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*: support client srv target

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This commit is contained in:
Xiang Li 2016-01-11 20:22:53 -08:00
parent 133f46246e
commit bfa21001a1
3 changed files with 30 additions and 4 deletions
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26
Documentation/clustering.md
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@ -285,6 +285,13 @@ The following DNS SRV records are looked up in the listed order:
If `_etcd-server-ssl._tcp.example.com` is found then etcd will attempt the bootstrapping process over SSL. If `_etcd-server-ssl._tcp.example.com` is found then etcd will attempt the bootstrapping process over SSL.
To help clients discover the etcd cluster, the following DNS SRV records are looked up in the listed order:
* _etcd-client._tcp.example.com
* _etcd-client-ssl._tcp.example.com
If `_etcd-client-ssl._tcp.example.com` is found, clients will attempt to communicate with the etcd cluster over SSL.
#### Create DNS SRV records #### Create DNS SRV records
``` ```
@ -294,6 +301,13 @@ _etcd-server._tcp.example.com. 300 IN SRV 0 0 2380 infra1.example.com.
_etcd-server._tcp.example.com. 300 IN SRV 0 0 2380 infra2.example.com. _etcd-server._tcp.example.com. 300 IN SRV 0 0 2380 infra2.example.com.
``` ```
```
$ dig +noall +answer SRV _etcd-client._tcp.example.com
_etcd-client._tcp.example.com. 300 IN SRV 0 0 2379 infra0.example.com.
_etcd-client._tcp.example.com. 300 IN SRV 0 0 2379 infra1.example.com.
_etcd-client._tcp.example.com. 300 IN SRV 0 0 2379 infra2.example.com.
```
``` ```
$ dig +noall +answer infra0.example.com infra1.example.com infra2.example.com $ dig +noall +answer infra0.example.com infra1.example.com infra2.example.com
infra0.example.com. 300 IN A 10.0.1.10 infra0.example.com. 300 IN A 10.0.1.10
@ -382,6 +396,18 @@ DNS SRV records can also be used to configure the list of peers for an etcd serv
$ etcd --proxy on -discovery-srv example.com $ etcd --proxy on -discovery-srv example.com
``` ```
#### etcd client configuration
DNS SRV records can also be used to help clients discover the etcd cluster.
The official [etcd/client](../client) supports [DNS Discovery](https://godoc.org/github.com/coreos/etcd/client#Discoverer).
`etcdctl` also supports DNS Discovery by specifying the `--discovery-srv` option.
```
$ etcdctl --discovery-srv example.com set foo bar
```
#### Error Cases #### Error Cases
You might see an error like `cannot find local etcd $name from SRV records.`. That means the etcd member fails to find itself from the cluster defined in SRV records. The resolved address in `-initial-advertise-peer-urls` *must match* one of the resolved addresses in the SRV targets. You might see an error like `cannot find local etcd $name from SRV records.`. That means the etcd member fails to find itself from the cluster defined in SRV records. The resolved address in `-initial-advertise-peer-urls` *must match* one of the resolved addresses in the SRV targets.

4
client/srv.go
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@ -50,8 +50,8 @@ func (d *srvDiscover) Discover(domain string) ([]string, error) {
return nil return nil
} }
errHTTPS := updateURLs("etcd-server-ssl", "https") errHTTPS := updateURLs("etcd-client-ssl", "https")
errHTTP := updateURLs("etcd-server", "http") errHTTP := updateURLs("etcd-client", "http")
if errHTTPS != nil && errHTTP != nil { if errHTTPS != nil && errHTTP != nil {
return nil, fmt.Errorf("dns lookup errors: %s and %s", errHTTPS, errHTTP) return nil, fmt.Errorf("dns lookup errors: %s and %s", errHTTPS, errHTTP)

4
client/srv_test.go
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@ -78,10 +78,10 @@ func TestSRVDiscover(t *testing.T) {
for i, tt := range tests { for i, tt := range tests {
lookupSRV = func(service string, proto string, domain string) (string, []*net.SRV, error) { lookupSRV = func(service string, proto string, domain string) (string, []*net.SRV, error) {
if service == "etcd-server-ssl" { if service == "etcd-client-ssl" {
return "", tt.withSSL, nil return "", tt.withSSL, nil
} }
if service == "etcd-server" { if service == "etcd-client" {
return "", tt.withoutSSL, nil return "", tt.withoutSSL, nil
} }
return "", nil, errors.New("Unknown service in mock") return "", nil, errors.New("Unknown service in mock")