Flask integration guide

Add Bugsnag to your Flask applications.

Installation

Using PyPI:

pip install 'bugsnag[flask]'

Basic configuration

Configure Bugsnag and attach it to Flask’s exception handler.

# Import bugsnag
import bugsnag
from bugsnag.flask import handle_exceptions

# Configure Bugsnag
bugsnag.configure(
  api_key = "YOUR_API_KEY_HERE",
  project_root = "/path/to/your/app",
)

# Attach Bugsnag to Flask's exception handler
app = Flask(__name__)
handle_exceptions(app)

You can find your API key in Project Settings.

If you are running your app using uWSGI, run uwsgi with the --enable-threads option to allow events and sessions to be sent.

Logging configuration

You can connect Bugsnag up to Python’s logging framework so that anything of level “error” or above is logged to Bugsnag.

Here is a plain Python example:

import logging

from bugsnag.handlers import BugsnagHandler

# ... (call bugsnag.configure() here)
logger = logging.getLogger("test.logger")
handler = BugsnagHandler()
# send only ERROR-level logs and above
handler.setLevel(logging.ERROR)
logger.addHandler(handler)

To record breadcrumbs for log messages, you can add the leave_breadcrumbs log filter:

from bugsnag.handlers import BugsnagHandler

logger = logging.getLogger("test.logger")
handler = BugsnagHandler()

logger.addFilter(handler.leave_breadcrumbs)

This will capture a breadcrumb for each log message at or above the configured breadcrumb_log_level, which defaults to INFO.

Reporting unhandled errors

At this point, Bugsnag should be installed and configured, and any unhandled exceptions will be automatically detected and should appear in your Bugsnag dashboard.

Automatic detection of unhandled exceptions in threads relies on threading.excepthook, which is only supported in Python 3.8 and above.

Reporting handled errors

If you would like to send handled exceptions to Bugsnag, you should import the bugsnag module:

import bugsnag

Then to notify Bugsnag of an error, you can call bugsnag.notify:

bugsnag.notify(Exception("Something broke!"))

You can also pass additional configuration options in as named parameters. These parameters will only affect the current call to notify.

Sending diagnostic data

Automatically captured diagnostics

As well as a full stacktrace for every exception, Bugsnag will automatically capture the following diagnostic data:

  • Request information, including ip, headers, URL, HTTP method, and HTTP params
  • Session data
  • Release stage (production, beta, staging, etc)
  • Hostname

Custom diagnostics

The metadata field is a dictionary of dictionaries which will be rendered as a tab in a Bugsnag error report. This example would create a special_info tab:

bugsnag.notify(Exception("Something broke!"),
    context="myContext",
    metadata={"special_info":{"request_id": 12345, "message_id": 854}}
)

For more information, see reporting handled errors.

Logging diagnostic data

The BugsnagHandler accepts a special keyword argument to its __init__() function: extra_fields. This is optional and may be a dictionary of extra attributes to gather from each LogRecord and insert into metadata to be attached to Bugsnag error reports.

The keys in the extra_fields dictionary should be tab names for where you would like the data displayed in Bugsnag, and the values should be attributes to pull off each log record and enter into section. The attributes are not required to exist on the log record, and any non-existent attribute will be ignored. Example:

bs_handler = BugsnagHandler(extra_fields={"some_tab":["context_attribute"]})

This is very useful if you are assigning context-specific attributes to your LogRecord objects, as described in the python logging cookbook.

Session tracking

Bugsnag tracks the number of “sessions” that happen within your application. This allows you to compare stability scores between releases and helps you to understand the quality of your releases.

Sessions are captured and reported by default. This behavior can be disabled using the auto_capture_sessions configuration option.

Using this option, Bugsnag will report a session each time a request is made to the server.

If you want control over what is deemed a session, rather than using the auto_capture_sessions option, you can call Bugsnag.start_session when appropriate for your application.

Identifying users

The user field is information about the person currently using your application. It should be a dictionary containing id, email, and/or name.

bugsnag.notify(e, user={"id":"bob-hoskins", name: "Bob Hoskins", email: "foo@bar.com"})

For more information, see reporting handled errors. To set user information for every report, see customizing error reports.

Logging breadcrumbs

In order to understand what happened in your application before each crash, it can be helpful to leave short log statements that we call breadcrumbs. A configurable number of breadcrumbs are attached to each error report to help diagnose what events led to the error.

Automatically captured breadcrumbs

By default, Bugsnag captures the following events as breadcrumbs:

  • Error reports

  • HTTP requests

This can be controlled using the enabled_breadcrumb_types configuration option.

Leaving manual breadcrumbs

You can use the leave_breadcrumb method to log potentially useful events in your own applications:

bugsnag.leave_breadcrumb("Something happened!")

Additional data can also be attached to breadcrumbs by providing the optional type and metadata parameters. For more information and examples for how custom breadcrumbs can be integrated, see customizing breadcrumbs.

Next steps