Create and Send a PDF Invoice using AWS/Serverless

Using Serverless to create a Lambda that generates a PDF, stores to S3 and sends via SES. Uses a Lambda Layer with wkhtmltopdf for PDF generation

Links

• https://www.serverless.com/blog/handling-aws-lambda-python-dependencies
• https://blog.richardkeller.net/building-a-pdf-generator-on-aws-lambda-with-python3-and-wkhtmltopdf/

Overview

Usage

Configure AWS

Use export AWS_PROFILE=XXX to set the profile before you run the following sls actions

Commands

export AWS_PROFILE=joec
sls deploy
sls invoke -f invoice -p event_sample.json
sls invoke local -f invoice -p event_sample.json

Bundling dependencies

In case you would like to include third-party dependencies, you will need to use a plugin called serverless-python-requirements. You can set it up by running the following command:

sls plugin install -n serverless-python-requirements

Running the above will automatically add serverless-python-requirements to plugins section in your serverless.yml file and add it as a devDependency to package.json file. The package.json file will be automatically created if it doesn't exist beforehand. Now you will be able to add your dependencies to requirements.txt file (Pipfile and pyproject.toml is also supported but requires additional configuration) and they will be automatically injected to Lambda package during build process. For more details about the plugin's configuration, please refer to official documentation.

Takeaways

• If config looks correct but still having deploy issues, manually delete CF stack and run sls deploy again
• Wasted a lot of time trying to package wkhtmltopdf with this, using a shared Lambda Layer was really nice!
• seems like can't get far evolving the stack without having to do nuclear deletes - likely more of a CloudFormation issue but still probably best to manage all related entities separately or more reliably (Terraform?)
• Serverless will generate wrapper s_<function> files and use these to set the handler
• filename containing the core lambda code has to be a certain length??? (see https://forum.serverless.com/t/serverless-sdk-get-user-handler-module-has-no-attribute/9659)

DDB queries

Simple update

aws dynamodb update-item --table-name invoices --key "S":"MX" 

All active clients have a simple counter in this DDB table to track invoice index: https://us-east-1.console.aws.amazon.com/dynamodbv2/home?region=us-east-1#item-explorer?maximize=true&operation=SCAN&table=invoices

A360

Running these locally now given the more custom nature of these

sls invoke local -f invoice -p aes-000002.json

TODO

• fix the bolding for TOTALS in both inline email and PDF attachment
• integrate with invoicing solution like Quickbooks