What's the source of Error: getaddrinfo EAI_AGAIN?

If you get this error with Firebase Cloud Functions, this is due to the limitations of the free tier (outbound networking only allowed to Google services).

Upgrade to the Flame or Blaze plans for it to work.

EAI_AGAIN is a DNS lookup timed out error, means it is a network connectivity error or proxy related error.

My main question is what does dns.js do?

• The dns.js is there for node to get ip address of the domain(in brief).

Some more info: http://www.codingdefined.com/2015/06/nodejs-error-errno-eaiagain.html

If you get this error from within a docker container, e.g. when running npm install inside of an alpine container, the cause could be that the network changed since the container was started.

To solve this, just stop and restart the container

docker-compose down
docker-compose up

Source: https://github.com/moby/moby/issues/32106#issuecomment-578725551

As xerq's excellent answer explains, this is a DNS timeout issue.

I wanted to contribute another possible answer for those of you using Windows Subsystem for Linux - there are some cases where something seems to be askew in the client OS after Windows resumes from sleep. Restarting the host OS will fix these issues (it's also likely restarting the WSL service will do the same).