[Mono-dev] Bug in System.Web.Caching.Get() / Timer.Change() ?

[jriepshoff at ujam.com]

Sorry Michal,

i made a mistake. we DISABLED it to make it work.
Since the code in System.Web.Cache looks as follows:

public object Get(string key)

{

Dictionary<string, CacheItem> V_0 = this.cache;

Monitor.Enter(V_0);

try

{

}

finally

{

Monitor.Exit(V_0);

}

if (!this.cache.TryGetValue(key, &CacheItem V_1))

{

object V_2 = null;

}

else

{

if (V_1.Dependency)

{

if (V_1.Dependency.HasChanged)

{

this.Remove(V_1.Key, 4, 0);

V_2 = null;

}

else

{

if (V_1.SlidingExpiration != Cache.NoSlidingExpiration)

{

V_1.AbsoluteExpiration = DateTime.get_Now() + V_1.SlidingExpiration;

V_1.Timer.Change((long)&V_1.SlidingExpiration.get_TotalMilliseconds(), (long)-1);

}

else

{

if (DateTime.get_Now() >= V_1.AbsoluteExpiration)

{

this.Remove(key, 2, 0);

V_2 = null;

}

else

{

V_2 = V_1.Value;

}

}

}

}

}

return V_2;

}


So, you have to take a look at System.Web.Cache.Insert()
Insert the items with AbsoluteExpiration + ((SlidingExpiration = TimeSpan.Zero (TimeSpanZero == Cache.NoSlidingExpiration))
Of course if you do this, you have to take care of the AsoluteExpiration DateTime to be so much in the future that it doesn't break the user's session and - not less important - to remove the item from the cache again when the user left and you've chosen a very long expiration time.


I do it as follows:
HttpRuntime.Cache.Insert(client.Id, client, null,  DateTime.Now.AddDays(1), TimeSpan.Zero, CacheItemPriority.NotRemovable, new CacheItemRemovedCallback(this.RemovedCallback));


And on ClientAppLeave i remove the cache item again.

Not the cleanest solution but better than the mono bug - which only happens when many users are connected for a short time and reconnect again and again (Stress Test in my case).
Under which circumstances does this bug occur in your app?




Best
Jan




On Dec 8, 2010, at 9:09 PM, <michal.x.malek at us.hsbc.com<mailto:michal.x.malek at us.hsbc.com>> wrote:

Hi J,

Could you confirm if enabling sliding expiration is still working for you
(preventing System.ArgumentException: Key 'System.Threading.Timer' already
exists in list issue).
I will be glad if you let me know, as we are planning to enable this in our
production environment today.

I appreciate any kind of feedback.

Best Regards,
--
Michal X Malek
HSBC Securities / Barracuda IT
Senior Development Specialist
michal.x.malek at us.hsbc.com<mailto:michal.x.malek at us.hsbc.com>



 From:       Michal X Malek/HBUS/HSBC

 To:         "jriepshoff at ujam.com" <jriepshoff at ujam.com>

 Date:       12/06/2010 09:21 AM

 Subject:    Re: [Mono-dev] Bug in System.Web.Caching.Get() / Timer.Change() ?





Hi,

Thanks for the response, we will test it.

Best Regards,
--
Michal X Malek
HSBC Securities / Barracuda IT
Senior Development Specialist
michal.x.malek at us.hsbc.com




 From:       "jriepshoff at ujam.com" <jriepshoff at ujam.com>

 To:         Michal X Malek/HBUS/HSBC at HSBC02

 Date:       12/05/2010 06:16 AM

 Subject:    Re: [Mono-dev] Bug in System.Web.Caching.Get() / Timer.Change() ?






I just enabled sliding expiration. That prevents the error - but costs
security, which is not an issue in my case.









On Dec 3, 2010, at 8:27 PM, michalm82 wrote:


I'm experiencing same issue, I'm on mono 2.6.7. Does migration to 2.8.1
helps
?
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