Status

Current state: Under Discussion Accepted

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

Vote thread: here

JIRA:

Motivation

All Kafka component components register AppInfo   metrics to track the application details such as start time or and commit-id etc. These metrics are useful valuable for monitoring and debugging. However, the AppInfo doesn't provide AppInfo does not include the client-id for Worker and MM2 clients, which is an important piece of information for custom metrics reporter. metrics reporters. While most Kafka clients (consumer, producer, admin) already register their client-id in the metrics config, there are cases in MM2 and Worker where AppInfo is registered without the client-id.

The AppInfoParser As the AppInfoParser  class registers a JMX MBean with the provided client-id, but when it adds adding metrics to the Metrics registry, the client-id is not included. This KIP proposes adding the client-id as a metric tag.

Public Interfaces

Currently MetricName for Worker and MM2 clients:

• [name=start-time-ms, group=app-info, description=Metric indicating start-time-ms, tags={}]
• [name=commit-id, group=app-info, description=Metric indicating commit-id, tags={}]
• [name=version, group=app-info, description=Metric indicating version, tags={}]

New MetricName for Worker and MM2 clients:

• [name=start-time-ms, group=app-info, description=Metric indicating start-time-ms, tags={client-id=<component-id>}]
• [name=commit-id, group=app-info, description=Metric indicating commit-id, tags={client-id=<component-id>}]
• [name=version, group=app-info, description=Metric indicating version, tags={client-id=<component-id>}]org.apache.kafka.common.utils.AppInfoParser.AppInfoMBean

Proposed Changes

1) Update the AppInfoMBean interface add new method getClientId() The new MBean will include a new tag, client-id

publicprivate interfacestatic AppInfoMBean {
   void registerMetrics(Metrics metrics, AppInfo appInfo, String getVersion(clientId); {
    Stringif getCommitId();
metrics    Long getStartTimeMs();
    String getClientId();
}

2) Deprecated old AppInfoMBean implementation and mark it deprecated

@Deprecated(since = "4.2")
public static class DeprecatedAppInfo implements AppInfoMBean {
} 

3) Add new AppInfoMBeanimplementation

public static class AppInfo implements AppInfoMBean {

    private final Long startTimeMs;

    public AppInfo(long startTimeMs) {
        this.startTimeMs = startTimeMs;
        log.info("Kafka version: {}", AppInfoParser.getVersion());
        log.info("Kafka commitId: {}", AppInfoParser.getCommitId== null) return;
    // Most Kafka clients (producer/consumer/admin) set the client-id tag in the metrics config.
    // Although we don’t explicitly parse client-id here, these metrics are automatically tagged with client-id.
    metrics.addMetric(metricName(metrics, "version", Map.of()), (Gauge<String>) (config, now) -> appInfo.getVersion());
        log.info("Kafka startTimeMs: {}", startTimeMs);
        log.info("Kafka client id: {}", AppInfoParser.getClientId());
    }

	// skip...

    @Override
    public String getClientId() {
        return AppInfoParser.getClientId();
    }
}

4) When AppInfoParser register MBean, we will register the new one and the deprecated one

public class AppInfoParser {
    private static final Logger log = LoggerFactory.getLogger(AppInfoParser.classmetrics.addMetric(metricName(metrics, "commit-id", Map.of()), (Gauge<String>) (config, now) -> appInfo.getCommitId());
    metrics.addMetric(metricName(metrics, "start-time-ms", Map.of()), (Gauge<Long>) (config, now) -> appInfo.getStartTimeMs());
    private static final String VERSION;
    private static final String COMMIT_ID;
    private static final String CLIENT_ID;
// MirrorMaker/Worker doesn't set client-id tag into the metrics config, so we need to set it here.
    protected static final String DEFAULT_VALUE = "unknown";

    staticif (!metrics.config().tags().containsKey("client-id") && clientId != null) {
        Properties props = new Properties();
        try (InputStream resourceStream = AppInfoParser.class.getResourceAsStream("/kafka/kafka-version.properties")) {
            props.load(resourceStreammetrics.addMetric(metricName(metrics, "version", Map.of("client-id", clientId)), (Gauge<String>) (config, now) -> appInfo.getVersion());
        } catch (Exception e) {
            log.warn("Error while loading kafka-version.properties: {}", e.getMessage());
        }
        VERSION = props.getProperty("version", DEFAULT_VALUE).trim(metrics.addMetric(metricName(metrics, "commit-id", Map.of("client-id", clientId)), (Gauge<String>) (config, now) -> appInfo.getCommitId());
        COMMIT_ID = props.getProperty("commitId", DEFAULT_VALUE).trim();
        CLIENT_ID = props.getProperty("clientId", DEFAULT_VALUE).trim(metrics.addMetric(metricName(metrics, "start-time-ms", Map.of("client-id", clientId)), (Gauge<Long>) (config, now) -> appInfo.getStartTimeMs());
    }

    public static String getClientId(}

2) When unregisters an MBean, also remove the new and deprecated MBean.

private static void unregisterMetrics(Metrics metrics, String clientId) {
    if (metrics == null) return CLIENT_ID;

    }

    public static synchronized void registerAppInfo(String prefix, String id, Metrics metrics, long nowMs) {metrics.removeMetric(metricName(metrics, "version", Map.of()));
    metrics.removeMetric(metricName(metrics, "commit-id", Map.of()));
    metrics.removeMetric(metricName(metrics,    try {"start-time-ms", Map.of()));

            // skip...
            DeprecatedAppInfo deprecatedMBean = new DeprecatedAppInfo(nowMs);
            AppInfo mBean = new AppInfo(nowMs);if (!metrics.config().tags().containsKey("client-id") && clientId != null) {
        metrics.removeMetric(metricName(metrics,    server.registerMBean(deprecatedMBean, name"version", Map.of("client-id", clientId)));
        metrics.removeMetric(metricName(metrics,    server.registerMBean(mBean, name"commit-id", Map.of("client-id", clientId)));

            registerMetricsmetrics.removeMetric(metricName(metrics, mBean); // prefix will be added later by JmxReporter
        } catch (JMException e) {
            log.warn("Error registering AppInfo mbean", e);
    "start-time-ms", Map.of("client-id", clientId)));
    }
    }

}

Compatibility, Deprecation, and Migration Plan

Since this is a newly introduced behavior, there are no compatibility concerns.

For users currently relying on the metric name without client-id tag, it will remain available until Kafka 5.0. New users are encouraged to use the new metric name, which includes the client-id tag. This deprecation will be documented in upgrade.html.

In Kafka 5.0, the following metric name will be removed. 

• [name=start-time-ms, group=app-info, description=Metric indicating start-time-ms, tags={}]
• [name=commit-id, group=app-info, description=Metric indicating commit-id, tags={}]
• [name=version, group=app-info, description=Metric indicating version, tags={}]

Test Plan

change unit test or Integration test to verify the new method.

Rejected Alternatives

A new deprecated configuration could be introduced to control the registration of this MBean.

Nevertheless, this approach is considered unnecessary, as it would introduce complexity without significant benefit.n/a