common/fdlimit: cap on MacOS file limits, fixes #18994 (#19035)

* common/fdlimit: cap on MacOS file limits, fixes #18994

* common/fdlimit: fix Maximum-check to respect OPEN_MAX

* common/fdlimit: return error if OPEN_MAX is exceeded in Raise()

* common/fdlimit: goimports

* common/fdlimit: check value after setting fdlimit

* common/fdlimit: make comment a bit more descriptive

* cmd/utils: make fdlimit happy path a bit cleaner

Author: holiman

cmd/utils/flags.go

@@ -950,10 +950,11 @@ func makeDatabaseHandles() int {
 	if err != nil {
 		Fatalf("Failed to retrieve file descriptor allowance: %v", err)
 	}
-	if err := fdlimit.Raise(uint64(limit)); err != nil {
+	raised, err := fdlimit.Raise(uint64(limit))
+	if err != nil {
 		Fatalf("Failed to raise file descriptor allowance: %v", err)
 	}
-	return limit / 2 // Leave half for networking and other stuff
+	return int(raised / 2) // Leave half for networking and other stuff
 }
 
 // MakeAddress converts an account specified directly as a hex encoded string or

common/fdlimit/fdlimit_freebsd.go

@@ -26,21 +26,24 @@ import "syscall"
 
 // Raise tries to maximize the file descriptor allowance of this process
 // to the maximum hard-limit allowed by the OS.
-func Raise(max uint64) error {
+func Raise(max uint64) (uint64, error) {
 	// Get the current limit
 	var limit syscall.Rlimit
 	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
-		return err
+		return 0, 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 0, err
+	}
+	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
+		return 0, err
 	}
-	return nil
+	return limit.Cur, nil
 }
 
 // Current retrieves the number of file descriptors allowed to be opened by this

common/fdlimit/fdlimit_test.go

@@ -36,7 +36,7 @@ func TestFileDescriptorLimits(t *testing.T) {
 	if limit, err := Current(); err != nil || limit <= 0 {
 		t.Fatalf("failed to retrieve file descriptor limit (%d): %v", limit, err)
 	}
-	if err := Raise(uint64(target)); err != nil {
+	if _, err := Raise(uint64(target)); err != nil {
 		t.Fatalf("failed to raise file allowance")
 	}
 	if limit, err := Current(); err != nil || limit < target {

common/fdlimit/fdlimit_unix.go

@@ -22,21 +22,26 @@ import "syscall"
 
 // Raise tries to maximize the file descriptor allowance of this process
 // to the maximum hard-limit allowed by the OS.
-func Raise(max uint64) error {
+// Returns the size it was set to (may differ from the desired 'max')
+func Raise(max uint64) (uint64, error) {
 	// Get the current limit
 	var limit syscall.Rlimit
 	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
-		return err
+		return 0, 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 0, err
+	}
+	// MacOS can silently apply further caps, so retrieve the actually set limit
+	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &limit); err != nil {
+		return 0, err
 	}
-	return nil
+	return limit.Cur, nil
 }
 
 // Current retrieves the number of file descriptors allowed to be opened by this

common/fdlimit/fdlimit_windows.go

@@ -20,7 +20,7 @@ import "errors"
 
 // Raise tries to maximize the file descriptor allowance of this process
 // to the maximum hard-limit allowed by the OS.
-func Raise(max uint64) error {
+func Raise(max uint64) (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
@@ -30,7 +30,7 @@ func Raise(max uint64) error {
 	if max > 16384 {
 		return errors.New("file descriptor limit (16384) reached")
 	}
-	return nil
+	return max, nil
 }
 
 // Current retrieves the number of file descriptors allowed to be opened by this