Speed up DNS lookups when using the .local TLD pointing to on macOS

July 21, 2018   

I was using httpstat to test out some nginx changes when I noticed it was taking over five seconds just to perform the DNS lookup. As the host I was hitting was running on, this seemed crazy to me. Something like that should be instant as I had mapped the entry in /etc/hosts.

I eventually stumbled upon this writeup which explained what was going on. Apparently Bonjour intercepts requests for .local TLDs instead of following configured DNS settings (or, in my case, /etc/hosts).

The fix is to add IPv6 entries alongside the IPv4 entry inside /etc/hosts:

::1 example.local
fe80::1%lo0 example.local example.local

To keep things simple for myself, I also whipped up a shell function to handle it going forward:

# ~/.bashrc
addhost() {
  cat <<EOF | sudo tee -a /etc/hosts >/dev/null

# Start of $1
::1 $1
fe80::1%lo0 $1 $1
# End of $1

$ addhost example.local
$ tail /etc/hosts
# [... snip ...]

# Start of example.local
::1 example.local
fe80::1%lo0 example.local example.local
# End of example.local

After making the change, DNS lookups dropped from around 5.5s to about 14ms.

Given that I do all of my personal and professional web development work on localhost mapped to .local TLDs the thought of how much time I’ve wasted over the years waiting for these slow DNS lookups is… 😬