[PYTHON] Determine if AWS Chalice is chalice local

Introduction

WEB service using API Gateway and Lambda on AWS AWS Chalice, a Python framework that is useful when creating. One of the convenient points is that with a single chalice local command, a WEB server starts up on your PC (local) and the same thing that runs on AWS runs [^ 1]. Testing and debugging is insanely fast.

Task

It's a convenient chalice local, but there seemed to be no direct way to determine that it was running locally with code, so I thought about it.

• The reason is that I tried to change the log format when running on AWS and when running locally, as shown in Example [^ 2]. *

Solution

You can do it with: Take advantage of environment variables [^ 3].

--Define the stage for chalice local in the chalice configuration file (config.json) and set the appropriate environment variables in the defined stage. --When doing chalice local, specify the stage defined above with the --stage option.

This allows the code to determine if it is chalice local (running locally) by checking for the existence of environment variables.

Example

setting file

config.json

{
  "version": "2.0",
  "app_name": "testapp",
  "environment_variables": {
  },
  "stages": {
    "dev": {
      "api_gateway_stage": "api"
    },
    "local": {
      "environment_variables": {
        "IS_LOCAL": "true"
      }
    }
  }
}

An environment variable called ʻIS_LOCAL is set in the stage called local`.

Code body

app.Part of py

import logging
import os

# setup logger
logger = logging.getLogger()
logger.setLevel(logging.INFO)
logformat = (
    '[%(levelname)s] %(asctime)s.%(msecs)dZ (%(aws_request_id)s) '
    '%(filename)s:%(funcName)s[%(lineno)d] %(message)s'
)
if os.environ.get('IS_LOCAL'):
    logformat = (
        '[%(levelname)s] %(asctime)s.%(msecs)dZ '
        '%(filename)s:%(funcName)s[%(lineno)d] %(message)s'
    )
formatter = logging.Formatter(logformat, '%Y-%m-%dT%H:%M:%S')
for handler in logger.handlers:
    handler.setFormatter(formatter)

I am changing the log format when running on AWS and when running locally [^ 2].

Execution method

$ chalice local --stage local

When doing chalice local, specify the defined stage with the --stage option.

in conclusion

This method, the place where it is necessary to always add the --stage option to chalice local is not good, but the problem is certainly solved, so I am using it.

• I would like to know if there are any usage examples other than log format. .. .. * (-;