flask_middleware.py

import flask
from opencensus.ext.flask.flask_middleware import FlaskMiddleware
from opencensus.trace import utils, execution_context
from opencensus.trace.blank_span import BlankSpan

ATTR_REQUEST_BLACKLISTED = "request_blacklisted"


class FixedFlaskMiddleware(FlaskMiddleware):
    def _before_request(self):
        """
        Works around a grey area in opencensus' FlaskMiddleware where spans
        created during requests that are blacklisted end up polluting the
        previous span.
        """
        # Do not trace if the url is blacklisted
        if utils.disable_tracing_url(flask.request.url, self.blacklist_paths):
            execution_context.set_current_span(BlankSpan())
            execution_context.set_opencensus_attr(
                ATTR_REQUEST_BLACKLISTED, True
            )
            return

        execution_context.set_opencensus_attr(ATTR_REQUEST_BLACKLISTED, False)

        return super(FixedFlaskMiddleware, self)._before_request()