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From Santiago Gala <sg...@hisitech.com>
Subject Re: I propose to upgrade Turbine again - eez ok?
Date Mon, 18 Mar 2002 19:24:55 GMT
Chris Kimpton wrote:

>Hi,
>
>>>I am currently testing with the new turbine at the moment - anyone
>>>got any concerns about me upgrading turbine...
>>>
>
>Just looked at the turbine-dev list and looks like they are trying to
>do a release - so I will hold off and try upgrading jetspeed after
>the release/with the release later...
>
The problem is the patch about race conditions on service 
initialization. I will not be able to test it, so it will not go to the 
release.

The problem seems to be that, when you ask for a service twice (in 
separate threads),

- the first one triggers (early and then late) initialization of the service
- the second one tries to get it and, since it is not (yet) in the 
services hashmap, initializes a new instance.

So the singleton paradigm breaks, and after this the workings of turbine 
are rather messed up. We have a race condition going on. It happens 
about one in three times in my setup, depending on DNS times and HTTP 
proxies being filled up or not.

It happens in Jetspeed because the CastorRegistryService is *very* slow 
to initialize, uses remote resources with unpredictable delays, and it 
is requested by quite a few services (and service initialized threads) 
in Jetspeed. The most problematic seems to be the DaemonService, since 
it spawns threads.

I'm trying to find a solution where Turbine does not need to be patched 
for single singletons and avoiding double lock synchronization, but I'm 
not sure if I will be able.

I thought that there was a contract in Turbine where services were 
singletons, so I think this behaviour looks like a bug in turbine-2.

"Spamming" turbine-dev, to look for further insight. :)

>
>Chris
>
>=====
>http://wc2002.kimptoc.net - someone has got to win...
>
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