpose of this section is to concisely call out the public contract that will come along with this feature.

A public interface is any change to the following:

• Binary log format

• The network protocol and api behavior

• Any class in the public packages under clientsConfiguration, especially client configuration

  • org/apache/kafka/common/serialization

  • org/apache/kafka/common

  • org/apache/kafka/common/errors

  • org/apache/kafka/clients/producer

  • org/apache/kafka/clients/consumer (eventually, once stable)

• Monitoring

• Command line tools and arguments

• Anything else that will likely break existing users in some way when they upgrade

Proposed Changes

Kafka closes connections that have been idle for a given amount of time (based on connection.max.idle.ms configuration, that has by default 10 minutes in the latest version).

There might be cases where clients become idle for a while, for example when a Change Data Capture is streaming changes but updated happen in batched series.  As of now,  the only way to notice when a connection is closed because of being idle is by enabling TRACE logs, however, it would be very useful to have a JMX metric to track this behaviour from the monitoring stack of choice.

Public Interfaces

A new sensor is going to be created to track the number of idle connections closed under the Selector.java class, only affected interface is the monitoring. This change is backwards compatible as no old sensors are touched.

The change should look something like this:

this.idleConnectionClosed = sensor("idle-connections-closed:" + tagsSuffix);

this.idleConnectionClosed.add(createMeter(metrics, metricGrpName, metricTags, "idle-connection-close", "idle connections closed"));

Proposed Changes

The change is actually small, first part would be to add a sensor and register it properly, it would look something like:

this.idleConnectionClosed = sensor("idle-connections-closed:" + tagsSuffix);

this.idleConnectionClosed.add(createMeter(metrics, metricGrpName, metricTags, "idle-connection-close", "idle connections closed"));

In the SelectorMetrics constructor. This would create a new meter that we can use to record the closed connections when happening.

Once this is done, we can just record the event when the connection is closed, this would mean adding a line like:

sensors.idleConnectionClosed.record();

At the end of the method maybeCloseOldestConnection in the Selector class.

With these changes, all idle connections closed will be reported in the JMX reportersDescribe the new thing you want to do in appropriate detail. This may be fairly extensive and have large subsections of its own. Or it may be a few sentences. Use judgement based on the scope of the change.

Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users?
• If we are changing behavior how will we phase out the older behavior?
• If we need special migration tools, describe them here.
• When will we remove the existing behavior?No impact to current users as the change adds a new metric, no former behaviour is altered.

Rejected Alternatives

If there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.