common/fdlimit: Move fdlimit files to separate package (#15850)

* common/fdlimit: Move fdlimit files to separate package

When go-ethereum is used as a library the calling program need to set
the FD limit.

This commit extract fdlimit files to a separate package so it can be
used outside of go-ethereum.

* common/fdlimit: Remove FdLimit from functions signature

* common/fdlimit: Rename fdlimit functions

5 files changed, 3 insertions, 218 deletions

diff --git a/cmd/utils/fdlimit_freebsd.go b/cmd/utils/fdlimit_freebsd.go
deleted file mode 100644
index f9ed8937e..000000000
--- a/cmd/utils/fdlimit_freebsd.go
+++ /dev/null
@@ -1,64 +0,0 @@
-// Copyright 2016 The go-ethereum Authors
-// This file is part of go-ethereum.
-//
-// go-ethereum is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// go-ethereum is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
-
-// +build freebsd
-
-package utils
-
-import "syscall"
-
-// This file is largely identical to fdlimit_unix.go,
-// but Rlimit fields have type int64 on FreeBSD so it needs
-// an extra conversion.
-
-// raiseFdLimit tries to maximize the file descriptor allowance of this process
-// to the maximum hard-limit allowed by the OS.
-func raiseFdLimit(max uint64) error {
-	// Get the current limit
-	var limit syscall.Rlimit
-	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
-		return err
-	}
-	// Try to update the limit to the max allowance
-	limit.Cur = limit.Max
-	if limit.Cur > int64(max) {
-		limit.Cur = int64(max)
-	}
-	if err := syscall.Setrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
-		return err
-	}
-	return nil
-}
-
-// getFdLimit retrieves the number of file descriptors allowed to be opened by this
-// process.
-func getFdLimit() (int, error) {
-	var limit syscall.Rlimit
-	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
-		return 0, err
-	}
-	return int(limit.Cur), nil
-}
-
-// getFdMaxLimit retrieves the maximum number of file descriptors this process is
-// allowed to request for itself.
-func getFdMaxLimit() (int, error) {
-	var limit syscall.Rlimit
-	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
-		return 0, err
-	}
-	return int(limit.Max), nil
-}
diff --git a/cmd/utils/fdlimit_test.go b/cmd/utils/fdlimit_test.go
deleted file mode 100644
index 48489cf4c..000000000
--- a/cmd/utils/fdlimit_test.go
+++ /dev/null
@@ -1,45 +0,0 @@
-// Copyright 2016 The go-ethereum Authors
-// This file is part of go-ethereum.
-//
-// go-ethereum is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// go-ethereum is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
-
-package utils
-
-import (
-	"fmt"
-	"testing"
-)
-
-// TestFileDescriptorLimits simply tests whether the file descriptor allowance
-// per this process can be retrieved.
-func TestFileDescriptorLimits(t *testing.T) {
-	target := 4096
-	hardlimit, err := getFdMaxLimit()
-	if err != nil {
-		t.Fatal(err)
-	}
-	if hardlimit < target {
-		t.Skip(fmt.Sprintf("system limit is less than desired test target: %d < %d", hardlimit, target))
-	}
-
-	if limit, err := getFdLimit(); err != nil || limit <= 0 {
-		t.Fatalf("failed to retrieve file descriptor limit (%d): %v", limit, err)
-	}
-	if err := raiseFdLimit(uint64(target)); err != nil {
-		t.Fatalf("failed to raise file allowance")
-	}
-	if limit, err := getFdLimit(); err != nil || limit < target {
-		t.Fatalf("failed to retrieve raised descriptor limit (have %v, want %v): %v", limit, target, err)
-	}
-}
diff --git a/cmd/utils/fdlimit_unix.go b/cmd/utils/fdlimit_unix.go
deleted file mode 100644
index c08d1fab0..000000000
--- a/cmd/utils/fdlimit_unix.go
+++ /dev/null
@@ -1,60 +0,0 @@
-// Copyright 2016 The go-ethereum Authors
-// This file is part of go-ethereum.
-//
-// go-ethereum is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// go-ethereum is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
-
-// +build linux darwin netbsd openbsd solaris
-
-package utils
-
-import "syscall"
-
-// raiseFdLimit tries to maximize the file descriptor allowance of this process
-// to the maximum hard-limit allowed by the OS.
-func raiseFdLimit(max uint64) error {
-	// Get the current limit
-	var limit syscall.Rlimit
-	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
-		return err
-	}
-	// Try to update the limit to the max allowance
-	limit.Cur = limit.Max
-	if limit.Cur > max {
-		limit.Cur = max
-	}
-	if err := syscall.Setrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
-		return err
-	}
-	return nil
-}
-
-// getFdLimit retrieves the number of file descriptors allowed to be opened by this
-// process.
-func getFdLimit() (int, error) {
-	var limit syscall.Rlimit
-	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
-		return 0, err
-	}
-	return int(limit.Cur), nil
-}
-
-// getFdMaxLimit retrieves the maximum number of file descriptors this process is
-// allowed to request for itself.
-func getFdMaxLimit() (int, error) {
-	var limit syscall.Rlimit
-	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
-		return 0, err
-	}
-	return int(limit.Max), nil
-}
diff --git a/cmd/utils/fdlimit_windows.go b/cmd/utils/fdlimit_windows.go
deleted file mode 100644
index f239683d2..000000000
--- a/cmd/utils/fdlimit_windows.go
+++ /dev/null
@@ -1,47 +0,0 @@
-// Copyright 2016 The go-ethereum Authors
-// This file is part of go-ethereum.
-//
-// go-ethereum is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// go-ethereum is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
-
-package utils
-
-import "errors"
-
-// raiseFdLimit tries to maximize the file descriptor allowance of this process
-// to the maximum hard-limit allowed by the OS.
-func raiseFdLimit(max uint64) error {
-	// This method is NOP by design:
-	//  * Linux/Darwin counterparts need to manually increase per process limits
-	//  * On Windows Go uses the CreateFile API, which is limited to 16K files, non
-	//    changeable from within a running process
-	// This way we can always "request" raising the limits, which will either have
-	// or not have effect based on the platform we're running on.
-	if max > 16384 {
-		return errors.New("file descriptor limit (16384) reached")
-	}
-	return nil
-}
-
-// getFdLimit retrieves the number of file descriptors allowed to be opened by this
-// process.
-func getFdLimit() (int, error) {
-	// Please see raiseFdLimit for the reason why we use hard coded 16K as the limit
-	return 16384, nil
-}
-
-// getFdMaxLimit retrieves the maximum number of file descriptors this process is
-// allowed to request for itself.
-func getFdMaxLimit() (int, error) {
-	return getFdLimit()
-}
diff --git a/cmd/utils/flags.go b/cmd/utils/flags.go
index edf3dc2c2..94ab64c2e 100644
--- a/cmd/utils/flags.go
+++ b/cmd/utils/flags.go
@@ -31,6 +31,7 @@ import (
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/fdlimit"
 	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/consensus/clique"
 	"github.com/ethereum/go-ethereum/consensus/ethash"
@@ -721,10 +722,10 @@ func setIPC(ctx *cli.Context, cfg *node.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 {
-	if err := raiseFdLimit(2048); err != nil {
+	if err := fdlimit.Raise(2048); err != nil {
 		Fatalf("Failed to raise file descriptor allowance: %v", err)
 	}
-	limit, err := getFdLimit()
+	limit, err := fdlimit.Current()
 	if err != nil {
 		Fatalf("Failed to retrieve file descriptor allowance: %v", err)
 	}