utils/cache_gc nitpick: more precise error prints

3 files changed, 19 insertions, 3 deletions

diff --git a/utils/cache_gc/db.c b/utils/cache_gc/db.c
index c71fabf6..3a853b43 100644
--- a/utils/cache_gc/db.c
+++ b/utils/cache_gc/db.c
@@ -179,12 +179,15 @@ int kr_gc_cache_iter(knot_db_t * knot_db, const  kr_cache_gc_cfg_t *cfg,
 		return ret;
 	}
 
-	it = api->iter_begin(&txn, KNOT_DB_FIRST);
+	it = api->iter_begin(&txn, KNOT_DB_NOOP); // _FIRST is split for easier debugging
 	if (it == NULL) {
-		printf("Error iterating database.\n");
+		printf("Error: failed to create an iterator.\n");
 		api->txn_abort(&txn);
 		return KNOT_ERROR;
 	}
+	it = api->iter_seek(it, NULL, KNOT_DB_FIRST);
+	if (it == NULL)
+		printf("Suspicious: completely empty LMDB at this moment?\n");
 
 	int txn_steps = 0;
 	while (it != NULL) {
@@ -267,7 +270,7 @@ int kr_gc_cache_iter(knot_db_t * knot_db, const  kr_cache_gc_cfg_t *cfg,
 			}
 			it = api->iter_begin(&txn, KNOT_DB_NOOP);
 			if (it == NULL) {
-				printf("Error iterating database.\n");
+				printf("Error: failed to create an iterator.\n");
 				api->txn_abort(&txn);
 				return KNOT_ERROR;
 			}
diff --git a/utils/cache_gc/db.h b/utils/cache_gc/db.h
index 44cfbec2..0e20df19 100644
--- a/utils/cache_gc/db.h
+++ b/utils/cache_gc/db.h
@@ -22,3 +22,9 @@ int kr_gc_cache_iter(knot_db_t * knot_db, const  kr_cache_gc_cfg_t *cfg,
 			kr_gc_iter_callback callback, void *ctx);
 
 const uint16_t *kr_gc_key_consistent(knot_db_val_t key);
+
+#ifdef DEBUG
+/** Printf a *binary* string in a human-readable way. */
+void debug_printbin(const char *str, unsigned int len);
+#endif
+
diff --git a/utils/cache_gc/kr_cache_gc.c b/utils/cache_gc/kr_cache_gc.c
index 1308c75e..5aae95f0 100644
--- a/utils/cache_gc/kr_cache_gc.c
+++ b/utils/cache_gc/kr_cache_gc.c
@@ -281,6 +281,13 @@ int kr_cache_gc(kr_cache_gc_cfg_t *cfg, kr_cache_gc_state_t **state)
 			break;
 		case KNOT_ENOENT:
 			already_gone++;
+#ifdef DEBUG
+			// kresd normally only inserts (or overwrites),
+			// so it's generally suspicious when a key goes missing.
+			printf("Record already gone (key len %zu): ", (*i)->len);
+			debug_printbin((*i)->data, (*i)->len);
+			printf("\n");
+#endif
 			break;
 		case KNOT_ESPACE:
 			printf("Warning: out of space, bailing out to retry later.\n");