Merge pull request #35116 from shashidharatd/fed-coredns-provider

Automatic merge from submit-queue

Add CoreDNS as Federation DNS provider

This PR contains following
1. DNS provider implementation for CoreDNS with etcd as backend
2. Script for optionally deploying CoreDNS in federation control plane

Still to do:
1. HA for CoreDNS service need to be handled, would be taken up in subsequent PR
2. Need to configure CoreDNS as fallback DNS to in-cluster KubeDNS(Manual Step). Need to consider automation.

Request for review: @quinton-hoole @madhusudancs @nikhiljindal @kshafiee @deepak-vij
cc @kubernetes/sig-cluster-federation

cmd/federation-controller-manager/app/BUILD

@@ -22,6 +22,7 @@ go_library(
         "//federation/cmd/federation-controller-manager/app/options:go_default_library",
         "//federation/pkg/dnsprovider:go_default_library",
         "//federation/pkg/dnsprovider/providers/aws/route53:go_default_library",
+        "//federation/pkg/dnsprovider/providers/coredns:go_default_library",
         "//federation/pkg/dnsprovider/providers/google/clouddns:go_default_library",
         "//federation/pkg/federation-controller/cluster:go_default_library",
         "//federation/pkg/federation-controller/configmap:go_default_library",

cmd/federation-controller-manager/app/plugins.go

@@ -22,5 +22,6 @@ package app
 import (
 	// DNS providers
 	_ "k8s.io/kubernetes/federation/pkg/dnsprovider/providers/aws/route53"
+	_ "k8s.io/kubernetes/federation/pkg/dnsprovider/providers/coredns"
 	_ "k8s.io/kubernetes/federation/pkg/dnsprovider/providers/google/clouddns"
 )

pkg/dnsprovider/dns.go

@@ -52,6 +52,8 @@ type Zone interface {
 type ResourceRecordSets interface {
 	// List returns the ResourceRecordSets of the Zone, or an error if the list operation failed.
 	List() ([]ResourceRecordSet, error)
+	// Get returns the ResourceRecordSet with the name in the Zone. if the named resource record set does not exist, but no error occurred, the returned set, and error, are both nil.
+	Get(name string) (ResourceRecordSet, error)
 	// New allocates a new ResourceRecordSet, which can then be passed to ResourceRecordChangeset Add() or Remove()
 	// Arguments are as per the ResourceRecordSet interface below.
 	New(name string, rrdatas []string, ttl int64, rrstype rrstype.RrsType) ResourceRecordSet

pkg/dnsprovider/providers/aws/route53/rrsets.go

@@ -48,6 +48,21 @@ func (rrsets ResourceRecordSets) List() ([]dnsprovider.ResourceRecordSet, error)
 	return list, nil
 }
 
+func (rrsets ResourceRecordSets) Get(name string) (dnsprovider.ResourceRecordSet, error) {
+	var newRrset dnsprovider.ResourceRecordSet
+	rrsetList, err := rrsets.List()
+	if err != nil {
+		return nil, err
+	}
+	for _, rrset := range rrsetList {
+		if rrset.Name() == name {
+			newRrset = rrset
+			break
+		}
+	}
+	return newRrset, nil
+}
+
 func (r ResourceRecordSets) StartChangeset() dnsprovider.ResourceRecordChangeset {
 	return &ResourceRecordChangeset{
 		zone:   r.zone,

pkg/dnsprovider/providers/coredns/BUILD

@@ -0,0 +1,48 @@
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])
+
+load(
+    "@io_bazel_rules_go//go:def.bzl",
+    "go_binary",
+    "go_library",
+    "go_test",
+    "cgo_library",
+)
+
+go_library(
+    name = "go_default_library",
+    srcs = [
+        "coredns.go",
+        "interface.go",
+        "rrchangeset.go",
+        "rrset.go",
+        "rrsets.go",
+        "zone.go",
+        "zones.go",
+    ],
+    tags = ["automanaged"],
+    deps = [
+        "//federation/pkg/dnsprovider:go_default_library",
+        "//federation/pkg/dnsprovider/providers/coredns/stubs:go_default_library",
+        "//federation/pkg/dnsprovider/rrstype:go_default_library",
+        "//vendor:github.com/coreos/etcd/client",
+        "//vendor:github.com/golang/glog",
+        "//vendor:github.com/miekg/coredns/middleware/etcd/msg",
+        "//vendor:golang.org/x/net/context",
+        "//vendor:gopkg.in/gcfg.v1",
+    ],
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = ["coredns_test.go"],
+    library = "go_default_library",
+    tags = ["automanaged"],
+    deps = [
+        "//federation/pkg/dnsprovider:go_default_library",
+        "//federation/pkg/dnsprovider/providers/coredns/stubs:go_default_library",
+        "//federation/pkg/dnsprovider/rrstype:go_default_library",
+        "//federation/pkg/dnsprovider/tests:go_default_library",
+    ],
+)

pkg/dnsprovider/providers/coredns/coredns.go

@@ -0,0 +1,94 @@
+/*
+Copyright 2016 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package coredns is the implementation of pkg/dnsprovider interface for CoreDNS
+package coredns
+
+import (
+	"fmt"
+	etcdc "github.com/coreos/etcd/client"
+	"github.com/golang/glog"
+	"gopkg.in/gcfg.v1"
+	"io"
+	"k8s.io/kubernetes/federation/pkg/dnsprovider"
+	"strconv"
+	"strings"
+)
+
+// "coredns" should be used to use this DNS provider
+const (
+	ProviderName = "coredns"
+)
+
+// Config to override defaults
+type Config struct {
+	Global struct {
+		EtcdEndpoints string `gcfg:"etcd-endpoints"`
+		DNSZones      string `gcfg:"zones"`
+	}
+}
+
+func init() {
+	dnsprovider.RegisterDnsProvider(ProviderName, func(config io.Reader) (dnsprovider.Interface, error) {
+		return newCoreDNSProviderInterface(config)
+	})
+}
+
+// newCoreDnsProviderInterface creates a new instance of an CoreDNS DNS Interface.
+func newCoreDNSProviderInterface(config io.Reader) (*Interface, error) {
+	etcdEndpoints := "http://federation-dns-server-etcd:2379"
+	etcdPathPrefix := "skydns"
+	dnsZones := ""
+
+	// Possibly override defaults with config below
+	if config != nil {
+		var cfg Config
+		if err := gcfg.ReadInto(&cfg, config); err != nil {
+			glog.Errorf("Couldn't read config: %v", err)
+			return nil, err
+		}
+		etcdEndpoints = cfg.Global.EtcdEndpoints
+		dnsZones = cfg.Global.DNSZones
+	}
+	glog.Infof("Using CoreDNS DNS provider")
+
+	if dnsZones == "" {
+		return nil, fmt.Errorf("Need to provide at least one DNS Zone")
+	}
+
+	etcdCfg := etcdc.Config{
+		Endpoints: strings.Split(etcdEndpoints, ","),
+		Transport: etcdc.DefaultTransport,
+	}
+
+	c, err := etcdc.New(etcdCfg)
+	if err != nil {
+		return nil, fmt.Errorf("Create etcd client from the config failed")
+	}
+	etcdKeysAPI := etcdc.NewKeysAPI(c)
+
+	intf := newInterfaceWithStub(etcdKeysAPI)
+	intf.etcdPathPrefix = etcdPathPrefix
+	zoneList := strings.Split(dnsZones, ",")
+
+	intf.zones = Zones{intf: intf}
+	for index, zoneName := range zoneList {
+		zone := Zone{domain: zoneName, id: strconv.Itoa(index), zones: &intf.zones}
+		intf.zones.zoneList = append(intf.zones.zoneList, zone)
+	}
+
+	return intf, nil
+}