From 81b7d3f536804b9c7535d8e2d3c7dc50ed410f2f Mon Sep 17 00:00:00 2001
From: Alejandro Lopez <a.lopez@yadro.com>
Date: Fri, 21 Apr 2023 14:01:30 +0300
Subject: [PATCH] Check NOFILE limit before creating local storage engine

Signed-off-by: Alejandro Lopez <a.lopez@yadro.com>
---
 internal/local/local.go | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/internal/local/local.go b/internal/local/local.go
index 7f34100..aab5b45 100644
--- a/internal/local/local.go
+++ b/internal/local/local.go
@@ -31,6 +31,7 @@ import (
 	"go.k6.io/k6/js/modules"
 	"go.k6.io/k6/metrics"
 	"go.uber.org/zap"
+	"golang.org/x/sys/unix"
 )
 
 // RootModule is the global module object type. It is instantiated once per test
@@ -77,6 +78,28 @@ func NewLocalModuleInstance(vu modules.VU, resolveEngine func(context.Context, s
 	}
 }
 
+// checkResourceLimits checks the current limit on NOFILE.
+//
+// The usual default is around 1024 and this is too low for production clusters where a value of
+// about 65536 is needed in order to not run into errors because of attempting to open too many files.
+// This is needed for the local storage engine scenarios, where the user running the scenario is not
+// necessarily the service user, for which the limits are preconfigured correctly.
+//
+// See: https://k6.io/docs/misc/fine-tuning-os/
+func checkResourceLimits() error {
+	const (
+		minNofileLimit = 1 << 16
+	)
+	rlimit := &unix.Rlimit{}
+	if err := unix.Getrlimit(unix.RLIMIT_NOFILE, rlimit); err != nil {
+		return fmt.Errorf("getting resource limits: %v", err)
+	}
+	if rlimit.Cur < minNofileLimit {
+		return fmt.Errorf("nofile limit is too low: %d", rlimit.Cur)
+	}
+	return nil
+}
+
 // GetOrCreateEngine returns the current engine instance for the given configuration file,
 // creating a new one if none exists. Note that the identity of configuration files is their
 // file name for the purposes of test runs.
@@ -96,6 +119,9 @@ func (r *RootModule) GetOrCreateEngine(ctx context.Context, configFile string, d
 		if err != nil {
 			return nil, fmt.Errorf("creating engine options from config: %v", err)
 		}
+		if err := checkResourceLimits(); err != nil {
+			return nil, err
+		}
 		r.ng = engine.New(ngOpts...)
 		for i, opts := range shardOpts {
 			if _, err := r.ng.AddShard(opts...); err != nil {