Add a check of the session state before take a task

We need to check of a session state before take a task after wait()
because session maybe in disconnecting state and task will be
hang in a take state after the session will be disconnected

Fixes #104

Author: LeonidVas

queue/abstract.lua

@@ -93,6 +93,7 @@ function tube.put(self, data, opts)
 end
 
 local conds = {}
+local releasing_sessions = {}
 
 function tube.take(self, timeout)
     timeout = time(timeout or TIMEOUT_INFINITY)
@@ -114,6 +115,13 @@ function tube.take(self, timeout)
         conds[fid]:free()
         box.space._queue_consumers:delete{ sid, fid }
 
+        -- We don't take a task if the session is in a
+        -- disconnecting state.
+        if releasing_sessions[fid] then
+            releasing_sessions[fid] = nil
+            return nil
+        end
+
         task = self.raw:take()
 
         if task ~= nil then
@@ -376,6 +384,7 @@ function method._on_consumer_disconnect()
         box.space._queue_consumers:delete{ waiter[1], waiter[2] }
         local cond = conds[waiter[2]]
         if cond then
+            releasing_sessions[waiter[2]] = true
             cond:signal(waiter[2])
         end
     end

t/120-take-task-after-reconnect.t

@@ -0,0 +1,62 @@
+#!/usr/bin/env tarantool
+
+local fiber = require('fiber')
+local netbox = require('net.box')
+local os = require('os')
+local queue = require('queue')
+local tap = require('tap')
+local tnt = require('t.tnt')
+
+
+local test = tap.test('take a task after reconnect')
+test:plan(1)
+
+local listen = 'localhost:1918'
+tnt.cfg{listen = listen}
+
+
+local function test_take_task_after_disconnect(test)
+    test:plan(1)
+    local driver = 'fifottl'
+    local tube = queue.create_tube('test_tube', driver,
+        {if_not_exists = true})
+    rawset(_G, 'queue', require('queue'))
+    tube:grant('guest', {call = true})
+    local task_id = tube:put('test_data')[1]
+    -- Now we have one task in a ready state
+
+    local connection = netbox.connect(listen)
+    local fiber_1 = fiber.create(function()
+        connection:call('queue.tube.test_tube:take')
+        connection:call('queue.tube.test_tube:take')
+    end)
+
+    -- This is not a best practice but we need to use the fiber.sleep()
+    -- (not fiber.yield()).
+    -- Expected results from a sleep() calling:
+    -- 1) Execute first connection:call('queue.tube.test_tube:take')
+    --    Now one task in a taken state
+    -- 2) Call the second connection:call('queue.tube.test_tube:take')
+    --  and to hang the fiber_1
+    -- 3) Start a fiber on the server side of connection which will execute
+    --  second queue.tube.test_tube:take call and hang because the queue
+    --  is empty
+    fiber.sleep(0.1)
+
+    connection:close()
+
+    fiber.sleep(0.1)
+    -- The taken task will be released (cause - disconnection).
+    -- After that the fiber which waiting of a ready task (into take procedure)
+    -- will try to take this task (before the fix).
+
+
+    test:is(tube:peek(task_id)[2] == 'r', true, 'Task in ready state')
+end
+
+
+test:test('Don\'t take a task after disconnect', test_take_task_after_disconnect)
+
+
+tnt.finish()
+os.exit(test:check() and 0 or 1)