From a78786119dd171daaff7b9a8b4eee1935375c127 Mon Sep 17 00:00:00 2001
From: Kyle Carberry <kyle@coder.com>
Date: Wed, 8 Mar 2023 21:12:20 -0600
Subject: [PATCH] chore: resolve race when running load tests with logs (#6523)

See https://github.com/coder/coder/actions/runs/4370166746/jobs/7644793277
---
 scaletest/agentconn/run.go           |  5 +++--
 scaletest/loadtestutil/syncwriter.go | 15 +++++++++++++--
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/scaletest/agentconn/run.go b/scaletest/agentconn/run.go
index 02f9fc66a1..8e65a232ce 100644
--- a/scaletest/agentconn/run.go
+++ b/scaletest/agentconn/run.go
@@ -45,11 +45,12 @@ func NewRunner(client *codersdk.Client, cfg Config) *Runner {
 }
 
 // Run implements Runnable.
-func (r *Runner) Run(ctx context.Context, _ string, logs io.Writer) error {
+func (r *Runner) Run(ctx context.Context, _ string, w io.Writer) error {
 	ctx, span := tracing.StartSpan(ctx)
 	defer span.End()
 
-	logs = loadtestutil.NewSyncWriter(logs)
+	logs := loadtestutil.NewSyncWriter(w)
+	defer logs.Close()
 	logger := slog.Make(sloghuman.Sink(logs)).Leveled(slog.LevelDebug)
 	r.client.Logger = logger
 	r.client.LogBodies = true
diff --git a/scaletest/loadtestutil/syncwriter.go b/scaletest/loadtestutil/syncwriter.go
index caeb362af9..f0b603ccb6 100644
--- a/scaletest/loadtestutil/syncwriter.go
+++ b/scaletest/loadtestutil/syncwriter.go
@@ -7,8 +7,9 @@ import (
 
 // SyncWriter wraps an io.Writer in a sync.Mutex.
 type SyncWriter struct {
-	mut *sync.Mutex
-	w   io.Writer
+	mut    *sync.Mutex
+	w      io.Writer
+	closed bool
 }
 
 func NewSyncWriter(w io.Writer) *SyncWriter {
@@ -22,5 +23,15 @@ func NewSyncWriter(w io.Writer) *SyncWriter {
 func (sw *SyncWriter) Write(p []byte) (n int, err error) {
 	sw.mut.Lock()
 	defer sw.mut.Unlock()
+	if sw.closed {
+		return -1, io.ErrClosedPipe
+	}
 	return sw.w.Write(p)
 }
+
+func (sw *SyncWriter) Close() error {
+	sw.mut.Lock()
+	defer sw.mut.Unlock()
+	sw.closed = true
+	return nil
+}