some work done

pkg/haproxy/haproxy.go

@@ -1,7 +1,10 @@
 package haproxy
 
 import (
+	"bytes"
 	"context"
+	"crypto/sha256"
+	"io"
 	"io/ioutil"
 	"os"
 	"sync"
@@ -18,6 +21,7 @@ type HAProxyManager struct {
 	configFile     string
 	serviceManager ServiceManager
 	template       *template.Template
+	hash           []byte
 }
 
 func NewHAProxyManager(configFile string) (*HAProxyManager, error) {
@@ -32,26 +36,32 @@ func NewHAProxyManager(configFile string) (*HAProxyManager, error) {
 	}, nil
 }
 
-func (ha *HAProxyManager) checkConfig(ctx context.Context, configFile string) error {
-	return exec.CommandContext(ctx, "haproxy", "-c", "-f", configFile).Run()
-}
-
-func (ha *HAProxyManager) UpdateConfig(ctx context.Context, lbs []config.LoadBalancer) error {
-	ha.Lock()
-	defer ha.Unlock()
+func (ha *HAProxyManager) checkConfig(ctx context.Context, lbs Config) (hash []byte, err error) {
 	tmp, err := ioutil.TempFile(os.TempDir(), "haproxy_")
 	if err != nil {
-		return err
+		return
 	}
 	defer tmp.Close()
 	defer os.Remove(tmp.Name())
-	err = ha.template.Execute(tmp, lbs)
+	h := sha256.New()
+	w := io.MultiWriter(tmp, h)
+	err = ha.template.Execute(w, lbs)
+	if err != nil {
+		return
+	}
+	hash = h.Sum(nil)
+	return hash, exec.CommandContext(ctx, "haproxy", "-c", "-f", tmp.Name()).Run()
+}
+
+func (ha *HAProxyManager) UpdateConfig(ctx context.Context, lbs Config) error {
+	ha.Lock()
+	defer ha.Unlock()
+	hash, err := ha.checkConfig(ctx, lbs)
 	if err != nil {
 		return err
 	}
-	err = ha.checkConfig(ctx, tmp.Name())
-	if err != nil {
-		return err
+	if bytes.Equal(ha.hash, hash) {
+		return nil
 	}
 	file, err := os.OpenFile(ha.configFile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
 	if err != nil {
@@ -63,5 +73,6 @@ func (ha *HAProxyManager) UpdateConfig(ctx context.Context, lbs []config.LoadBal
 		return err
 	}
 	file.Close()
+	ha.hash = hash
 	return ha.serviceManager.Reload()
 }