Re: [Firebird-devel] Max transaction duration

[Pavel C. <pc...@us...>]

David,

On 13 Dec 2002 at 10:02, David Jencks wrote:

> Resource manager == database == firebird engine:-)

Ah, I see :-)

> While it might be possible to  put a timeout manager on the client side of
> the connection, I dont' think there is any way to make it as reliable as
> putting it on the engine/server side.  I think there will always be some
> failure modes where the connection is not killed but the remote timeout
> manager stops working.

There should not be any such modes that will leave the dead connection 
open forever. Server should always notice, sooner or later, that 
connection is dead/broken. Of course, this doesn't solve the problem when 
client gets a connection and then goes to infinite loop. I agree that we 
should handle that in some way, to prevent malicious code or DOS attacks, 
but this is still IMO related to connections, not transaction level.

> I think your argument at root is that the "lost connection" detection by
> firebird is sufficient to detect problems.  I dont'  completely know how
> this works but think it is based on a heartbeat of some kind, pinging the
> clients.  is this correct?

Yes (see my reply to Ivan in this thread). Actually, the code is pretty 
tricky and depends on some assumptions about connection behaviour at OS 
level. I have my doubts about the quality of this code and its design, 
because I saw over years many different kind of troubles tracked to it in 
some way.
 
> I still think that transaction timeouts would be a really useful  and
> standard feature, although they don't appear to fit in the Delphi
> transaction model if I remember correctly.

First, what's the definition of "timeout" ? Total amount of time ? Total 
time of inactivity ?  

What's more important to you, transaction or connection timeout ? 
Connection timeout is there already, and could be improved (for example: 
closing connection after some time of inactivity at FB protocol level).

Best regards
Pavel Cisar
http://www.ibphoenix.com
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