This library is a Python platform API for OpenTracing.
In order to understand the Python platform API, one must first be familiar with the OpenTracing project and terminology more specifically.
In the current version, opentracing-python provides only the API and a
basic no-op implementation that can be used by instrumentation libraries to
collect and propagate distributed tracing context.
Future versions will include a reference implementation utilizing an abstract Recorder interface, as well as a Zipkin-compatible Tracer.
The work of instrumentation libraries generally consists of three steps:
- When a service receives a new request (over HTTP or some other protocol), it uses OpenTracing's inject/extract API to continue an active trace, creating a Span object in the process. If the request does not contain an active trace, the service starts a new trace and a new root Span.
- The service needs to store the current Span in some request-local storage, where it can be retrieved from when a child Span must be created, e.g. in case of the service making an RPC to another service.
- When making outbound calls to another service, the current Span must be
retrieved from request-local storage, a child span must be created (e.g., by
using the
start_child_span()helper), and that child span must be embedded into the outbound request (e.g., using HTTP headers) via OpenTracing's inject/extract API.
Below are the code examples for steps 1 and 3. Implementation of request-local storage needed for step 2 is specific to the service and/or frameworks / instrumentation libraries it is using (TODO: reference to other OSS projects with examples of instrumentation).
Somewhere in your server's request handler code:
def handle_request(request):
span = before_request(request, opentracing.tracer)
# use span as Context Manager to ensure span.finish() will be called
with span:
# store span in some request-local storage
with RequestContext(span):
# actual business logic
handle_request_for_real(request)
def before_request(request, tracer):
span_context = tracer.extract(
format=Format.HTTP_HEADERS,
carrier=request.headers,
)
span = tracer.start_span(
operation_name=request.operation,
child_of(span_context))
span.set_tag('http.url', request.full_url)
remote_ip = request.remote_ip
if remote_ip:
span.set_tag(tags.PEER_HOST_IPV4, remote_ip)
caller_name = request.caller_name
if caller_name:
span.set_tag(tags.PEER_SERVICE, caller_name)
remote_port = request.remote_port
if remote_port:
span.set_tag(tags.PEER_PORT, remote_port)
return spanSomewhere in your service that's about to make an outgoing call:
# create and serialize a child span and use it as context manager
with before_http_request(
request=out_request,
current_span_extractor=RequestContext.get_current_span):
# actual call
return urllib2.urlopen(request)
def before_http_request(request, current_span_extractor):
op = request.operation
parent_span = current_span_extractor()
outbound_span = opentracing.tracer.start_span(
operation_name=op,
parent=parent_span
)
outbound_span.set_tag('http.url', request.full_url)
service_name = request.service_name
host, port = request.host_port
if service_name:
outbound_span.set_tag(tags.PEER_SERVICE, service_name)
if host:
outbound_span.set_tag(tags.PEER_HOST_IPV4, host)
if port:
outbound_span.set_tag(tags.PEER_PORT, port)
http_header_carrier = {}
opentracing.tracer.inject(
span=outbound_span,
format=Format.HTTP_HEADERS,
carrier=http_header_carrier)
)
for key, value in http_header_carrier.iteritems():
request.add_header(key, value)
return outbound_spanvirtualenv env
source env/bin/activate
make bootstrap
make test
Before new release, add a summary of changes since last version to CHANGELOG.rst
pip install zest.releaser[recommended]
prerelease
release
git push origin master --follow-tags
python setup.py sdist upload -r pypi
postrelease
git push