internal/lsp/regtest: add a simple stress test

Using the new run options to configure a testing environment suitable
for long-running tests, a trivial stress test is added to type
arbitrarily in a known problematic repository
(github.com/pilosa/pilosa).

Change-Id: I2c8237843111f17ff5a096515cb4704c62513ed0
Reviewed-on: https://go-review.googlesource.com/c/tools/+/244441
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>

internal/lsp/regtest/stress_test.go

@@ -0,0 +1,81 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package regtest
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"testing"
+	"time"
+)
+
+// Pilosa is a repository that has historically caused significant memory
+// problems for Gopls. We use it for a simple stress test that types
+// arbitrarily in a file with lots of dependents.
+
+var pilosaPath = flag.String("pilosa_path", "", "Path to a directory containing "+
+	"github.com/pilosa/pilosa, for stress testing. Do not set this unless you "+
+	"know what you're doing!")
+
+func stressTestOptions(dir string) []RunOption {
+	return []RunOption{
+		// Run in an existing directory, since we're trying to simulate known cases
+		// that cause gopls memory problems.
+		InExistingDir(dir),
+
+		// Enable live debugging.
+		WithDebugAddress(":8087"),
+
+		// Skip logs and hooks, as they buffer up memory unnaturally.
+		SkipLogs(),
+		NoHooks(),
+		// The Debug server only makes sense if running in singleton mode.
+		WithModes(Singleton),
+		// Set a generous timeout. Individual tests should control their own
+		// graceful termination.
+		WithTimeout(20 * time.Minute),
+
+		// Use the actual proxy, since we want our builds to succeed.
+		WithGOPROXY("https://proxy.golang.org"),
+	}
+}
+
+func TestPilosaStress(t *testing.T) {
+	if *pilosaPath == "" {
+		t.Skip("-pilosa_path not configured")
+	}
+	opts := stressTestOptions(*pilosaPath)
+
+	withOptions(opts...).run(t, "", func(t *testing.T, env *Env) {
+		files := []string{
+			"cmd.go",
+			"internal/private.pb.go",
+			"roaring/roaring.go",
+			"roaring/roaring_internal_test.go",
+			"server/handler_test.go",
+		}
+		for _, file := range files {
+			env.OpenFile(file)
+		}
+		ctx, cancel := context.WithTimeout(env.Ctx, 10*time.Minute)
+		defer cancel()
+
+		i := 1
+		// MagicNumber is an identifier that occurs in roaring.go. Just change it
+		// arbitrarily.
+		env.RegexpReplace("roaring/roaring.go", "MagicNumber", fmt.Sprintf("MagicNumber%d", 1))
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			default:
+			}
+			env.RegexpReplace("roaring/roaring.go", fmt.Sprintf("MagicNumber%d", i), fmt.Sprintf("MagicNumber%d", i+1))
+			time.Sleep(20 * time.Millisecond)
+			i++
+		}
+	})
+}