134 lines
4.6 KiB
Markdown
134 lines
4.6 KiB
Markdown
# kubernetes
|
|
|
|
*kubernetes* enables reading zone data from a kubernetes cluster.
|
|
It implements the spec defined for kubernetes DNS-Based service discovery:
|
|
https://github.com/kubernetes/dns/blob/master/docs/specification.md
|
|
|
|
Examples:
|
|
|
|
Service `A` records are constructed as "myservice.mynamespace.svc.coredns.local" where:
|
|
|
|
* "myservice" is the name of the k8s service
|
|
* "mynamespace" is the k8s namespace for the service, and
|
|
* "svc" indicates this is a service
|
|
* "coredns.local" is the zone
|
|
|
|
Pod `A` records are constructed as "1-2-3-4.mynamespace.pod.coredns.local" where:
|
|
|
|
* "1-2-3-4" is derived from the ip address of the pod (1.2.3.4 in this example)
|
|
* "mynamespace" is the k8s namespace for the service, and
|
|
* "pod" indicates this is a pod
|
|
* "coredns.local" is the zone
|
|
|
|
Endpoint `A` records are constructed as "epname.myservice.mynamespace.svc.coredns.local" where:
|
|
|
|
* "epname" is the hostname (or name constructed from IP) of the endpoint
|
|
* "myservice" is the name of the k8s service that the endpoint serves
|
|
* "mynamespace" is the k8s namespace for the service, and
|
|
* "svc" indicates this is a service
|
|
* "coredns.local" is the zone
|
|
|
|
Also supported are PTR and SRV records for services/endpoints.
|
|
|
|
## Configuration Syntax
|
|
|
|
This is an example kubernetes middle configuration block, with all options described:
|
|
|
|
```
|
|
# kubernetes <zone> [<zone>] ...
|
|
#
|
|
# Use kubernetes middleware for domain "coredns.local"
|
|
# Reverse domain zones can be defined here (e.g. 0.0.10.in-addr.arpa),
|
|
# or instead with the "cidrs" option.
|
|
#
|
|
kubernetes coredns.local {
|
|
|
|
# resyncperiod <period>
|
|
#
|
|
# Kubernetes data API resync period. Default is 5m
|
|
# Example values: 60s, 5m, 1h
|
|
#
|
|
resyncperiod 5m
|
|
|
|
# endpoint <url>
|
|
#
|
|
# Use url for a remote k8s API endpoint. If omitted, it will connect to
|
|
# k8s in-cluster using the cluster service account.
|
|
#
|
|
endpoint https://k8s-endpoint:8080
|
|
|
|
# tls <cert-filename> <key-filename> <cacert-filename>
|
|
#
|
|
# The tls cert, key and the CA cert filenanames for remote k8s connection.
|
|
# This option is ignored if connecting in-cluster (i.e. endpoint is not
|
|
# specified).
|
|
#
|
|
tls cert key cacert
|
|
|
|
# namespaces <namespace> [<namespace>] ...
|
|
#
|
|
# Only expose the k8s namespaces listed. If this option is omitted
|
|
# all namespaces are exposed
|
|
#
|
|
namespaces demo
|
|
|
|
# lables <expression> [,<expression>] ...
|
|
#
|
|
# Only expose the records for kubernetes objects
|
|
# that match this label selector. The label
|
|
# selector syntax is described in the kubernetes
|
|
# API documentation: http://kubernetes.io/docs/user-guide/labels/
|
|
# Example selector below only exposes objects tagged as
|
|
# "application=nginx" in the staging or qa environments.
|
|
#
|
|
labels environment in (staging, qa),application=nginx
|
|
|
|
# pods <disabled|insecure|verified>
|
|
#
|
|
# Set the mode of responding to pod A record requests.
|
|
# e.g 1-2-3-4.ns.pod.zone. This option is provided to allow use of
|
|
# SSL certs when connecting directly to pods.
|
|
# Valid values: disabled, verified, insecure
|
|
# disabled: Do not process pod requests, always returning NXDOMAIN
|
|
# insecure: Always return an A record with IP from request (without
|
|
# checking k8s). This option is is vulnerable to abuse if
|
|
# used maliciously in conjuction with wildcard SSL certs.
|
|
# verified: Return an A record if there exists a pod in same
|
|
# namespace with matching IP. This option requires
|
|
# substantially more memory than in insecure mode, since it
|
|
# will maintain a watch on all pods.
|
|
# Default value is "disabled".
|
|
#
|
|
pods disabled
|
|
|
|
# cidrs <cidr> [<cidr>] ...
|
|
#
|
|
# Expose cidr ranges to reverse lookups. Include any number of space
|
|
# delimited cidrs, and or multiple cidrs options on separate lines.
|
|
# kubernetes middleware will respond to PTR requests for ip addresses
|
|
# that fall within these ranges.
|
|
#
|
|
cidrs 10.0.0.0/24 10.0.10.0/25
|
|
|
|
}
|
|
|
|
```
|
|
|
|
## Wildcards
|
|
|
|
Some query labels accept a wildcard value to match any value.
|
|
If a label is a valid wildcard (\*, or the word "any"), then that label will match
|
|
all values. The labels that accept wildcards are:
|
|
* _service_ in an `A` record request: _service_.namespace.svc.zone.
|
|
* e.g. `*.ns.svc.myzone.local`
|
|
* _namespace_ in an `A` record request: service._namespace_.svc.zone.
|
|
* e.g. `nginx.*.svc.myzone.local`
|
|
* _port and/or protocol_ in an `SRV` request: __port_.__protocol_.service.namespace.svc.zone.
|
|
* e.g. `_http.*.service.ns.svc.`
|
|
* multiple wild cards are allowed in a single query.
|
|
* e.g. `A` Request `*.*.svc.zone.` or `SRV` request `*.*.*.*.svc.zone.`
|
|
|
|
## Deployment in Kubernetes
|
|
|
|
See the [deployment](https://github.com/coredns/deployment) repository for details on how
|
|
to deploy CoreDNS in Kubernetes.
|