api: fix INIT state stuck

Sometimes, instance could enter the queue initialization
while still not running (for example, left in the orphan mode).
This resulted in "lazy start". But Tarantool does not call
`box.cfg {}` after leaving orphan mode, so queue could stuck in the
`INIT` state.

Now we wait in the background for instances, that are not running.
It is similar to lazy init for read-only instances.

Note that this fix works only for Tarantool versions >= 2.10.0.
This is because of used watchers.

Closes #226

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+
+- Stuck in `INIT` state if an instance failed to enter the `running` mode
+  in time (#226). This fix works only for Tarantool versions >= 2.10.0.
+
 ## [1.3.3] - 2023-09-13
 
 ### Fixed

queue/init.lua

@@ -1,3 +1,5 @@
+local fiber = require('fiber')
+
 local abstract = require('queue.abstract')
 local queue_state = require('queue.abstract.queue_state')
 local queue = nil
@@ -11,6 +13,10 @@ local core_drivers = {
     limfifottl  = require('queue.abstract.driver.limfifottl')
 }
 
+-- since:
+-- https://github.com/locker/tarantool/commit/8cf5151cb4f05cee3fd0ea831add2b3187a01fe4
+local watchers_supported = box.watch ~= nil
+
 local function register_driver(driver_name, tube_ctr)
     if type(tube_ctr.create_space) ~= 'function' or
         type(tube_ctr.new) ~= 'function' then
@@ -62,6 +68,18 @@ local orig_call = nil
 
 local wrapper_impl
 
+local function running_waiter()
+    local wait_cond = fiber.cond()
+    local w = box.watch('box.status', function(_, new_status)
+        if new_status.status == 'running' then
+            wait_cond:signal()
+        end
+    end)
+    wait_cond:wait()
+    w:unregister()
+    return wrapper_impl()
+end
+
 local function cfg_wrapper(...)
     box.cfg = orig_cfg
     return wrapper_impl(...)
@@ -79,10 +97,15 @@ local function wrap_box_cfg()
         orig_cfg = box.cfg
         box.cfg = cfg_wrapper
     elseif type(box.cfg) == 'table' then
-        -- box.cfg after the first box.cfg call
-        local cfg_mt = getmetatable(box.cfg)
-        orig_call = cfg_mt.__call
-        cfg_mt.__call = cfg_call_wrapper
+        if watchers_supported and box.info.status ~= 'running' then
+            -- Wait for the running state and initialize the queue.
+            fiber.new(running_waiter)
+        else
+            -- box.cfg after the first box.cfg call
+            local cfg_mt = getmetatable(box.cfg)
+            orig_call = cfg_mt.__call
+            cfg_mt.__call = cfg_call_wrapper
+        end
     else
         error('The box.cfg type is unexpected: ' .. type(box.cfg))
     end