EDESSA

A highly opinionated wrapper around async.waterfall.

• Pass some external state into the first item in the waterfall
• Retrieve configuration parameters from DynamoDB
• Execute the waterfall

Setup

const edessa = require('edessa')({

  // options concerning the config store go here
  config: {

    // which backend to use. currently, only dynamodb is supported
    backend: 'dynamodb',

    // how the dynamodb table is set up.
    dynamodb: {
      // which table you are using. defaults to "Config"
      table: 'Config',
      // the names of the three columns edessa expects
      // what's shown is the defaults
      field: [ 'key', 'stage', 'value' ]
    }
  },

  // the location of the personal config file.
  // if this file exists and is provided, its keys will override the
  // values retrieved from the config backend
  configFile: 'personalconfig.yaml',

  // if a key requested is missing, this will cause edessa to pipe
  // an error through to the error condition of the waterfall. this defaults
  // to true.
  errOnMissing: true,

})

Usage

edessa({
  config: [
    'mainDatabaseUrl',
  ],
  userId: '12345',

  // this variables decides which config parameters to get from the config
  // backend. if it is not provided, it defaults to process.env.NODE_ENV.
  // you can always override this.
  stage: process.env.NODE_ENV,

}, [
  component1,
  component2,
  component3,
], (err, result) => {
  ...
})

const component1 = (state, done) => {
  console.log(state)
  // state.mainDatabaseUrl
  // state.stage
  // state.userId
}

DynamoDB

A table has to be set up in dynamodb with three fields.

• key
• the configuration key for that given configuration parameter
• hash key
• stage
• the deployment stage this configuration parameter applies to
• range key
• value
• the actual value of the configuration parameter
• this can be any DynamoDB type you'd like

The read/write capacity of this table is totally up to you and might be something you have to play with.

AWS Authentication

Authentication currently must be provided by the environment.

Future Improvements

• Cascading Stages
• The ability to explicitly state priority levels for stages.
• So something like: [ "dev", "dev-mike", "$configfile" ]
• Values in config file override values from backend in stage dev-mike, which override values in dev
• etcd support