Context OTEL processor

A processor to manipulate the Context Medatada in OTEL Collector. This processor allows to move resource attributes of Metrics, Logs and Traces to the context, which makes possible to use extensions like headers_setter dynamically.

Typical use cases:

• Be able to dynamically define tenants for Mimir/Cortex, Loki and Tempo
• Dynamically define metadata attributes in the context, to offer a link to pass resource attribute to extensions
• Change metadata generated from the receivers

The purpose of this code is quickly integrate a new component "Context processor" in our OpenTelemetry collectors. This is a temporary solution while this functionality is not available in upstream.

You can read about what Context Processor does in otelcol-dev/contextprocessor/README.md. And you can see an example configuration in otelcol-dev/otelcol.yaml

About

To get starting contributing in OpenTelemetry, please have a look at these resources:

• OpenTelemetry Collector: https://github.com/open-telemetry/opentelemetry-collector/blob/main/CONTRIBUTING.md
• OpenTelemetry Collector-Contrib: https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/CONTRIBUTING.md

Building the collector

1. Get golang installed: https://go.dev/doc/install
2. Install the ocb tool: https://github.com/open-telemetry/opentelemetry-collector/releases

If you want to get to your own custom collector compiled or updated:

1. Update the file builder-config.yaml, specially the new custom version in version. To completely update all components and add new ones as in the Contrib distribution, you can copy it from upstream https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/cmd/otelcontribcol/builder-config.yaml and adjust name, output_path, otelcol_version and all the gomod versions and make sure you remove the section replaces.

   dist:
       name: otelcol-dev
       description: Local OpenTelemetry Collector Contrib binary, testing only.
       output_path: ./otelcol-dev
       version: 0.105.0-sn3
       otelcol_version: 0.105.0
   

2. Add the Context processor component to the processors section of builder-config.yaml (with the same reference you used in the go mod init ...). Create another section to replace this module name with the local directory where the code is (./contextprocessor in this case). Put the same version as the rest of the modules (this only to avoid a build error with ocb, is not important for the compiler!)

   processors:
   - gomod: github.com/springernature/o11y-otel-contextprocessor/processor/contextprocessor v0.105.0
   
   replaces:
   - github.com/springernature/o11y-otel-contextprocessor/processor/contextprocessor => ./contextprocessor
   

3. Run ocb --config builder-config.yaml. A new directory otelcol-dev (or what you have defined in output_path) is created. The code generated should not be touched, all changes should be done via the builder-config.yaml file.

4. Go to new otelcold-dev and you will see a new executable otelcol-dev (or the value defined in name). You can execute it by providing a basic configuration file otelcold-dev --config otelcol.yaml:

   cat <<EOF > otelcol.yaml
   extensions:
   health_check:
   pprof:
       endpoint: 0.0.0.0:1777
   zpages:
       endpoint: 0.0.0.0:55679
   
   receivers:
   prometheus:
       config:
       scrape_configs:
           - job_name: 'otel-collector'
           scrape_interval: 30s
           static_configs:
               - targets: ['0.0.0.0:8888']
   
   exporters:
   debug:
       verbosity: detailed
   
   service:
   telemetry:
       logs:
       level: "debug"
   pipelines:
       metrics:
       receivers: [prometheus]
       processors: []
       exporters: [debug]
   extensions: 
   - health_check
   - pprof
   - zpages
   

   With this configuration the collector will scrape its own metrics.