@wmfs/statebox

statebox

Orchestrate Node functions using Amazon States Language

Useful links

• https://aws.amazon.com/step-functions/
• http://docs.aws.amazon.com/step-functions/latest/dg/concepts-amazon-states-language.html
• http://docs.aws.amazon.com/step-functions/latest/apireference/API_SendTaskSuccess.html

Install

$ npm install statebox --save

Usage

const Statebox = require('statebox')
const statebox = new Statebox()

// STEP 1:
// Create some 'module' resources (i.e. Javascript 
// classes with 'run' and optional 'init' methods) 
// that state machines can then refer to...
// -------------------------------------------------

statebox.createModuleResources(
  {
    // Simple module to add two numbers together
    add: class Add {
      run (event, context) {
        context.sendTaskSuccess(event.number1 + event.number2)
      }
    },
    // Simple module to subtract one number from another
    subtract: class Subtract {
      // Init methods are optional, but all allow  
      // resource-instances to be configured...
      init (resourceConfig, env, callback) {
          callback(null)
        }
      run (event, context) {
        context.sendTaskSuccess(event.number1 - event.number2)
      }      
    }
  }
)

// STEP 2:
// Next create a new 'calculator' state
// machine using Amazon States Language...
// ---------------------------------------

const info = statebox.createStateMachines(
  {
    'calculator': {
      Comment: 'A simple calculator',
      StartAt: 'OperatorChoice',
      States: {
        OperatorChoice: {
          Type: 'Choice',
          Choices: [
            {
              Variable: '$.operator',
              StringEquals: '+',
              Next: 'Add'
            },
            {
              Variable: '$.operator',
              StringEquals: '-',
              Next: 'Subtract'
            }
          ]
        },
        Add: {
          Type: 'Task',
          InputPath: '$.numbers',
          Resource: 'module:add', // See createModuleResources()
          ResultPath : '$.result',
          End: true
        },
        Subtract: {
          Type: 'Task',
          InputPath: '$.numbers',
          Resource: 'module:subtract',
          ResultPath : '$.result',
          End: true
        }
      }
    }  
  },
  {}, // 'env': An environment/context/sandbox
  function (err) {
    // All good-to-go!
  }    
)

// STEP 3:
// Start a new execution on a state machine
// ----------------------------------------

executionDescription = await statebox.startExecution(
  {
    numbers: {
      number1: 3,
      number2: 2
    },
    operator: '-'
  },  // input
  'calculator', // state machine name
  {} // options
)
// Result object
// -------------
//  {
//    executionName: '01e1e288-9533-11e7-8fec-54d168e2e610',
//    ctx: {
//      numbers: {
//        number1: 3,
//        number2: 2
//      },
//      operator: '-'
//    },
//    currentStateName: 'OperatorChoice',
//    stateMachineName: 'calculator',
//    status: 'RUNNING',
//    startDate: '2017-09-10T09:40:22.589Z'
//  }

// STEP 4:
// Look at the results...
// ----------------------
executionDescription = await statebox.describeExecution(
  '01e1e288-9533-11e7-8fec-54d168e2e610'
)
//  Result object
//  -------------
// {
//   executionName: '01e1e288-9533-11e7-8fec-54d168e2e610',
//   ctx: {
//     numbers': {
//       number1: 3,
//       number2: 2
//     },
//     operator: '-',
//     result: 1 <--- The important bit :-)
//   },
//   currentStateName: 'Subtract',
//   stateMachineName: 'calculator',
//   status: 'SUCCEEDED',
//   startDate: '2017-09-10T09:59:50.711Z'
// }

Testing

$ npm test

License

MIT