Refuse connections if not enough RAM

socketserver/server/backend.go

@@ -307,9 +307,10 @@ func httpError(statusCode int) error {
 func GenerateKeys(outputFile, serverID, theirPublicStr string) {
 	var err error
 	output := ConfigFile{
-		ListenAddr:   "0.0.0.0:8001",
+		ListenAddr:     "0.0.0.0:8001",
-		SocketOrigin: "localhost:8001",
+		SocketOrigin:   "localhost:8001",
-		BackendURL:   "http://localhost:8002/ffz",
+		BackendURL:     "http://localhost:8002/ffz",
+		MinMemoryBytes: 1024 * 1024 * 24,
 	}
 
 	output.ServerID, err = strconv.Atoi(serverID)

socketserver/server/handlecore.go

@@ -107,6 +107,13 @@ var BannerHTML []byte
 // It either uses the SocketUpgrader or writes out the BannerHTML.
 func HTTPHandleRootURL(w http.ResponseWriter, r *http.Request) {
 	if r.Header.Get("Connection") == "Upgrade" {
+		updateSysMem()
+
+		if Statistics.SysMemTotal-Statistics.SysMemFree < Configuration.MinMemoryBytes {
+			w.WriteHeader(503)
+			return
+		}
+
 		conn, err := SocketUpgrader.Upgrade(w, r, nil)
 		if err != nil {
 			fmt.Fprintf(w, "error: %v", err)

socketserver/server/stats.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	linuxproc "github.com/c9s/goprocinfo/linux"
+	"sync"
 )
 
 type StatsData struct {
@@ -24,6 +25,8 @@ type StatsData struct {
 
 	PubSubChannelCount int
 
+	SysMemTotal uint64
+	SysMemFree  uint64
 	MemoryInUse uint64
 	MemoryRSS   uint64
 
@@ -72,6 +75,7 @@ func newStatsData() *StatsData {
 	}
 }
 
+// SetBuildStamp should be called from the main package to identify the git build hash and build time.
 func SetBuildStamp(buildTime, buildHash string) {
 	Statistics.BuildTime = buildTime
 	Statistics.BuildHash = buildHash
@@ -107,6 +111,7 @@ func updatePeriodicStats() {
 			Statistics.MemoryRSS = uint64(pstat.Rss * pageSize)
 			Statistics.MemoryPerClient = Statistics.MemoryRSS / Statistics.CurrentClientCount
 		}
+		updateSysMem()
 	}
 
 	{
@@ -124,6 +129,27 @@ func updatePeriodicStats() {
 	}
 }
 
+var sysMemLastUpdate time.Time
+var sysMemUpdateLock sync.Mutex
+
+func updateSysMem() {
+	if time.Now().Add(-2 * time.Second).After(sysMemLastUpdate) {
+		sysMemUpdateLock.Lock()
+		defer sysMemUpdateLock.Unlock()
+		if !time.Now().Add(-2 * time.Second).After(sysMemLastUpdate) {
+			return
+		}
+	} else {
+		return
+	}
+	sysMemLastUpdate = time.Now()
+	memInfo, err := linuxproc.ReadMemInfo("/proc/meminfo")
+	if err == nil {
+		Statistics.SysMemTotal = memInfo.MemTotal
+		Statistics.SysMemFree = memInfo.MemAvailable
+	}
+}
+
 func HTTPShowStatistics(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/json")
 

socketserver/server/types.go

@@ -20,6 +20,9 @@ type ConfigFile struct {
 	// URL to the backend server
 	BackendURL string
 
+	// Minimum memory to accept a new connection
+	MinMemoryBytes uint64
+
 	// SSL/TLS
 	UseSSL             bool
 	SSLCertificateFile string