From 1fc19462b17aa958552f5aba0d3fbe9083b4bc19 Mon Sep 17 00:00:00 2001
From: Mikhail Galanin <mgalanin@mimecast.com>
Date: Mon, 10 Sep 2018 15:12:22 +0100
Subject: [PATCH] [Minor] Added coroutines to redis API

---
 src/lua/lua_redis.c | 564 ++++++++++++++++++++++++++------------------
 1 file changed, 331 insertions(+), 233 deletions(-)

diff --git a/src/lua/lua_redis.c b/src/lua/lua_redis.c
index 0fc9c43b7..1c407b2fd 100644
--- a/src/lua/lua_redis.c
+++ b/src/lua/lua_redis.c
@@ -87,7 +87,7 @@ static const struct luaL_reg redislib_m[] = {
 #endif
 
 #ifdef WITH_HIREDIS
-struct lua_redis_specific_userdata;
+struct lua_redis_request_specific_userdata;
 /**
  * Struct for userdata representation
  */
@@ -100,19 +100,21 @@ struct lua_redis_userdata {
 	struct rspamd_redis_pool *pool;
 	gchar *server;
 	gchar *reqline;
-	struct lua_redis_specific_userdata *specific;
+	struct lua_redis_request_specific_userdata *specific;
 	gdouble timeout;
 	guint16 port;
 	guint16 terminated;
 };
 
 #define LUA_REDIS_SPECIFIC_REPLIED (1 << 0)
+/* session was finished */
 #define LUA_REDIS_SPECIFIC_FINISHED (1 << 1)
 #define LUA_REDIS_ASYNC (1 << 0)
 #define LUA_REDIS_TEXTDATA (1 << 1)
+#define LUA_REDIS_TERMINATED (1 << 2)
 #define IS_ASYNC(ctx) ((ctx)->flags & LUA_REDIS_ASYNC)
 
-struct lua_redis_specific_userdata {
+struct lua_redis_request_specific_userdata {
 	gint cbref;
 	guint nargs;
 	gchar **args;
@@ -120,19 +122,27 @@ struct lua_redis_specific_userdata {
 	struct rspamd_async_watcher *w;
 	struct lua_redis_userdata *c;
 	struct lua_redis_ctx *ctx;
-	struct lua_redis_specific_userdata *next;
+	struct lua_redis_request_specific_userdata *next;
 	struct event timeout;
 	guint flags;
 };
 
 struct lua_redis_ctx {
 	guint flags;
-	union {
-		struct lua_redis_userdata async;
-		redisContext *sync;
-	} d;
+	struct lua_redis_userdata async;
 	guint cmds_pending;
 	ref_entry_t ref;
+	GQueue *replies; /* for sync connection only */
+	GQueue *events_cleanup; /* for sync connection only */
+	struct thread_entry *thread; /* for sync mode, set only if there was yield */
+};
+
+struct lua_redis_result {
+	gboolean is_error;
+	gint result_ref;
+	struct rspamd_async_watcher *w;
+	struct rspamd_async_session *s;
+	struct lua_redis_request_specific_userdata *sp_ud;
 };
 
 static struct lua_redis_ctx *
@@ -162,46 +172,50 @@ static void
 lua_redis_dtor (struct lua_redis_ctx *ctx)
 {
 	struct lua_redis_userdata *ud;
-	struct lua_redis_specific_userdata *cur, *tmp;
+	struct lua_redis_request_specific_userdata *cur, *tmp;
 	gboolean is_successful = TRUE;
 	struct redisAsyncContext *ac;
 
-	if (IS_ASYNC (ctx)) {
-		msg_debug ("desctructing %p", ctx);
-		ud = &ctx->d.async;
-
-		if (ud->ctx) {
+	ud = &ctx->async;
+	msg_debug ("desctructing %p", ctx);
 
-			LL_FOREACH_SAFE (ud->specific, cur, tmp) {
-				event_del (&cur->timeout);
+	if (ud->ctx) {
 
-				if (!(cur->flags & LUA_REDIS_SPECIFIC_REPLIED)) {
-					is_successful = FALSE;
-				}
+		LL_FOREACH_SAFE (ud->specific, cur, tmp) {
+			event_del (&cur->timeout);
 
-				cur->flags |= LUA_REDIS_SPECIFIC_FINISHED;
+			if (!(cur->flags & LUA_REDIS_SPECIFIC_REPLIED)) {
+				is_successful = FALSE;
 			}
 
-			ud->terminated = 1;
-			ac = ud->ctx;
-			ud->ctx = NULL;
-			rspamd_redis_pool_release_connection (ud->pool, ac, is_successful);
+			cur->flags |= LUA_REDIS_SPECIFIC_FINISHED;
 		}
 
-		LL_FOREACH_SAFE (ud->specific, cur, tmp) {
-			lua_redis_free_args (cur->args, cur->arglens, cur->nargs);
+		ctx->flags |= LUA_REDIS_TERMINATED;
 
-			if (cur->cbref != -1) {
-				luaL_unref (ud->cfg->lua_state, LUA_REGISTRYINDEX, cur->cbref);
-			}
+		ud->terminated = 1;
+		ac = ud->ctx;
+		ud->ctx = NULL;
+		rspamd_redis_pool_release_connection (ud->pool, ac, is_successful);
+	}
+
+	LL_FOREACH_SAFE (ud->specific, cur, tmp) {
+		lua_redis_free_args (cur->args, cur->arglens, cur->nargs);
 
-			g_free (cur);
+		if (cur->cbref != -1) {
+			luaL_unref (ud->cfg->lua_state, LUA_REGISTRYINDEX, cur->cbref);
 		}
+
+		g_free (cur);
 	}
-	else {
-		if (ctx->d.sync) {
-			redisFree (ctx->d.sync);
-		}
+
+	if (ctx->events_cleanup) {
+		g_queue_free (ctx->events_cleanup);
+		ctx->events_cleanup = NULL;
+	}
+	if (ctx->replies) {
+		g_queue_free (ctx->replies);
+		ctx->replies = NULL;
 	}
 
 	g_free (ctx);
@@ -222,7 +236,7 @@ lua_redis_gc (lua_State *L)
 static void
 lua_redis_fin (void *arg)
 {
-	struct lua_redis_specific_userdata *sp_ud = arg;
+	struct lua_redis_request_specific_userdata *sp_ud = arg;
 	struct lua_redis_ctx *ctx;
 
 	ctx = sp_ud->ctx;
@@ -241,7 +255,7 @@ lua_redis_fin (void *arg)
 static void
 lua_redis_push_error (const gchar *err,
 	struct lua_redis_ctx *ctx,
-	struct lua_redis_specific_userdata *sp_ud,
+	struct lua_redis_request_specific_userdata *sp_ud,
 	gboolean connected)
 {
 	struct lua_redis_userdata *ud = sp_ud->c;
@@ -327,7 +341,7 @@ lua_redis_push_reply (lua_State *L, const redisReply *r, gboolean text_data)
  */
 static void
 lua_redis_push_data (const redisReply *r, struct lua_redis_ctx *ctx,
-		struct lua_redis_specific_userdata *sp_ud)
+		struct lua_redis_request_specific_userdata *sp_ud)
 {
 	struct lua_redis_userdata *ud = sp_ud->c;
 	struct lua_callback_state cbs;
@@ -373,7 +387,7 @@ static void
 lua_redis_callback (redisAsyncContext *c, gpointer r, gpointer priv)
 {
 	redisReply *reply = r;
-	struct lua_redis_specific_userdata *sp_ud = priv;
+	struct lua_redis_request_specific_userdata *sp_ud = priv;
 	struct lua_redis_ctx *ctx;
 	struct lua_redis_userdata *ud;
 	redisAsyncContext *ac;
@@ -431,10 +445,180 @@ lua_redis_callback (redisAsyncContext *c, gpointer r, gpointer priv)
 	REDIS_RELEASE (ctx);
 }
 
+static gint
+lua_redis_push_results (struct lua_redis_ctx *ctx, lua_State *L)
+{
+	gint results = g_queue_get_length (ctx->replies);
+	gint i;
+	gboolean can_use_lua = TRUE;
+
+	results = g_queue_get_length (ctx->replies);
+
+	if (!lua_checkstack (L, (results * 2) + 1)) {
+		luaL_error (L, "cannot resize stack to fit %d commands",
+				ctx->cmds_pending);
+
+		can_use_lua = FALSE;
+	}
+
+	for (i = 0; i < results; i ++) {
+		struct lua_redis_result *result = g_queue_pop_head (ctx->replies);
+
+		if (can_use_lua) {
+			lua_pushboolean (L, !result->is_error);
+			lua_rawgeti (L, LUA_REGISTRYINDEX, result->result_ref);
+		}
+
+		luaL_unref (L, LUA_REGISTRYINDEX, result->result_ref);
+
+		g_queue_push_tail (ctx->events_cleanup, result);
+	}
+
+	return can_use_lua ? results * 2 : 0;
+}
+
+static void
+lua_redis_cleanup_events (struct lua_redis_ctx *ctx)
+{
+	while (!g_queue_is_empty (ctx->events_cleanup)) {
+		struct lua_redis_result *result = g_queue_pop_head (ctx->events_cleanup);
+
+		rspamd_session_watcher_pop (result->s, result->w);
+		rspamd_session_remove_event (result->s, lua_redis_fin, result->sp_ud);
+
+		g_free (result);
+	}
+}
+
+/**
+ * Callback for redis replies
+ * @param c context of redis connection
+ * @param r redis reply
+ * @param priv userdata
+ */
+static void
+lua_redis_callback_sync (redisAsyncContext *ac, gpointer r, gpointer priv)
+{
+	redisReply *reply = r;
+
+	struct lua_redis_request_specific_userdata *sp_ud = priv;
+	struct lua_redis_ctx *ctx;
+	struct lua_redis_userdata *ud;
+	struct thread_entry* thread;
+	gint results;
+
+	ctx = sp_ud->ctx;
+	ud = sp_ud->c;
+	lua_State *L = ctx->async.cfg->lua_state;
+
+	sp_ud->flags |= LUA_REDIS_SPECIFIC_REPLIED;
+
+	if (ud->terminated) {
+		/* We are already at the termination stage, just go out */
+		/* TODO:
+		   if somebody is waiting for us (ctx->thread), return result,
+		   otherwise, indeed, ignore
+		 */
+		return;
+	}
+
+	event_del (&sp_ud->timeout);
+
+	msg_debug ("got reply from redis %p for query %p", ctx, sp_ud);
+
+	struct lua_redis_result *result = g_malloc0 (sizeof *result);
+
+	/* If session is finished, we cannot call lua callbacks */
+	if (ac->err == 0) {
+		if (r != NULL) {
+			if (reply->type != REDIS_REPLY_ERROR) {
+				result->is_error = FALSE;
+				lua_redis_push_reply (L, reply, ctx->flags & LUA_REDIS_TEXTDATA);
+			}
+			else {
+				result->is_error = TRUE;
+				lua_pushstring (L, reply->str);
+			}
+		}
+		else {
+			result->is_error = TRUE;
+			lua_pushliteral (L, "received no data from server");
+		}
+	}
+	else {
+		result->is_error = TRUE;
+		if (ac->err == REDIS_ERR_IO) {
+			lua_pushstring (L, strerror (errno));
+		}
+		else {
+			lua_pushstring (L, ac->errstr);
+		}
+	}
+	/* if error happened, we should terminate the connection,
+	   and release it */
+
+	if (result->is_error) {
+		/* Set to NULL to avoid double free in dtor */
+		sp_ud->c->ctx = NULL;
+		ctx->flags |= LUA_REDIS_TERMINATED;
+
+		/*
+		 * This will call all callbacks pending so the entire context
+		 * will be destructed
+		 */
+		rspamd_redis_pool_release_connection (sp_ud->c->pool, ac, TRUE);
+	}
+
+	result->result_ref = luaL_ref (L, LUA_REGISTRYINDEX);
+	result->s = ud->s;
+	result->w = sp_ud->w;
+	result->sp_ud = sp_ud;
+
+	g_queue_push_tail (ctx->replies, result);
+
+	ctx->cmds_pending --;
+
+	if (ctx->cmds_pending == 0) {
+		if (ctx->thread) {
+			/* somebody yielded and waits for results */
+			thread = ctx->thread;
+			ctx->thread = NULL;
+
+			results = lua_redis_push_results (ctx, thread->lua_state);
+
+			lua_thread_resume (thread, results);
+
+			lua_redis_cleanup_events (ctx);
+		}
+	}
+}
+
+static void
+lua_redis_timeout_sync (int fd, short what, gpointer priv)
+{
+	struct lua_redis_request_specific_userdata *sp_ud = priv;
+	struct lua_redis_ctx *ctx = sp_ud->ctx;
+	redisAsyncContext *ac;
+
+	ac = sp_ud->c->ctx;
+
+	/* Set to NULL to avoid double free in dtor */
+	sp_ud->c->ctx = NULL;
+	ac->err = REDIS_ERR_IO;
+	errno = ETIMEDOUT;
+	ctx->flags |= LUA_REDIS_TERMINATED;
+
+	/*
+	 * This will call all callbacks pending so the entire context
+	 * will be destructed
+	 */
+	rspamd_redis_pool_release_connection (sp_ud->c->pool, ac, TRUE);
+}
+
 static void
 lua_redis_timeout (int fd, short what, gpointer u)
 {
-	struct lua_redis_specific_userdata *sp_ud = u;
+	struct lua_redis_request_specific_userdata *sp_ud = u;
 	struct lua_redis_ctx *ctx;
 	redisAsyncContext *ac;
 
@@ -562,7 +746,7 @@ lua_redis_parse_args (lua_State *L, gint idx, const gchar *cmd,
 }
 
 static struct lua_redis_ctx *
-rspamd_lua_redis_prepare_connection (lua_State *L, gint *pcbref)
+rspamd_lua_redis_prepare_connection (lua_State *L, gint *pcbref, gboolean is_async)
 {
 	struct lua_redis_ctx *ctx;
 	rspamd_inet_addr_t *ip = NULL;
@@ -621,6 +805,12 @@ rspamd_lua_redis_prepare_connection (lua_State *L, gint *pcbref)
 			if (cfg && ev_base) {
 				ret = TRUE;
 			}
+			else if (!cfg) {
+				msg_err_task_check ("config is not passed");
+			}
+			else {
+				msg_err_task_check ("ev_base is not set");
+			}
 		}
 		else {
 			cfg = task->cfg;
@@ -687,15 +877,23 @@ rspamd_lua_redis_prepare_connection (lua_State *L, gint *pcbref)
 		lua_pop (L, 1); /* table */
 
 		if (session && rspamd_session_is_destroying (session)) {
+			msg_err_task_check ("Session is being destroying");
 			ret = FALSE;
 		}
 
-
 		if (ret && addr != NULL) {
 			ctx = g_malloc0 (sizeof (struct lua_redis_ctx));
 			REF_INIT_RETAIN (ctx, lua_redis_dtor);
-			ctx->flags |= flags | LUA_REDIS_ASYNC;
-			ud = &ctx->d.async;
+			if (is_async) {
+				ctx->flags |= flags | LUA_REDIS_ASYNC;
+				ud = &ctx->async;
+			}
+			else {
+				ud = &ctx->async;
+				ctx->replies = g_queue_new ();
+				ctx->events_cleanup = g_queue_new ();
+
+			}
 			ud->s = session;
 			ud->cfg = cfg;
 			ud->pool = cfg->redis_pool;
@@ -767,7 +965,7 @@ static int
 lua_redis_make_request (lua_State *L)
 {
 	LUA_TRACE_POINT;
-	struct lua_redis_specific_userdata *sp_ud;
+	struct lua_redis_request_specific_userdata *sp_ud;
 	struct lua_redis_userdata *ud;
 	struct lua_redis_ctx *ctx, **pctx;
 	const gchar *cmd = NULL;
@@ -776,10 +974,10 @@ lua_redis_make_request (lua_State *L)
 	gint cbref = -1;
 	gboolean ret = FALSE;
 
-	ctx = rspamd_lua_redis_prepare_connection (L, &cbref);
+	ctx = rspamd_lua_redis_prepare_connection (L, &cbref, TRUE);
 
 	if (ctx) {
-		ud = &ctx->d.async;
+		ud = &ctx->async;
 		sp_ud = g_malloc0 (sizeof (*sp_ud));
 		sp_ud->cbref = cbref;
 		sp_ud->c = ud;
@@ -1022,10 +1220,10 @@ lua_redis_connect (lua_State *L)
 	struct lua_redis_ctx *ctx, **pctx;
 	gdouble timeout = REDIS_DEFAULT_TIMEOUT;
 
-	ctx = rspamd_lua_redis_prepare_connection (L, NULL);
+	ctx = rspamd_lua_redis_prepare_connection (L, NULL, TRUE);
 
 	if (ctx) {
-		ud = &ctx->d.async;
+		ud = &ctx->async;
 
 		lua_pushstring (L, "timeout");
 		lua_gettable (L, 1);
@@ -1061,33 +1259,14 @@ static int
 lua_redis_connect_sync (lua_State *L)
 {
 	LUA_TRACE_POINT;
-	struct rspamd_lua_ip *addr = NULL;
 	rspamd_inet_addr_t *ip = NULL;
-	const gchar *host;
-	struct timeval tv;
-	gboolean ret = FALSE;
-	guint flags = 0;
 	gdouble timeout = REDIS_DEFAULT_TIMEOUT;
 	struct lua_redis_ctx *ctx, **pctx;
 
-	if (lua_istable (L, 1)) {
-		lua_pushstring (L, "host");
-		lua_gettable (L, -2);
-		if (lua_type (L, -1) == LUA_TUSERDATA) {
-			addr = lua_check_ip (L, -1);
-		}
-		else if (lua_type (L, -1) == LUA_TSTRING) {
-			host = lua_tostring (L, -1);
-			if (rspamd_parse_inet_address (&ip, host, strlen (host))) {
-				addr = g_alloca (sizeof (*addr));
-				addr->addr = ip;
+	ctx = rspamd_lua_redis_prepare_connection (L, NULL, FALSE);
 
-				if (rspamd_inet_address_get_port (ip) == 0) {
-					rspamd_inet_address_set_port (ip, 6379);
-				}
-			}
-		}
-		lua_pop (L, 1);
+
+	if (ctx) {
 
 		lua_pushstring (L, "timeout");
 		lua_gettable (L, -2);
@@ -1096,52 +1275,7 @@ lua_redis_connect_sync (lua_State *L)
 		}
 		lua_pop (L, 1);
 
-		lua_pushstring (L, "opaque_data");
-		lua_gettable (L, -2);
-		if (!!lua_toboolean (L, -1)) {
-			flags |= LUA_REDIS_TEXTDATA;
-		}
-		lua_pop (L, 1);
-
-		if (addr) {
-			ret = TRUE;
-		}
-	}
-
-	if (ret) {
-		double_to_tv (timeout, &tv);
-		ctx = g_malloc0 (sizeof (struct lua_redis_ctx));
-		REF_INIT_RETAIN (ctx, lua_redis_dtor);
-		ctx->flags = flags;
-
-		if (rspamd_inet_address_get_af (addr->addr) == AF_UNIX) {
-			ctx->d.sync = redisConnectUnixWithTimeout (
-					rspamd_inet_address_to_string (addr->addr), tv);
-		}
-		else {
-			ctx->d.sync = redisConnectWithTimeout (
-					rspamd_inet_address_to_string (addr->addr),
-					rspamd_inet_address_get_port (addr->addr), tv);
-		}
-
-		if (ip) {
-			rspamd_inet_address_free (ip);
-		}
-
-		if (ctx->d.sync == NULL || ctx->d.sync->err) {
-			lua_pushboolean (L, FALSE);
-
-			if (ctx->d.sync) {
-				lua_pushstring (L, ctx->d.sync->errstr);
-			}
-			else {
-				lua_pushstring (L, "unknown error");
-			}
-
-			REDIS_RELEASE (ctx);
-
-			return 2;
-		}
+		ctx->async.timeout = timeout;
 
 		lua_pushboolean (L, TRUE);
 		pctx = lua_newuserdata (L, sizeof (ctx));
@@ -1174,118 +1308,107 @@ lua_redis_add_cmd (lua_State *L)
 {
 	LUA_TRACE_POINT;
 	struct lua_redis_ctx *ctx = lua_check_redis (L, 1);
-	struct lua_redis_specific_userdata *sp_ud;
+	struct lua_redis_request_specific_userdata *sp_ud;
 	struct lua_redis_userdata *ud;
 	const gchar *cmd = NULL;
 	gint args_pos = 2;
-	gchar **args = NULL;
-	gsize *arglens = NULL;
-	guint nargs = 0;
 	gint cbref = -1, ret;
 	struct timeval tv;
 
 	if (ctx) {
+		if (ctx->flags & LUA_REDIS_TERMINATED) {
+			lua_pushboolean (L, FALSE);
+			lua_pushstring (L, "Connection is terminated");
 
-		if (IS_ASYNC (ctx)) {
-			ud = &ctx->d.async;
+			return 2;
+		}
 
-			/* Async version */
-			if (lua_type (L, 2) == LUA_TSTRING) {
-				/* No callback version */
-				cmd = lua_tostring (L, 2);
-				args_pos = 3;
-			}
-			else if (lua_type (L, 2) == LUA_TFUNCTION) {
-				lua_pushvalue (L, 2);
-				cbref = luaL_ref (L, LUA_REGISTRYINDEX);
-				cmd = lua_tostring (L, 3);
-				args_pos = 4;
-			}
-			else {
-				return luaL_error (L, "invalid arguments");
-			}
+		/* Async version */
+		if (lua_type (L, 2) == LUA_TSTRING) {
+			/* No callback version */
+			cmd = lua_tostring (L, 2);
+			args_pos = 3;
+		}
+		else if (lua_type (L, 2) == LUA_TFUNCTION) {
+			lua_pushvalue (L, 2);
+			cbref = luaL_ref (L, LUA_REGISTRYINDEX);
+			cmd = lua_tostring (L, 3);
+			args_pos = 4;
+		}
+		else {
+			return luaL_error (L, "invalid arguments");
+		}
 
-			sp_ud = g_malloc0 (sizeof (*sp_ud));
+		sp_ud = g_malloc0 (sizeof (*sp_ud));
+		if (IS_ASYNC (ctx)) {
+			sp_ud->c = &ctx->async;
+			ud = &ctx->async;
 			sp_ud->cbref = cbref;
-			sp_ud->c = &ctx->d.async;
-			sp_ud->ctx = ctx;
+		}
+		else {
+			sp_ud->c = &ctx->async;
+			ud = &ctx->async;
+		}
+		sp_ud->ctx = ctx;
 
-			lua_redis_parse_args (L, args_pos, cmd, &sp_ud->args,
-						&sp_ud->arglens, &sp_ud->nargs);
+		lua_redis_parse_args (L, args_pos, cmd, &sp_ud->args,
+					&sp_ud->arglens, &sp_ud->nargs);
 
-			LL_PREPEND (sp_ud->c->specific, sp_ud);
+		LL_PREPEND (sp_ud->c->specific, sp_ud);
 
-			if (ud->s && rspamd_session_is_destroying (ud->s)) {
-				lua_pushboolean (L, 0);
-				lua_pushstring (L, "session is terminating");
+		if (ud->s && rspamd_session_is_destroying (ud->s)) {
+			lua_pushboolean (L, 0);
+			lua_pushstring (L, "session is terminating");
 
-				return 2;
-			}
+			return 2;
+		}
 
+		if (IS_ASYNC (ctx)) {
 			ret = redisAsyncCommandArgv (sp_ud->c->ctx,
 					lua_redis_callback,
 					sp_ud,
 					sp_ud->nargs,
 					(const gchar **)sp_ud->args,
 					sp_ud->arglens);
+		}
+		else {
+			ret = redisAsyncCommandArgv (sp_ud->c->ctx,
+					lua_redis_callback_sync,
+					sp_ud,
+					sp_ud->nargs,
+					(const gchar **)sp_ud->args,
+					sp_ud->arglens);
+		}
 
-			if (ret == REDIS_OK) {
-				if (ud->s) {
-					rspamd_session_add_event (ud->s,
-							lua_redis_fin,
-							sp_ud,
-							g_quark_from_static_string ("lua redis"));
-					sp_ud->w = rspamd_session_get_watcher (ud->s);
-					rspamd_session_watcher_push (ud->s);
-				}
+		if (ret == REDIS_OK) {
+			if (ud->s) {
+				rspamd_session_add_event (ud->s,
+						lua_redis_fin,
+						sp_ud,
+						g_quark_from_static_string ("lua redis"));
+				sp_ud->w = rspamd_session_get_watcher (ud->s);
+				rspamd_session_watcher_push (ud->s);
+			}
 
-				double_to_tv (sp_ud->c->timeout, &tv);
+			double_to_tv (sp_ud->c->timeout, &tv);
+			if (IS_ASYNC (ctx)) {
 				event_set (&sp_ud->timeout, -1, EV_TIMEOUT, lua_redis_timeout, sp_ud);
-				event_base_set (ud->ev_base, &sp_ud->timeout);
-				event_add (&sp_ud->timeout, &tv);
-				REDIS_RETAIN (ctx);
-				ctx->cmds_pending ++;
 			}
 			else {
-				msg_info ("call to redis failed: %s",
-						sp_ud->c->ctx->errstr);
-				lua_pushboolean (L, 0);
-				lua_pushstring (L, sp_ud->c->ctx->errstr);
-
-				return 2;
+				event_set (&sp_ud->timeout, -1, EV_TIMEOUT, lua_redis_timeout_sync, sp_ud);
 			}
+			event_base_set (ud->ev_base, &sp_ud->timeout);
+			event_add (&sp_ud->timeout, &tv);
+			REDIS_RETAIN (ctx);
+			ctx->cmds_pending ++;
 		}
 		else {
-			/* Synchronous version */
-			if (lua_type (L, 2) == LUA_TSTRING) {
-				cmd = lua_tostring (L, 2);
-				args_pos = 3;
-			}
-			else {
-				return luaL_error (L, "invalid arguments");
-			}
-
-			if (ctx->d.sync) {
-				lua_redis_parse_args (L, args_pos, cmd, &args, &arglens, &nargs);
-
-				if (nargs > 0) {
-					if (redisAppendCommandArgv (ctx->d.sync, nargs,
-							(const char **)args, arglens) == REDIS_OK) {
-						ctx->cmds_pending ++;
-					}
-
-					lua_redis_free_args (args, arglens, nargs);
-				}
-				else {
-					lua_pushstring (L, "cannot append commands when not connected");
-					return lua_error (L);
-				}
+			msg_info ("call to redis failed: %s",
+					sp_ud->c->ctx->errstr);
+			lua_pushboolean (L, 0);
+			lua_pushstring (L, sp_ud->c->ctx->errstr);
 
-			}
-			else {
-				lua_pushstring (L, "cannot append commands when not connected");
-				return lua_error (L);
-			}
+			return 2;
 		}
 	}
 
@@ -1304,9 +1427,6 @@ lua_redis_exec (lua_State *L)
 {
 	LUA_TRACE_POINT;
 	struct lua_redis_ctx *ctx = lua_check_redis (L, 1);
-	redisReply *r;
-	gint ret;
-	guint i, nret = 0, pending;
 
 	if (ctx == NULL) {
 		lua_error (L);
@@ -1320,48 +1440,26 @@ lua_redis_exec (lua_State *L)
 		return 0;
 	}
 	else {
-		if (!ctx->d.sync) {
+		if (false /* !ctx->d.sync */) {
 			lua_pushstring (L, "cannot exec commands when not connected");
 			lua_error (L);
 			return 0;
 		}
 		else {
-			if (!lua_checkstack (L, (ctx->cmds_pending * 2) + 1)) {
-				return luaL_error (L, "cannot resize stack to fit %d commands",
-					ctx->cmds_pending);
+			if (ctx->cmds_pending == 0 && g_queue_get_length (ctx->replies) == 0) {
+				lua_pushstring (L, "No pending commands to execute");
+				lua_error (L);
 			}
-
-			pending = ctx->cmds_pending;
-			ctx->cmds_pending = 0;
-
-			for (i = 0; i < pending; i ++) {
-				ret = redisGetReply (ctx->d.sync, (void **)&r);
-
-				if (ret == REDIS_OK) {
-					if (r->type != REDIS_REPLY_ERROR) {
-						lua_pushboolean (L, TRUE);
-						lua_redis_push_reply (L, r,
-								ctx->flags & LUA_REDIS_TEXTDATA);
-					}
-					else {
-						lua_pushboolean (L, FALSE);
-						lua_pushlstring (L, r->str, r->len);
-					}
-
-					freeReplyObject (r);
-				}
-				else {
-					msg_info ("call to redis failed: %s", ctx->d.sync->errstr);
-					lua_pushboolean (L, FALSE);
-					lua_pushstring (L, ctx->d.sync->errstr);
-				}
-
-				nret += 2;
+			if (ctx->cmds_pending == 0 && g_queue_get_length (ctx->replies) > 0) {
+				gint results = lua_redis_push_results (ctx, L);
+				return results;
+			}
+			else {
+				ctx->thread = lua_thread_pool_get_running_entry (ctx->async.cfg->lua_thread_pool);
+				return lua_thread_yield (ctx->thread, 0);
 			}
 		}
 	}
-
-	return nret;
 }
 #else
 static int
-- 
2.39.5