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.
Errors from Falcon resources are properly caught and recorded.

Configuration

Exclude lists

To exclude certain URLs from tracking, set the environment variable OTEL_PYTHON_FALCON_EXCLUDED_URLS (or OTEL_PYTHON_EXCLUDED_URLS to cover all instrumentations) to a string of comma delimited regexes that match the URLs.

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 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 the query_string and uri_template attributes from every traced request and add them as span attributes.

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

This instrumentation supports request and response hooks. These are functions that get called right after a span is created for a request and right before the span is finished for the 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 specified HTTP headers as span attributes, according to the semantic convention.

Request headers

To capture HTTP request headers as span attributes, set the environment variable OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST to a comma delimited 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 the request headers and add them as span attributes.

Request header names in Falcon are case-insensitive and - characters are replaced by _. So, giving the header name as CUStom_Header in the environment variable will capture the header named custom-header.

Regular expressions may also be used to match multiple headers that correspond to the given pattern. For example:

export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST="Accept.*,X-.*"

Would match all request headers that start with Accept and X-.

To capture all request headers, set OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST to ".*".

export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST=".*"

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

For example: http.request.header.custom_request_header = ["<value1>,<value2>"]

Response headers

To capture HTTP response headers as span attributes, set the environment variable OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE to a comma delimited 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 the response headers and add them as span attributes.

Response header names in Falcon are case-insensitive. So, giving the header name as CUStom-Header in the environment variable will capture the header named custom-header.

Regular expressions may also be used to match multiple headers that correspond to the given pattern. For example:

export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE="Content.*,X-.*"

Would match all response headers that start with Content and X-.

To capture all response headers, set OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE to ".*".

export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE=".*"

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

For example: http.response.header.custom_response_header = ["<value1>,<value2>"]

Sanitizing headers

In order to prevent storing sensitive data such as personally identifiable information (PII), session keys, passwords, etc, set the environment variable OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS to a comma delimited list of HTTP header names to be sanitized. Regexes may be used, and all header names will be matched in a case-insensitive manner.

For example,

export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS=".*session.*,set-cookie"

will replace the value of headers such as session-id and set-cookie with [REDACTED] in the span.

Note

The environment variable names used to capture HTTP headers are still experimental, and thus are subject to change.

API

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

Bases: 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 pyproject.toml.

For example, if an instrumentation instruments requests 1.x, this method should look like: :rtype: Collection[str]

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.