leaderless gossip-based service discovery w/ consul compatibility
initial dns implementation
+312
-15
+1
api/agent.go
+1
api/agent.go
+2
-2
go.mod
+2
-2
go.mod
···
4
4
5
5
require (
6
6
github.com/hashicorp/serf v0.10.1
7
+
github.com/miekg/dns v1.1.41
8
+
go.etcd.io/bbolt v1.4.3
7
9
golang.org/x/exp v0.0.0-20230213192124-5e25df0256eb
8
10
)
9
11
···
17
19
github.com/hashicorp/go-sockaddr v1.0.0 // indirect
18
20
github.com/hashicorp/golang-lru v0.5.0 // indirect
19
21
github.com/hashicorp/memberlist v0.5.0 // indirect
20
-
github.com/miekg/dns v1.1.41 // indirect
21
22
github.com/sean-/seed v0.0.0-20170313163322-e2103e2c3529 // indirect
22
-
go.etcd.io/bbolt v1.4.3 // indirect
23
23
golang.org/x/net v0.0.0-20210410081132-afb366fc7cd1 // indirect
24
24
golang.org/x/sys v0.29.0 // indirect
25
25
)
+4
-5
go.sum
+4
-5
go.sum
···
57
57
github.com/sean-/seed v0.0.0-20170313163322-e2103e2c3529/go.mod h1:DxrIzT+xaE7yg65j358z/aeFdxmN0P9QXhEzd20vsDc=
58
58
github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
59
59
github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
60
-
github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
61
60
github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
62
61
github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
62
+
github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
63
63
go.etcd.io/bbolt v1.4.3 h1:dEadXpI6G79deX5prL3QRNP6JB8UxVkqo4UPnHaNXJo=
64
64
go.etcd.io/bbolt v1.4.3/go.mod h1:tKQlpPaYCVFctUIgFKFnAlvbmB3tpy1vkTnDWohtc0E=
65
65
golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
···
73
73
golang.org/x/net v0.0.0-20210410081132-afb366fc7cd1 h1:4qWs8cYYH6PoEFy4dfhDFgoMGkwAcETd+MmPdCPMzUc=
74
74
golang.org/x/net v0.0.0-20210410081132-afb366fc7cd1/go.mod h1:9tjilg8BloeKEkVJvy7fQ90B1CfIiPueXVOjqfkSzI8=
75
75
golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
76
-
golang.org/x/sync v0.0.0-20210220032951-036812b2e83c h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
77
76
golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
78
77
golang.org/x/sync v0.10.0 h1:3NQrjDixjgGwUOCaF8w2+VYHv0Ve/vGYSbdkTa98gmQ=
78
+
golang.org/x/sync v0.10.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
79
79
golang.org/x/sys v0.0.0-20180823144017-11551d06cbcc/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
80
80
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
81
81
golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
···
88
88
golang.org/x/sys v0.0.0-20210303074136-134d130e1a04/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
89
89
golang.org/x/sys v0.0.0-20210330210617-4fbd30eecc44/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
90
90
golang.org/x/sys v0.0.0-20220728004956-3c1f35247d10/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
91
-
golang.org/x/sys v0.1.0 h1:kunALQeHf1/185U1i0GOB/fy1IPRDDpuoOOqRReG57U=
92
-
golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
93
91
golang.org/x/sys v0.29.0 h1:TPYlXGxvx1MGTn2GiZDhnjPA9wZzZeGKHHmKhHYvgaU=
94
92
golang.org/x/sys v0.29.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
95
93
golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
···
101
99
golang.org/x/tools v0.0.0-20190907020128-2ca718005c18/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
102
100
golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
103
101
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
104
-
gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
105
102
gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
103
+
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
104
+
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+13
internal/agent/agent.go
+13
internal/agent/agent.go
···
87
87
// services holds the agent's own + gossipped service catalog.
88
88
services *ServiceStore
89
89
90
+
// dns is the optional DNS server that resolves
91
+
// <node>.node.<domain> and <svc>.service.<domain>.
92
+
dns *DNSServer
93
+
90
94
// We receive serf events on this channel
91
95
eventCh chan serf.Event
92
96
logger *slog.Logger
···
332
336
apiHandler := a.httpHandlers.handler()
333
337
go a.serveAPI(apiHandler)
334
338
339
+
// Start DNS server
340
+
a.dns = newDNSServer(a)
341
+
if err := a.dns.Start(); err != nil {
342
+
return err
343
+
}
344
+
335
345
return nil
336
346
}
337
347
···
363
373
364
374
EXIT:
365
375
a.logger.Info("complete serf shutdown")
376
+
if a.dns != nil {
377
+
a.dns.Shutdown()
378
+
}
366
379
if a.services != nil {
367
380
if err := a.services.Close(); err != nil {
368
381
a.logger.Warn("close service store", "err", err)
+2
internal/agent/agent_endpoint.go
+2
internal/agent/agent_endpoint.go
···
28
28
DNSBindAddr string
29
29
HTTPBindAddr string
30
30
SerfBindAddr string
31
+
DNSDomain string
31
32
}{
32
33
NodeName: s.agent.Config.NodeName,
33
34
Version: s.agent.Config.VersionWithMetadata(),
34
35
DNSBindAddr: s.agent.Config.DNSBindAddr.String(),
35
36
HTTPBindAddr: s.agent.Config.HTTPBindAddr.String(),
36
37
SerfBindAddr: s.agent.Config.SerfBindAddr.String(),
38
+
DNSDomain: s.agent.Config.DNSDomain,
37
39
}
38
40
39
41
self := Self{
+7
-4
internal/agent/config.go
+7
-4
internal/agent/config.go
···
6
6
)
7
7
8
8
const (
9
-
DefaultDNSPort int = 8600
10
-
DefaultHTTPPort int = 8500
11
-
DefaultSerfPort int = 8301
12
-
DefaultDataDir string = "./cascade-data"
9
+
DefaultDNSPort int = 8600
10
+
DefaultHTTPPort int = 8500
11
+
DefaultSerfPort int = 8301
12
+
DefaultDataDir string = "./cascade-data"
13
+
DefaultDNSDomain string = "consul"
13
14
)
14
15
15
16
func DefaultConfig() *Config {
···
24
25
cfg.SerfBindAddr = &net.TCPAddr{IP: net.ParseIP("0.0.0.0"), Port: DefaultSerfPort}
25
26
cfg.NodeName = hostname
26
27
cfg.DataDir = DefaultDataDir
28
+
cfg.DNSDomain = DefaultDNSDomain
27
29
28
30
return &cfg
29
31
}
···
36
38
NodeName string
37
39
StartJoin []string
38
40
DataDir string
41
+
DNSDomain string
39
42
40
43
//// non user-configurable
41
44
// HTTPResponseHeaders are used to add HTTP header response fields to the HTTP API responses.
+266
internal/agent/dns.go
+266
internal/agent/dns.go
···
1
+
package agent
2
+
3
+
import (
4
+
"fmt"
5
+
"net"
6
+
"strings"
7
+
"sync"
8
+
9
+
"github.com/hashicorp/serf/serf"
10
+
"github.com/miekg/dns"
11
+
)
12
+
13
+
// DNSServer answers queries for <node>.node.<domain> and
14
+
// <svc>.service.<domain>. The domain is configurable via Config.DNSDomain
15
+
// and defaults to "consul" so consul SDKs that hardcode .consul resolve
16
+
// without changes.
17
+
type DNSServer struct {
18
+
agent *Agent
19
+
domain string // normalized: lowercase, no leading/trailing dot
20
+
21
+
udp *dns.Server
22
+
tcp *dns.Server
23
+
wg sync.WaitGroup
24
+
}
25
+
26
+
func newDNSServer(a *Agent) *DNSServer {
27
+
domain := strings.ToLower(strings.Trim(a.Config.DNSDomain, "."))
28
+
if domain == "" {
29
+
domain = DefaultDNSDomain
30
+
}
31
+
return &DNSServer{agent: a, domain: domain}
32
+
}
33
+
34
+
// Start binds the UDP and TCP DNS listeners. Returns once both are
35
+
// listening; serving happens in background goroutines.
36
+
func (d *DNSServer) Start() error {
37
+
addr := fmt.Sprintf("%s:%d", d.agent.Config.DNSBindAddr.IP, d.agent.Config.DNSBindAddr.Port)
38
+
handler := dns.HandlerFunc(d.handle)
39
+
40
+
udpConn, err := net.ListenPacket("udp", addr)
41
+
if err != nil {
42
+
return fmt.Errorf("dns udp listen %s: %w", addr, err)
43
+
}
44
+
tcpListener, err := net.Listen("tcp", addr)
45
+
if err != nil {
46
+
udpConn.Close()
47
+
return fmt.Errorf("dns tcp listen %s: %w", addr, err)
48
+
}
49
+
50
+
d.udp = &dns.Server{PacketConn: udpConn, Handler: handler}
51
+
d.tcp = &dns.Server{Listener: tcpListener, Handler: handler}
52
+
53
+
d.wg.Add(2)
54
+
go func() {
55
+
defer d.wg.Done()
56
+
if err := d.udp.ActivateAndServe(); err != nil {
57
+
d.agent.logger.Error("dns udp serve", err)
58
+
}
59
+
}()
60
+
go func() {
61
+
defer d.wg.Done()
62
+
if err := d.tcp.ActivateAndServe(); err != nil {
63
+
d.agent.logger.Error("dns tcp serve", err)
64
+
}
65
+
}()
66
+
return nil
67
+
}
68
+
69
+
// Shutdown stops both listeners. Safe to call multiple times.
70
+
func (d *DNSServer) Shutdown() {
71
+
if d.udp != nil {
72
+
_ = d.udp.Shutdown()
73
+
}
74
+
if d.tcp != nil {
75
+
_ = d.tcp.Shutdown()
76
+
}
77
+
d.wg.Wait()
78
+
}
79
+
80
+
// handle is the single dispatch entrypoint for all DNS queries.
81
+
func (d *DNSServer) handle(w dns.ResponseWriter, req *dns.Msg) {
82
+
resp := new(dns.Msg)
83
+
resp.SetReply(req)
84
+
resp.Authoritative = true
85
+
resp.RecursionAvailable = false
86
+
87
+
if len(req.Question) == 0 {
88
+
resp.SetRcode(req, dns.RcodeFormatError)
89
+
_ = w.WriteMsg(resp)
90
+
return
91
+
}
92
+
q := req.Question[0]
93
+
94
+
labels, ok := d.stripDomain(q.Name)
95
+
if !ok {
96
+
resp.SetRcode(req, dns.RcodeRefused)
97
+
_ = w.WriteMsg(resp)
98
+
return
99
+
}
100
+
101
+
switch {
102
+
case isService(labels):
103
+
d.answerService(resp, q, labels)
104
+
case isNode(labels):
105
+
d.answerNode(resp, q, labels)
106
+
default:
107
+
resp.SetRcode(req, dns.RcodeNameError) // NXDOMAIN
108
+
}
109
+
110
+
_ = w.WriteMsg(resp)
111
+
}
112
+
113
+
// stripDomain returns the labels left of the configured domain. For
114
+
// "web.service.consul." with domain "consul", returns ["web", "service"].
115
+
// Returns false if the query isn't in our domain.
116
+
func (d *DNSServer) stripDomain(qname string) ([]string, bool) {
117
+
name := strings.ToLower(strings.TrimSuffix(qname, "."))
118
+
suffix := "." + d.domain
119
+
if name == d.domain {
120
+
return nil, true
121
+
}
122
+
if !strings.HasSuffix(name, suffix) {
123
+
return nil, false
124
+
}
125
+
trimmed := strings.TrimSuffix(name, suffix)
126
+
if trimmed == "" {
127
+
return nil, true
128
+
}
129
+
return strings.Split(trimmed, "."), true
130
+
}
131
+
132
+
func isService(labels []string) bool {
133
+
return len(labels) >= 2 && labels[len(labels)-1] == "service"
134
+
}
135
+
136
+
func isNode(labels []string) bool {
137
+
return len(labels) >= 2 && labels[len(labels)-1] == "node"
138
+
}
139
+
140
+
// answerNode handles <name>.node.<domain> queries (A only).
141
+
func (d *DNSServer) answerNode(resp *dns.Msg, q dns.Question, labels []string) {
142
+
// labels = [name, "node"]. anything more specific is an NXDOMAIN.
143
+
if len(labels) != 2 {
144
+
resp.Rcode = dns.RcodeNameError
145
+
return
146
+
}
147
+
name := labels[0]
148
+
member, ok := d.findMember(name)
149
+
if !ok {
150
+
resp.Rcode = dns.RcodeNameError
151
+
return
152
+
}
153
+
if q.Qtype == dns.TypeA || q.Qtype == dns.TypeANY {
154
+
if ip := member.Addr.To4(); ip != nil {
155
+
resp.Answer = append(resp.Answer, &dns.A{
156
+
Hdr: dns.RR_Header{Name: q.Name, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 0},
157
+
A: ip,
158
+
})
159
+
}
160
+
}
161
+
}
162
+
163
+
// answerService handles <svc>.service.<domain> and
164
+
// <tag>.<svc>.service.<domain> queries (A + SRV).
165
+
func (d *DNSServer) answerService(resp *dns.Msg, q dns.Question, labels []string) {
166
+
// shapes: [name, "service"] or [tag, name, "service"]
167
+
var name, tag string
168
+
switch len(labels) {
169
+
case 2:
170
+
name = labels[0]
171
+
case 3:
172
+
tag = labels[0]
173
+
name = labels[1]
174
+
default:
175
+
resp.Rcode = dns.RcodeNameError
176
+
return
177
+
}
178
+
179
+
instances := d.agent.CatalogServiceInstances(name)
180
+
if tag != "" {
181
+
instances = filterByTag(instances, tag)
182
+
}
183
+
if len(instances) == 0 {
184
+
resp.Rcode = dns.RcodeNameError
185
+
return
186
+
}
187
+
188
+
wantA := q.Qtype == dns.TypeA || q.Qtype == dns.TypeANY
189
+
wantSRV := q.Qtype == dns.TypeSRV || q.Qtype == dns.TypeANY
190
+
191
+
for _, inst := range instances {
192
+
ip := d.serviceIP(inst)
193
+
if ip == nil {
194
+
continue
195
+
}
196
+
if wantA {
197
+
resp.Answer = append(resp.Answer, &dns.A{
198
+
Hdr: dns.RR_Header{Name: q.Name, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 0},
199
+
A: ip,
200
+
})
201
+
}
202
+
if wantSRV {
203
+
target := dns.Fqdn(fmt.Sprintf("%s.node.%s", normalizeLabel(inst.Node), d.domain))
204
+
resp.Answer = append(resp.Answer, &dns.SRV{
205
+
Hdr: dns.RR_Header{Name: q.Name, Rrtype: dns.TypeSRV, Class: dns.ClassINET, Ttl: 0},
206
+
Priority: 1,
207
+
Weight: 1,
208
+
Port: uint16(inst.Service.Port),
209
+
Target: target,
210
+
})
211
+
// add an A record in Extra so clients don't need a second lookup
212
+
resp.Extra = append(resp.Extra, &dns.A{
213
+
Hdr: dns.RR_Header{Name: target, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 0},
214
+
A: ip,
215
+
})
216
+
}
217
+
}
218
+
}
219
+
220
+
// serviceIP resolves a NodeService to an IP, honoring the ServiceAddress
221
+
// fallback convention (empty service addr → use node addr).
222
+
func (d *DNSServer) serviceIP(inst NodeService) net.IP {
223
+
if inst.Service.Address != "" {
224
+
if ip := net.ParseIP(inst.Service.Address); ip != nil {
225
+
return ip.To4()
226
+
}
227
+
}
228
+
if m, ok := d.findMember(inst.Node); ok {
229
+
return m.Addr.To4()
230
+
}
231
+
return nil
232
+
}
233
+
234
+
func (d *DNSServer) findMember(name string) (serf.Member, bool) {
235
+
target := strings.ToLower(name)
236
+
for _, m := range d.agent.serf.Members() {
237
+
if strings.ToLower(normalizeLabel(m.Name)) == target {
238
+
return m, true
239
+
}
240
+
}
241
+
return serf.Member{}, false
242
+
}
243
+
244
+
func filterByTag(instances []NodeService, tag string) []NodeService {
245
+
tag = strings.ToLower(tag)
246
+
out := instances[:0:0]
247
+
for _, inst := range instances {
248
+
for _, t := range inst.Service.Tags {
249
+
if strings.ToLower(t) == tag {
250
+
out = append(out, inst)
251
+
break
252
+
}
253
+
}
254
+
}
255
+
return out
256
+
}
257
+
258
+
// normalizeLabel makes a node or service name safe to embed in a DNS label.
259
+
// Currently just lowercases and replaces spaces with hyphens, which covers
260
+
// the common cases (hostnames are already valid, but `cascade agent` test
261
+
// nodes are named "agent 1" etc.).
262
+
func normalizeLabel(s string) string {
263
+
s = strings.ToLower(s)
264
+
s = strings.ReplaceAll(s, " ", "-")
265
+
return s
266
+
}
+12
-3
internal/cli/agent.go
+12
-3
internal/cli/agent.go
···
21
21
flagBindDNS string
22
22
flagBindHTTP string
23
23
flagBindSerf string
24
-
flagJoin string
25
-
flagNode string
26
-
flagDataDir string
24
+
flagJoin string
25
+
flagNode string
26
+
flagDataDir string
27
+
flagDNSDomain string
27
28
}
28
29
29
30
func (c *agentCommand) Usage() {
···
52
53
53
54
-data-dir=<path>
54
55
directory for cascade's local state (default = ./cascade-data)
56
+
57
+
-domain=<name>
58
+
DNS suffix served by the agent (default = consul). consul-compat by
59
+
default so consul SDKs that hardcode .consul resolve unchanged.
55
60
`)
56
61
}
57
62
···
66
71
flags.StringVar(&c.flagJoin, "join", "", "")
67
72
flags.StringVar(&c.flagNode, "node", "", "")
68
73
flags.StringVar(&c.flagDataDir, "data-dir", "", "")
74
+
flags.StringVar(&c.flagDNSDomain, "domain", "", "")
69
75
70
76
if err := flags.Parse(args); err != nil {
71
77
fmt.Println(err)
···
209
215
}
210
216
if c.flagDataDir != "" {
211
217
config.DataDir = c.flagDataDir
218
+
}
219
+
if c.flagDNSDomain != "" {
220
+
config.DNSDomain = c.flagDNSDomain
212
221
}
213
222
return config, nil
214
223
}
+5
-1
internal/cli/status.go
+5
-1
internal/cli/status.go
···
64
64
65
65
self, err := agent.SelfTyped()
66
66
nodeName := "<unknown>"
67
-
var dnsAddr, httpAddr, serfAddr string
67
+
var dnsAddr, httpAddr, serfAddr, dnsDomain string
68
68
if err == nil {
69
69
nodeName = self.Config.NodeName
70
70
dnsAddr = self.Config.DNSBindAddr
71
71
httpAddr = self.Config.HTTPBindAddr
72
72
serfAddr = self.Config.SerfBindAddr
73
+
dnsDomain = self.Config.DNSDomain
73
74
}
74
75
75
76
statusCounts := map[string]int{}
···
107
108
fmt.Fprintf(tw, " dns\t%s\n", dnsAddr)
108
109
fmt.Fprintf(tw, " http\t%s\n", httpAddr)
109
110
fmt.Fprintf(tw, " serf\t%s\n", serfAddr)
111
+
if dnsDomain != "" {
112
+
fmt.Fprintf(tw, " domain\t.%s\n", dnsDomain)
113
+
}
110
114
fmt.Fprintln(tw)
111
115
}
112
116