dns-service-discovery

HAProxy DNS Service Discovery

This example uses dns service discovery for service named web

Prerequisites

This document has the following prerequisites:

• Deploy HAProxy Ingress controller

Using DNS Service Discovery

Example - using internal kubernetes resources

Note: Configure IP address of your cluster DNS server

• Update ingress with simple configmap

$ kubectl apply -f haproxy-config-map.yml

• configmap with all options displayed configmap

$ kubectl apply -f all-options-haproxy-config-map.yml

Note: If using kube-dns, the cache ttl defaults to 30s. Add --max-ttl and --max-cache-ttl to the dns container to a proper value, otherwise the HAProxy backend could take up to 30s to update

• Install pods replication-controler

$ kubectl apply -f web-rc.yml

• Configure ingress

$ kubectl annotate ingress/app --overwrite ingress.kubernetes.io/use-resolver=kubernetes

Two important settings:

• ingress.kubernetes.io/use-resolver: kubernetes: resolver with name kubernetes
• clusterIP: None: service must be headless. See also dns headless doc.

Configmap options

• cluster-dns-domain can be used if kubedns does not points to cluster.local

• dns-resolvers multiline list of DNS resolvers

  • DNS resolver can be written in multiple ways:
    • resolver=ip
    • resolver=ip:port
    • resolver=ip[:port],ip[:port] where port is optional

• dns-timeout-retry default: 1s

• dns-hold-obsoletedefault: 0s

• dns-hold-valid default: 1s

• dns-accepted-payload-size default: 8192

Annotations

ingress.kubernetes.io/use-resolver: resolvername