diff --git a/middleware/etcd/backend.go b/middleware/etcd/backend.go new file mode 100644 index 000000000..c601629d3 --- /dev/null +++ b/middleware/etcd/backend.go @@ -0,0 +1,159 @@ +// Package etcd provides the etcd server Backend implementation, +package etcd + +import ( + "encoding/json" + "fmt" + "strings" + + "github.com/miekg/coredns/middleware/etcd/msg" + + etcdc "github.com/coreos/etcd/client" +) + +func (g *Backend) Records(name string, exact bool) ([]msg.Service, error) { + path, star := msg.PathWithWildcard(name) + r, err := g.get(path, true) + if err != nil { + return nil, err + } + segments := strings.Split(msg.Path(name), "/") + switch { + case exact && r.Node.Dir: + return nil, nil + case r.Node.Dir: + return g.loopNodes(r.Node.Nodes, segments, star, nil) + default: + return g.loopNodes([]*etcdc.Node{r.Node}, segments, false, nil) + } +} + +func (g *Backend) ReverseRecord(name string) (*msg.Service, error) { + path, star := msg.PathWithWildcard(name) + if star { + return nil, fmt.Errorf("reverse can not contain wildcards") + } + r, err := g.get(path, true) + if err != nil { + return nil, err + } + if r.Node.Dir { + return nil, fmt.Errorf("reverse must not be a directory") + } + segments := strings.Split(msg.Path(name), "/") + records, err := g.loopNodes([]*etcdc.Node{r.Node}, segments, false, nil) + if err != nil { + return nil, err + } + if len(records) != 1 { + return nil, fmt.Errorf("must be only one service record") + } + return &records[0], nil +} + +// get is a wrapper for client.Get that uses SingleInflight to suppress multiple +// outstanding queries. +func (g *Backend) get(path string, recursive bool) (*etcdc.Response, error) { + resp, err := g.inflight.Do(path, func() (interface{}, error) { + r, e := g.client.Get(g.ctx, path, &etcdc.GetOptions{Sort: false, Recursive: recursive}) + if e != nil { + return nil, e + } + return r, e + }) + if err != nil { + return nil, err + } + return resp.(*etcdc.Response), err +} + +type bareService struct { + Host string + Port int + Priority int + Weight int + Text string +} + +// skydns/local/skydns/east/staging/web +// skydns/local/skydns/west/production/web +// +// skydns/local/skydns/*/*/web +// skydns/local/skydns/*/web + +// loopNodes recursively loops through the nodes and returns all the values. The nodes' keyname +// will be match against any wildcards when star is true. +func (g *Backend) loopNodes(ns []*etcdc.Node, nameParts []string, star bool, bx map[bareService]bool) (sx []msg.Service, err error) { + if bx == nil { + bx = make(map[bareService]bool) + } +Nodes: + for _, n := range ns { + if n.Dir { + nodes, err := g.loopNodes(n.Nodes, nameParts, star, bx) + if err != nil { + return nil, err + } + sx = append(sx, nodes...) + continue + } + if star { + keyParts := strings.Split(n.Key, "/") + for i, n := range nameParts { + if i > len(keyParts)-1 { + // name is longer than key + continue Nodes + } + if n == "*" || n == "any" { + continue + } + if keyParts[i] != n { + continue Nodes + } + } + } + serv := new(msg.Service) + if err := json.Unmarshal([]byte(n.Value), serv); err != nil { + return nil, err + } + b := bareService{serv.Host, serv.Port, serv.Priority, serv.Weight, serv.Text} + if _, ok := bx[b]; ok { + continue + } + bx[b] = true + + serv.Key = n.Key + serv.Ttl = g.calculateTtl(n, serv) + if serv.Priority == 0 { + serv.Priority = int(g.config.Priority) + } + sx = append(sx, *serv) + } + return sx, nil +} + +// calculateTtl returns the smaller of the etcd TTL and the service's +// TTL. If neither of these are set (have a zero value), the server +// default is used. +func (g *Backend) calculateTtl(node *etcdc.Node, serv *msg.Service) uint32 { + etcdTtl := uint32(node.TTL) + + if etcdTtl == 0 && serv.Ttl == 0 { + return g.config.Ttl + } + if etcdTtl == 0 { + return serv.Ttl + } + if serv.Ttl == 0 { + return etcdTtl + } + if etcdTtl < serv.Ttl { + return etcdTtl + } + return serv.Ttl +} + +// Client exposes the underlying Etcd client (used in tests). +func (g *Backend) Client() etcdc.KeysAPI { + return g.client +} diff --git a/middleware/etcd/etcd.go b/middleware/etcd/etcd.go new file mode 100644 index 000000000..84d5dd3a4 --- /dev/null +++ b/middleware/etcd/etcd.go @@ -0,0 +1,34 @@ +// Package etcd provides the etcd backend. +package etcd + +import ( + "github.com/skynetservices/skydns/singleflight" + + etcd "github.com/coreos/etcd/client" + "golang.org/x/net/context" +) + +type ( + Etcd struct { + Ttl uint32 + Priority uint16 + Backend *Backend + } +) + +type Backend struct { + client etcd.KeysAPI + ctx context.Context + config *Config + inflight *singleflight.Group +} + +// NewBackend returns a new Backend. +func NewBackend(client etcd.KeysAPI, ctx context.Context, config *Config) *Backend { + return &Backend{ + client: client, + ctx: ctx, + config: config, + inflight: &singleflight.Group{}, + } +} diff --git a/middleware/etcd/etcd.md b/middleware/etcd/etcd.md new file mode 100644 index 000000000..60f53e9be --- /dev/null +++ b/middleware/etcd/etcd.md @@ -0,0 +1,26 @@ +# etcd + +`etcd` enabled reading zone data from an etcd instance. The data in etcd has to be encoded as +a [message](https://github.com/skynetservices/skydns/blob/2fcff74cdc9f9a7dd64189a447ef27ac354b725f/msg/service.go#L26) +like SkyDNS. + +## Syntax + +~~~ +etcd [address...] +~~~ + +* `address` is the endpoint of etcd. + +The will default to `/skydns` as the path and the local etcd proxy (http://127.0.0.1:2379). + +~~~ +etcd { + round_robin + path /skydns + address address... + stubzones +} +~~~ + +## Examples diff --git a/middleware/etcd/TODO b/middleware/etcd/handler.go similarity index 100% rename from middleware/etcd/TODO rename to middleware/etcd/handler.go diff --git a/middleware/etcd/msg/service.go b/middleware/etcd/msg/service.go new file mode 100644 index 000000000..540cc8806 --- /dev/null +++ b/middleware/etcd/msg/service.go @@ -0,0 +1,212 @@ +package msg + +import ( + "net" + "path" + "strings" + + "github.com/miekg/dns" +) + +// PathPrefix is the prefix used to store CoreDNS data in etcd. +var PathPrefix string = "skydns" + +// This *is* the rdata from a SRV record, but with a twist. +// Host (Target in SRV) must be a domain name, but if it looks like an IP +// address (4/6), we will treat it like an IP address. +type Service struct { + Host string `json:"host,omitempty"` + Port int `json:"port,omitempty"` + Priority int `json:"priority,omitempty"` + Weight int `json:"weight,omitempty"` + Text string `json:"text,omitempty"` + Mail bool `json:"mail,omitempty"` // Be an MX record. Priority becomes Preference. + Ttl uint32 `json:"ttl,omitempty"` + + // When a SRV record with a "Host: IP-address" is added, we synthesize + // a srv.Target domain name. Normally we convert the full Key where + // the record lives to a DNS name and use this as the srv.Target. When + // TargetStrip > 0 we strip the left most TargetStrip labels from the + // DNS name. + TargetStrip int `json:"targetstrip,omitempty"` + + // Group is used to group (or *not* to group) different services + // together. Services with an identical Group are returned in the same + // answer. + Group string `json:"group,omitempty"` + + // Etcd key where we found this service and ignored from json un-/marshalling + Key string `json:"-"` +} + +// NewSRV returns a new SRV record based on the Service. +func (s *Service) NewSRV(name string, weight uint16) *dns.SRV { + host := targetStrip(dns.Fqdn(s.Host), s.TargetStrip) + + return &dns.SRV{Hdr: dns.RR_Header{Name: name, Rrtype: dns.TypeSRV, Class: dns.ClassINET, Ttl: s.Ttl}, + Priority: uint16(s.Priority), Weight: weight, Port: uint16(s.Port), Target: host} +} + +// NewMX returns a new MX record based on the Service. +func (s *Service) NewMX(name string) *dns.MX { + host := targetStrip(dns.Fqdn(s.Host), s.TargetStrip) + + return &dns.MX{Hdr: dns.RR_Header{Name: name, Rrtype: dns.TypeMX, Class: dns.ClassINET, Ttl: s.Ttl}, + Preference: uint16(s.Priority), Mx: host} +} + +// NewA returns a new A record based on the Service. +func (s *Service) NewA(name string, ip net.IP) *dns.A { + return &dns.A{Hdr: dns.RR_Header{Name: name, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: s.Ttl}, A: ip} +} + +// NewAAAA returns a new AAAA record based on the Service. +func (s *Service) NewAAAA(name string, ip net.IP) *dns.AAAA { + return &dns.AAAA{Hdr: dns.RR_Header{Name: name, Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: s.Ttl}, AAAA: ip} +} + +// NewCNAME returns a new CNAME record based on the Service. +func (s *Service) NewCNAME(name string, target string) *dns.CNAME { + return &dns.CNAME{Hdr: dns.RR_Header{Name: name, Rrtype: dns.TypeCNAME, Class: dns.ClassINET, Ttl: s.Ttl}, Target: target} +} + +// NewNS returns a new NS record based on the Service. +func (s *Service) NewNS(name string, target string) *dns.NS { + return &dns.NS{Hdr: dns.RR_Header{Name: name, Rrtype: dns.TypeNS, Class: dns.ClassINET, Ttl: s.Ttl}, Ns: target} +} + +// NewTXT returns a new TXT record based on the Service. +func (s *Service) NewTXT(name string) *dns.TXT { + return &dns.TXT{Hdr: dns.RR_Header{Name: name, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: s.Ttl}, Txt: split255(s.Text)} +} + +// NewPTR returns a new PTR record based on the Service. +func (s *Service) NewPTR(name string, ttl uint32) *dns.PTR { + return &dns.PTR{Hdr: dns.RR_Header{Name: name, Rrtype: dns.TypePTR, Class: dns.ClassINET, Ttl: ttl}, Ptr: dns.Fqdn(s.Host)} +} + +// As Path, but if a name contains wildcards (* or any), the name will be +// chopped of before the (first) wildcard, and we do a highler evel search and +// later find the matching names. So service.*.skydns.local, will look for all +// services under skydns.local and will later check for names that match +// service.*.skydns.local. If a wildcard is found the returned bool is true. +func PathWithWildcard(s string) (string, bool) { + l := dns.SplitDomainName(s) + for i, j := 0, len(l)-1; i < j; i, j = i+1, j-1 { + l[i], l[j] = l[j], l[i] + } + for i, k := range l { + if k == "*" || k == "any" { + return path.Join(append([]string{"/" + PathPrefix + "/"}, l[:i]...)...), true + } + } + return path.Join(append([]string{"/" + PathPrefix + "/"}, l...)...), false +} + +// Path converts a domainname to an etcd path. If s looks like service.staging.skydns.local., +// the resulting key will be /skydns/local/skydns/staging/service . +func Path(s string) string { + l := dns.SplitDomainName(s) + for i, j := 0, len(l)-1; i < j; i, j = i+1, j-1 { + l[i], l[j] = l[j], l[i] + } + return path.Join(append([]string{"/" + PathPrefix + "/"}, l...)...) +} + +// Domain is the opposite of Path. +func Domain(s string) string { + l := strings.Split(s, "/") + // start with 1, to strip /skydns + for i, j := 1, len(l)-1; i < j; i, j = i+1, j-1 { + l[i], l[j] = l[j], l[i] + } + return dns.Fqdn(strings.Join(l[1:len(l)-1], ".")) +} + +// Group checks the services in sx, it looks for a Group attribute on the shortest +// keys. If there are multiple shortest keys *and* the group attribute disagrees (and +// is not empty), we don't consider it a group. +// If a group is found, only services with *that* group (or no group) will be returned. +func Group(sx []Service) []Service { + if len(sx) == 0 { + return sx + } + + // Shortest key with group attribute sets the group for this set. + group := sx[0].Group + slashes := strings.Count(sx[0].Key, "/") + length := make([]int, len(sx)) + for i, s := range sx { + x := strings.Count(s.Key, "/") + length[i] = x + if x < slashes { + if s.Group == "" { + break + } + slashes = x + group = s.Group + } + } + + if group == "" { + return sx + } + + ret := []Service{} // with slice-tricks in sx we can prolly save this allocation (TODO) + + for i, s := range sx { + if s.Group == "" { + ret = append(ret, s) + continue + } + + // Disagreement on the same level + if length[i] == slashes && s.Group != group { + return sx + } + + if s.Group == group { + ret = append(ret, s) + } + } + return ret +} + +// Split255 splits a string into 255 byte chunks. +func split255(s string) []string { + if len(s) < 255 { + return []string{s} + } + sx := []string{} + p, i := 0, 255 + for { + if i <= len(s) { + sx = append(sx, s[p:i]) + } else { + sx = append(sx, s[p:]) + break + + } + p, i = p+255, i+255 + } + + return sx +} + +// targetStrip strips "targetstrip" labels from the left side of the fully qualified name. +func targetStrip(name string, targetStrip int) string { + if targetStrip == 0 { + return name + } + + offset, end := 0, false + for i := 0; i < targetStrip; i++ { + offset, end = dns.NextLabel(name, offset) + } + if end { + // We overshot the name, use the orignal one. + offset = 0 + } + name = name[offset:] + return name +} diff --git a/middleware/etcd/singleflight/singleflight.go b/middleware/etcd/singleflight/singleflight.go new file mode 100644 index 000000000..ff2c2ee4f --- /dev/null +++ b/middleware/etcd/singleflight/singleflight.go @@ -0,0 +1,64 @@ +/* +Copyright 2012 Google Inc. + +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 singleflight provides a duplicate function call suppression +// mechanism. +package singleflight + +import "sync" + +// call is an in-flight or completed Do call +type call struct { + wg sync.WaitGroup + val interface{} + err error +} + +// Group represents a class of work and forms a namespace in which +// units of work can be executed with duplicate suppression. +type Group struct { + mu sync.Mutex // protects m + m map[string]*call // lazily initialized +} + +// Do executes and returns the results of the given function, making +// sure that only one execution is in-flight for a given key at a +// time. If a duplicate comes in, the duplicate caller waits for the +// original to complete and receives the same results. +func (g *Group) Do(key string, fn func() (interface{}, error)) (interface{}, error) { + g.mu.Lock() + if g.m == nil { + g.m = make(map[string]*call) + } + if c, ok := g.m[key]; ok { + g.mu.Unlock() + c.wg.Wait() + return c.val, c.err + } + c := new(call) + c.wg.Add(1) + g.m[key] = c + g.mu.Unlock() + + c.val, c.err = fn() + c.wg.Done() + + g.mu.Lock() + delete(g.m, key) + g.mu.Unlock() + + return c.val, c.err +}