Event listeners get registered multiple times

[dodomedia]

It seems the event system is not able to handle the execution of multiple spiders.
I have written a console command which triggers multiple runs of various spiders.

For example, there are spiders A and B which are called by Roach::startSpider in the same command.

They get executed and the requests are performed once which is correct, but it seems the event listeners are registered for each spider, so spider B gets logged twice when the LoggerExtension is active:

local.INFO: Run starting  
local.INFO: Dispatching request {"uri":"xxxxxxxxxxxxxxxxxx1"} 
local.INFO: Run finished  
local.INFO: Run starting  
local.INFO: Run starting  
local.INFO: Dispatching request {"uri":"xxxxxxxxxxxxxxxxxx2"} 
local.INFO: Dispatching request {"uri":"xxxxxxxxxxxxxxxxxx2"} 
local.INFO: Run finished  
local.INFO: Run finished  

If there are three spiders running in one script call, event listeners are getting registered thrice and the output is as follows:

local.INFO: Run starting  
local.INFO: Dispatching request {"uri":"xxxxxxxxxxxxxxxxxx1"} 
local.INFO: Run finished  
local.INFO: Run starting  
local.INFO: Run starting  
local.INFO: Dispatching request {"uri":"xxxxxxxxxxxxxxxxxx2"} 
local.INFO: Dispatching request {"uri":"xxxxxxxxxxxxxxxxxx2"} 
local.INFO: Run finished  
local.INFO: Run finished  
local.INFO: Run starting  
local.INFO: Run starting  
local.INFO: Run starting  
local.INFO: Dispatching request {"uri":"xxxxxxxxxxxxxxxxxx3"} 
local.INFO: Dispatching request {"uri":"xxxxxxxxxxxxxxxxxx3"} 
local.INFO: Dispatching request {"uri":"xxxxxxxxxxxxxxxxxx3"} 
local.INFO: Run finished  
local.INFO: Run finished 
local.INFO: Run finished 

For 5 running spiders I had the problem, that each event was listened 5 times (and so on)...
The problem also occurs when the same spider is called multiple times in the same script.

[ksassnowski]

Closing this in favor of #36