https://github.com/eclecticlogic/stepper

Stepper allows you to write AWS Step Functions using a higher level programmatic language.
https://github.com/eclecticlogic/stepper

aws step-functions

Last synced: 6 months ago
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Stepper allows you to write AWS Step Functions using a higher level programmatic language.

Host: GitHub
URL: https://github.com/eclecticlogic/stepper
Owner: eclecticlogic
License: apache-2.0
Created: 2014-12-20T21:51:28.000Z (over 11 years ago)
Default Branch: master
Last Pushed: 2019-07-27T12:40:24.000Z (almost 7 years ago)
Last Synced: 2024-04-16T07:32:29.395Z (about 2 years ago)
Topics: aws, step-functions
Language: Java
Homepage:
Size: 345 KB
Stars: 14
Watchers: 2
Forks: 4
Open Issues: 0
Metadata Files:
- Readme: README.md
- License: LICENSE

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README

Stepper
====

**Stepper** is to *Step Functions* as **High level language** is to *Assembly*.

Stepper allows you to write AWS Step Functions using modern programming constructs such as `if else` branching, `for`
and `while` loops, `try catch` for error handling and natural expressions such as `a = arr.length + 1`.
To illustrate, let us create a step function that generates the first 10 Fibonnaci numbers and stores them into an SQS
queue.

```Javascript

@Comment("Generate Fibonnaci numbers")
@TimeoutSeconds(120)
@Version("1.0")
stepper Fibonnaci {

previous = 1;
fib = 0;

for (c = 1 to 10) {
body = fib + ""; // queue message must be a string
sqs = task { // write to queue
"Resource": "arn:aws:states:::sqs:sendMessage",
"Parameters": {
"MessageBody.$": "$.body",
"QueueUrl": "https://sqs.us-east-1.amazonaws.com/1570xxxx/fibo"
}
}
temp = fib;
fib += previous;
previous = temp;
}
}

```

As you can see, the above code feels like a modern programming language (Stepper seeks compatibility with Javascript
expression syntax and built-in functions). The Stepper compiler turns the variables used into ASL json attributes and
then creates a supporting Lambda function to evaluate expressions used. Stepper will compile the code above into the
following state machine.

JSON for Fibonnaci step function ... (click to expand).

```json
{
"Comment": "Generate Fibonnaci numbers",
"TimeoutSeconds": 120,
"Version": "1.0",
"StartAt": "Fibonnaci000",
"States": {
"Fibonnaci000": {
"Type": "Pass",
"Result": 1,
"ResultPath": "$.previous",
"Next": "Fibonnaci001"
},
"Fibonnaci001": {
"Type": "Pass",
"Result": 0,
"ResultPath": "$.fib",
"Next": "Fibonnaci002"
},
"Fibonnaci002": {
"Type": "Task",
"Parameters": {
"cmd__sm": "Fibonnaci002"
},
"Resource": "arn:aws:lambda:us-east-1:1570xxxx:function:Fibonnaci_stepperLambda",
"ResultPath": "$.c",
"Next": "Fibonnaci003"
},
"Fibonnaci003": {
"Type": "Task",
"Parameters": {
"cmd__sm": "Fibonnaci003",
"c.$": "$.c"
},
"Resource": "arn:aws:lambda:us-east-1:1570xxxx:function:Fibonnaci_stepperLambda",
"ResultPath": "$.Fibonnacivar__000",
"Next": "Fibonnaci004"
},
"Fibonnaci004": {
"Type": "Choice",
"Choices": [
{
"Variable": "$.Fibonnacivar__000",
"BooleanEquals": true,
"Next": "Fibonnaci006"
},
{
"Variable": "$.Fibonnacivar__000",
"BooleanEquals": false,
"Next": "Fibonnaci.Success"
}
]
},
"Fibonnaci006": {
"Type": "Task",
"Parameters": {
"cmd__sm": "Fibonnaci006",
"fib.$": "$.fib"
},
"ResultPath": "$.body",
"Resource": "arn:aws:lambda:us-east-1:1570xxxx:function:Fibonnaci_stepperLambda",
"Next": "Fibonnaci007"
},
"Fibonnaci007": {
"Type": "Task",
"Resource": "arn:aws:states:::sqs:sendMessage",
"Parameters": {
"MessageBody.$": "$.body",
"QueueUrl": "https://sqs.us-east-1.amazonaws.com/1570xxxx/fibo"
},
"ResultPath": "$.sqs",
"Next": "Fibonnaci008"
},
"Fibonnaci008": {
"Type": "Task",
"Parameters": {
"cmd__sm": "Fibonnaci008",
"fib.$": "$.fib"
},
"ResultPath": "$.temp",
"Resource": "arn:aws:lambda:us-east-1:1570xxxx:function:Fibonnaci_stepperLambda",
"Next": "Fibonnaci009"
},
"Fibonnaci009": {
"Type": "Task",
"Parameters": {
"cmd__sm": "Fibonnaci009",
"previous.$": "$.previous",
"fib.$": "$.fib"
},
"ResultPath": "$.fib",
"Resource": "arn:aws:lambda:us-east-1:1570xxxx:function:Fibonnaci_stepperLambda",
"Next": "Fibonnaci010"
},
"Fibonnaci010": {
"Type": "Task",
"Next": "Fibonnaci005",
"Parameters": {
"cmd__sm": "Fibonnaci010",
"temp.$": "$.temp"
},
"ResultPath": "$.previous",
"Resource": "arn:aws:lambda:us-east-1:1570xxxx:function:Fibonnaci_stepperLambda"
},
"Fibonnaci005": {
"Type": "Task",
"Parameters": {
"cmd__sm": "Fibonnaci005",
"c.$": "$.c"
},
"Resource": "arn:aws:lambda:us-east-1:1570xxxx:function:Fibonnaci_stepperLambda",
"ResultPath": "$.c",
"Next": "Fibonnaci003"
},
"Fibonnaci.Success": {
"Type": "Succeed"
}
}
}
```

Stepper can automatically register the Lambda and create the Step Function or it can output the code for those pieces
and you can manually register them. Stepper supports:

- [variables, assignments and expressions](../../wiki/Language-Reference#variables)
- [if/else](../../wiki/Language-Reference#branching) branching
- for [loops](../../wiki/Language-Reference#loops) over range with step and looping over collections
- [while loops](../../wiki/Language-Reference#while)
- "[when](../../wiki/Language-Reference#when)" statement, a variation of the traditional switch statement for multi-predicate branching
- [task](../../wiki/Language-Reference#tasks) ASL state for calling activities, accessing queues, etc.
- [wait and fail](../../wiki/Language-Reference#errors) construct
- annotation driven retry logic
- control over state names
- [parallel](../../wiki/Language-Reference#parallel) state that simply includes other stepper programs to be run concurrently
- [goto](../../wiki/Language-Reference#goto) statement for complex logic
- [try/catch](../../wiki/Language-Reference#trycatch) construct for error handling.

To learn how to get started with Stepper, head over to the [Getting Started](../../wiki/Getting-Started) page of the wiki. The [language reference](../../wiki/Language-Reference) is
also accessible from the wiki pages.

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