OpenTelemetry Falcon Instrumentation

This library builds on the OpenTelemetry WSGI middleware to track web requests in Falcon applications. In addition to opentelemetry-instrumentation-wsgi, it supports falcon-specific features such as:

  • The Falcon resource and method name is used as the Span name.

  • The falcon.resource Span attribute is set so the matched resource.

  • Error from Falcon resources are properly caught and recorded.

Configuration

Exclude lists

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

For example,

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

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

Request attributes

To extract certain attributes from Falcon’s request object and use them as span attributes, set the environment variable OTEL_PYTHON_FALCON_TRACED_REQUEST_ATTRS to a comma delimited list of request attribute names.

For example,

export OTEL_PYTHON_FALCON_TRACED_REQUEST_ATTRS='query_string,uri_template'

will extract query_string and uri_template attributes from every traced request and add them as span attritbues.

Falcon Request object reference: https://falcon.readthedocs.io/en/stable/api/request_and_response.html#id1

Usage

from falcon import API
from opentelemetry.instrumentation.falcon import FalconInstrumentor

FalconInstrumentor().instrument()

app = falcon.API()

class HelloWorldResource(object):
    def on_get(self, req, resp):
        resp.body = 'Hello World'

app.add_route('/hello', HelloWorldResource())

Request and Response hooks

The instrumentation supports specifying request and response hooks. These are functions that get called back by the instrumentation right after a Span is created for a request and right before the span is finished while processing a response. The hooks can be configured as follows:

def request_hook(span, req):
    pass

def response_hook(span, req, resp):
    pass

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

Capture HTTP request and response headers

You can configure the agent to capture predefined HTTP headers as span attributes, according to the semantic convention.

Request headers

To capture predefined HTTP request headers as span attributes, set the environment variable OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST to a comma-separated list of HTTP header names.

For example,

export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST="content-type,custom_request_header"

will extract content-type and custom_request_header from request headers and add them as span attributes.

It is recommended that you should give the correct names of the headers to be captured in the environment variable. Request header names in falcon are case insensitive and - characters are replaced by _. So, giving header name as CUStom_Header in environment variable will be able capture header with name custom-header.

The name of the added span attribute will follow the format http.request.header.<header_name> where <header_name> being the normalized HTTP header name (lowercase, with - characters replaced by _ ). The value of the attribute will be single item list containing all the header values.

Example of the added span attribute, http.request.header.custom_request_header = ["<value1>,<value2>"]

Response headers

To capture predefined HTTP response headers as span attributes, set the environment variable OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE to a comma-separated list of HTTP header names.

For example,

export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE="content-type,custom_response_header"

will extract content-type and custom_response_header from response headers and add them as span attributes.

It is recommended that you should give the correct names of the headers to be captured in the environment variable. Response header names captured in falcon are case insensitive. So, giving header name as CUStomHeader in environment variable will be able capture header with name customheader.

The name of the added span attribute will follow the format http.response.header.<header_name> where <header_name> being the normalized HTTP header name (lowercase, with - characters replaced by _ ). The value of the attribute will be single item list containing all the header values.

Example of the added span attribute, http.response.header.custom_response_header = ["<value1>,<value2>"]

Note

Environment variable names to capture http headers are still experimental, and thus are subject to change.

API

class opentelemetry.instrumentation.falcon.FalconInstrumentor(*args, **kwargs)[source]

Bases: opentelemetry.instrumentation.instrumentor.BaseInstrumentor

An instrumentor for falcon.API

See BaseInstrumentor

instrumentation_dependencies()[source]

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 setup.py.

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

Collection[str]