/saga-aws-serverless

Primary LanguagePython

Saga Pattern Implementation using Serverless Framework, Python, DynamoDB, and AWS Step Functions

Project structure

  • serverless.yaml this yaml file is the core file for our implementation, it contains all the declaration and configurations needed for the Severless framework to be able to create all the AWS resources we need to implement the Saga design pattern (Lambda functions, DynamoDB table creation, IAM roles, State machine model, and other configurations).

  • functions this folder has all the Python lambda functions:

    • create_order
    • process_payment
    • process_shipment
    • delete_order
    • refund_payment
    • cancel_shipment

If you prefer using Docker then you can skip the Install steps and pull the docker image:

docker run -it -v `pwd`:/saga-aws-serverless amahfouz/serverless /bin/bash

and start Configure

Install

You need first to install the Serverless framework and all its prereqs:

Configure

After installing the Serverless framework you need to start setting it up. Run serverless command and you will be asked several questions as follow:

Serverless: No project detected. Do you want to create a new one?

You won't get this question if you already running it from an existing serverless project.

If you answered Yes to create a new project you will be asked some other questions:

Serverless: What do you want to make? AWS Python
Serverless: What do you want to call this project? saga-aws-serverless

Project successfully created in 'saga-aws-serverless' folder.

I chose AWS Python for the programming language the serverless functions will be using, and then I gave the project name to be saga-aws-serverless.

You can monitor, troubleshoot, and test your new service with a free Serverless account.

Serverless: Would you like to enable this? No
You can run the “serverless” command again if you change your mind later.

For the above two questions, it's all up to you.

If you already have your AWS credentials setup on your machine you should be fine, otherwise, you will get the below prompt to configure your AWS credentials:

No AWS credentials were found on your computer, you need these to host your application.

Serverless: Do you want to set them up now? Yes
Serverless: Do you have an AWS account? Yes

If your browser does not open automatically, please open the URL: https://console.aws.amazon.com/iam/home?region=us-east-1#/users$new?step=final&accessKey&userNames=serverless&permissionType=policies&policies=arn:aws:iam::aws:policy%2FAdministratorAccess

Serverless: Press Enter to continue after creating an AWS user with access keys
Serverless: AWS Access Key Id: ####
Serverless: AWS Secret Access Key: ####

AWS credentials saved on your machine at ~/.aws/credentials. Go there to change them at any time.

Serverless: Would you like the Framework to update automatically? Yes

Auto updates were succesfully turned on.
You may turn off at any time with "serverless config --no-autoupdate"

The auto-complete if you don't have this already setup on your linux/Mac machine it will be nice to have it setup:

Serverless: Would you like to setup a command line <tab> completion? Yes
Serverless: Which Shell do you use ? bash
Serverless: We will install completion to ~/.bashrc, is it ok ? Yes

Command line <tab> completion was successfully setup. Make sure to reload your SHELL.
You may uninstall it by running: serverless config tabcompletion uninstall

Congrats now you have Serverless framework installed and configured on your machine.

Deploy

To deploy first you need to install the project dependencies:

npm install

Now you are all set to deploy all the lambda functions and create the AWS Step state machine model:

sls deploy

(sls is short for serverless)

If you would like to invoke any function all you need to do:

sls invoke -f create_order -d {"order_id":"1", "total":100}

Remove

Finally to remove all the AWS resources you created all you need to do is:

sls remove

Testing

  • To test the state machine model, go to AWS console, Services and search for Step Functions.
  • Select State machines from the left menu.
  • Select the state machine model created with OrderFulfilment in its name.
  • Click on Start Execution

Successful Input:

{
  "order_id": "1",
  "total": 100,
  "card_no": "123-1234",
  "address": "123 st"
}

Successful Order

Failure Input:

Failed Order

Missing total

{
  "order_id": "2"
}

Failed Order

Failed Payment

Missing card_no

{
  "order_id": "3",
  "total": 100
}

Failed Payment

Failed Shipment

Missing address

{
  "order_id": "5",
  "total": 100,
  "card_no": "123-1234"
}

Failed Shipment

Addition information