Ulimit check is incorrect (#327)

* close test connection to google DNS

* ulimit fix: # threads == # open sockets

* rename

* adding margin fo ulimit

pkg/zdns/ulimit_check.go

@@ -22,18 +22,18 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
-func ulimit_check(max_open_files uint64) {
+func ulimitCheck(maxOpenFiles uint64) {
 	var rLimit syscall.Rlimit
 	err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &rLimit)
 	if err != nil {
 		log.Fatal("Failed to fetch ulimit ", err)
 	}
 
-	if max_open_files > rLimit.Cur {
-		log.Warn("Current nofile limit (", rLimit.Cur, ") lower than maximum connection count (", max_open_files, "), try to update.")
+	if maxOpenFiles > rLimit.Cur {
+		log.Warn("Current nofile limit (", rLimit.Cur, ") lower than maximum connection count (", maxOpenFiles, "), trying to update.")
 
-		rLimit.Max = max_open_files
-		rLimit.Cur = max_open_files
+		rLimit.Max = maxOpenFiles
+		rLimit.Cur = maxOpenFiles
 		err = syscall.Setrlimit(syscall.RLIMIT_NOFILE, &rLimit)
 		if err != nil {
 			log.Fatal("Error setting nofile limit to ", rLimit.Cur, ": ", err)

pkg/zdns/ulimit_check_unknown.go

@@ -16,6 +16,6 @@
  */
 package zdns
 
-func ulimit_check(max_open_files uint64) {
+func ulimitCheck(maxOpenFiles uint64) {
 	// fallback for ulimit check on unsupported platform
 }

pkg/zdns/zdns.go

@@ -203,6 +203,10 @@ func Run(gc GlobalConf, flags *pflag.FlagSet,
 			log.Fatal("Unable to find default IP address: ", err)
 		} else {
 			gc.LocalAddrs = append(gc.LocalAddrs, conn.LocalAddr().(*net.UDPAddr).IP)
+			err := conn.Close()
+			if err != nil {
+				log.Warn("Unable to close test connection to Google Public DNS: ", err)
+			}
 		}
 	}
 	if *nanoSeconds {
@@ -216,11 +220,13 @@ func Run(gc GlobalConf, flags *pflag.FlagSet,
 
 	if gc.GoMaxProcs != 0 {
 		runtime.GOMAXPROCS(gc.GoMaxProcs)
-		ulimit_check(uint64(gc.GoMaxProcs * gc.Threads))
-	} else {
-		ulimit_check(uint64(runtime.NumCPU() * gc.Threads))
 	}
 
+	// the margin for limit of open files covers different build platforms (linux/darwin), metadata files, or
+	// input and output files etc.
+	// check ulimit if value is high enough and if not, try to fix it
+	ulimitCheck(uint64(gc.Threads + 100))
+
 	if gc.UDPOnly && gc.TCPOnly {
 		log.Fatal("TCP Only and UDP Only are conflicting")
 	}