Log when a cache slot is claimed by a colliding key

1 file changed, 8 insertions, 0 deletions

diff --git a/source/cache.c b/source/cache.c
index d6e450a..435cc96 100644
--- a/source/cache.c
+++ b/source/cache.c
@@ -354,6 +354,14 @@ static int process_slot(struct cache_slot *slot)
 		return err;
 	}
 
+	// A slot that opened cleanly but holds another key is a collision,
+	// and two popular pages sharing one slot evict each other on every
+	// alternating visit. Nothing else makes that visible, because the
+	// cache keeps working and only quietly stops helping.
+	if (!err)
+		log_error("[cgit] cache slot %s holds a different key, "
+			  "consider a larger cache-size\n", slot->path);
+
 	// If any part of creating a slot fails the page is still rendered
 	// straight to the client and the caller is told the request succeeded,
 	// because it did.