# opentelemetry.propagate package

## Module contents

API for propagation of context.

The propagators for the `opentelemetry.propagators.composite.CompositePropagator` can be defined via configuration in the `OTEL_PROPAGATORS` environment variable. This variable should be set to a comma-separated string of names of values for the `opentelemetry_propagator` entry point. For example, setting `OTEL_PROPAGATORS` to `tracecontext,baggage` (which is the default value) would instantiate `opentelemetry.propagators.composite.CompositePropagator` with 2 propagators, one of type `opentelemetry.trace.propagation.tracecontext.TraceContextTextMapPropagator` and other of type `opentelemetry.baggage.propagation.W3CBaggagePropagator`. Notice that these propagator classes are defined as `opentelemetry_propagator` entry points in the `pyproject.toml` file of `opentelemetry`.

Example:

    import flask
    import requests
    from opentelemetry import propagate

    PROPAGATOR = propagate.get_global_textmap()

    def get_header_from_flask_request(request, key):
        return request.headers.get_all(key)

    def set_header_into_requests_request(request: requests.Request,
                                            key: str, value: str):
        request.headers[key] = value

    def example_route():
        context = PROPAGATOR.extract(
            get_header_from_flask_request,
            flask.request
        )
        request_to_downstream = requests.Request(
            "GET", "http://httpbin.org/get"
        )
        PROPAGATOR.inject(
            set_header_into_requests_request,
            request_to_downstream,
            context=context
        )
        session = requests.Session()
        session.send(request_to_downstream.prepare())

opentelemetry.propagate.extract(carrier, context=None, getter=<opentelemetry.propagators.textmap.DefaultGetter object>)

  Uses the configured propagator to extract a Context from the carrier.

  Parameters:

    - getter (`Getter`[`TypeVar`(`CarrierT`)]) – an object which contains a get function that can retrieve zero or more values from the carrier and a keys function that can get all the keys from carrier.

    - carrier (`TypeVar`(`CarrierT`)) – and object which contains values that are used to construct a Context. This object must be paired with an appropriate getter which understands how to extract a value from it.

    - context (`Context` | `None`) – an optional Context to use. Defaults to root context if not set.

  Return type:

    `Context`

opentelemetry.propagate.inject(carrier, context=None, setter=<opentelemetry.propagators.textmap.DefaultSetter object>)

  Uses the configured propagator to inject a Context into the carrier.

  Parameters:

    - carrier (`TypeVar`(`CarrierT`)) – the medium used by Propagators to read values from and write values to. Should be paired with setter, which should know how to set header values on the carrier.

    - context (`Context` | `None`) – An optional Context to use. Defaults to current context if not set.

    - setter (`Setter`[`TypeVar`(`CarrierT`)]) – An optional `Setter` object that can set values on the carrier.

  Return type:

    `None`

opentelemetry.propagate.get_global_textmap()
  Return type:

    `TextMapPropagator`

opentelemetry.propagate.set_global_textmap(http_text_format)
  Return type:

    `None`