A prodlike dev flow part 1 - dnsmasq

June 4, 2015
development devops docker dnsmasq

DNS for development just like your production setup

dnsmasq is one part of the equation to making our development environments behave like a production environment. Instead of coding in URLs like http://localhost:8080/ we want to provide http://testing.coolwebsite.dev/. This way we can have websites hosted on subdomains where we browse and function locally, the same as you will with a production environment. In addition, we are planning to use Consul for service discovery which leverages DNS. This post solves the DNS problem associated with this flow. In order to completely get the dev-prod parity, additional tools will be necessary, such as load balancers or reverse proxies (think nginx and watch for a follow up post to elaborate).

The Setup

brew up
brew install dnsmasq
cp /usr/local/opt/dnsmasq/dnsmasq.conf.example /usr/local/etc/dnsmasq.conf
sudo cp -fv /usr/local/opt/dnsmasq/*.plist /Library/LaunchDaemons
sudo chown root /Library/LaunchDaemons/homebrew.mxcl.dnsmasq.plist
sudo launchctl load /Library/LaunchDaemons/homebrew.mxcl.dnsmasq.plist

At this point you now a have locally running dns server. Let’s go configure it so that we can browse like we are in a production environment.

We need to tell our DNS server where to lookup hostnames for our development environment. I typically use a domain name with a .dev top level domain. For instance when working on http://www.client.com my test domain is client.dev. This is configured by adding the name address pair as follows:

sed -i.bak '/#address=\/double-click\.net\/127\.0\.0\.1/a\
  address=/client.dev/\' /usr/local/etc/dnsmasq.conf

The whitespace in this command for OSX must match exactly or you will discover the GNU vs BSD sed differences. As an alternative you can just open /usr/local/etc/dnsmasq.conf in your favorite editor and append this line.

This setup is preparing us to pair with Docker Compose. If you are not going to use Docker Compose, then you probably just want to use the loopback address as below:

sed -i.bak '/#address=\/double-click\.net\/127\.0\.0\.1/a\
  address=/client.dev/' /usr/local/etc/dnsmasq.conf

Finally in order to get these changes into dnsmasq we need to restart the server with:

sudo launchctl stop homebrew.mxcl.dnsmasq
sudo launchctl start homebrew.mxcl.dnsmasq

Just to make sure we are working let’s test with dig:

dig this.is.totally.using.local.client.dev @

The response should be very quick and contain something similar to:

this.is.totally.using.local.client.dev. 0    IN      A

If you were configuring for pure local not boot2docker the would be

Resolve all the things

Now that we have a DNS server running and configured locally, we need to tell OSX how to use dnsmasq. There are a couple of options, but we are going to keep this simple and use resolvers to only affect the client.dev domain.

For more information on what we are about to do see the resolver(5) manual page:

man 5 resolver

We need a new resolver file, but first make sure you have an /etc/resolver/ directory, if not make one with:

mkdir /etc/resolver/

Then lets quickly make the file:

sudo tee /etc/resolver/coolwebsite.dev >/dev/null <<EOF

This file tells OSX to ask our local dns server for any domain in coolwebsite.dev. We should do a quick test make sure all this works:

ping -c 1 www.google.com

This verifies we didn’t break our original DNS. You’re good to go if you see something like:

PING www.google.com ( 56 data bytes
64 bytes from icmp_seq=0 ttl=45 time=34.782 ms

Now we should test something new:

ping -c 1 this.will.go.to.my.coolwebsite.dev 

Success will look similar to:

PING this.will.go.to.my.coolwebsite.dev ( 56 data bytes
64 bytes from icmp_seq=0 ttl=64 time=2.973 ms

If you configured that for local host you should see instead of the 192.

Finally if you are super lazy and trust me 100 % you can use a bash script to automate this similar to the one you see here

Guest posted by: moofish32