Blackhole

The Blackhole sink discards observability events instead of delivering them to an external system. Events are accepted by the pipeline and then intentionally dropped. This sink is primarily used for debugging, testing, benchmarking, or temporarily disabling downstream delivery without changing upstream topology.

Because events still flow through worker's pipeline, the Blackhole sink is useful for validating sources, transforms, buffering behavior, and throughput without producing external side effects.

This sink supports logs, metrics, and traces.

The Blackhole sink consumes events and immediately drops them. No external network connections are made, and no persistent storage is involved. From the perspective of upstream components, events are considered successfully handled.

This makes the sink suitable for scenarios where you want to observe pipeline behavior, measure event rates, or validate configuration correctness without exporting data.

Buffer (optional) The Blackhole sink supports buffering in the same way as other sinks. Buffering determines how many events can be temporarily held before being processed (and discarded).

Memory buffering offers higher performance but does not survive restarts. Disk buffering provides durability across restarts, although durability has limited practical value since events are ultimately dropped.

When buffers are full, behavior can be configured to either apply backpressure to upstream components or drop newer events, depending on whether loss or throughput is preferred during testing.

Rate (optional) Limits the number of events per second that the sink is allowed to consume. This is particularly useful for simulating slow downstream systems or testing how the pipeline behaves under constrained throughput conditions.

If not set, the sink consumes events as fast as they are produced.

Print Interval (optional) Controls how frequently the sink reports a summary of its activity, such as the number of events processed. This is useful for visibility during debugging or performance testing.

Setting the interval to zero disables reporting entirely.

The Blackhole sink is commonly used during pipeline development to validate sources and transforms before enabling real delivery targets.

It is also useful for load testing, where you want to measure ingestion or transformation performance without involving external systems.

In production environments, it can temporarily replace a real sink during maintenance windows or incident investigation to isolate pipeline behavior without exporting data.