dict-sql: Cache reading settings files.

The settings were read for every dict init, which was done for every new
dict connection. This was using a lot of CPU. There are usually only a
couple dict-sql settings files, so we cache all of the ones we read.

src/lib-dict/dict-sql-settings.c

@@ -3,6 +3,7 @@
 #include "lib.h"
 #include "array.h"
 #include "str.h"
+#include "hash.h"
 #include "settings.h"
 #include "dict-sql-settings.h"
 
@@ -42,6 +43,14 @@ static const struct setting_def dict_sql_map_setting_defs[] = {
 	{ 0, NULL, 0 }
 };
 
+struct dict_sql_settings_cache {
+	pool_t pool;
+	const char *path;
+	struct dict_sql_settings *set;
+};
+
+static HASH_TABLE(const char *, struct dict_sql_settings_cache *) dict_sql_settings_cache;
+
 static const char *pattern_read_name(const char **pattern)
 {
 	const char *p = *pattern, *name;
@@ -235,9 +244,20 @@ parse_section(const char *type, const char *name ATTR_UNUSED,
 }
 
 struct dict_sql_settings *
-dict_sql_settings_read(pool_t pool, const char *path, const char **error_r)
+dict_sql_settings_read(const char *path, const char **error_r)
 {
 	struct setting_parser_ctx ctx;
+	struct dict_sql_settings_cache *cache;
+	pool_t pool = pool_alloconly_create("dict sql settings", 1024);
+
+	if (!hash_table_is_created(dict_sql_settings_cache)) {
+		hash_table_create(&dict_sql_settings_cache, default_pool, 0,
+				  str_hash, strcmp);
+	}
+
+	cache = hash_table_lookup(dict_sql_settings_cache, path);
+	if (cache != NULL)
+		return cache->set;
 
 	memset(&ctx, 0, sizeof(ctx));
 	ctx.pool = pool;
@@ -246,14 +266,39 @@ dict_sql_settings_read(pool_t pool, const char *path, const char **error_r)
 	p_array_init(&ctx.set->maps, pool, 8);
 
 	if (!settings_read(path, NULL, parse_setting, parse_section,
-			   &ctx, error_r))
+			   &ctx, error_r)) {
+		pool_unref(&pool);
 		return NULL;
+	}
 
 	if (ctx.set->connect == NULL) {
 		*error_r = t_strdup_printf("Error in configuration file %s: "
 					   "Missing connect setting", path);
+		pool_unref(&pool);
 		return NULL;
 	}
 
+	cache = p_new(pool, struct dict_sql_settings_cache, 1);
+	cache->pool = pool;
+	cache->path = p_strdup(pool, path);
+	cache->set = ctx.set;
+
+	hash_table_insert(dict_sql_settings_cache, cache->path, cache);
 	return ctx.set;
 }
+
+void dict_sql_settings_deinit(void)
+{
+	struct hash_iterate_context *iter;
+	struct dict_sql_settings_cache *cache;
+	const char *key;
+
+	if (!hash_table_is_created(dict_sql_settings_cache))
+		return;
+
+	iter = hash_table_iterate_init(dict_sql_settings_cache);
+	while (hash_table_iterate(iter, dict_sql_settings_cache, &key, &cache))
+		pool_unref(&cache->pool);
+	hash_table_iterate_deinit(&iter);
+	hash_table_destroy(&dict_sql_settings_cache);
+}

src/lib-dict/dict-sql-settings.h

@@ -33,6 +33,8 @@ struct dict_sql_settings {
 };
 
 struct dict_sql_settings *
-dict_sql_settings_read(pool_t pool, const char *path, const char **error_r);
+dict_sql_settings_read(const char *path, const char **error_r);
+
+void dict_sql_settings_deinit(void);
 
 #endif

src/lib-dict/dict-sql.c

@@ -88,7 +88,7 @@ sql_dict_init(struct dict *driver, const char *uri,
 	dict->pool = pool;
 	dict->dict = *driver;
 	dict->username = p_strdup(pool, set->username);
-	dict->set = dict_sql_settings_read(pool, uri, error_r);
+	dict->set = dict_sql_settings_read(uri, error_r);
 	if (dict->set == NULL) {
 		pool_unref(&pool);
 		return -1;
@@ -1266,4 +1266,5 @@ void dict_sql_unregister(void)
 		dict_driver_unregister(&dict_sql_drivers[i]);
 	i_free(dict_sql_drivers);
 	sql_db_cache_deinit(&dict_sql_db_cache);
+	dict_sql_settings_deinit();
 }