don't write secret-data if not needed

Dockerfile

@@ -1,5 +1,5 @@
 # ------------------------------------------------------------------------
-from mcluseau/golang-builder:1.13.4 as build
+from mcluseau/golang-builder:1.13.5 as build
 
 # ------------------------------------------------------------------------
 from debian:stretch

cmd/dkl-local-server/secrets.go

@@ -13,6 +13,7 @@ import (
 	"sort"
 	"sync"
 
+	"github.com/cespare/xxhash"
 	"github.com/cloudflare/cfssl/config"
 	"github.com/cloudflare/cfssl/csr"
 	"github.com/cloudflare/cfssl/helpers"
@@ -32,6 +33,8 @@ var (
 type SecretData struct {
 	l sync.Mutex
 
+	prevHash uint64
+
 	clusters map[string]*ClusterSecrets
 	changed  bool
 	config   *config.Config
@@ -85,6 +88,8 @@ func loadSecretData(config *config.Config) (err error) {
 		return
 	}
 
+	sd.prevHash = xxhash.Sum64(ba)
+
 	secretData = sd
 	return
 }
@@ -93,20 +98,32 @@ func (sd *SecretData) Changed() bool {
 	return sd.changed
 }
 
-func (sd *SecretData) Save() error {
+func (sd *SecretData) Save() (err error) {
 	if DontSave {
-		return nil
+		return
 	}
 
 	sd.l.Lock()
 	defer sd.l.Unlock()
 
-	log.Info("Saving secret data")
 	ba, err := json.Marshal(sd.clusters)
 	if err != nil {
-		return err
+		return
 	}
-	return ioutil.WriteFile(secretDataPath(), ba, 0600)
+
+	h := xxhash.Sum64(ba)
+	if h == sd.prevHash {
+		return
+	}
+
+	log.Info("Saving secret data")
+	err = ioutil.WriteFile(secretDataPath(), ba, 0600)
+
+	if err == nil {
+		sd.prevHash = h
+	}
+
+	return
 }
 
 func newClusterSecrets() *ClusterSecrets {

go.mod

@@ -3,6 +3,7 @@ module novit.nc/direktil/local-server
 require (
 	github.com/agl/ed25519 v0.0.0-20170116200512-5312a6153412
 	github.com/cavaliercoder/go-cpio v0.0.0-20180626203310-925f9528c45e
+	github.com/cespare/xxhash v1.1.0
 	github.com/cloudflare/cfssl v0.0.0-20181213083726-b94e044bb51e
 	github.com/emicklei/go-restful v2.10.0+incompatible
 	github.com/emicklei/go-restful-openapi v1.2.0

go.sum

@@ -1,5 +1,6 @@
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/NYTimes/gziphandler v0.0.0-20170623195520-56545f4a5d46/go.mod h1:3wb06e3pkSAbeQ52E9H9iFoQsEEwGN64994WTCIhntQ=
+github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
 github.com/PuerkitoBio/purell v1.0.0/go.mod h1:c11w/QuzBsJSee3cPx9rAFu61PvFxuPbtSwDGJws/X0=
 github.com/PuerkitoBio/purell v1.1.0/go.mod h1:c11w/QuzBsJSee3cPx9rAFu61PvFxuPbtSwDGJws/X0=
 github.com/PuerkitoBio/purell v1.1.1 h1:WEQqlqaGbrPkxLJWfBwQmfEAE1Z7ONdDLqrN38tNFfI=
@@ -14,6 +15,8 @@ github.com/armon/consul-api v0.0.0-20180202201655-eb2c6b5be1b6/go.mod h1:grANhF5
 github.com/armon/go-socks5 v0.0.0-20160902184237-e75332964ef5/go.mod h1:wHh0iHkYZB8zMSxRWpUBQtwG5a7fFgvEO+odwuTv2gs=
 github.com/cavaliercoder/go-cpio v0.0.0-20180626203310-925f9528c45e h1:hHg27A0RSSp2Om9lubZpiMgVbvn39bsUmW9U5h0twqc=
 github.com/cavaliercoder/go-cpio v0.0.0-20180626203310-925f9528c45e/go.mod h1:oDpT4efm8tSYHXV5tHSdRvBet/b/QzxZ+XyyPehvm3A=
+github.com/cespare/xxhash v1.1.0 h1:a6HrQnmkObjyL+Gs60czilIUGqrzKutQD6XZog3p+ko=
+github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=
 github.com/cloudflare/cfssl v0.0.0-20181213083726-b94e044bb51e h1:Qux+lbuMaRzkQyTdzgtz8MgzPtzmaPQy6DXmxpdxT3U=
 github.com/cloudflare/cfssl v0.0.0-20181213083726-b94e044bb51e/go.mod h1:yMWuSON2oQp+43nFtAV/uvKQIFpSPerB57DCt9t8sSA=
 github.com/coreos/etcd v3.3.10+incompatible/go.mod h1:uF7uidLiAD3TWHmW31ZFd/JWoc32PjwdhPthX9715RE=
@@ -153,6 +156,7 @@ github.com/russross/blackfriday v1.5.2/go.mod h1:JO/DiYxRf+HjHt06OyowR9PTA263kcR
 github.com/sergi/go-diff v1.0.0 h1:Kpca3qRNrduNnOQeazBd0ysaKrUJiIuISHxogkT9RPQ=
 github.com/sergi/go-diff v1.0.0/go.mod h1:0CfEIISq7TuYL3j771MWULgwwjU+GofnZX9QAmXWZgo=
 github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6MwdIuYE2rE=
+github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
 github.com/spf13/afero v1.1.2/go.mod h1:j4pytiNVoe2o6bmDsKpLACNPDBIoEAkihy7loJ1B0CQ=
 github.com/spf13/cast v1.3.0/go.mod h1:Qx5cxh0v+4UWYiBimWS+eyWzqEqokIECu5etghLkUJE=
 github.com/spf13/cobra v0.0.5/go.mod h1:3K3wKZymM7VvHMDS9+Akkh4K60UwM26emMESw8tLCHU=