From b53fb5f7c20dba1b5a647527e778edfc35ef8bd7 Mon Sep 17 00:00:00 2001
From: Radu Berinde <radu@cockroachlabs.com>
Date: Fri, 5 Sep 2025 09:08:52 -0700
Subject: [PATCH] datadriven: log slow commands

This change adds a `t.Log` every 10 seconds if the function that runs
a directive takes a long time. This should show the cause of a test
timeout.
---
 datadriven.go | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/datadriven.go b/datadriven.go
index 8f8cf7e..4fc2045 100644
--- a/datadriven.go
+++ b/datadriven.go
@@ -337,6 +337,23 @@ func runDirective(t testing.TB, r *testDataReader, f func(testing.TB, *TestData)
 				panic(r)
 			}
 		}()
+
+		// Set up a goroutine to log periodically if the function is taking a long
+		// time. This is useful to pinpoint the cause of a test timeout.
+		done := make(chan struct{})
+		defer close(done)
+		go func() {
+			startTime := time.Now()
+			for {
+				select {
+				case <-done:
+					return
+				case <-time.After(10 * time.Second):
+					t.Logf("%s: still running after %s\n", d.Pos, time.Since(startTime))
+				}
+			}
+		}()
+
 		actual := f(t, d)
 		if actual != "" && !strings.HasSuffix(actual, "\n") {
 			actual += "\n"