Redis (ioredis) - Unable to catch connection error in order to handle them gracefully

Connection errors are reported as an error event on the client Redis object.

According to the "Auto-reconnect" section of the docs, ioredis will automatically try to reconnect when the connection to Redis is lost (or, presumably, unable to be established in the first place). Only after maxRetriesPerRequest attempts will the pending commands "be flushed with an error", i.e. get to the catch here:

  try {
    cachedItem = await redisClient.get(queryString); // This emit an error on the redis client, because it fails to connect (that's intended, to test the behaviour)
  } catch (e) {
    logger.error(e); // It never goes there, as the error isn't "thrown", but rather "emitted" and handled by redis its own way
    epsagon.setError(e);
  }

Since you stop your program on the first error:

  client.on('error', function (e) {
    // ...
    if (e.message === 'ERR invalid password') {
      logger.error(`Fatal error occurred "${e.message}". Stopping server.`);
      throw e; // Fatal error, don't attempt to fix

...the retries and the subsequent "flushing with an error" never get the chance to run.

Ignore the errors in client.on('error', and you should get the error returned from await redisClient.get().

Here is what my team has done with IORedis in a TypeScript project:

  let redis;
  const redisConfig: Redis.RedisOptions = {
    port: parseInt(process.env.REDIS_PORT, 10),
    host: process.env.REDIS_HOST,
    autoResubscribe: false,
    lazyConnect: true,
    maxRetriesPerRequest: 0, // <-- this seems to prevent retries and allow for try/catch
  };

  try {

    redis = new Redis(redisConfig);

    const infoString = await redis.info();
    console.log(infoString)

  } catch (err) {

    console.log(chalk.red('Redis Connection Failure '.padEnd(80, 'X')));
    console.log(err);
    console.log(chalk.red(' Redis Connection Failure'.padStart(80, 'X')));
    // do nothing

  } finally {
    await redis.disconnect();
  }