csharp

The State Machine

This is an example CDK stack to deploy The State Machine stack described by Jeremy Daly here - https://www.jeremydaly.com/serverless-microservice-patterns-for-aws/#statemachine

You would use this pattern for simple or complex business logic in a synchronous or an asynchronous setup. Step Functions come with lots of built in robustness features that will reduce your code liability

Testing It Out

After deployment you should have an API Gateway HTTP API where on the base url you can send a POST request with a payload in the following format:

// for a succesful execution
{
    "flavour": "pepperoni"
}

//to see a failure
{
    "flavour": "pineapple"
}

If you pass in pineapple or hawaiian you should see the step function flow fail in the response payload

The response returned is the raw and full output from the step function so will look something like this:

// A successful execution, note the status of SUCCEEDED
{
    "billingDetails": {
        "billedDurationInMilliseconds": 500,
        "billedMemoryUsedInMB": 64
    },
    "executionArn": "arn:aws:...",
    "input": "{ \"flavour\": \"pepperoni\"}",
    "inputDetails": {
        "__type": "com.amazonaws.swf.base.model#CloudWatchEventsExecutionDataDetails",
        "included": true
    },
    "name": "6e520263-96db-4b80-9b70-659a6972c806",
    "output": "{\"containsPineapple\":false}",
    "outputDetails": {
        "__type": "com.amazonaws.swf.base.model#CloudWatchEventsExecutionDataDetails",
        "included": true
    },
    "startDate": 1.629880767853E9,
    "stateMachineArn": "arn:aws:...",
    "status": "SUCCEEDED",
    "stopDate": 1.629880768343E9,
    "traceHeader": "Root=1-612601bf-c54eff48a04f8cc9ce170772;Sampled=1"
}

// a failed execution, notice status: FAILED and the cause/error properties
{
    "billingDetails": {
        "billedDurationInMilliseconds": 500,
        "billedMemoryUsedInMB": 64
    },
    "cause": "They asked for Pineapple",
    "error": "Failed To Make Pizza",
    "executionArn": "arn:aws:...",
    "input": "{ \"flavour\": \"pineapple\"}",
    "inputDetails": {
        "__type": "com.amazonaws.swf.base.model#CloudWatchEventsExecutionDataDetails",
        "included": true
    },
    "name": "26d19050-7f9a-4b08-bea3-4106a403774f",
    "outputDetails": {
        "__type": "com.amazonaws.swf.base.model#CloudWatchEventsExecutionDataDetails",
        "included": true
    },
    "startDate": 1.629883060124E9,
    "stateMachineArn": "arn:aws:...",
    "status": "FAILED",
    "stopDate": 1.629883060579E9,
    "traceHeader": "Root=1-61260ab4-8c35f155b7a908d900562f1e;Sampled=1"
}

Useful commands

• dotnet build src compile this app
• cdk deploy deploy this stack to your default AWS account/region
• cdk diff compare deployed stack with current state
• cdk synth emits the synthesized CloudFormation template

Deploy with AWS Cloud9

• Create an Ubuntu AWS Cloud9 EC2 development environment
• Add the Microsoft repository

  wget https://packages.microsoft.com/config/ubuntu/20.04/packages-microsoft-prod.deb -O packages-microsoft-prod.deb
  

  sudo dpkg -i packages-microsoft-prod.deb
  

• Install the .NET Core SDK

  sudo apt-get update; \
  sudo apt-get install -y apt-transport-https && \
  sudo apt-get update && \
  sudo apt-get install -y dotnet-sdk-3.1
  

• Clone the CDK Patterns repo

  git clone https://github.com/cdk-patterns/serverless.git
  

• Change directory

  cd serverless/the-scalable-webhook/csharp
  

• Build the project to see if .NET Core has been setup correctly (optional)

  dotnet build src
  

• Deploy the stack

  cdk deploy