create_distributed_trace_payload

For general information on how the Python agent API calls relate to each other, see the API guide.

newrelic.agent.create_distributed_trace_payload()
This method is used for generating payloads used to connect transactions within a distributed trace.

Requirements

Python agent version 4.2.0.100 or higher.

Distributed tracing must be enabled.

Description

This API requires distributed tracing to be enabled.

For instructions on how to use this call, along with its partner call accept_distributed_trace_payload, see Enable distributed tracing with agent APIs.

This call is used to implement distributed tracing. It generates a payload that is read by the receiving application with the accept_distributed_trace_payload method.

Return value(s)

When successful, returns a DistributedTracePayload object, which inherits from Python's builtin dict type and has the following additional methods:

  • text: Generate a JSON encoded string version of the payload.
  • http_safe: Generate a base64 encoded string version of the payload.

When unsuccessful, returns None. This can happen when distributed tracing is not enabled or when called from outside an active transaction.

Example(s)

In order to maintain proper ordering of spans in a trace, you must generate the payload in the context of the span that sends it.

Create a distributed trace payload inside a background task

An example of using create_distributed_trace_payload in creating two external traces from within single a background task:

@newrelic.agent.background_task()
def main(url):
    header_key = newrelic.agent.ExternalTrace.cat_distributed_trace_key

    with newrelic.agent.ExternalTrace('my_external_library',
            url, method='GET'):
        # Generate the payload in the context of the ExternalTrace
        # span that sends it
        payload = newrelic.agent.create_distributed_trace_payload()
        headers = {header_key: payload.http_safe()}
        response = my_external_library._get(url, headers=headers)

    data = _process_response(response)
    
    with newrelic.agent.ExternalTrace('my_external_library',
            url, method='POST'):
        # Generate the payload in the context of the ExternalTrace
        # span that sends it
        payload = newrelic.agent.create_distributed_trace_payload()
        headers = {header_key: payload.http_safe()}
        response = my_external_library._post(url, data=data, headers=headers)

Create a distributed trace payload inside an external trace

An example of using create_distributed_trace_payload in creating an external trace:

def _bind_url(url, *args, **kwargs):
    # _bind_url is called with the args and kwargs sent to the `get`
    # method below
    return url

@newrelic.agent.external_trace('my_external_library', _bind_url, method='GET')
def get(url):
    payload = newrelic.agent.create_distributed_trace_payload()
    header_key = newrelic.agent.ExternalTrace.cat_distributed_trace_key
    headers = {header_key: payload.http_safe()}
    return my_external_library._get(url, headers=headers)

For more help

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