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reverb-template

This is part of the Reverb project. Read the case study here

This is the template project for a reverb function server. A reverb function server is a customizable server for defining functions, events, and crons for Reverb.

Installation

To get started with your own reverb function server you can either download and extract this repo, or use the command:

npm create reverb <app-name>

This will copy the repo to ./<app-name> and allow you to start customizing your server. You should then use npm install in that directory.

Usage

Please do not install any dev dependencies that are needed to compile the application, they should be installed as regular dependecies as the docker image compiles the typescript in a production environment.

Environmental Variables

For developmental purposes there are two environmental variables that need to be set.

  1. PORT - the port the server will listen to. We provide a .env file that has this set to 3002 to worker with the docker compose file provided.
  2. GRAPHILE_CONNECTION_STRING - the postgres connection string for the database used for the queue. This is set inside the provided .env file to work with the docker compose provided.

Docker Compose

For development purposes, a compose.yaml file has been provided. This will start servers for both mongo and postgres as well as the reverb ingress server( http://localhost:3001 ) and the reverb worker server. They are preconfigured to work with the environmental variables provided to this server.

To test your server, you may run these commands:

docker compose up
npm run dev

This will start up the provided dev infrastructure and your server.

Function Server API

To use the function server API, you need to first import it:

import reverb from "@reverb-app/functions";

You can then define functions with the createFunction method. The createFunction method takes 1 argument, an FunctionData object. There are four properties that can be applied to this object:

  1. id - This is the unique string identifier for the object
  2. fn - The function's code
    • Has the type (event: Event, step: Step) => Promise<any>
  3. event - [Optional] If the function is tied to an event, this is the event's name
    • Can not be present with a cron property
  4. cron - [Optional] If the function is tied to a cron, this is the cron string
    • Can not be present with an event property
    • Proper format can be found here

A FunctionData must have either an event or cron property, but not both, for it to be valid.

Inside the fn function we provide two parameters. These must always be awaited:

  1. event - The data tied to the event being fired
    • id - The unique string ID generated when the event was fired. Is an empty string for a cron.
    • name - The name of the event that was fired.
    • payload - [Optional] Any data passed with the event when it was fired.
      • object type. This will be defined by you and you should check the typing when you run the function.
  2. step - An object to provide step functionality. It provides these methods:
    1. run - (id: string, callback: () => Promise<any>) => Promise<any>
      • id must be unique
      • callback is used to run an individual step.
      • The return value is the return value of the callback
    2. delay - (id: string, timePeriod: string) => Promise<any>
      • id must be unique
      • timePeriod is the period of time before continuing the function.
        • Can be any combination of number[period] and any number of spaces between
        • period can be s(seconds), m(minutes), h(hours), d(days), w(weeks), o(months)
        • Sample 1d 12h 10m30s would be 1 day, 12 hours, 10 minutes, and 30 seconds.
    3. emitEvent - (id: string, eventId: string, payload?: object) => Promise<any>
      • id must be unique
      • eventId is the event name to be emitted
      • payload [Optional] is the payload you wish to pass to the event
    4. invoke = (id: string, invokedFnName: string, payload?: object) => Promise<any>
      • id must be unique
      • invokedFnName is the function name to be invoked
      • payload [Optional] is the payload you wish to pass to the function via the event object

Once you have created your functions, you can start your server with the reverb.serve() method.

Deployment

Currently we need a docker image of the function server deployed to dockerhub in order to deploy the application. To do this we have provided a Dockerfile for you to create your own image. You first need to deploy the Reverb Infrastructure CDK, then a github action on this repository can deploy this to the deployed infrastructure.

The infrastructure deployment can be made easy by following these steps:

  1. Follow this guide to getting started with the CDK. This will have you:

  2. Download the Reverb cli tool with the command npm install -g @reverb-app/cli

  3. Run the command reverb-cli cdk:deploy

Github action

To automate doing so, we have provided a github action in order to automate the dockerization and deployment of the image. To use this action, your github repository must include these secrets:

  • DOCKER_USER - Your dockerhub account username
  • DOCKER_PASS - Your dockerhub access token
  • DOCKER_TAG - The Image tag you want to give the docker image
    • it should be something like <user>/<appname>
  • UPDATE_LAMBDA_NAME - the lambda name that is output by the CDK
  • AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY
    • You should create an IAM user specifically for this task with the lambda:InvokeFunction allowed.
    • These are the access key and secret for this account
  • ENVIRONMENT - The environment variables you want to pass to the server. Should be a json array of environmental variable objects
    • If you have none, should be []

Example of the ENVIRONMENT secret:

[
  {
    "name": "API_KEY",
    "value": "SOME_VALUE"
  },
  {
    "name": "WHO_AM_I",
    "value": "reverb"
  }
]