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listener.go
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listener.go
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package motu
import (
"encoding/json"
"fmt"
"io/ioutil"
"log"
"net/http"
"time"
)
type Listener struct {
Motu *motu
Ch chan *Event
client *http.Client
etag string
}
func (l *Listener) Start() {
tr := &http.Transport{
MaxIdleConns: 1,
IdleConnTimeout: 30 * time.Second,
}
l.client = &http.Client{Transport: tr}
initialized := false
for {
datastore, err := l.fetchDatastore()
if err != nil {
log.Printf("Fetching datastore failed: %v\n", err)
time.Sleep(3 * time.Second)
continue
}
for k, v := range *datastore {
l.Motu.Datastore[k] = v
if initialized {
event := new(Event)
event.Path = k
event.Value = v
l.Ch <- event
}
}
initialized = true
}
}
func (l *Listener) fetchDatastore() (*Datastore, error) {
for {
req, err := http.NewRequest("GET", "http://"+l.Motu.Addr+"/datastore", nil)
if err != nil {
return nil, fmt.Errorf("failed to create http request: %v", err)
}
if l.etag != "" {
req.Header.Set("If-None-Match", l.etag)
}
resp, err := l.client.Do(req)
if err != nil {
// Timeout o.i.d.
return nil, fmt.Errorf("http request failed: %v", err)
}
defer resp.Body.Close()
if l.etag != "" && resp.StatusCode == 304 {
// No change
// MOTU API will have waited 10 seconds before returning HTTP 304, so
// we can immediately continue
continue
}
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, fmt.Errorf("reading HTTP response failed: %v", err)
}
if resp.StatusCode >= 400 {
return nil, fmt.Errorf("got HTTP %d response", resp.StatusCode)
}
if !json.Valid(body) {
return nil, fmt.Errorf("got invalid JSON response: %v", body)
}
datastore := new(Datastore)
if err := json.Unmarshal(body, datastore); err != nil {
return nil, fmt.Errorf("failed to parse JSON: %v", body)
}
l.etag = resp.Header.Get("Etag")
log.Printf("Got datastore, etag is now: %v\n", l.etag)
log.Printf("Datastore = %v\n", datastore)
return datastore, nil
}
}