====== Turbo LUA ======

Getting ioloop instance:
<code lua>
local turbo = require 'turbo'
local tio = turbo.ioloop.instance()
</code>
There is only one instance at time. Multiple requests always return the same instance.

====== Always use pcall ======
For example: if you register periodic action using <code lua>tio:set_interval()</code> and registered handler
fails from some reason, it will be removed by tio.
<file | ioloop.lua>
Because errors can always happen! If a handler errors, the handler is removed from the IOLoop, and never called again.
</file>


===== tio:add_handler =====
Add handler function for given event mask on fd
<code lua>
function MyClass:procesData()
...
end
function MyClass:init()
  tio:add_handler(TCPSocketFd, turbo.ioloop.READ, self.processData, self)
end
</code>
Internally function is performing:
<code lua>
self._poll:register()
self.handlers[fs] = {handler, arg}
</code>

When FD is closed:
  * Q6 Will the close of an fd cause it to be removed from all epoll sets automatically? 
  * A6 Yes. 

But tio behaves in stupid way, and starts calling handler in unfinished loop. Registered FD has to be manually removed:
<code>tio:remove_handler(TCPSocketFd)</code>
It will show short notice about already removed socket which can be ignored:
''[ioloop.lua] unregister() in remove_handler() failed: Bad file descriptor''


===== tio:set_interval =====
<code lua>
tio:set_interval (10000, self.method, self)
local ref = tio:set_interval (10000, self.method, self)
tio:clear_interval (ref)
</code>

===== tio:add_timeout =====
<code lua>
tio:add_timeout (turbo.util.gettimemonotonic() + 10000, self.method, self)
local ref = tio:add_timeout (turbo.util.gettimemonotonic() + 10000, self.method, self)
tio:remove_timeout (ref)
</code>