--- In firebird-support@yahoogroups.com, "precari0" <douglas@...> wrote:

>
> Hi!
>
> I´m having problems with a multi-threaded middle-tier I´m working on.
> Every now and then I get "invalid request handle" errors. At first I
> thought I could be messing with the connection pool and two threads
> could be trying to use the same connection at the same time. But after
> a deeper analisys I realize that is not the problem. Imagine the
> following:
>
> - Thread T1 creates connection C1 and uses it for some select/update.
> - C1 returns to the pool, waiting for new requests.
> - Thread T2 uses C1 for some operations.
> - C1 is in use by T2, a new request arrives.
> - Now T3 creates C2 and uses it for some operations.
> - C1 returns to the pool.
> - C2 returns to the pool.
>
> Is this sequence correct from a thread-safe perspective? Should it work?
> If this kind of sequence goes on for a while, the "invalid request
> handle" appears. But if I change my app so that every thread gets its
> own unique connection, the problem doesn´t happen. For example:
>
> - Thread T1 creates connection C1 and uses it for some select/update
> - C1 *does not* return to the pool, it is locked to T1
> - T2 creates C2, uses it for some operations and keeps it for later use
> - T3 creates C3, uses it for some operations and keeps it for later use
>
> It seems to me that it has something to do with the connection being
> created by a certain thread and later on being used by another thread.
> How can I track down this problem? I thought of posting a stack-trace
> including fbclient´s stack but I don´t know how to do it.
>
> The problem happens with FB 1.0.3, 1.5.3, 2.0RC3 and RC4.
> I´m using Delphi 6.
> The connection pool is RemObjects´s DataAbstract.
> The problem happens with FIBPlus, IBObjects and IBX.
>
> Any help greatly appreciated.
> Thanks and sorry my poor English.

FBClient is not threadsafe.

You must either:

Give each thread its own connection component, or make sure using
critical sections or equiv that at most a single thread is using a
single connection at a time.

Adam