Re: [Playerstage-developers] Player crash (sometimes) when receiving opaque messages

[Peter N. <pet...@li...>]

I have tried it now and sadly it did not solve my problem. When I was sending data from two threads through the same PlayerClient the crash would happen very fast, within 30 seconds. When creating a different PlayerClient for the opaque data it takes a lot longer before the crash occur. Sometimes a few minutes and sometimes up to 20 minutes. (I have not tried it that many times). The crash (or "message is larger than" warning) will happen eventually. I have tried using a mutex to lock before every write as well as using different PlacyrClients for the stuff that should be written. 

The opaque data I am sending has a size of 4380 byte. Is there any risk of the playerserver incoming message buffer not being large enough, so that messages overwrite each other under some kind of circumstances? I have tried to change the message size but the crash behavior seems to be the same regardless of message size. I have tried up to 4752060 bytes. And also very low values, around 200 bytes.

Can any problems be expected when reading (ReadIfWating) and writing in different threads. Could it be dangerous to read and write at the same time? 

I am going to replace the opaque proxy with a normal position2d proxy and see if the problem remains. Of course I cant send the same kind of data. I just want to see what happens.  

Peter

-----Original Message-----
From: Peter Nordin [mailto:pet...@li...]
Sent: Mon 12/15/2008 9:48 PM
To: pla...@li...
Subject: RE: [Playerstage-developers] Player crash (sometimes) when	receiving opaque messages
 
Ok, that sounds reasonable, thank you. I am going to try this tomorrow afternoon. Either by splitting it up into several different player clients or by adding a "write mutex" to prevent double writing. I will post my results after I have tried it.

/Peter


-----Original Message-----
From: Toby Collett [mailto:tco...@pl...]
Sent: Mon 12/15/2008 9:31 PM
To: pla...@li...
Subject: Re: [Playerstage-developers] Player crash (sometimes) when	receiving opaque messages
 
In the past these sorts of errors have related to two threads sending
commands through a single client at the same time. I suspect this is what is
happening in your case. Basically the command data ends up interleaved on
the socket and so player gets a corrupt header which then causes the rest of
the problems. Possibly we should stick a checksum on the header to protect
against this in the future...

However to actually fix the problem you will either need seperate clients
for each thread to to implement a locking mechanism so your client threads
dont both send commands at the same time.

Toby

2008/12/16 Peter Nordin <pet...@li...>

> I am not using boost enabled multithreading. But I am using my own threads
> (pthread). In one of these threads the opaqueproxy send command is called.
> The crash is happening at the server side. The playerserver crashes when it
> receives an opaque message that has be corrupted or something. Right now
> both client and server is running on the same computer. But if I run the
> relay driver on another computer it is that computer that crashes instead.
> So the player server receiving the faulty messages is the one that crashes.
> It only seems to be the opaque messages that are affected. I am also using
> sick lasers and psoition2d interfaces at the same time and they all seem to
> work fine. The opaque messages work for a while (not long usually the
> problem occurs within a minute). I am not sure if my code somewhere does
> something wrong or if there is something wrong in player itself. Thats why a
> was asking if anyone can confirm that it should work. If anyone has tried it
> and been successful than I probably have something wrong in my code.
>
> Peter
>
>
> -----Original Message-----
> From: Toby Collett [mailto:tco...@pl...<tcollett%2Bp...@pl...>
> ]
> Sent: Mon 12/15/2008 8:21 PM
> To: pla...@li...
> Subject: Re: [Playerstage-developers] Player crash (sometimes) when
> receiving opaque messages
>
> Are the crashes happening on the server side or the client side? and also,
> are you trying to run a multithreaded client?
>
> Toby
>
>
>
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