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etcd-trigger.go
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etcd-trigger.go
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package main
import (
"fmt"
"io/ioutil"
"log"
"net/http"
"net/url"
"os"
"strings"
"time"
"github.com/codegangsta/cli"
"github.com/coreos/go-etcd/etcd"
"github.com/jcomputing/dns-clb-go/clb"
)
func watch(c *etcd.Client, watch string, read string) (trigger string, value string, err error) {
var r *etcd.Response
log.Print("watching ", watch)
r, err = c.Watch(watch, 0, false, nil, nil)
if err != nil {
return
}
trigger = r.Node.Value
if read != watch {
r, err = c.Get(read, false, false)
if err != nil {
return
}
value = r.Node.Value
} else {
value = trigger
}
return
}
func lookup(c clb.LoadBalancer, u string) (string, error) {
if c == nil {
return u, nil
}
x, err := url.Parse(u)
if err != nil {
return "", err
}
components := strings.Split(x.Host, ":")
if len(components) == 1 {
h := components[0]
a, err := c.GetAddress(h)
if err == nil {
x.Host = fmt.Sprintf("%s:%d", a.Address, a.Port)
}
}
return x.String(), nil
}
func notify(u, value string) (err error) {
var (
body []byte
res *http.Response
req *http.Request
)
c := &http.Client{}
req, err = http.NewRequest("PUT", u, strings.NewReader(value))
if err != nil {
return
}
res, err = c.Do(req)
if err != nil {
return
}
defer res.Body.Close()
body, err = ioutil.ReadAll(res.Body)
if err != nil {
return
}
log.Print("notified: ", u, " (", res.StatusCode, " ", string(body), ")")
return
}
func retrigger(c *etcd.Client, key string, trigger string) (err error) {
_, err = c.Set(key, trigger, 0)
if err == nil {
log.Print("retriggered: ", key, " value: ", trigger)
}
return
}
func main() {
app := cli.NewApp()
app.Name = "etcd-trigger"
app.Usage = "sends values from etcd to HTTP end points on change"
app.Version = "0.0.1"
app.Flags = []cli.Flag{
cli.StringFlag{"dns", "", "DNS server for SRV lookups (default: no SRV lookups)", "DNS"},
cli.StringFlag{"dns-port", "53", "DNS server for SRV lookups (default: 53)", "DNS_PORT"},
cli.StringFlag{"machines", "http://127.0.0.1:4001", "comma-separated list of etcd machines", "ETCD_MACHINES"},
cli.StringFlag{"notifies", "http://127.0.0.1:8080/", "comma-separated list of URLs to notify", "NOTIFIES"},
cli.StringFlag{"read", "", "etcd key whose value to send to notify URLs (default: same as --trigger)", "READ"},
cli.StringFlag{"retrigger", "", "etcd key to write after notifications (default: no retrigger)", "RETRIGGER"},
cli.StringFlag{"trigger", "", "etcd key to watch (required)", "TRIGGER"},
}
app.Action = func(c *cli.Context) {
var (
client *etcd.Client
dnsClb clb.LoadBalancer
err error
trigger, value string
u string
)
machines := strings.Split(c.String("machines"), ",")
notifies := strings.Split(c.String("notifies"), ",")
triggerKey := c.String("trigger")
readKey := c.String("read")
retriggerKey := c.String("retrigger")
if triggerKey == "" {
log.Fatal("-trigger flag required")
}
if readKey == "" {
readKey = triggerKey
}
if c.String("dns") != "" {
dnsClb = clb.NewClb(c.String("dns"), c.String("dns-port"), clb.RoundRobin)
}
client = etcd.NewClient(machines)
for {
trigger, value, err = watch(client, triggerKey, readKey)
if err != nil {
goto Error
}
for _, u = range notifies {
u, err = lookup(dnsClb, u)
if err != nil {
goto Error
}
err = notify(u, value)
if err != nil {
goto Error
}
}
if retriggerKey != "" {
err = retrigger(client, triggerKey, trigger)
if err != nil {
goto Error
}
}
continue
Error:
log.Print("error: ", err)
time.Sleep(time.Second)
}
}
app.Run(os.Args)
}