Cross application tracing

import newrelic.agent

transaction = newrelic.agent.current_transaction()
# returns a list of tuples in the form (header_name, header_value)
outgoing_headers = newrelic.agent.ExternalTrace.generate_request_headers(transaction)
for header_name, header_value in outgoing_headers:
    ...request.putheader(header_name, header_value) # code to be instrumented
...make_request(request) # code to be instrumented

import newrelic.agent

transaction = newrelic.agent.current_transaction()
trace = newrelic.agent.ExternalTrace(transaction, 'library', 'http://example.com', 'get')
with trace:
    response = fetch_example_dot_com() # code to be instrumented
    trace.process_response_headers(...response.headers)

import newrelic.agent

transaction = newrelic.agent.current_transaction()
# returns a string value
outgoing_metadata = newrelic.agent.ExternalTrace.get_request_metadata(transaction)
...request.add_metadata(outgoing_metadata) # code to be instrumented
...make_request(request) # code to be instrumented

import newrelic.agent

transaction = newrelic.agent.current_transaction()
trace = newrelic.agent.ExternalTrace(transaction, 'library', 'myproto://service', 'fetch')
with trace:
    ...response = fetch_from_service() # code to be instrumented
    # extract the metadata string sent from the service
    metadata_value = response.metadata # code to be instrumented
    trace.process_response_metadata(metadata_value)

import newrelic.agent

def handle_incoming_request(request):
    transaction = newrelic.agent.current_transaction()
    if transaction:
        transaction.process_request_metadata(...request.metadata)

    response = generate_response() # code to be instrumented

    if transaction:
        # get_response_metadata returns a string
        ...response.metadata = transaction.get_response_metadata()
    return response