Fixing "SocketError: getaddrinfo: Name or service not known" with Ruby's resolv-replace.rb

Update 6/3/2014: there are other advantages to using a pure-Ruby DNS implementation.

Recently we had a problem with DNS lookups for a particular API that only afflicted our Heroku-based workers (host name changed to protect the innocent):

irb(main):009:0> Socket.gethostbyname("example.net")
SocketError: getaddrinfo: Name or service not known

That line of code works fine in other places I tried, like my dev machine. The specific error had to do with a call that Ruby's net/http library was making. I filed a ticket with Heroku support using the above example, and they suggested I try using Ruby's Resolv library, something I had not encountered before. This post is a little breadcrumb to help others who may have the same problem.

Resolv uses Ruby code to do DNS lookups, instead of relying on the system's libc installation like gethostbyname does. Rather than having to monkeypatch net/http, all I had do to was add require "resolv-replace.rb" to our startup code which automatically added this fix. I never found out why the normal lookup process wasn't working on Heroku, but this worked. Thanks to the thoughtful soul who wrote resolv-replace.rb!

Looking for a Rubyist

Staq is growing fast. There is so much demand for our products that we need to add another developer to our team to keep up. If you are a Ruby programmer who has experience building large web apps, who is excited about working in a culture of delegated responsibility, who can help coach the rest of the team and help with system design, please get in touch!

We offer all of the usual startup perquisites: salary, plenty of equity, autonomy, and the opportunity to grow your career along with the company.

PS We also write a lot of JavaScript and even a smattering of Python.