Commenting service on Google App Engine

A commenting service which is run on Google App Engine and some Google Cloud Platform services, based on Clean Architecture, Domain Driven Design and Microservices Architecture

About this project

This project provides commenting API service. For example, this API can be called from a commenting form which is put into your blog site. By using this API your commenting form can post a comment, delete a comment and get the list of comments.

Purpose of this project

A purpose of this project is learning about followings.

• Clean Architecture
• Domain Driven Design
• Microservices Architecture (just a little)

This project keeps these principles as much as possible.
So this project has some over-engineered parts.

Application Architecture Overview

• Based on Domain Driven Design, this project has 3 bounded contexts.
  • Commenting context
  • Auth context
  • Notification context
• These contexts are separated into services which independent of each other, like Microservices.
• Commenting service is based on Clean Architecture.

Domain Driven Design in this project

Bounded contexts

Commenting context (core domain)

Post a comment, delete a comment and view posted comments.

Notification context (generic sub domain)

Notify about some events to users or administrators.
In this project Google Cloud Pub/Sub are used for publishing/subscribing domain event. This domain subscribes domain events and then notifies to appropriate persons.

Auth context (generic sub domain)

This domain helps user authentication.
In this project Firebase Authentication Service has auth domain role.

Clean Architecture in Commenting API

Architecture overview

To be written

Benefits of Clean Architecture

Because of Clean Architecture, application logic and domain logic are independent with detail of infrastructure.
Followings are not appeared in the core of the application.

• Various packages which is related to Google App Engine infrastructure
• Technological details of web application on golang (e.g. context.Context)

Setup

Requirements

• go 1.8
• google-cloud-sdk
  • goapp
  • dev_appserver.py
• dep

For local development

setup

• Create yaml file for your Google App Engine environment

  $ cd /path/to/comment-api-on-gae/src/commenting
  $ cp app/app.template.yaml app/app.yaml
  $ cd /path/to/comment-api-on-gae/src/notification
  $ cp app/app.template.yaml app/app.yaml

• Resolve dependencies

  $ cd /path/to/comment-api-on-gae/src/commenting
  $ GOPATH=/path/to/comment-api-on-gae dep ensure
  $ cd /path/to/comment-api-on-gae/src/notification
  $ GOPATH=/path/to/comment-api-on-gae dep ensure

Run

You can run local servers of commenting and notification services for development.

$ cd /path/to/comment-api-on-gae/src/commenting
$ GOPATH=/path/to/comment-api-on-gae dev_appserver.py app/XXX.yaml --enable_watching_go_path --log_level=debug --datastore_path=.storage
$ cd /path/to/comment-api-on-gae/src/notification
$ GOPATH=/path/to/comment-api-on-gae dev_appserver.py app/XXX.yaml --enable_watching_go_path --log_level=debug --datastore_path=.storage

For production/staging

Setup Cloud Services

Firebase

• Enable anonymous login

Google Cloud Pub/Sub

• Create topic domain-event
• Create subscriptions which push to following URLs
  • https://commenting-dot-[YOUR-PROJECT-NAME].appspot.com/_ah/push-handlers/domain-event
  • https://notification-dot-[YOUR-PROJECT-NAME].appspot.com/_ah/push-handlers/domain-event

Google App Engine

• Commenting service
  • Create datastore index
  • Issue service account which have following privileges
    • Firebase data manager
    • Pubsub editor
• Notification service
  • Issue service account which have following privileges
    • Pubsub editor
  • Add authorized mail sender

Deploy

• Rewrite yaml for your environment

• Execute following commands

  $ cd /path/to/comment-api-on-gae/src/commenting
  $ GOPATH=/path/to/comment-api-on-gae goapp deploy app/[YOUR-GAE-CONFIG-FILE].yaml
  $ cd /path/to/comment-api-on-gae/src/notification
  $ GOPATH=/path/to/comment-api-on-gae goapp deploy /app/[YOUR-GAE-CONFIG-FILE].yaml

Testing

todo