saga1015 / birdwatcher

healthchecker for BIRD-anycasted services

birdwatcher

healthchecker for BIRD-anycasted services

This project is heavily influenced by anycast-healthchecker. If you want to know more about use cases of birdwatcher, please read their excellent documention about anycasted services and how a healthchecker can contribute to a more stable service availability.

In a nutshell: birdwatcher periodically checks a specific service and tells BIRD which prefixes to announce or to withdraw when the service appears to be up or down respectively.

Why birdwatcher

When I found out about anycast-healthchecker (sadly only recently on HaproxyConf 2019), I figured this would solve the missing link between BIRD and whatever anycasted services I have running (mostly haproxy though). Currently however in anycast-healthchecker, it is not possible to specify multiple prefixes to a service. Some machines in these kind of setups are announcing many /32 and /128 prefixes and I ended up specifiying so many services (one per prefix) that python crashed giving me a too many open files error. At first I tried to patch anycast-healthchecker but ended up writing something similar, hence birdwatcher.

It is written in Go because I like it and running multiple threads is easy.

Example usage

This simple configuration enables managing IPv4 daemon of BIRD, runs haproxy_check.sh every second and manages 2 prefixes based on the exit code of the script:

[ipv4]
enable = true

[services]
  [services."foo"]
  command = "/usr/bin/haproxy_check.sh"
  prefixes = ["192.168.0.0/24", "192.168.1.0/24"]
  

Sample output in /etc/bird/birdwatcher.conf if haproxy_check.sh checks out would be:

# DO NOT EDIT MANUALLY
function match_route()
{
	return net ~ [
		192.168.0.0/24,
		192.168.1.0/24
	];
}

As soon as birdwatcher finds out haproxy is down, it will change the content in /etc/bird/birdwatcher.conf to:

# DO NOT EDIT MANUALLY
function match_route()
{
	return false;
}

and reconfigures BIRD by given reloadcommand. Obviously, if you have multiple services being checked by birdwatcher, only the prefixes of that particular service would be removed from the list in match_route.

Integration in BIRD is a matter of including /etc/bird/birdwatcher.conf and birdwatcher6.conf (or whatever you configured at configfile) in the configuration for bird and bird6 respectively and use it in a protocol like this:

protocol bgp my_bgp_proto {
  local as 12345;
  neighbor 1.2.3.4 as 23435;
  ...
  export where match_route();
}

Configuration

[ipv4]

Configuration section specific to manage the IPv4 BIRD daemon, bird.

key	description
enable	Whether or not to manage IPv4 daemon of BIRD. Note that at least on of both ipv4 or ipv6 should be enabled for birdwatcher to start. Defaults to false.
configfile	Path to configuration file that will be generated and should be included in the BIRD configuration. Defaults to /etc/bird/birdwatcher.conf.
reloadcommand	Command to invoke to signal BIRD the configuration should be reloaded. Defaults to /usr/sbin/birdc configure.

[ipv6]

Configuration section specific to manage the IPv6 BIRD daemon, bird6.

key	description
enable	Whether or not to manage IPv6 daemon of BIRD. Note that at least on of both ipv4 or ipv6 should be enabled for birdwatcher to start. Defaults to false.
configfile	Path to configuration file that will be generated and should be included in the BIRD configuration. Defaults to /etc/bird/birdwatcher6.conf.
reloadcommand	Command to invoke to signal BIRD the configuration should be reloaded. Defaults to /usr/sbin/birdc6 configure.

[services]

Each service under this section can have the following settings:

key	description
command	Command that will be periodically run to check if the service should be considered up or down. The result is based on the exit code: a non-zero exit codes makes birdwatcher decide the service is down, otherwise it's up. Required
functionname	Specify the name of the function birdwatcher will generate. You can use this function name to use in your protocol export filter in BIRD. Defaults to match_route.
interval	The interval in seconds at which birdwatcher will check the service. Defaults to 1
timeout	Time in seconds in which the check command should complete. Afterwards it will be handled as if the check command failed. Defaults to 10
fail	The amount of times the check command should fail before the service is considered to be down. Defaults to 1
rise	The amount of times the check command should succeed before the service is considered to be up. Defaults to 1
prefixes	Array of prefixes, mixed IPv4 and IPv6. At least 1 prefix is required per service