transformprocessor

Transform Processor

Supported pipeline types: traces

The transform processor modifies telemetry based on configuration using the Telemetry Query Language. It takes a list of queries which are performed in the order specified in the config.

Queries are composed of the following parts

• Path expressions: Fields within the incoming data can be referenced using expressions composed of the names as defined in the OTLP protobuf definition. e.g., status.code, attributes["http.method"]. If the path expression begins with resource. or instrumentation_library., it will reference those values.
  • The name instrumentation_library within OpenTelemetry is currently under discussion and may be changed in the future.
• Literals: Strings, ints, and floats can be referenced as literal values
• Function invocations: Functions can be invoked with arguments matching the function's expected arguments
• Where clause: Telemetry to modify can be filtered by appending where a <op> b, with a and b being any of the above.

Supported functions:

• set(target, value) - target is a path expression to a telemetry field to set value into. value is any value type. e.g., set(attributes["http.path"], "/foo"), set(name, attributes["http.route"]). If value resolves to nil, e.g. it references an unset map value, there will be no action.

• keep_keys(target, string...) - target is a path expression to a map type field. The map will be mutated to only contain the fields specified by the list of strings. e.g., keep_keys(attributes, "http.method"), keep_keys(attributes, "http.method", "http.route")

Supported where operations:

• == - matches telemetry where the values are equal to each other
• != - matches telemetry where the values are not equal to each other

Example configuration:

receivers:
  otlp:
    protocols:
      grpc:

exporters:
  nop

processors:
  transform:
    traces:
      queries:
        - set(status.code, 1) where attributes["http.path"] == "/health"
        - keep_keys(resource.attributes, "service.name", "service.namespace", "cloud.region")
        - set(name, attributes["http.route"])
service:
  pipelines:
    traces:
      receivers: [otlp]
      processors: [transform]
      exporters: [nop]

This processor will perform the operations in order for all spans

1. Set status code to OK for all spans with a path /health
2. Keep only service.name, service.namespace, cloud.region resource attributes
3. Set name to the http.route attribute if it is set