Leetbot AWS

Leetbot in the cloud. See the project dashboard.

Leetbot is a Discord bot that monitors messages in Discord servers during specific time windows (13:36-13:39) to detect and track "leet" messages. It provides statistics and leaderboards for users based on their messaging patterns.

Features

• 🕐 Time-based message monitoring (13:36-13:39 daily)
• 📊 Message type tracking (leet, leeb, failed_leet)
• 🏆 User statistics and leaderboards
• ☁️ Fully serverless AWS architecture
• 🌍 Timezone-aware scheduling with daylight savings support

Prerequisites

Before setting up the project, ensure you have:

• Node.js (version 18 or higher)
• AWS CLI configured with appropriate permissions
• aws-vault (recommended for credential management)
• A Discord bot token (see Discord Developer Portal)

---

• Leetbot AWS
  • Features
  • Prerequisites
• Development
  • Scripts
• Architecture
  • Lambda Layers
  • DynamoDB Design
• Deployment
  • Deployment Troubleshooting

Development

Start by installing dependencies for both the main application and the Discord Lambda layer

npm install && npm install --prefix src/layers/discord/nodejs

The CDK stack itself is located in the lib directory.

Scripts

Some scripts are included to help set up and test the application. They are located in the scripts folder.

⚠️ These scripts natively use aws-vault.

Set Discord Bot Token

This script sets the AWS Secrets Manager value for the Discord bot's token. Usage:

./scrips/setBotToken.sh <bot_token> <aws_profile>

Start Discord Bot

This script starts the Discord bot by invoking the Discord Watcher Lambda function. You can supply test event parameters to, for example, reduce the run time of the Lambda, or allow customized behavior. See the TestEvent interface in types.ts for all the options.

./scripts/invokeDiscordWatcher.sh <json_payload> <aws_profile>

# Example:
# ./scripts/invokeDiscordWatcher.sh '{"timeoutOverrideMs": 12000}' sandbox

Clean DynamoDB Table

Removes all items from the deployed DynamoDB table. Can optionally be given a specific target table name.

./scripts/cleanDynamoDbTable.sh <aws_profile> [<table_name>]

Architecture

Leetbot needs to sit in a Discord server every day within the time window ]13:36, 13:39[. This is achieved with a Lambda that keeps itself alive for the duration. An EventBridge scheduled event invokes that Lambda at the same time on each day and even takes daylight savings into account.

flowchart TD
    Discord((Discord))
    EventBridge[EventBridge<br/>Schedule]

    DiscordWatcher{{Lambda: discordWatcher}}
    DiscordOutTopic[DiscordOutTopic]
    MessageEvalQueue[MessageEvaluationQueue]
    MessageEvaluator{{Lambda: messageEvaluator}}
    MessageEvalOutTopic[MessageEvaluationOutTopic]
    DiscordInQueue[DiscordInQueue]
    DynamoDB[(DynamoDB)]

    EventBridge --> DiscordWatcher
    Discord <--> DiscordWatcher
    DiscordWatcher <-.-> DynamoDB
    DiscordWatcher --> DiscordOutTopic
    DiscordOutTopic --> MessageEvalQueue
    MessageEvalQueue --> MessageEvaluator
    MessageEvaluator <-.-> DynamoDB
    MessageEvaluator --> MessageEvalOutTopic
    MessageEvalOutTopic --> DiscordInQueue
    DiscordInQueue --> DiscordWatcher

    classDef discord stroke: #55f, fill: #224
    classDef lambda stroke: #fa0, fill: #320
    classDef sns stroke: #f84, fill: #410
    classDef sqs stroke: #fda, fill: #430
    classDef dynamo stroke: #a7f, fill: #213
    classDef schedule stroke: #8af, fill: #134

    class Discord discord
    class DiscordWatcher,MessageEvaluator lambda
    class DiscordOutTopic,MessageEvalOutTopic sns
    class MessageEvalQueue,DiscordInQueue sqs
    class DynamoDB dynamo
    class EventBridge schedule

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Lambda Layers

The Discord SDK, date-fns, and possibly other libraries are installed on Lambda layers in lib/constructs/LambdaLayers.ts. For each Lambda function that wants to use, for example, the Discord API, the Layer should be given in the function definition.

new NodejsFunction(this, "MyNodejsFunction", {
  layers: [props.layer],
  // ...other NodejsFunction configuration...
});

The Discord SDK (or other layers) can then be used in each Lambda handler from /opt/nodejs/discord. This is because Lambda functions mount their layers in the /opt directory.

import discord from "/opt/nodejs/discord";

When adding more layers, update tsconfig.json with a matching path to that layer.

DynamoDB Design

See the types.ts files in src/repository for detailed descriptions about database indices and access patterns.

Deployment

If you are using aws-vault, prefix pretty much every command here with aws-vault exec <your-role-name> -- <command>

Run npm run aws:deploy to deploy the application.

Each CfnOutput will be saved to a cdk-outputs.json file, should you need to reference them.

Deployment Troubleshooting

No bucket named xyz. Is account 123 bootstrapped?

Fix this by doing one of the following:

Option 1: CLI

Run this script: npm run aws:unbootstrap

Option 2: AWS Management Console

1. Log in to the AWS Management Console and navigate to Cloudformation.
2. Delete the CDKToolkit stack.
3. Run npx cdk bootstrap.

Finally, re-bootstrap the environment with npm run aws:bootstrap. Deployment should work now.