# sns_error_notification

## Source
The latest version of this code can be found at
https://github.com/fdamstra/sns_error_notification

## Description
This is a simple python decorate for the aws serverless (lambda) 
functions to make it easy to add email notification (or other SNS
handling) for errors and exceptions.

You can use CloudWatch to alert on errors, but then you just know that
something went wrong, not _what_ went wrong. 

I'm sure there are other ways to do this, but I didn't have luck finding them
and getting the information I needed, so here's what I came up with.

## Caveats
This could generate a LOT of email. I am not responsible for your email
administrator's wrath. You could always set up a different subscriber to
the SNS topic instead of directly emailing.

This won't report syntax errors when loading the code. Make it a best practice
to run `python3 -m py_compile lambda_function.py` before deploying to python. 
For that matter, add some unit or doc tests.

It also won't catch errors with deployment of the lambda environment, which
does happen from time to time.

It will also report errors even if a retry of the script succeeds. See
[AWS Lambda Retry Behavior](https://docs.aws.amazon.com/lambda/latest/dg/retries-on-errors.html)
for information on when it may automatically be retried.

Lastly, it won't catch issues with the SNS queue itself. If that isn't 
set up right, you won't get emails.

## If you know a better way
Please share it. Create an issue on this git repo, email me, whatever. I'm very
interested in better ways. I want to see:
* The full stack trace
* The event received as input
* The context (or at least important parts)

Additionally, it needs to handle rates of thousands of executions per
second.

## Set Up
1. Configure an SNS topic.
2. Subscribe to the SNS topic using your email address.
3. Grant your lanbda function `sns:Publish` permission.
4. Set the environment variable `sns_error_topic` to your SNS topic's arn. 
5. (Optional) Add the environment variable `sns_notifications_enabled` and set
   to either the string `true` or `false` to quickly enable or disable email
   notifications without code changes.
6. Add `from sns_error_notification import sns_error_notification` to your handler.
7. Add the line `@sns_error_notification` directly before your handler function.

See the example.py for an example.