I get errors when trying to run my flask app in AWS Lambda

Question

I am trying to deploy a flask app that run very well locally to AWS Lambda using severless . The deployment is good but I can't use the aws lambda app. I get an error 502 Bad Gateway message: Internal server error .

I checked the logs and here what I found:

2021-03-12T01:49:27.685+01:00   Traceback (most recent call last):

2021-03-12T01:49:27.685+01:00   File "/var/task/wsgi_handler.py", line 44, in import_app

2021-03-12T01:49:27.685+01:00   wsgi_module = importlib.import_module(wsgi_fqn_parts[-1])

2021-03-12T01:49:27.685+01:00   File "/var/lang/lib/python3.8/importlib/__init__.py", line 127, in import_module

2021-03-12T01:49:27.685+01:00   return _bootstrap._gcd_import(name[level:], package, level)

2021-03-12T01:49:27.685+01:00   File "<frozen importlib._bootstrap>", line 1014, in _gcd_import

2021-03-12T01:49:27.685+01:00   File "<frozen importlib._bootstrap>", line 991, in _find_and_load

2021-03-12T01:49:27.685+01:00   File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked

2021-03-12T01:49:27.685+01:00   File "<frozen importlib._bootstrap>", line 671, in _load_unlocked

2021-03-12T01:49:27.685+01:00   File "<frozen importlib._bootstrap_external>", line 783, in exec_module

2021-03-12T01:49:27.685+01:00   File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed

2021-03-12T01:49:27.685+01:00   File "/var/task/app.py", line 10, in <module>

2021-03-12T01:49:27.685+01:00   from common.helpers import *

2021-03-12T01:49:27.685+01:00   File "/var/task/common/helpers.py", line 1, in <module>

2021-03-12T01:49:27.685+01:00   from common.db import db

2021-03-12T01:49:27.685+01:00   File "/var/task/common/db.py", line 1, in <module>

2021-03-12T01:49:27.685+01:00   from flask_pymongo import pymongo

2021-03-12T01:49:27.685+01:00   ModuleNotFoundError: No module named 'flask_pymongo'

2021-03-12T01:49:27.686+01:00   [ERROR] Exception: Unable to import app.app Traceback (most recent call last):   File "/var/lang/lib/python3.8/imp.py", line 234, in load_module     return load_source(name, filename, file)   File "/var/lang/lib/python3.8/imp.py", line 171, in load_source     module = _load(spec)   File "<frozen importlib._bootstrap>", line 702, in _load   File "<frozen importlib._bootstrap>", line 671, in _load_unlocked   File "<frozen importlib._bootstrap_external>", line 783, in exec_module   File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed   File "/var/task/wsgi_handler.py", line 119, in <module>     wsgi_app = import_app(config)   File "/var/task/wsgi_handler.py", line 49, in import_app     raise Exception("Unable to import {}".format(config["app"]))

2021-03-12T01:49:27.803+01:00   START RequestId: cd231555-23cb-4444-b6fe-36e2ce590dc7 Version: $LATEST

2021-03-12T01:49:29.040+01:00   Traceback (most recent call last):

2021-03-12T01:49:29.040+01:00   File "/var/task/wsgi_handler.py", line 44, in import_app

2021-03-12T01:49:29.040+01:00   wsgi_module = importlib.import_module(wsgi_fqn_parts[-1])

2021-03-12T01:49:29.040+01:00   File "/var/lang/lib/python3.8/importlib/__init__.py", line 127, in import_module

2021-03-12T01:49:29.040+01:00   return _bootstrap._gcd_import(name[level:], package, level)

2021-03-12T01:49:29.040+01:00   File "<frozen importlib._bootstrap>", line 1014, in _gcd_import

2021-03-12T01:49:29.040+01:00   File "<frozen importlib._bootstrap>", line 991, in _find_and_load

2021-03-12T01:49:29.040+01:00   File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked

2021-03-12T01:49:29.040+01:00   File "<frozen importlib._bootstrap>", line 671, in _load_unlocked

2021-03-12T01:49:29.040+01:00   File "<frozen importlib._bootstrap_external>", line 783, in exec_module

2021-03-12T01:49:29.040+01:00   File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed

2021-03-12T01:49:29.040+01:00   File "/var/task/app.py", line 10, in <module>

2021-03-12T01:49:29.040+01:00   from common.helpers import *

2021-03-12T01:49:29.040+01:00   File "/var/task/common/helpers.py", line 1, in <module>

2021-03-12T01:49:29.040+01:00   from common.db import db

I don't understand ModuleNotFoundError: No module named 'flask_pymongo' When I use the app in local I don't have this. I've tried to install it anyway but it still doesn't work.

My serverless config:

service: serverless-flask
plugins:
  - serverless-python-requirements
  - serverless-wsgi
custom:
  wsgi:
    # This is the file name and the app name of the application 
    # Where file name is app.py and Flask app name is app
    # ie. app = Flask(__name__) 
    app: app.app
    packRequirements: false
  pythonRequirements:
    dockerizePip: non-linux
provider:
  name: aws
  runtime: python3.8
  stage: dev
  region: us-east-1
functions:
  app:
    handler: wsgi.handler
    events:
      - http: ANY /
      - http: 'ANY {proxy+}'

Any suggestion?

Answer 1

Can you try packaging & installing your module in a containerised lambda env.

As sometimes modules packed in windows will not work on other os.

I had a similar issue with psycopg2 then installed and packaged in lambci docker and everything was working fine.