Lower CPU usage at idle by reducing db polling

cmd/syncthing/gui.go

@@ -91,6 +91,7 @@ func startGUI(cfg config.GUIConfiguration, assetDir string, m *model.Model) erro
 	router.Get("/", getRoot)
 	router.Get("/rest/version", restGetVersion)
 	router.Get("/rest/model", restGetModel)
+	router.Get("/rest/model/version", restGetModelVersion)
 	router.Get("/rest/need", restGetNeed)
 	router.Get("/rest/connections", restGetConnections)
 	router.Get("/rest/config", restGetConfig)
@@ -144,6 +145,17 @@ func restGetVersion() string {
 	return Version
 }
 
+func restGetModelVersion(m *model.Model, w http.ResponseWriter, r *http.Request) {
+	var qs = r.URL.Query()
+	var repo = qs.Get("repo")
+	var res = make(map[string]interface{})
+
+	res["version"] = m.Version(repo)
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(res)
+}
+
 func restGetModel(m *model.Model, w http.ResponseWriter, r *http.Request) {
 	var qs = r.URL.Query()
 	var repo = qs.Get("repo")
@@ -168,6 +180,7 @@ func restGetModel(m *model.Model, w http.ResponseWriter, r *http.Request) {
 	res["inSyncFiles"], res["inSyncBytes"] = globalFiles-needFiles, globalBytes-needBytes
 
 	res["state"] = m.State(repo)
+	res["version"] = m.Version(repo)
 
 	w.Header().Set("Content-Type", "application/json")
 	json.NewEncoder(w).Encode(res)

gui/app.js

@@ -103,9 +103,20 @@ syncthing.controller('SyncthingCtrl', function ($scope, $http) {
             getFailed();
         });
         Object.keys($scope.repos).forEach(function (id) {
-            $http.get(urlbase + '/model?repo=' + encodeURIComponent(id)).success(function (data) {
-                $scope.model[id] = data;
-            });
+            if (typeof $scope.model[id] === 'undefined') {
+                // Never fetched before
+                $http.get(urlbase + '/model?repo=' + encodeURIComponent(id)).success(function (data) {
+                    $scope.model[id] = data;
+                });
+            } else {
+                $http.get(urlbase + '/model/version?repo=' + encodeURIComponent(id)).success(function (data) {
+                    if (data.version > $scope.model[id].version) {
+                        $http.get(urlbase + '/model?repo=' + encodeURIComponent(id)).success(function (data) {
+                            $scope.model[id] = data;
+                        });
+                    }
+                });
+            }
         });
         $http.get(urlbase + '/connections').success(function (data) {
             var now = Date.now(),

model/model.go

@@ -872,3 +872,18 @@ func (m *Model) Override(repo string) {
 
 	r.Update(cid.LocalID, fs)
 }
+
+// Version returns the change version for the given repository. This is
+// guaranteed to increment if the contents of the local or global repository
+// has changed.
+func (m *Model) Version(repo string) uint64 {
+	var ver uint64
+
+	m.rmut.Lock()
+	for _, n := range m.repoNodes[repo] {
+		ver += m.repoFiles[repo].Changes(m.cm.Get(n))
+	}
+	m.rmut.Unlock()
+
+	return ver
+}

model/puller.go

@@ -11,6 +11,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"time"
+
 	"github.com/calmh/syncthing/cid"
 	"github.com/calmh/syncthing/config"
 	"github.com/calmh/syncthing/osutil"
@@ -135,6 +136,7 @@ func (p *puller) run() {
 	walkTicker := time.Tick(time.Duration(p.cfg.Options.RescanIntervalS) * time.Second)
 	timeout := time.Tick(5 * time.Second)
 	changed := true
+	var prevVer uint64
 
 	for {
 		// Run the pulling loop as long as there are blocks to fetch
@@ -197,8 +199,11 @@ func (p *puller) run() {
 		default:
 		}
 
-		// Queue more blocks to fetch, if any
-		p.queueNeededBlocks()
+		if v := p.model.Version(p.repoCfg.ID); v > prevVer {
+			// Queue more blocks to fetch, if any
+			p.queueNeededBlocks()
+			prevVer = v
+		}
 	}
 }