AWS SNS to Slack Lambda Function

sns-to-slack.js

const https = require('https')
const url = require('url')

const slackWebhookUrl = process.env.slackWebhookURL
const slackChannel = process.env.slackChannel

const postMessage = message => new Promise((resolve, reject) => {
  const data = JSON.stringify(message)

  const slackRequest = Object.assign(url.parse(slackWebhookUrl), {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'Content-Length': Buffer.byteLength(data),
    }
  })

  const httpsRequest = https.request(slackRequest, httpsResponse => {
    const chunks = []

    httpsResponse.setEncoding('utf8')
    httpsResponse.on('data', chunk => chunks.push(chunk))
    httpsResponse.on('end', () => {
      resolve({
        data: chunks.join(''),
        statusCode: httpsResponse.statusCode,
        statusMessage: httpsResponse.statusMessage,
      })
    })
  }).on('error', e => reject(e.message)).end(data)
})

const processEvent = async event => {
  const snsMessage = event.Records[0].Sns.Message

  try {
    const result = await postMessage({
      channel: slackChannel,
      text: `${snsMessage.AlarmName} state has changed to ${snsMessage.NewStateValue}: ${snsMessage.NewStateReason}`,
    })
    
    if (result.statusCode === 200) {
      console.log('Slack Webhook Request Succeeded')
    }else{
      console.log(`Slack Webhook Request Failed: ${result.statusCode} ${result.statusMessage}`)
    }

    return null
  } catch (error) {
    console.log(`Slack Webhook Request Failed: ${error}`)

    return false
  }
}

exports.handler = async (event, context, callback) => {
  const isSuccess = await processEvent(event)
  callback(isSuccess)
}