serf-dns

DNS service with serf backend

Goal

Provide a DNS interface to query serf's host, either by name or by tags. For example:

To query redis servers in Oregon (or any host with tags service=redis and region=oregon):

$ dig +short redis.service.oregon.region.serf
192.168.10.11
192.168.10.12
192.168.10.13

Tags' order doesn't matter

$ dig +short oregon.region.redis.service.serf
192.168.10.11
192.168.10.13
192.168.10.12

Or to query a pre-configured domain name us-web.serf with name web-.* and tag dc=us-.*:

$ dig +short us-web.serf
192.168.6.17
192.168.7.18
192.168.8.29
192.168.9.105

Note: please see custom-domain-name.md for more information.

Develop

This project is currently develop in Golang 1.6 with docker and make

Test

To test the project:

make test

Build

To build the binary executable file serf-dns:

make build

Play

After building serf-dns, you can play with it:

./serf-dns

And in another terminal, send some DNS requests to it:

dig @localhost -p 5327 web.role.serf
dig @localhost -p 5327 db.role.serf
dig @localhost -p 5327 oreg.dc.web.role.serf
dig @localhost -p 5327 db.role.cali.dc.serf
dig @localhost -p 5327 foo.srv.serf
dig @localhost -p 5327 bar.srv.serf

And you can compare the result using serf members

Clean

Testing and playing with the project need a few serf agents running in docker containers. To clean those up, run:

make clean

Configuration

Serf-dns can be configured using environment variables or command line parameters. If both environment variable and parameter for the same directive are provided, serf-dns will use environment variable.

• bind: bind with IP address and port.
  Default: Bind all interfaces with port 5327.
  Use environment variable BIND or parameter --bind=.
  For example, to bind localhost with port 5300:

BIND='127.0.0.1:5300' ./serf-dns
./serf-dns --bind='127.0.0.1:5300'

• domain-name: domain name for serf hosts
  Default: serf.
  Use environment variable DOMAIN_NAME or parameter --domain-name=.
  For example, to use domain name my.dn.:

DOMAIN_NAME='my.dn.' ./serf-dns
./serf-dns --domain-name='my.dn.'

Note: It is important to have . at the end of domain name

• serf: serf RPC address
  Default: 127.0.0.1:7373
  Use environment variable SERF or parameter --serf=.
  For example, if serf agent is run at localhost port 8000, use:

SERF='127.0.0.1:8000' ./serf-dns
./serf-dns --serf='127.0.0.1:8000'

• serf-auth: serf RPC auth key
  Default: empty
  Use environment variable SERF_AUTH or parameter --serf-auth=
  For example, if serf agent RPC interface require key S3creTT0k3n, use:

SERF_AUTH='S3creTT0k3n' ./serf-dns
./serf-dns --serf-auth='S3creTT0k3n'

• custom: path to custom domain name file
  Default: empty
  Use environment variable CUSTOM or parameter --custom=
  For example, to load custom domain names from /etc/serf-dns/custom.json:

CUSTOM='/etc/serf-dns/custom.json' ./serf-dns
./serf-dns --custom='/etc/serf-dns/custom.json'

Please see custom-domain-name.md for more information.

TODO

• Support configuration with file
• Clean and test functions in main.go
• Proper logging
• Support custom TTL