Status

Current state: Under Discussion

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

JIRA:

Motivation

All Kafka component register AppInfo  metrics to track the application start time or commit-id etc. These metrics are useful for monitoring and debugging. However, the AppInfo doesn't provide client-id, which is an important information for custom metrics reporter. 

As the AppInfoParser  class registers a JMX MBean with the provided client-id but when it adds metrics to the Metrics registry the client-id is not included.

Public Interfaces

Proposed Changes

1) Update the AppInfoMBean interface add new method getClientId() 

public interface AppInfoMBean {
    String getVersion();
    String getCommitId();
    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());
        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.class);
    private static final String VERSION;
    private static final String COMMIT_ID;
    private static final String CLIENT_ID;

    protected static final String DEFAULT_VALUE = "unknown";

    static {
        Properties props = new Properties();
        try (InputStream resourceStream = AppInfoParser.class.getResourceAsStream("/kafka/kafka-version.properties")) {
            props.load(resourceStream);
        } catch (Exception e) {
            log.warn("Error while loading kafka-version.properties: {}", e.getMessage());
        }
        VERSION = props.getProperty("version", DEFAULT_VALUE).trim();
        COMMIT_ID = props.getProperty("commitId", DEFAULT_VALUE).trim();
        CLIENT_ID = props.getProperty("clientId", DEFAULT_VALUE).trim();
    }

    public static String getClientId() {
        return CLIENT_ID;
    }

    public static synchronized void registerAppInfo(String prefix, String id, Metrics metrics, long nowMs) {
        try {
            // skip...
            DeprecatedAppInfo deprecatedMBean = new DeprecatedAppInfo(nowMs);
            AppInfo mBean = new AppInfo(nowMs);
            server.registerMBean(deprecatedMBean, name);
            server.registerMBean(mBean, name);

            registerMetrics(metrics, mBean); // prefix will be added later by JmxReporter
        } catch (JMException e) {
            log.warn("Error registering AppInfo mbean", e);
        }
    }

}

Compatibility, Deprecation, and Migration Plan

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

Test Plan

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

Rejected Alternatives

n/a