Rusty CloudFlare DNS Balancer

This services scopes to be an external health-checker which checks a specified set of targets and manages CloudFlare's DNS settings.

If a target is down, it is removed from the specified DNS entry. When it is back up, it will be added again.

Limitations

• This only works if the DNS entries have the Cloud/CF-Proxy enabled, since otherwise DNS caches would destroy the purpose of this balancer.
• ICMP only works on linux machines

Configuration

Env Name	Default Value	Description
RUST_LOG		The log level used for stdout. Recommended: info
CF_TOKEN		The API Token used to interact with the CloudFlare API
SERVICE_TARGETS		The services which are supposed to be monitored.
CHECK_INTERVAL	30	The interval between checks on the targets in seconds
PROMETHEUS_ENABLED	false	Whether a prometheus webserver with /metrics endpoint should be started
PROMETHEUS_HOST	0.0.0.0	The host on which the prometheus server will listen
PROMETHEUS_PORT	8080	The port on which the prometheus server will listen

The service targets are an array of the following struct(s):

#[derive(Debug, Deserialize, Serialize, Clone)]
pub struct SerializedServiceTarget {
    pub ip: String,
    pub cf_zone: String,
    pub cf_dns: String,
    pub check: SerializedServiceUri,
    pub response_threshold_ms: Option<u32>,
}

#[derive(Debug, Deserialize, Serialize, Clone)]
pub struct SerializedServiceUri {
    pub r#type: String,
    pub port: Option<u16>,
    pub method: Option<String>,
    pub route: Option<String>,
}

An example value for this would look like that:

[
  {
    "ip": "1.2.3.4",
    "cf_zone": "067bd5dbafe54a4270adc9a1742cb8ae",
    "cf_dns": "testfailover.example.org",
    "check": {
      "type": "TcpProbe",
      "port": 443
    }
  },
  {
    "ip": "5.6.7.8",
    "cf_zone": "067bd5dbafe54a4270adc9a1742cb8ae",
    "cf_dns": "testfailover.example.org",
    "response_threshold_ms": 500,
    "check": {
      "type": "https",
      "port": 443,
      "method": "GET",
      "route": "/"
    }
  }
]

Side Notes

Updating the dependencies requires to update the recipe.

Update the recipe using cargo chef prepare.

Todo

• IPv6 Support
• Status Code checks for HTTP(S)