How do I get a stack trace from Zappa with Python on AWS Lambda

Question

I'm using the Zappa framework https://github.com/Miserlou/Zappa with Python and Flask on AWS Lambda. When it raises an exception it appears in the CloudWatch log but is illegible to me. I do get a normal Flask stack trace returned from a HTTP GET in debug builds however.

My question is how do I get a reasonable (Flask) stack trace in logs / from production code? When exceptions are raised in production all I have is log messages.

Nice stack trace from HTTP GET:

Traceback (most recent call last):
  File "/var/task/handler.py", line 96, in handler
    response = Response.from_app(app, environ)
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-v6XvIH/Werkzeug/werkzeug/wrappers.py", line 865, in from_app
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-v6XvIH/Werkzeug/werkzeug/wrappers.py", line 57, in _run_wsgi_app
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-v6XvIH/Werkzeug/werkzeug/test.py", line 871, in run_wsgi_app
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-v6XvIH/zappa/zappa/middleware.py", line 78, in __call__
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-v6XvIH/flask/flask/app.py", line 1836, in __call__
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-v6XvIH/flask/flask/app.py", line 1820, in wsgi_app
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-jvEYWI/flask-restful/flask_restful/__init__.py", line 271, in error_router
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-v6XvIH/flask/flask/app.py", line 1403, in handle_exception
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-jvEYWI/flask-restful/flask_restful/__init__.py", line 268, in error_router
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-v6XvIH/flask/flask/app.py", line 1817, in wsgi_app
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-v6XvIH/flask/flask/app.py", line 1477, in full_dispatch_request
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-jvEYWI/flask-restful/flask_restful/__init__.py", line 271, in error_router
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-v6XvIH/flask/flask/app.py", line 1381, in handle_user_exception
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-jvEYWI/flask-restful/flask_restful/__init__.py", line 268, in error_router
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-v6XvIH/flask/flask/app.py", line 1475, in full_dispatch_request
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-v6XvIH/flask/flask/app.py", line 1461, in dispatch_request
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-jvEYWI/flask-restful/flask_restful/__init__.py", line 477, in wrapper
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-v6XvIH/flask/flask/views.py", line 84, in view
  File "/private/var/folders/1j/5zcxjzkx29b8tfgrh2y90wt80000gn/T/pip-build-jvEYWI/flask-restful/flask_restful/__init__.py", line 587, in dispatch_request
  File "/Users/notacat/src/aws-lambda/zappa/controllers/error_controller.py", line 15, in get
TestError: 'This is a test error'

Hard to understand stack trace from CloudWatch log:

...Rlc3RFcnJvcjogJ1RoaXMgaXMgYSB0ZXN0IGVycm9yJzxiciAvPjwvcHJlPg==: 
Exception Traceback (most recent call last): 
File "/var/task/handler.py", line 161, in lambda_handler return LambdaHandler.lambda_handler(event, context) 
File "/var/task/handler.py", line 55, in lambda_handler return cls().handler(event, context) 
File "/var/task/handler.py", line 155, in handler raise Exception(exception) 
Exception: PCFET0NUWVBFIGh0bWw+NTAwLiBGcm9tIFphcHBhOiA8cHJlPidUaGlzIGl...

Nadir Sidi Nadir Sidi · Accepted Answer · 2018-03-21T21:27:50

This looks like an old question, but I'm using Zappa 0.45.1 and I can see my python stack trace when an error occurs through both the CloudWatch AWS terminal and by using zappa tail which provides the CloudWatch logs and some added information.

How do I get a stack trace from Zappa with Python on AWS Lambda

1 Answers