Gslb - Coredns Io — ContextQMD

+++ title = "gslb" description = "gslb (Global Server Load Balancing) functionality in CoreDNS." weight = 10 tags = [ "plugin" , "gslb" ] categories = [ "plugin", "external" ] date = "2025-02-09T17:00:00+02:00" repo = "https://github.com/dmachard/coredns-gslb" home = "https://github.com/dmachard/coredns-gslb#readme" +++

Description

This plugin provides support for GSLB, enabling advanced load balancing and failover mechanisms based on backend health checks and policies. It is particularly useful for managing geographically distributed services or for ensuring high availability and resilience.

Features:

IPv4 and IPv6 support
Health Checks:
- HTTPS
- TCP
- ICMP
Selection Modes:
- Failover: Routes traffic to the highest-priority available backend.
- Random: Distributes traffic randomly across backends.
- Round Robin: Cycles through backends in sequence.

Syntax

gslb DB_YAML_FILE [ZONES...] {
    max_stagger_start "120s"
    resolution_idle_timeout "3600s"
    batch_size_start 100
}

DB_YAML_FILE The GSLB configuration file in YAML format. If the path is relative, the path from the root plugin will be prepended to it.
ZONES Specifies the zones the plugin should be authoritative for. If not provided, the zones from the CoreDNS configuration block are used.

Examples

Load the gslb.example.com zone from db.gslb.example.com and enable GSLB records on it

corefile

. {
    file db.gslb.example.com
    gslb gslb_config.example.com.yml db.gslb.example.com {
        max_stagger_start "120s"
        resolution_idle_timeout "3600s"
        batch_size_start 100
    }
}

Where db.gslb.example.com would contain

text

$ORIGIN gslb.example.com.
@       3600    IN      SOA     ns1.example.com. admin.example.com. (
                                2024010101 ; Serial
                                7200       ; Refresh
                                3600       ; Retry
                                1209600    ; Expire
                                3600       ; Minimum TTL
                                )
        3600    IN      NS      ns1.gslb.example.com.
        3600    IN      NS      ns2.gslb.example.com.

And gslb_config.example.com.yml would contain

yaml

records:
  webapp.gslb.example.com.:
    mode: "failover"
    record_ttl: 30
    scrape_interval: 10s
    backends:
    - address: "172.16.0.10"
      priority: 1
      healthchecks:
      - type: http
        params:
          port: 443
          uri: "/"
          host: "localhost"
          expected_code: 200
          enable_tls: true
    - address: "172.16.0.11"
      priority: 2
      healthchecks:
      - type: http
        params:
          port: 443
          uri: "/"
          host: "localhost"
          expected_code: 200
          enable_tls: true