From: Vladimír Čunát <vladimir.cunat@nic.cz>
Date: Fri, 28 Feb 2020 14:02:27 +0000 (+0100)
Subject: gc: make state in kr_cache_gc() explicit
X-Git-Tag: v5.1.0~40^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f991063a50dfd95386edf934190d1ec0166dd450;p=thirdparty%2Fknot-resolver.git

gc: make state in kr_cache_gc() explicit

It really is nicer to work with.
Additionally re-open cache after any GC errors.
---

diff --git a/utils/cache_gc/db.c b/utils/cache_gc/db.c
index 168c005ba..7dbccd31d 100644
--- a/utils/cache_gc/db.c
+++ b/utils/cache_gc/db.c
@@ -10,6 +10,7 @@
 #include <time.h>
 #include <sys/stat.h>
 
+//TODO: we rely on mirrors of these two structs not changing layout in knot-dns and knot-resolver!
 struct libknot_lmdb_env {
 	bool shared;
 	unsigned dbi;
diff --git a/utils/cache_gc/kr_cache_gc.c b/utils/cache_gc/kr_cache_gc.c
index 5913d29b0..8b8ecf5b9 100644
--- a/utils/cache_gc/kr_cache_gc.c
+++ b/utils/cache_gc/kr_cache_gc.c
@@ -142,27 +142,39 @@ int cb_delete_categories(const knot_db_val_t * key, gc_record_info_t * info,
 	return KNOT_EOK;
 }
 
-int kr_cache_gc(kr_cache_gc_cfg_t * cfg)
+struct kr_cache_gc_state {
+	struct kr_cache kres_db;
+	knot_db_t *db;
+};
+
+void kr_cache_gc_free_state(kr_cache_gc_state_t **state)
 {
-	// statically open cache, its clean up and initialization
-	static bool is_open = false;
-	static struct kr_cache kres_db = { 0 };
-	static knot_db_t *db = NULL;
-	if (!cfg) {
-		if (is_open) {
-			kr_gc_cache_close(&kres_db, db);
-			is_open = false;
-		}
-		return 0;
+	assert(state);
+	if (!*state) { // not open
+		return;
 	}
-	if (!is_open) {
-		int ret = kr_gc_cache_open(cfg->cache_path, &kres_db, &db);
+	kr_gc_cache_close(&(*state)->kres_db, (*state)->db);
+	free(*state);
+	*state = NULL;
+}
+
+int kr_cache_gc(kr_cache_gc_cfg_t *cfg, kr_cache_gc_state_t **state)
+{
+	assert(cfg && state);
+	if (!*state) { // Cache not open -> do that.
+		*state = calloc(1, sizeof(**state));
+		if (!*state) {
+			return KNOT_ENOMEM;
+		}
+		int ret = kr_gc_cache_open(cfg->cache_path, &(*state)->kres_db,
+					   &(*state)->db);
 		if (ret) {
+			free(*state);
+			*state = NULL;
 			return ret;
-		} else {
-			is_open = true;
 		}
 	}
+	knot_db_t *const db = (*state)->db; // frequently used shortcut
 
 	const size_t db_size = knot_db_lmdb_get_mapsize(db);
 	const size_t db_usage_abs = knot_db_lmdb_get_usage(db);
@@ -193,6 +205,7 @@ int kr_cache_gc(kr_cache_gc_cfg_t * cfg)
 	};
 	int ret = kr_gc_cache_iter(db, cb_compute_categories, &cats);
 	if (ret != KNOT_EOK) {
+		kr_cache_gc_free_state(state);
 		return ret;
 	}
 
@@ -232,6 +245,7 @@ int kr_cache_gc(kr_cache_gc_cfg_t * cfg)
 	ret = kr_gc_cache_iter(db, cb_delete_categories, &to_del);
 	if (ret != KNOT_EOK) {
 		entry_dynarray_deep_free(&to_del.to_delete);
+		kr_cache_gc_free_state(state);
 		return ret;
 	}
 	printf
@@ -252,6 +266,7 @@ int kr_cache_gc(kr_cache_gc_cfg_t * cfg)
 		printf("Error starting R/W DB transaction (%s).\n",
 		       knot_strerror(ret));
 		entry_dynarray_deep_free(&to_del.to_delete);
+		kr_cache_gc_free_state(state);
 		return ret;
 	}
 
@@ -311,8 +326,7 @@ finish:
 	entry_dynarray_deep_free(&to_del.to_delete);
 
 	// OK, let's close it in this case.
-	kr_gc_cache_close(&kres_db, db);
-	is_open = false;
+	kr_cache_gc_free_state(state);
 
 	return ret;
 }
diff --git a/utils/cache_gc/kr_cache_gc.h b/utils/cache_gc/kr_cache_gc.h
index 34b475e7e..261115d00 100644
--- a/utils/cache_gc/kr_cache_gc.h
+++ b/utils/cache_gc/kr_cache_gc.h
@@ -30,6 +30,12 @@ typedef struct {
 	bool dry_run;
 } kr_cache_gc_cfg_t;
 
-int kr_cache_gc(kr_cache_gc_cfg_t * cfg);
+/** State persisting across kr_cache_gc() invocations (opaque).
+ * NULL pointer represents a clean state. */
+typedef struct kr_cache_gc_state kr_cache_gc_state_t;
+
+/** Do one iteration of cache-size check and (if necessary) GC pass. */
+int kr_cache_gc(kr_cache_gc_cfg_t *cfg, kr_cache_gc_state_t **state);
+void kr_cache_gc_free_state(kr_cache_gc_state_t **state);
 
 #define KR_CACHE_GC_VERSION "0.2"
diff --git a/utils/cache_gc/main.c b/utils/cache_gc/main.c
index 538456253..6738ba03d 100644
--- a/utils/cache_gc/main.c
+++ b/utils/cache_gc/main.c
@@ -117,8 +117,9 @@ int main(int argc, char *argv[])
 	}
 
 	int exit_code = 0;
+	kr_cache_gc_state_t *gc_state = NULL;
 	do {
-		int ret = kr_cache_gc(&cfg);
+		int ret = kr_cache_gc(&cfg, &gc_state);
 		// ENOENT: kresd may not be started yet or cleared the cache now
 		if (ret && ret != -ENOENT) {
 			printf("Error (%s)\n", knot_strerror(ret));
@@ -128,8 +129,8 @@ int main(int argc, char *argv[])
 
 		usleep(cfg.gc_interval);
 	} while (cfg.gc_interval > 0 && !killed);
-	// clean up any state
-	kr_cache_gc(NULL);
+
+	kr_cache_gc_free_state(&gc_state);
 
 	return exit_code;
 }