openzipkin/zipkin · error · NullPointerException

metrics == null

Error message

metrics == null

What it means

ScribeCollector.Builder.metrics(CollectorMetrics) throws NullPointerException when metrics is null. The metrics instance is scoped to the 'scribe' transport and passed through to the delegate Collector; the builder requires it non-null at configuration time. Omitting the call is fine — the builder defaults to NOOP metrics.

Source

Thrown at zipkin-collector/scribe/src/main/java/zipkin2/collector/scribe/ScribeCollector.java:39

  public static Builder newBuilder() {
    return new Builder();
  }

  /** Configuration including defaults needed to receive spans from a Scribe category. */
  public static final class Builder extends CollectorComponent.Builder {
    Collector.Builder delegate = Collector.newBuilder(ScribeCollector.class);
    CollectorMetrics metrics = CollectorMetrics.NOOP_METRICS;
    String category = "zipkin";
    int port = 9410;

    @Override public Builder storage(StorageComponent storage) {
      delegate.storage(storage);
      return this;
    }

    @Override public Builder metrics(CollectorMetrics metrics) {
      if (metrics == null) throw new NullPointerException("metrics == null");
      this.metrics = metrics.forTransport("scribe");
      delegate.metrics(this.metrics);
      return this;
    }

    @Override public Builder sampler(CollectorSampler sampler) {
      delegate.sampler(sampler);
      return this;
    }

    /** Category zipkin spans will be consumed from. Defaults to "zipkin" */
    public Builder category(String category) {
      if (category == null) throw new NullPointerException("category == null");
      this.category = category;
      return this;
    }

    /** The port to listen on. Defaults to 9410 */

View on GitHub (pinned to 878ce2a1fa)

Solutions

1. Pass CollectorMetrics.NOOP_METRICS or a real metrics implementation
2. Provide a default CollectorMetrics bean in the DI container
3. Do not call metrics() at all to keep the NOOP default

Example fix

// before
builder.metrics(enabled ? metricsImpl : null);

// after
builder.metrics(enabled ? metricsImpl : CollectorMetrics.NOOP_METRICS);

builder.metrics(metrics != null ? metrics : CollectorMetrics.NOOP_METRICS);

When it happens

Trigger: Calling .metrics(null) — typically a DI wiring path where no CollectorMetrics bean exists, or a conditional that uses null to mean 'metrics disabled'.

Common situations: Custom server bootstrap code where metrics are optional and null is used as a sentinel.

Related errors

• metrics == null
• metrics == null
• bootstrapServers == null
• groupId == null
• overrides == null

AI-assisted analysis of openzipkin/zipkin@878ce2a1fa (2026-08-14). Data as JSON: /api/errors/2a94ea03e8f74bb8. Report an issue: GitHub.