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main.go
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main.go
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package main
import (
"context"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/http/cookiejar"
"net/url"
"os"
"time"
"github.com/Luzifer/rconfig"
"github.com/cenkalti/backoff"
"github.com/satori/go.uuid"
log "github.com/sirupsen/logrus"
)
const RequestIDKey = "request_id"
var (
cfg = struct {
User string `flag:"user,u" default:"" env:"USER" description:"Username for Grafana login"`
Pass string `flag:"pass,p" default:"" env:"PASS" description:"Password for Grafana login"`
BaseURL string `flag:"baseurl" default:"" env:"BASEURL" description:"BaseURL (excluding last /) of Grafana"`
Listen string `flag:"listen" default:"127.0.0.1:8081" description:"IP/Port to listen on"`
Token string `flag:"token" default:"" env:"TOKEN" description:"(optional) require a ?token=xyz parameter to show the dashboard"`
LogFormat string `flag:"log-format" default:"text" env:"LOG_FORMAT" description:"Output format for logs (text/json)"`
}{}
cookieJar *cookiejar.Jar
client *http.Client
base *url.URL
)
func init() {
if err := rconfig.Parse(&cfg); err != nil {
log.Fatalf("Unable to parse commandline options: %s", err)
}
switch cfg.LogFormat {
case "text":
log.SetFormatter(&log.TextFormatter{})
case "json":
log.SetFormatter(&log.JSONFormatter{})
default:
log.Fatalf("Unknown log format: %s", cfg.LogFormat)
}
log.SetLevel(log.InfoLevel)
if cfg.User == "" || cfg.Pass == "" || cfg.BaseURL == "" {
rconfig.Usage()
os.Exit(1)
}
cookieJar, _ = cookiejar.New(nil)
client = &http.Client{
Jar: cookieJar,
}
}
func loadLogin(ctx context.Context) {
backoff.Retry(func() error {
resp, err := client.PostForm(fmt.Sprintf("%s/login", cfg.BaseURL), url.Values{
"user": {cfg.User},
"password": {cfg.Pass},
})
if err != nil {
log.WithError(err).WithFields(log.Fields{
"user": cfg.User,
"request_id": requestIDFromContext(ctx),
}).Error("Login failed")
return err
}
defer resp.Body.Close()
return nil
}, backoff.NewExponentialBackOff())
}
type proxy struct{}
func (p proxy) ServeHTTP(res http.ResponseWriter, r *http.Request) {
requestID := uuid.NewV4().String()
bgCtx := context.Background()
ctx := context.WithValue(bgCtx, RequestIDKey, requestID)
requestLog := log.WithFields(log.Fields{
"http_user_agent": r.Header.Get("User-Agent"),
"host": r.Host,
"remote_addr": r.Header.Get("X-Forwarded-For"),
"request": r.URL.Path,
"request_full": r.URL.String(),
"request_method": r.Method,
"request_id": requestIDFromContext(ctx),
})
bo := backoff.NewExponentialBackOff()
bo.MaxElapsedTime = 5 * time.Second
if err := backoff.Retry(func() error {
r.URL.Host = base.Host
r.URL.Scheme = base.Scheme
r.RequestURI = ""
r.Host = base.Host
suppliedToken := r.URL.Query().Get("token")
if authCookie, err := r.Cookie("grafana-proxy-auth"); err == nil {
suppliedToken = authCookie.Value
}
if cfg.Token != "" && suppliedToken != cfg.Token {
requestLog.Error("Token parameter is wrong")
http.Error(res, "Please add the `?token=xyz` parameter with correct token", http.StatusForbidden)
return nil
}
// Do not forward cookies set by the client, use our own cookie jar
r.Header.Del("Cookie")
resp, err := client.Do(r)
if err != nil {
requestLog.WithError(err).Error("Request failed")
return err
}
defer resp.Body.Close()
res.Header().Del("Content-Type")
res.Header().Del("Set-Cookie") // Client does not need to handle cookies but Grafana passes them
for k, v := range resp.Header {
for _, v1 := range v {
res.Header().Set(k, v1)
}
}
if r.URL.Query().Get("token") != "" {
http.SetCookie(res, &http.Cookie{
Name: "grafana-proxy-auth",
Value: r.URL.Query().Get("token"),
MaxAge: 31536000, // 1 Year
Path: "/",
})
}
if resp.StatusCode == 401 {
errmsg, _ := ioutil.ReadAll(resp.Body)
requestLog.WithFields(log.Fields{
"error": string(errmsg),
"header": r.Header,
}).Info("Unauthorized, trying to login")
loadLogin(ctx)
return fmt.Errorf("Need to relogin")
}
res.WriteHeader(resp.StatusCode)
written, _ := io.Copy(res, resp.Body)
requestLog.WithFields(log.Fields{
"status": resp.StatusCode,
"bytes_sent": written,
}).Info("Request completed")
return nil
}, bo); err != nil {
requestLog.WithError(err).WithFields(log.Fields{
"status": http.StatusInternalServerError,
}).Error("Backend request failed")
http.Error(res, fmt.Sprintf("Woot?\n%s", err), http.StatusInternalServerError)
}
}
func requestIDFromContext(ctx context.Context) string {
if id, ok := ctx.Value(RequestIDKey).(string); ok {
return id
}
return ""
}
func main() {
loadLogin(context.Background())
var err error
base, err = url.Parse(cfg.BaseURL)
if err != nil {
log.WithError(err).WithField("base_url", base).Fatalf("BaseURL is not parsesable")
}
log.Fatal(http.ListenAndServe(cfg.Listen, proxy{}))
}