openzipkin/zipkin · error · NullPointerException

connectionFactory == null

Error message

connectionFactory == null

What it means

ActiveMQCollector.Builder.connectionFactory rejects null because the collector needs a configured ActiveMQConnectionFactory to create connections and message listeners on the zipkin queue. Unlike metrics/storage, there is no default: an ActiveMQ broker connection is mandatory for this collector type.

Source

Thrown at zipkin-collector/activemq/src/main/java/zipkin2/collector/activemq/ActiveMQCollector.java:50

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

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

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

    public Builder connectionFactory(ActiveMQConnectionFactory connectionFactory) {
      if (connectionFactory == null) throw new NullPointerException("connectionFactory == null");
      this.connectionFactory = connectionFactory;
      return this;
    }

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

    /** Count of concurrent message listeners on the queue. Defaults to 1 */
    public Builder concurrency(int concurrency) {
      if (concurrency < 1) throw new IllegalArgumentException("concurrency < 1");
      this.concurrency = concurrency;
      return this;
    }

View on GitHub (pinned to 878ce2a1fa)

Solutions

1. Create and set the factory from the broker URL: new ActiveMQConnectionFactory("tcp://broker:61616") then pass it.
2. Verify the broker URL configuration property is present before building the collector.
3. In tests, use an embedded broker (e.g. vm://localhost) instead of passing null.

Example fix

// before
ActiveMQCollector.newBuilder(SERVER).connectionFactory(null); // NPE

// after
ActiveMQCollector.newBuilder(SERVER)
    .connectionFactory(new ActiveMQConnectionFactory("tcp://localhost:61616"));

java
Objects.requireNonNull(brokerUrl, "broker URL must be configured");
builder.connectionFactory(new ActiveMQConnectionFactory(brokerUrl));

When it happens

Trigger: Calling .connectionFactory(null) on the ActiveMQ collector builder — usually an unset broker URL property being passed straight through.

Common situations: Missing ACTIVEMQ_URL/broker configuration in env-driven setup; unit tests building the collector without a broker; refactoring that dropped the factory creation line.

Related errors

• metrics == null
• queue == null
• concurrency < 1
• storage == null
• metrics == null

AI-assisted analysis of openzipkin/zipkin@878ce2a1fa (2026-08-14). Data as JSON: /api/errors/fae09e1ac964becf. Report an issue: GitHub.