Mirrors/coredns
1
0
Fork 0
mirror of https://github.com/coredns/coredns.git synced 2026-08-20 23:08:28 -04:00
Code Issues Packages Projects Releases Wiki Activity

plugin/kubernetes: Add support for topology-aware headless services via "az-pinned" subdomains (#8388)

Browse Source
This commit is contained in:
rpb-ant
2026-08-10 16:24:50 -04:00
committed by GitHub
parent b2ef1a13e8
commit c2ca1b2c23
10 changed files with 624 additions and 39 deletions
Download Patch File Download Diff File Expand all files Collapse all files

50
plugin/kubernetes/parse.go
View File

@@ -17,6 +17,14 @@ type recordRequest struct {
protocol string
endpoint string
cluster string
// The topology zone from a zone-scoped name
// (zone.pin._zone.service.namespace.svc.zone); only set when the zonal
// option is enabled.
zone string
// zonePrefer is set for the prefer directive: a zone holding no
// endpoints falls back to all endpoints. The zero value is the pin
// directive, which answers NODATA instead.
zonePrefer bool
// The servicename used in Kubernetes.
service string
// The namespace used in Kubernetes.
@@ -25,15 +33,31 @@ type recordRequest struct {
podOrSvc string
}
// zoneLabel anchors a zone-scoped name:
// topozone.DIRECTIVE._zone.service.namespace.svc.zone. It sits three labels
// left of the service — a shape that has always been "query too long"
// (NXDOMAIN) — and the underscore keeps it out of every hostname-shaped
// grammar, so nothing served or servable collides with it. The directive
// label selects the semantics; bare words are safe there because the
// subtree is only reachable through the anchor.
const zoneLabel = "_zone"
// Zone-scoped name directives.
const (
directivePin = "pin" // zone-local endpoints, NODATA if none
directivePrefer = "prefer" // zone-local endpoints, all endpoints if none
)
// parseRequest parses the qname to find all the elements we need for querying k8s. Anything
// that is not parsed will have the wildcard "*" value (except r.endpoint).
// Potential underscores are stripped from _port and _protocol.
func parseRequest(name, zone string, multicluster bool) (r recordRequest, err error) {
// 4 Possible cases:
func parseRequest(name, zone string, multicluster, zonal bool) (r recordRequest, err error) {
// 5 Possible cases:
// 1. _port._protocol.service.namespace.pod|svc.zone
// 2. (endpoint): endpoint.service.namespace.pod|svc.zone
// 3. (service): service.namespace.pod|svc.zone
// 4. (endpoint multicluster): endpoint.cluster.service.namespace.pod|svc.zone
// 5. (zonal): topozone.pin|prefer._zone.service.namespace.svc.zone
base, _ := dnsutil.TrimZone(name, zone)
// return NODATA for apex queries
@@ -67,7 +91,8 @@ func parseRequest(name, zone string, multicluster bool) (r recordRequest, err er
return r, nil
}
// Because of ambiguity we check the labels left: 1: an endpoint. 2: port and protocol or endpoint and clusterid.
// Because of ambiguity we check the labels left: 1: an endpoint. 2: port and protocol or endpoint
// and clusterid. 3 or more: a zone-scoped name (the zone value may span labels).
// Anything else is a query that is too long to answer and can safely be delegated to return an nxdomain.
switch last {
case 0: // endpoint only
@@ -81,8 +106,23 @@ func parseRequest(name, zone string, multicluster bool) (r recordRequest, err er
r.endpoint = segs[last-1]
}
default: // too long
return r, errInvalidRequest
default: // zone-scoped name (topozone.pin|prefer._zone), or too long
// Kubernetes zone label values may contain dots, so the zone is
// every label left of the directive, joined. Not defined in
// multicluster zones; everything this arm rejects keeps the stock
// too-long NXDOMAIN, so behavior with the option off (or for
// unknown directives) is byte-identical to today.
if !zonal || multicluster || segs[last] != zoneLabel || r.podOrSvc != Svc {
return r, errInvalidRequest
}
switch segs[last-1] {
case directivePin:
case directivePrefer:
r.zonePrefer = true
default:
return r, errInvalidRequest
}
r.zone = strings.Join(segs[:last-1], ".")
}
return r, nil