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Sequencer

Provides an easy way to schedule tasks and add logic around how to progress from one task to the other.

Built as a serverless template, to be used inside your application and subsequently extended with your own custom task runners.

Getting Started

Requirements:

  • Postgresql (storage)
  • AWS account (to run your lambdas)
  • Docker (rebuilding node_modules to match deploy target)

Installation:

  • Run npm install

  • Change dir to lib and run npm install

    • Note, this is so the deploy does not get any development dependencies, to make the final package as small as possible

  • Create a crypt key in AWS KMS

  • Setup lib/config.yml

    • Update configuration to include postgres auth info, create a uniqueNamedKey for your password
    • vpc information is optional
    • Make sure to add the cryptkey that we generated earlier
    • Encrypt your postgres password in the lib dir 
      cd backend
sls encrypt -n uniqueNamedKey -t 'password' --stage prod --save
    • Commit the generated file to source control for your team to use

  • Duplicate /sequelizeExample.json and name it sequelize.json

    • Update all the config in there to match your database, do not commit this to source control, it has plaintext passwords

  • Run DB Migrations

    • sequelize db:migrate --env prod --config sequelize.json

  • Deploy from within the lib directory

    • sls deploy --stage prod
    • This command will take a little while

  • Setup the IAM Encryption Key to allow the new user's account

  • Phew. You are done with the initial install.

Task Runners

For your convenience we have provided a set of pre-made task runners:

  • Flow Control:
    • GoTo
    • Conditional
    • Goal
  • Generic Runners:
    • WaitForDate
    • WaitForDuration
    • WaitForDateComparison
    • Email
    • SMS

Anatomy of a runner

The runner will receive an event with config and a list of runners. The config can be completely custom, it's an arbitrary JSON object.

Expected response is an array of runner objects containing to keys:

  • id - The id of the runner
  • action The action to take for this runner
    • next - Will go to the next step
    • noop - Will wait at this step and be re-executed later
    • altNext - Will go to the alternate next step
  • message - Optional, used for logging

WaitForDate

Waits until the specified date is now or in the past to continue.

{
  // ISO 8601 date
  "date": "2018-06-08T17:49:31+00:00"
}

WaitForDateComparison

Waits until the specified day of the week

{
    // Moment.js getter https://momentjs.com/docs/#/get-set/get/
    "attribute": "year|month|date|hour|minute",
    // list of values to compare result to. If one matches it continues
    "values": [0,1,3,6]
}

WaitForDuration

Waits for a given amount of time

{
  "amount": 21, // {Number}
  "unit": "[years|quarters|weeks|months|days|hours|minutes|seconds|milliseconds]"
}

Email

Send an email

{
  "from": "email@example.com",
  "to": ["target@example.com", "target2@example.com"],
  "cc": ["target3@example.com"],
  "bcc": ["target4@example.com"],
  "text": "Custom Email Text",
  "html": "<h1>Hello</h1>",
  "subject": "this is an email"
}

SMS

Send an sms

{
  "from": "+11231231234",
  "to": "+11231231234",
  "message": "Hello world"
}

Goal

Checked every cycle to see if the conditional has been achieved. If it has, it will bypass all the other given steps and execute.

{
  "lodashCommand": "gt",,
  "value": {
    type: "get",
    value: "path.to.value"
  },
  "compareTo": {
    type: "raw",
    value: "myValue123"
  }
}

Conditional

If the conditional returns true, continue down the normal path. If false it will divert to the alternate path. Uses lodash under the hood. Will use _.get(obj, "path.to.value") to fetch values, since handlebars can't return anything other than strings as a response and you might want to compare numbers or objects

{
  "lodashCommand": "gt",
  "value": {
    type: "get",
    value: "path.to.value"
  },
  "compareTo": {
    type: "raw",
    value: "myValue123"
  }
}