Log spans may not be created when inside of a Flask Error Handler

[pglombardo]

Noted by @steveww:

Just calling logging.error('foo') works when in the body of the route.
It does not work when inside an error handler.

import instana
import logging
import json
from flask import Flask

app = Flask(__name__)

@app.errorhandler(Exception)
def exception_handler(err):
    app.logger.error(str(err))
    return str(err), 500

@app.route('/health', methods=['GET'])
def health():
    return 'OK'

@app.route('/warning', methods=['GET'])
def warning():
    app.logger.warn('This is a warning')
    return 'warning', 400

@app.route('/error', methods=['GET'])
def error():
    app.logger.error('This is an error')
    return 'error', 500

@app.route('/rerror', methods=['GET'])
def rerror():
    found_it = False
    my_list = None
    for i in my_list:
        if i == 'foo':
            found_it = True

    return found_it


if __name__ == '__main__':
    app.logger.setLevel(logging.INFO)
    app.logger.info('Starting')
    app.run(host='0.0.0.0', port=8080)

[steveww]

Looks like it's a clash with instrumentation/flask/vanilla.py
There is a wrapper around handle_user_exception that interferes. It closes the scope so there is None scope when the logging instrumentation tries to add an error span.

[steveww]

PR #173 created.