dynamically get open file limits from OS

common/oslimits.go

@@ -0,0 +1,16 @@
+// +build !windows
+
+package common
+
+import (
+	"syscall"
+)
+
+func MaxOpenFileLimit() int {
+	var nofile syscall.Rlimit
+	err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &nofile)
+	if err != nil {
+		return 1024
+	}
+	return int(nofile.Max)
+}

common/oslimits_windows.go

@@ -0,0 +1,9 @@
+package common
+
+import (
+)
+
+func MaxOpenFileLimit() int {
+	// From https://msdn.microsoft.com/en-us/library/kdfaxaay.aspx
+        return 512
+}

common/path.go

@@ -7,7 +7,6 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
-
 	"github.com/kardianos/osext"
 )
 

eth/backend.go

@@ -236,9 +236,9 @@ func New(config *Config) (*Ethereum, error) {
 		logger.NewJSONsystem(config.DataDir, config.LogJSON)
 	}
 
-	// Let the database take 3/4 of the max open files (TODO figure out a way to get the actual limit of the open files)
 	const dbCount = 3
-	ethdb.OpenFileLimit = 128 / (dbCount + 1)
+
+	ethdb.OpenFileLimit = common.MaxOpenFileLimit() / (dbCount + 1)
 
 	newdb := config.NewDB
 	if newdb == nil {

ethdb/database.go

@@ -1,6 +1,7 @@
 package ethdb
 
 import (
+        "github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/compression/rle"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
@@ -10,7 +11,8 @@ import (
 	"github.com/syndtr/goleveldb/leveldb/opt"
 )
 
-var OpenFileLimit = 64
+
+var OpenFileLimit = common.MaxOpenFileLimit()
 
 type LDBDatabase struct {
 	// filename for reporting