Allow file descriptor limit to be set via CLI

cmd/geth/main.go

@@ -118,6 +118,7 @@ var (
 		utils.CacheSnapshotFlag,
 		utils.CacheNoPrefetchFlag,
 		utils.CachePreimagesFlag,
+		utils.FdLimitFlag,
 		utils.ListenPortFlag,
 		utils.MaxPeersFlag,
 		utils.MaxPendingPeersFlag,

cmd/geth/usage.go

@@ -119,6 +119,7 @@ var AppHelpFlagGroups = []flags.FlagGroup{
 			utils.CacheSnapshotFlag,
 			utils.CacheNoPrefetchFlag,
 			utils.CachePreimagesFlag,
+			utils.FdLimitFlag,
 		},
 	},
 	{

cmd/utils/flags.go

@@ -433,6 +433,11 @@ var (
 		Name:  "cache.preimages",
 		Usage: "Enable recording the SHA3/keccak preimages of trie keys",
 	}
+	FdLimitFlag = cli.IntFlag{
+		Name:  "fdlimit",
+		Usage: "Raise the open file descriptor resource limit (default = system fd limit)",
+		Value: math.MaxInt32,
+	}
 	// Miner settings
 	MiningEnabledFlag = cli.BoolFlag{
 		Name:  "mine",
@@ -1057,11 +1062,14 @@ func setLes(ctx *cli.Context, cfg *ethconfig.Config) {
 
 // MakeDatabaseHandles raises out the number of allowed file handles per process
 // for Geth and returns half of the allowance to assign to the database.
-func MakeDatabaseHandles() int {
+func MakeDatabaseHandles(userFdLimit int) int {
 	limit, err := fdlimit.Maximum()
 	if err != nil {
 		Fatalf("Failed to retrieve file descriptor allowance: %v", err)
 	}
+	if userFdLimit < limit {
+		limit = userFdLimit
+	}
 	raised, err := fdlimit.Raise(uint64(limit))
 	if err != nil {
 		Fatalf("Failed to raise file descriptor allowance: %v", err)
@@ -1522,7 +1530,10 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *ethconfig.Config) {
 	if ctx.GlobalIsSet(CacheFlag.Name) || ctx.GlobalIsSet(CacheDatabaseFlag.Name) {
 		cfg.DatabaseCache = ctx.GlobalInt(CacheFlag.Name) * ctx.GlobalInt(CacheDatabaseFlag.Name) / 100
 	}
-	cfg.DatabaseHandles = MakeDatabaseHandles()
+	if ctx.GlobalIsSet(FdLimitFlag.Name) {
+		cfg.FdLimit = ctx.GlobalInt(FdLimitFlag.Name)
+	}
+	cfg.DatabaseHandles = MakeDatabaseHandles(cfg.FdLimit)
 	if ctx.GlobalIsSet(AncientFlag.Name) {
 		cfg.DatabaseFreezer = ctx.GlobalString(AncientFlag.Name)
 	}
@@ -1840,7 +1851,7 @@ func SplitTagsFlag(tagsFlag string) map[string]string {
 func MakeChainDatabase(ctx *cli.Context, stack *node.Node, readonly bool) ethdb.Database {
 	var (
 		cache   = ctx.GlobalInt(CacheFlag.Name) * ctx.GlobalInt(CacheDatabaseFlag.Name) / 100
-		handles = MakeDatabaseHandles()
+		handles = MakeDatabaseHandles(ctx.GlobalInt(FdLimitFlag.Name))
 
 		err     error
 		chainDb ethdb.Database

eth/ethconfig/config.go

@@ -18,6 +18,7 @@
 package ethconfig
 
 import (
+	"math"
 	"math/big"
 	"os"
 	"os/user"
@@ -83,6 +84,7 @@ var Defaults = Config{
 	TrieDirtyCache:          256,
 	TrieTimeout:             60 * time.Minute,
 	SnapshotCache:           102,
+	FdLimit:                 math.MaxInt32,
 	Miner: miner.Config{
 		GasCeil:  8000000,
 		GasPrice: big.NewInt(params.GWei),
@@ -169,6 +171,9 @@ type Config struct {
 	SnapshotCache           int
 	Preimages               bool
 
+	// FdLimit Tuning
+	FdLimit int
+
 	// Mining options
 	Miner miner.Config