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README.md	README.md
verify.js	verify.js

How to Build Slack Bot? (Node JS | AWS Lambda & DynamoDB - AWS Serverless | New Slack Apps)

1. Create Slack Bot App

Go to https://api.slack.com/apps
Select create an app From scratch
Give it a name WALL-E and select your namespace
Scroll down to App Credentials a Display Information
Give it a short description Compactor robot
Upload app icon and change color
Go to Event Subscriptions

2. Create IAM User with Full Access

Create admin user and place it in Admin group
Download credentials
Configure AWS profile with aws configure
Test profile with aws sts get-caller-identity

3. Create IAM Role for AWS Lambda

Create IAM Policy AWSLambdaSlackAccess

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "logs:CreateLogGroup",
            "Resource": "arn:aws:logs:us-east-1:424432388155:*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "logs:CreateLogStream",
                "logs:PutLogEvents"
            ],
            "Resource": "arn:aws:logs:us-east-1:424432388155:log-group:/aws/lambda/wall-e:*"
        },
        {
            "Effect": "Allow",
            "Action": "dynamodb:*",
            "Resource": "arn:aws:dynamodb:us-east-1:424432388155:table/todos"
        }
    ]
}

Create wall-e-role for Lambda and attach AWSLambdaSlackAccess IAM Policy
Optionally: aws iam get-role --role-name wall-e-role

4. Create AWS Lambda Function

Create wall-e directory
Run npm init from wall-e directory
Create app.js

exports.handler = (event, context, callback) => {
    const response = { 'message': `Hello World!` };
    callback(null, response);
};

Create Dockerfile

FROM public.ecr.aws/lambda/nodejs:14

COPY *.js package*.json  /var/task/

RUN npm install

CMD [ "app.handler" ]

Create ECR Repository wall-e

aws ecr get-login-password --region us-east-1 \
| docker login \
--username AWS \
--password-stdin 424432388155.dkr.ecr.us-east-1.amazonaws.com

docker build \
-t 424432388155.dkr.ecr.us-east-1.amazonaws.com/wall-e:v0.1.0 .

docker push \
424432388155.dkr.ecr.us-east-1.amazonaws.com/wall-e:v0.1.0

5. Deploy Lambda Using Container Image

Select Containerimage from the console
Call function wall-e
Use an existing role wall-e-role
Select wall-e ECR image

6. Create API Gateway for Lambda Function

Create HTTP API slack
Test Lambda with curl

curl -X POST https://uss0o5l3h3.execute-api.us-east-1.amazonaws.com/production/wall-e

Check logs
Use this URL for Slack

7. Use AWS Lambda for Slack Event Subscriptions

Create tests/event.json file

{
  "version": "2.0",
  "routeKey": "ANY /bot",
  "rawPath": "/default/bot",
  "rawQueryString": "",
  "headers": {
    "accept": "*/*",
    "accept-encoding": "gzip,deflate",
    "content-length": "129",
    "content-type": "application/json",
    "host": "4o68t2fwke.execute-api.us-east-1.amazonaws.com",
    "user-agent": "Slackbot 1.0 (+https://api.slack.com/robots)",
    "x-amzn-trace-id": "Root=1-60f9f121-0e6b301236f5d57d46fbd0e1",
    "x-forwarded-for": "3.94.92.68",
    "x-forwarded-port": "443",
    "x-forwarded-proto": "https",
    "x-slack-request-timestamp": "1626992929",
    "x-slack-signature": "v0=d12f7cb55add77074248241c2ec2d3c9fe4611e7879a965c92315edd8f0ec0cf"
  },
  "requestContext": {
    "accountId": "424432388155",
    "apiId": "4o68t2fwke",
    "domainName": "4o68t2fwke.execute-api.us-east-1.amazonaws.com",
    "domainPrefix": "4o68t2fwke",
    "http": {
      "method": "POST",
      "path": "/default/bot",
      "protocol": "HTTP/1.1",
      "sourceIp": "3.94.92.68",
      "userAgent": "Slackbot 1.0 (+https://api.slack.com/robots)"
    },
    "requestId": "C5KdVjAlIAMEPzg=",
    "routeKey": "ANY /bot",
    "stage": "default",
    "time": "22/Jul/2021:22:28:49 +0000",
    "timeEpoch": 1626992929961
  },
  "body": "{\"token\":\"UdG3UFNsPGoobvRzK5F2oIqe\",\"challenge\":\"6KaNtlamllYYaLZ7qhHxZbzyYut62TlDKu2wAZXp4rZlInRbcDTH\",\"type\":\"url_verification\"}",
  "isBase64Encoded": false
}

Update body of the function

exports.handler = (event, context, callback) => {
    const body = JSON.parse(event.body);
    switch (body.type) {
        case "url_verification": callback(null, body.challenge); break;
        default: callback(null);
    }
};

Package and upload docker image

docker build \
-t 424432388155.dkr.ecr.us-east-1.amazonaws.com/wall-e:v0.1.1 .

docker push \
424432388155.dkr.ecr.us-east-1.amazonaws.com/wall-e:v0.1.1

Redeploy AWS Lambda using v0.1.1 image tag
Go back to Slack and click Retry

8. Verify Slack Requests Using Signing Secret

Optionally: Create verify.js
Run with node verify.js
Compare string with event.json
Create security.js

const crypto = require("crypto");

exports.validateSlackRequest = (event, signingSecret) => {
    const requestBody = event["body"];
    const headers = makeLower(event.headers);
    const timestamp = headers["x-slack-request-timestamp"];
    const slackSignature = headers["x-slack-signature"];
    const baseString = 'v0:' + timestamp + ':' + requestBody;

    const hmac = crypto.createHmac("sha256", signingSecret)
        .update(baseString)
        .digest("hex");
    const computedSlackSignature = "v0=" + hmac;
    const isValid = computedSlackSignature === slackSignature;

    return isValid;
};

const makeLower = (headers) => {
    let lowerCaseHeaders = {}

    for (const key in headers) {
        if (headers.hasOwnProperty(key)) {
            lowerCaseHeaders[key.toLowerCase()] = headers[key].toLowerCase()
        }
    }

    return lowerCaseHeaders
}

Update app.js

const security = require('./security');

const signingSecret = process.env.SLACK_SIGNING_SECRET;

exports.handler = (event, context, callback) => {
    if (security.validateSlackRequest(event, signingSecret)) {
        const body = JSON.parse(event.body);
        switch (body.type) {
            case "url_verification": callback(null, body.challenge); break;
            default: callback(null);
        }
    }
    else callback("verification failed");
};

Add Environment variable to Lambda SLACK_SIGNING_SECRET (next video aws lambda secrets manager integration)
Create unit test security.test.js
Install Jest npm i --save-dev jest
Update test command to jest
Run tests npm test

9. Process Slack Messages

Create private Slack channel earth
Subscribe to following events
- message.groups
- message.channels
Install app to workspace
Optionally: set Always Show My Bot as Online from App Home
Go to OAuth & Permissions to check automatically added permissions
Add event_callback event

case "event_callback": processRequest(body, callback); break;

Create processRequest method

const processRequest = (body, callback) => {
    switch (body.event.type) {
        case "message": processMessages(body, callback); break;
        default: callback(null);
    }
};

Create processMessages method in app.js

const processMessages = (body, callback) => {
    console.debug("message:", body.event.text);
    callback(null);
};

Update Dockerfile to use npm ci --production
Package and upload docker image

docker build \
-t 424432388155.dkr.ecr.us-east-1.amazonaws.com/wall-e:v0.1.2 .

docker push \
424432388155.dkr.ecr.us-east-1.amazonaws.com/wall-e:v0.1.2

Update AWS Lambda to use v0.1.2 tag
Optionally: Delete all log streams
Inviite WALL-E to earth channel
Post hello message
Open CloudWatch logs

10. Save Messages Using AWS Lambda to DynamoDB

Create todos DynamoDB table with uuid primary key
Replace message.groups and message.channels with app_mention event
Add chat:write instead of message.*
Reinstall app
Install aws-sdk, uuid, and axios

npm i aws-sdk uuid axios

Create db.js

const AWS = require('aws-sdk');
const { v4: uuidv4 } = require('uuid');

AWS.config.update({ region: 'us-east-1' });

const ddb = new AWS.DynamoDB({ apiVersion: '2012-08-10' });

exports.saveItem = (item, callback) => {
    const params = {
        TableName: 'todos',
        Item: {
            'uuid': { S: uuidv4() },
            'item': { S: item }
        }
    };
    ddb.putItem(params, (error, data) => {
        if (error) {
            callback(new Error(error));
        } else {
            callback(null);
        }
    });
};

Add app_mention case

case "app_mention": processAppMention(body, callback); break;

Import axios and db

const axios = require('axios');
const db = require('./db');

Create token variable and add it to Lambda

const token = process.env.SLACK_BOT_TOKEN;

Create processAppMention method

const processAppMention = (body, callback) => {
    const item = body.event.text.split(":").pop().trim();
    db.saveItem(item, (error, result) => {
        if (error !== null) {
            callback(error)
        } else {
            const message = {
                channel: body.event.channel,
                text: `Item: \`${item}\` is saved to *Amazon DynamoDB*!`
            };
            axios({
                method: 'post',
                url: 'https://slack.com/api/chat.postMessage',
                headers: { 'Content-Type': 'application/json; charset=utf-8', 'Authorization': `Bearer ${token}` },
                data: message
            })
                .then((response) => {
                    callback(null);
                })
                .catch((error) => {
                    callback("failed to process app_mention");
                });
        }
    });
};

Package and upload docker image

docker build \
-t 424432388155.dkr.ecr.us-east-1.amazonaws.com/wall-e:v0.1.3 .

docker push \
424432388155.dkr.ecr.us-east-1.amazonaws.com/wall-e:v0.1.3

Redeploy Lambda using v0.1.3 tag
Post @WALL-E todo: Save the Planet! message
Open DynamoDB todos table

Clean Up

Delete ECR wall-e
Delete IAM User admin
Delete IAM Role wall-e-role
Delete IAM Policy AWSLambdaSlackAccess
Delete DynamoDB table todos
Delete Lambda wall-e
Delete CloudWatch log groups /aws/lambda/wall-e
Delete API Gateway slack
Delete docker images docker rmi -f $(docker images -a -q)
Delete slack bot wall-e
Delete earth Slack channel

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README.md

How to Build Slack Bot? (Node JS | AWS Lambda & DynamoDB - AWS Serverless | New Slack Apps)

1. Create Slack Bot App

2. Create IAM User with Full Access

3. Create IAM Role for AWS Lambda

4. Create AWS Lambda Function

5. Deploy Lambda Using Container Image

6. Create API Gateway for Lambda Function

7. Use AWS Lambda for Slack Event Subscriptions

8. Verify Slack Requests Using Signing Secret

9. Process Slack Messages

10. Save Messages Using AWS Lambda to DynamoDB

Clean Up

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parent directory

README.md

How to Build Slack Bot? (Node JS | AWS Lambda & DynamoDB - AWS Serverless | New Slack Apps)

1. Create Slack Bot App

2. Create IAM User with Full Access

3. Create IAM Role for AWS Lambda

4. Create AWS Lambda Function

5. Deploy Lambda Using Container Image

6. Create API Gateway for Lambda Function

7. Use AWS Lambda for Slack Event Subscriptions

8. Verify Slack Requests Using Signing Secret

9. Process Slack Messages

10. Save Messages Using AWS Lambda to DynamoDB

Clean Up

Links