flawless

Flawless

Flawless is a simple Python framework developed at shopkick for detecting bugs in a production environment. Flawless traps exceptions and then sends an email to the developer responsible for causing the exception. Flawless integrates with git and uses git-blame to determine which developer to email.

Project website: http://shopkick.github.com/flawless/

Why You Should Use Flawless

• Only sends 1 email per line of code. Even if a particular line of code causes thousands of exceptions, only one email will be sent.

• Only emails 1 developer. Flawless uses git-blame to figure out which developer is responsible for a particular exception, and will only email that developer.

• Flawless logs the values of every variable in the stack frame at the time the exception occurred. This makes debugging ten times faster.

• Don’t report exceptions in old code. If you set report_only_after_minimum_date, then Flawless will only report exceptions caused by code modified after report_only_after_minimum_date.

• Don’t alert on library code. You can mark certain files/functions as library code, and when an exception originates in those files/functions, the caller will be blamed for the error instead of the library code.

4 Step Setup Guide

1. Install Flawless. After this step you should have an executable named flawless in your path.

   $> python setup.py install

2. Setup the Flawless server. Go to the server which you want to host the Flawless backend. Then use the following command to start a short questionnaire to setup the server.

   $> flawless configure

3. Start the Flawless server

   $> flawless start -conf path/to/flawless.cfg

4. Integrate the Flawless client into your code. If you are running a WSGI application such as django or pylons/pyramid, simply add the flawless.client.middleware to your application. Otherwise you can wrap particular functions or entire classes by using flawless.client.decorators. View the examples directory for some actual code examples.

How it Works

The Flawless client wraps your code with a try/except block. When an exception is caught it then sends the entire traceback to the Flawless server. The Flawless server then aggregates exception reports from clients and figures out which line of code caused the exception. Once the line that caused the exception is identified, Flawless runs “git blame” to determine the email address of the developer that last touched that line of code. Flawless then sends the developer an email with the traceback.

Exceptions can be whitelisted if they are expected. To whitelist an exception you must specify the filename, function name, and the text from the line of code being whitelisted in the appropriate config file. Alternatively, exception emails include a link to automatically add an exception to the whitelist. It is possible to whitelist all exceptions from a particular function by leaving the line of code text blank. Likewise, an entire file can be whitelisted by leaving the line of code and function blank.

Server User Interface

/get_weekly_error_report - Shows all errors that happened this week. ses a leaderboard style format to show which developer is responsible for causing the most errors this week.

::

Parameters:
  timestamp - (optional) Specify which week you want to view. Default is the current week.
  include_known_errors - (optional) Include errors from config/known_errors. Default is False.
  include_modified_before_min_date - (optional) Include errors originating in code modified
  before flawless.cfg option "report_only_after_minimum_date". Default is False.

/check_health - Check if the server is up and running. Also displays server’s configuration parameters

/add_known_error - Webpage in which you can whitelist errors

/view_traceback - View the most recent traceback for a particular error

::

Parameters:
  filename - (required) Specify the filename in which the error occurred
  function_name - (required) Specify the name of the function in which the error occurred
  line_number - (required) Specify the line number on which the error occurred
  text - (required) Specify the full text that appears on line_number
  timestamp - (optional) Specify which week you want to view. Default is the current week.