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 if the instance is read-only,  separate fiber is watching for
updates of its mode.

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

@@ -1,5 +1,8 @@
+local fiber = require('fiber')
+
 local abstract = require('queue.abstract')
 local queue_state = require('queue.abstract.queue_state')
+local qc = require('queue.compat')
 local queue = nil
 
 -- load all core drivers
@@ -11,6 +14,10 @@ local core_drivers = {
     limfifottl  = require('queue.abstract.driver.limfifottl')
 }
 
+-- since:
+-- https://github.com/locker/tarantool/commit/8cf5151cb4f05cee3fd0ea831add2b3187a01fe4
+local watchers_supported = qc.check_version({2, 10, 0})
+
 local function register_driver(driver_name, tube_ctr)
     if type(tube_ctr.create_space) ~= 'function' or
         type(tube_ctr.new) ~= 'function' then
@@ -60,7 +67,20 @@ queue = setmetatable({
 local orig_cfg = nil
 local orig_call = nil
 
-local wrapper_impl
+local wrapper_impl, handle_instance_mode
+
+local function rw_waiter()
+    fiber.name('queue rw waiter')
+    local wait_cond = fiber.cond()
+    local w = box.watch('box.status', function(_, new_status)
+        if new_status.is_ro == false then
+            wait_cond:signal()
+        end
+    end)
+    wait_cond:wait()
+    w:unregister()
+    handle_instance_mode()
+end
 
 local function cfg_wrapper(...)
     box.cfg = orig_cfg
@@ -79,24 +99,22 @@ 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 box.info.ro_reason == 'config' or not watchers_supported then
+            -- box.cfg after the first box.cfg call.
+            -- The another call could switch the mode.
+            local cfg_mt = getmetatable(box.cfg)
+            orig_call = cfg_mt.__call
+            cfg_mt.__call = cfg_call_wrapper
+        else
+            -- Wait for the rw state.
+            fiber.new(rw_waiter)
+        end
     else
         error('The box.cfg type is unexpected: ' .. type(box.cfg))
     end
 end
 
-function wrapper_impl(...)
-    local result = { pcall(box.cfg,...) }
-    if result[1] then
-        table.remove(result, 1)
-    else
-        wrap_box_cfg()
-        error(result[2])
-    end
-
+function handle_instance_mode()
     if box.info.ro == false then
         local abstract = require 'queue.abstract'
         for name, val in pairs(abstract) do
@@ -113,6 +131,18 @@ function wrapper_impl(...)
         -- with read_only = false
         wrap_box_cfg()
     end
+end
+
+function wrapper_impl(...)
+    local result = { pcall(box.cfg,...) }
+    if result[1] then
+        table.remove(result, 1)
+    else
+        wrap_box_cfg()
+        error(result[2])
+    end
+
+    handle_instance_mode()
     return unpack(result)
 end
 

t/230-orphan-not-stalling-init.t

@@ -0,0 +1,97 @@
+#!/usr/bin/env tarantool
+
+local test  = require('tap').test('')
+local queue = require('queue')
+local tnt   = require('t.tnt')
+local fio   = require('fio')
+local fiber = require('fiber')
+
+rawset(_G, 'queue', require('queue'))
+
+local qc = require('queue.compat')
+if not qc.check_version({2, 10, 0}) then
+    require('log').info('Tests skipped, tarantool version < 2.10.0 ' ..
+        'does not support the lazy init')
+    return
+end
+
+local snapdir_optname = qc.snapdir_optname
+local logger_optname  = qc.logger_optname
+
+test:plan(1)
+
+test:test('Check orphan mode not stalling queue', function(test)
+    test:plan(4)
+    local engine = os.getenv('ENGINE') or 'memtx'
+    tnt.cluster.cfg{}
+
+    local dir_replica = fio.tempdir()
+    local cmd_replica = {
+        arg[-1],
+        '-e',
+        [[
+        box.cfg {
+            replication = {
+                'replicator:[email protected]:3399',
+                'replicator:[email protected]:3398',
+            },
+            listen = '127.0.0.1:3396',
+            wal_dir = ']] .. dir_replica .. '\'' ..
+            ',' .. snapdir_optname() .. ' = \'' .. dir_replica .. '\'' ..
+            ',' .. logger_optname() .. ' = \'' ..
+            fio.pathjoin(dir_replica, 'tarantool.log') .. '\'' ..
+        '}'
+    }
+
+    replica = require('popen').new(cmd_replica, {
+        stdin = 'devnull',
+        stdout = 'devnull',
+        stderr = 'devnull',
+    })
+
+    local attempts = 0
+    -- Wait for replica to connect.
+    while box.info.replication[3] == nil or
+        box.info.replication[3].downstream.status ~= 'follow' do
+
+        attempts = attempts + 1
+        if attempts == 30 then
+            error('wait for replica connection')
+        end
+        fiber.sleep(0.1)
+    end
+
+    local conn = require('net.box').connect('127.0.0.1:3396')
+
+    conn:eval([[
+        box.cfg{
+            replication = {
+                'replicator:[email protected]:3399',
+                'replicator:[email protected]:3398',
+                'replicator:[email protected]:3396',
+            },
+            listen = '127.0.0.1:3397',
+            replication_connect_quorum = 4,
+        }
+    ]])
+
+    conn:eval('rawset(_G, "queue", require("queue"))')
+
+    test:is(conn:call('queue.state'), 'INIT', 'check queue state')
+    test:is(conn:call('box.info').ro, true, 'check read only')
+    test:is(conn:call('box.info').ro_reason, 'orphan', 'check ro reason')
+
+    conn:eval('box.cfg{replication_connect_quorum = 2}')
+
+    local attempts = 0
+    while conn:call('queue.state') ~= 'RUNNING' and attempts < 50 do
+        fiber.sleep(0.1)
+        attempts = attempts + 1
+    end
+    test:is(conn:call('queue.state'), 'RUNNING', 'check queue state after orphan')
+end)
+
+rawset(_G, 'queue', nil)
+tnt.finish()
+os.exit(test:check() and 0 or 1)
+-- vim: set ft=lua :