[Minor] Use coroutine model in dns resolver API

src/lua/lua_common.h

@@ -408,6 +408,27 @@ void rspamd_lua_add_ref_dtor (lua_State *L, rspamd_mempool_t *pool,
 gboolean rspamd_lua_require_function (lua_State *L, const gchar *modname,
 		const gchar *funcname);
 
+struct thread_entry;
+/**
+ * Yields thread. should be only called in return statement
+ * @param thread_entry
+ * @param nresults
+ * @return
+ */
+gint
+lua_yield_thread (struct thread_entry *thread_entry, gint nresults);
+
+/**
+ *
+ * @param pool
+ * @param thread_entry
+ * @param narg
+ * @return
+ */
+void
+lua_resume_thread (struct rspamd_task *task, struct thread_entry *thread_entry, gint narg);
+
+
 /* Paths defs */
 #define RSPAMD_CONFDIR_INDEX "CONFDIR"
 #define RSPAMD_RUNDIR_INDEX "RUNDIR"

src/lua/lua_config.c

@@ -1206,6 +1206,9 @@ lua_metric_symbol_callback (struct rspamd_task *task, gpointer ud)
 	struct thread_entry *thread_entry = lua_thread_pool_get (task->cfg->lua_thread_pool);
 	cd->thread_entry = thread_entry;
 
+	g_assert(thread_entry->cd == NULL);
+	thread_entry->cd = cd;
+
 	lua_State *thread = thread_entry->lua_state;
 	cd->stack_level = lua_gettop (cd->L);
 
@@ -1232,6 +1235,29 @@ lua_metric_symbol_callback (struct rspamd_task *task, gpointer ud)
 	}
 }
 
+gint
+lua_yield_thread (struct thread_entry *thread_entry, gint nresults)
+{
+    g_assert (thread_entry->cd != NULL);
+
+	return lua_yield (thread_entry->lua_state, nresults);
+}
+
+void
+lua_resume_thread (struct rspamd_task *task, struct thread_entry *thread_entry, gint narg)
+{
+    g_assert (thread_entry->cd != NULL);
+
+	gint ret;
+
+	lua_thread_pool_set_running_entry (task->cfg->lua_thread_pool, thread_entry);
+	ret = lua_resume (thread_entry->lua_state, narg);
+
+	if (ret != LUA_YIELD) {
+		lua_metric_symbol_callback_return (task, thread_entry->cd, ret);
+	}
+}
+
 static void
 lua_metric_symbol_callback_return (struct rspamd_task *task, gpointer ud, gint ret)
 {
@@ -1337,7 +1363,7 @@ lua_metric_symbol_callback_return (struct rspamd_task *task, gpointer ud, gint r
 
 		g_assert (lua_gettop (thread) == cd->stack_level); /* we properly cleaned up the stack */
 
-		lua_thread_pool_return(task->cfg->lua_thread_pool, cd->thread_entry);
+		lua_thread_pool_return (task->cfg->lua_thread_pool, cd->thread_entry);
 	}
 
 	cd->thread_entry = NULL;

src/lua/lua_dns.c

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 #include "lua_common.h"
+#include "lua_thread_pool.h"
 #include "utlist.h"
 
 
@@ -78,6 +79,8 @@ lua_check_dns_resolver (lua_State * L)
 
 struct lua_dns_cbdata {
 	lua_State *L;
+	struct thread_entry *thread;
+	struct rspamd_task *task;
 	struct rspamd_dns_resolver *resolver;
 	gint cbref;
 	const gchar *to_resolve;
@@ -140,12 +143,15 @@ lua_dns_callback (struct rdns_reply *reply, gpointer arg)
 	struct rdns_reply_entry *elt;
 	rspamd_inet_addr_t *addr;
 
-	lua_rawgeti (cd->L, LUA_REGISTRYINDEX, cd->cbref);
-	presolver = lua_newuserdata (cd->L, sizeof (gpointer));
-	rspamd_lua_setclass (cd->L, "rspamd{resolver}", -1);
+	if (cd->cbref != -1) {
+		lua_rawgeti (cd->L, LUA_REGISTRYINDEX, cd->cbref);
 
-	*presolver = cd->resolver;
-	lua_pushstring (cd->L, cd->to_resolve);
+		presolver = lua_newuserdata (cd->L, sizeof (gpointer));
+		rspamd_lua_setclass (cd->L, "rspamd{resolver}", -1);
+
+		*presolver = cd->resolver;
+		lua_pushstring (cd->L, cd->to_resolve);
+	}
 
 	/*
 	 * XXX: rework to handle different request types
@@ -227,22 +233,41 @@ lua_dns_callback (struct rdns_reply *reply, gpointer arg)
 		lua_pushstring (cd->L, rdns_strerror (reply->code));
 	}
 
-	if (cd->user_str != NULL) {
-		lua_pushstring (cd->L, cd->user_str);
-	}
-	else {
-		lua_pushnil (cd->L);
+	if (cd->cbref != -1) {
+		if (cd->user_str != NULL) {
+			lua_pushstring (cd->L, cd->user_str);
+		}
+		else {
+			lua_pushnil (cd->L);
+		}
 	}
 
 	lua_pushboolean (cd->L, reply->authenticated);
 
-	if (lua_pcall (cd->L, 6, 0, 0) != 0) {
-		msg_info ("call to dns callback failed: %s", lua_tostring (cd->L, -1));
-		lua_pop (cd->L, 1);
-	}
+	if (cd->cbref != -1) {
+		/*
+		 * 1 - resolver
+		 * 2 - to_resolve
+		 * 3 - entries | nil
+		 * 4 - error | nil
+		 * 5 - user_str
+		 * 6 - reply->authenticated
+		 */
+		if (lua_pcall (cd->L, 6, 0, 0) != 0) {
+			msg_info ("call to dns callback failed: %s", lua_tostring (cd->L, -1));
+			lua_pop (cd->L, 1);
+		}
 
-	/* Unref function */
-	luaL_unref (cd->L, LUA_REGISTRYINDEX, cd->cbref);
+		/* Unref function */
+		luaL_unref (cd->L, LUA_REGISTRYINDEX, cd->cbref);
+	} else {
+		/*
+		 * 1 - entries
+		 * 2 - error | nil
+		 * 3 - reply->authenticated
+		 */
+		lua_resume_thread (cd->task, cd->thread, 3);
+	}
 
 	if (cd->s) {
 		rspamd_session_watcher_pop (cd->s, cd->w);
@@ -306,7 +331,7 @@ lua_dns_resolver_resolve_common (lua_State *L,
 
 	/* Check arguments */
 	if (!rspamd_lua_parse_table_arguments (L, first, &err,
-			"session=U{session};mempool=U{mempool};*name=S;*callback=F;"
+			"session=U{session};mempool=U{mempool};*name=S;callback=F;"
 			"option=S;task=U{task};forced=B",
 			&session, &pool, &to_resolve, &cbref, &user_str, &task, &forced)) {
 
@@ -325,7 +350,7 @@ lua_dns_resolver_resolve_common (lua_State *L,
 		session = task->s;
 	}
 
-	if (pool != NULL && to_resolve != NULL && cbref != -1) {
+	if (pool != NULL && to_resolve != NULL) {
 		cbdata = rspamd_mempool_alloc0 (pool, sizeof (struct lua_dns_cbdata));
 		cbdata->L = L;
 		cbdata->resolver = resolver;
@@ -375,6 +400,9 @@ lua_dns_resolver_resolve_common (lua_State *L,
 			}
 		}
 		else {
+			cbdata->thread = lua_thread_pool_get_running_entry (task->cfg->lua_thread_pool);
+			cbdata->task = task;
+
 			if (forced) {
 				ret = make_dns_request_task_forced (task,
 						lua_dns_callback,
@@ -391,10 +419,16 @@ lua_dns_resolver_resolve_common (lua_State *L,
 			}
 
 			if (ret) {
-				lua_pushboolean (L, TRUE);
 				cbdata->s = session;
 				cbdata->w = rspamd_session_get_watcher (session);
 				rspamd_session_watcher_push (session);
+				if (cbdata->cbref != -1) {
+					/* callback was set up */
+					lua_pushboolean (L, TRUE);
+				} else {
+					/* this is coroutine-based call */
+					return lua_yield_thread (cbdata->thread, 0);
+				}
 			}
 			else {
 				lua_pushnil (L);

src/lua/lua_thread_pool.c

@@ -14,7 +14,7 @@ static struct thread_entry *
 thread_entry_new (lua_State * L)
 {
 	struct thread_entry *ent;
-	ent = g_malloc (sizeof *ent);
+	ent = g_new0(struct thread_entry, 1);
 	ent->lua_state = lua_newthread (L);
 	ent->thread_index = luaL_ref (L, LUA_REGISTRYINDEX);
 
@@ -75,6 +75,8 @@ lua_thread_pool_get(struct lua_thread_pool *pool)
 		ent = thread_entry_new (pool->L);
 	}
 
+	pool->running_entry = ent;
+
 	return ent;
 }
 
@@ -88,6 +90,7 @@ lua_thread_pool_return(struct lua_thread_pool *pool, struct thread_entry *thread
 	}
 
 	if (g_queue_get_length (pool->available_items) <= pool->max_items) {
+		thread_entry->cd = NULL;
 		g_queue_push_head (pool->available_items, thread_entry);
 	}
 	else {

src/lua/lua_thread_pool.h

@@ -6,6 +6,7 @@
 struct thread_entry {
 	lua_State *lua_state;
 	gint thread_index;
+	gpointer cd;
 };
 
 struct thread_pool;