Skip to content

CNCF OpenTelemetry Passthrough

This example is the simplest possible configuration of tremor with support for CNCF OpenTelemetry interception and distribution. It shows the very basic building blocks: * CNCF OpenTelemetry Onramp * CNCF OpenTelemetry Offramp * Deployment configuration file

External open telemetry clients can use port 4316 to send OpenTelemetry logs, traces and metrics through tremor. Tremor prints the json mapping to standard out and forwards the events to the OpenTelemetry collector.


The onramp we use is the otel CNCF OpenTeletry onramp listening on a non-standard CNCF OpenTelemetry port 4316, it receives protocol buffer messages over gRPC on this port. The log, metric and trace events received are converted to tremor's value system and passed through a passthrough pipeline to the CNCF OpenTelemetry sink. The sink will try to connect to a downstream CNCF OpenTelemetry endpoint. In this workshop we will use the well known OpenTelemetry port of 4317 for our sink and run the standard OpenTelemetry collector on this port using its a simple collector configuration.

  - id: otlp
    type: otel # Use the OpenTelemetry gRPC listener source
    codec: json # Json is the only supported value
      port: 4316 # The TCP port to listen on
      host: "" # The IP address to bind on ( all interfaces in this case )

It connects to a simple passthrough pipeline. This pipeline forwards any received observability events downstream unchanged.

select event from in into out;

We connect the passthrough output events into an OpenTelemetry sink which distributes them to a downstream OpenTelemetry service.

  - id: otlp
    type: otel
    codec: json # Jsn is the only supported value
      host: ""
      port: 4317

The binding expresses these relations and gives deployment connectivity graph.

  - id: example
       - '/pipeline/example/{instance}/in'
       - '/offramp/stdout/{instance}/in'
       - '/offramp/otlp/{instance}/in'

Finally the mapping instanciates the binding with the given name and instance variable to activate the elements of the binding.

    instance: "passthrough"

Business Logic

select event from in into out

Command line testing during logic development

Use any compliant OpenTelemetry instrumented application and configure the server to our source on port 4316 instead of the default 4317.


For convenience, use the provided docker-compose.yaml to start and stop tremor and the opentelemetry collector as follows:

# Start
$ docker compose up

# Stop
$ docker compose stop