lambda to test health of services like postgres, redis, sqs

healthcheck.js

const pg = require('pg');
const asyncRedis = require("async-redis");

const key = "HEALTH_CHECK";
async function check_redis() {
  const client = asyncRedis.createClient();
  client.on("error", (err) => {
    throw err
  });

  await client.set(key, JSON.stringify({ success: true }), 'EX', 1); // 1 sec
  const val = await client.get(key);
  client.quit();
  return JSON.parse(val);
}

async function check_postgres() {
  const conn = 'postgres://postgres:changeme@localhost:5432/postgres';
  const client = new pg.Client(conn);
  client.connect();
  const res = await client.query('SELECT 1 + 2 AS success');
  client.end();
  return res.rows[0].success ==3 ? { success: true } : 0;
}

function successfulResponse(body) {
  return {
    statusCode: 200,
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(body)
  };
}

async function handler(event, context) {
  return {
    status: 'ok',
    redis: await check_redis(),
    postgres: await check_postgres()
  };
}

async function api_handler(event, context) {
  return successfulResponse(await handler(event, context));
}

api_handler().then((v) => { console.log(v.body) })