Friend Microservices Sample

This CDK project is a sample solution for friend microservices in games.
The sample solution contains AWS Lambda Functions, Amazon DynamoDB Tables, Amazon SQS Queues and Amazon API Gateway.

Key features

• the solution is constructed with only serverless services
• the solution handles friend state management asynchronously
• the solution utilizes DynamoDB Streams with Event Source Mapping Filters to reduce number of transactional writes
• the solution has an SQS queue in front, so multiple backend services can send friend actions
• the solution is decoupled from player management, it simply serves friend state management
• the solution handles duplicated messages from SQS using Event Source Mapping Filters

Assumptions

• another service, such as a notification service, has bidirectional connection with clients
• player metadata is stored separately with all player IDs matched

Architecture

As Shown in the diagram below, there are three Lambda functions (though State Handlers are made of four lambda functions), a single SQS queues in front and a DynamoDB table.
Front Queue intakes all friend actions from game backend services
Each State Handler handles different state, and triggered though different Event Source Mapping Filters
There also is an API Gateway and a Lambda Function for reading data

DynamoDB Tables

Friend Table

Each entry represents friend state from the perspective of a player with the player ID against a friend with the friend ID.

PK: player_id	SK: friend_id	state	last_updated
string: player ID	string: friend ID	string: friend state	time stamp

Friend States

• Requested
  • State that the requester sees on his/her entry after sending a friend request
• Pending
  • State that the receiver sees on his/her entry after receiving a friend request
• Friends
  • State that both players see on their entries once they become friends

Friend Actions

• Request
  • initial action to send a friend request to another player
• Accept
  • an action to accept a pending friend request from another player
  • this can only be triggered by the receiver
• Reject
  • an action to reject a pending friend request from another player
  • this can only be triggered by the receiver
• Unfriend
  • an action to break off a completed friend relationship between two players
  • this can be triggered by both players

Friend Action Message

{
    "player_id": string,
    "friend_id": string,
    "friend_action": Friend Action,
}

Prerequisites

• An AWS account
• Nodejs LTS installed, such as 18.x
• Install Docker Engine

Usage

Deployment

To deploy the example stack to your default AWS account/region, under project root folder, run:

1. yarn install to install all the dependencies
2. cdk deploy to deploy this stack to your default AWS account/region

Test

Send Test Friend Action Events

Since front SQS is Standard queue, you need to send test messages three times separately, to get to the final state. With AWS CLI:

aws sqs send-message-batch --queue-url <QUEUE URL> \
 --entries file://test/testMessages<First|Second|Third>.json

If you want to test corner cases, try this:

aws sqs send-message-batch --queue-url <QUEUE URL> \
 --entries file://test/cornerCase<1|2>.json

Get Test Friend Data

With curl:

$ curl -X GET 'https://<YOUR ENDPOINT>/friends/player1'

License

This solution is licensed under the MIT-0 License. See the LICENSE file.

Also, this application uses below open source project,

• aigle