cmd/utils: add check on fd hard limit, skip test if below target (#15684)

* cmd/utils: Add check on hard limit, skip test if below target

* cmd/utils: Cross platform compatible fd limit test

* cmd/utils: Remove syscall.Rlimit in test

* cmd/utils: comment fd utility method

cmd/utils/fdlimit_freebsd.go

@@ -52,3 +52,13 @@ func getFdLimit() (int, error) {
 	}
 	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
+}

cmd/utils/fdlimit_test.go

@@ -16,12 +16,22 @@
 
 package utils
 
-import "testing"
+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)

cmd/utils/fdlimit_unix.go

@@ -48,3 +48,13 @@ func getFdLimit() (int, error) {
 	}
 	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
+}

cmd/utils/fdlimit_windows.go

@@ -39,3 +39,9 @@ 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()
+}