How can I resolve, if EAI_AGAIN error happens on facebook messenger platform?

Question

Our Node.js app for facebook messenger platform threw the following error. We use "request" module to connect to facebook graph api and the module threw this error. And the problem was resolved without doing anything about 1 hour after I found the problem. So now it's working, but I'm afraid when it'll happen again. Could you teach me this problem and if there is any resolution?

{ Error: getaddrinfo EAI_AGAIN graph.facebook.com:443
    at Object.exports._errnoException (util.js:949:11)
    at errnoException (dns.js:33:15)
    at GetAddrInfoReqWrap.onlookup [as oncomplete] (dns.js:79:26)
  code: 'EAI_AGAIN',
  errno: 'EAI_AGAIN',
  syscall: 'getaddrinfo',
  hostname: 'graph.facebook.com',
  host: 'graph.facebook.com',
  port: 443 }

Answer 1

Short answer: This happens when you have lost connection to your DNS server or the DNS settings are wrong (this includes, but is not limited to, complete or partial disconnect from internet). That is: Please check if your cable or WiFi connection OR your internet provider does not have a (temporary) problem.

Details: When this happened, I could see in the debugger call stack that the system function getaddrinfo fails. Thus, it seemed like the trivial reason was - the system cannot map the host name to an IP (in your case the host name 'graph.facebook.com" could not be found).

Indeed, when I tried to ping the host name, which I wanted to reach I got the same as ping error like pinging an unknown host:

u@h:~$ ping someunknownhost.xyzdomain
ping: unknown host someunknownhost.xyzdomain

Additionally when, my connectivity to internet recovered and I could ping the host then the problem of node.js also disappeared.