apache/druid · error · IllegalStateException

Unknown Metric Type [ ]

Error message

Unknown Metric Type [%s]

What it means

updateMetric switches on the metric spec's configured type (meter, timer, counter, histogram, gauge); an unrecognized type value reaches the default branch and is rejected - usually a typo or unsupported type in the dropwizard metrics mapping file.

Solutions

1. Fix the `type` field in the dropwizard metrics mapping to one of meter/timer/counter/histogram/gauge.
2. Verify the type value parses into the expected enum as intended.

When it happens

Trigger: Thrown at extensions-contrib/dropwizard-emitter/src/main/java/org/apache/druid/emitter/dropwizard/DropwizardEmitter.java:159 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/21da0e899c13c985. Report an issue: GitHub.

Appendix: source

Thrown at extensions-contrib/dropwizard-emitter/src/main/java/org/apache/druid/emitter/dropwizard/DropwizardEmitter.java:159

      case meter:
        metricsRegistry.meter(name).mark(value.longValue());
        break;
      case timer:
        metricsRegistry.timer(name)
                       .update(value.longValue(), metricSpec.getTimeUnit());
        break;
      case counter:
        metricsRegistry.counter(name).inc(value.longValue());
        break;
      case histogram:
        metricsRegistry.histogram(name).update(value.longValue());
        break;
      case gauge:
        SettableGauge gauge = (SettableGauge) metricsRegistry.gauge(name, () -> new SettableGauge(value));
        gauge.setValue(value);
        break;
      default:
        throw new ISE("Unknown Metric Type [%s]", metricSpec.getType());
    }
  }

  @Override
  public void flush()
  {
    for (DropwizardReporter reporter : reporters) {
      reporter.flush();
    }
  }

  @Override
  public void close()
  {
    final boolean wasStarted = started.getAndSet(false);
    if (wasStarted) {
      for (DropwizardReporter reporter : reporters) {
        reporter.close();

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