OpenTelemetry Flask Instrumentation

This library builds on the OpenTelemetry WSGI middleware to track web requests in Flask applications. In addition to opentelemetry-util-http, it supports Flask-specific features such as:

  • The Flask url rule pattern is used as the Span name.

  • The http.route Span attribute is set so that one can see which URL rule matched a request.


from flask import Flask
from opentelemetry.instrumentation.flask import FlaskInstrumentor

app = Flask(__name__)


def hello():
    return "Hello!"

if __name__ == "__main__":


Exclude lists

To exclude certain URLs from being tracked, set the environment variable OTEL_PYTHON_FLASK_EXCLUDED_URLS (or OTEL_PYTHON_EXCLUDED_URLS as fallback) with comma delimited regexes representing which URLs to exclude.

For example,

export OTEL_PYTHON_FLASK_EXCLUDED_URLS="client/.*/info,healthcheck"

will exclude requests such as https://site/client/123/info and https://site/xyz/healthcheck.

You can also pass the comma delimited regexes to the instrument_app method directly:

FlaskInstrumentor().instrument_app(app, excluded_urls="client/.*/info,healthcheck")

Request/Response hooks

Utilize request/reponse hooks to execute custom logic to be performed before/after performing a request. Environ is an instance of WSGIEnvironment (flask.request.environ). Response_headers is a list of key-value (tuples) representing the response headers returned from the response.

def request_hook(span: Span, environ: WSGIEnvironment):
    if span and span.is_recording():
        span.set_attribute("custom_user_attribute_from_request_hook", "some-value")

def response_hook(span: Span, status: str, response_headers: List):
    if span and span.is_recording():
        span.set_attribute("custom_user_attribute_from_response_hook", "some-value")

FlaskInstrumentation().instrument(request_hook=request_hook, response_hook=response_hook)

Flask Request object reference:


class opentelemetry.instrumentation.flask.FlaskInstrumentor(*args, **kwargs)[source]

Bases: opentelemetry.instrumentation.instrumentor.BaseInstrumentor

An instrumentor for flask.Flask

See BaseInstrumentor


Return a list of python packages with versions that the will be instrumented.

The format should be the same as used in requirements.txt or

For example, if an instrumentation instruments requests 1.x, this method should look like:

def instrumentation_dependencies(self) -> Collection[str]:

return [‘requests ~= 1.0’]

This will ensure that the instrumentation will only be used when the specified library is present in the environment.

Return type


static instrument_app(app, request_hook=None, response_hook=None, tracer_provider=None, excluded_urls=None)[source]
static uninstrument_app(app)[source]