MINOR: lua: Add act:wake_time() function to set a timeout when an action yields

This function may be used to defined a timeout when a lua action returns
act:YIELD. It is a way to force to reexecute the script after a short time
(defined in milliseconds).

Unlike core:sleep() or core:yield(), the script is fully reexecuted if it
returns act:YIELD. With core functions to yield, the script is interrupted and
restarts from the yield point. When a script returns act:YIELD, it is finished
but the message analysis is blocked on the action waiting its end.

doc/lua-api/index.rst

@@ -2642,6 +2642,18 @@ Action class
 
   :returns: integer
 
+.. js:function:: act:wake_time(milliseconds)
+
+  **context**: action
+
+  Set the script pause timeout to the specified time, defined in
+  milliseconds.
+
+  :param integer milliseconds: the required milliseconds.
+
+  This function may be used when a lua action returns `act.YIELD`, to force its
+  wake-up at most after the specified number of milliseconds.
+
 External Lua libraries
 ======================
 

src/hlua.c

@@ -6053,6 +6053,24 @@ __LJMP static int hlua_register_fetches(lua_State *L)
 	return 0;
 }
 
+/* This function is a lua binding to set the wake_time from an action. It is
+ * only used if the action return ACT_RET_YIELD.
+ */
+__LJMP static int hlua_action_wake_time(lua_State *L)
+{
+	struct hlua *hlua = hlua_gethlua(L);
+	unsigned int delay;
+	unsigned int wakeup_ms;
+
+	MAY_LJMP(check_args(L, 1, "wake_time"));
+
+	delay = MAY_LJMP(luaL_checkinteger(L, 1));
+	wakeup_ms = tick_add(now_ms, delay);
+	hlua->wake_time = wakeup_ms;
+	return 0;
+}
+
+
 /* This function is a wrapper to execute each LUA function declared as an action
  * wrapper during the initialisation period. This function may return any
  * ACT_RET_* value. On error ACT_RET_CONT is returned and the action is
@@ -6157,6 +6175,15 @@ static enum act_return hlua_action(struct act_rule *rule, struct proxy *px,
 		if (lua_gettop(s->hlua->T) > 0)
 			act_ret = lua_tointeger(s->hlua->T, -1);
 
+		/* Set timeout in the required channel. */
+		if (act_ret == ACT_RET_YIELD && s->hlua->wake_time != TICK_ETERNITY) {
+			if (dir == SMP_OPT_DIR_REQ)
+				s->req.analyse_exp = s->hlua->wake_time;
+			else
+				s->res.analyse_exp = s->hlua->wake_time;
+		}
+		goto end;
+
 	/* yield. */
 	case HLUA_E_AGAIN:
 		/* Set timeout in the required channel. */
@@ -7637,6 +7664,8 @@ void hlua_init(void)
 	hlua_class_const_int(gL.T, "ABORT",    ACT_RET_ABRT);
 	hlua_class_const_int(gL.T, "INVALID",  ACT_RET_INV);
 
+	hlua_class_function(gL.T, "wake_time", hlua_action_wake_time);
+
 	lua_setglobal(gL.T, "act");
 
 	/*