Обсуждение: Problems with C Language Functions after upgrade to 7.3.2

Last friday we did an upgrade from postgres 7.1.3 to 7.3.2. In the
database there are triggers written in C, which start external programs
using the system calls fork+exec.
In 7.1.3 triggers worked fine. With 7.3.2 triggers work in most cases
but in some cases execution fails at fork or exec.

Any ideas?

Stefan


PS: We recompiled the shared libraries for 7.3.2. OS is Redhat Linux 7.1

--
-----------------------------
Dr. Stefan Holzheu
Tel.: 0921/55-5720
Fax.: 0921/55-5799
BITOeK Wiss. Sekretariat
Universitaet Bayreuth
D-95440 Bayreuth
-----------------------------

Stefan Holzheu <stefan.holzheu@bitoek.uni-bayreuth.de> writes:
> Last friday we did an upgrade from postgres 7.1.3 to 7.3.2. In the
> database there are triggers written in C, which start external programs
> using the system calls fork+exec.
> In 7.1.3 triggers worked fine. With 7.3.2 triggers work in most cases
> but in some cases execution fails at fork or exec.

Fails how?  What's the error code exactly?

The notion of running external programs from a trigger strikes me as a
really bad idea in any case.  (What happens if the transaction gets
rolled back later?  You won't be able to undo whatever the external
program did.)  But I don't know any reason why it would work less well
now than in 7.1.

            regards, tom lane

Thank, for the fast response

>>In 7.1.3 triggers worked fine. With 7.3.2 triggers work in most cases
>>but in some cases execution fails at fork or exec.

>
> Fails how?  What's the error code exactly?

fork: errno 2  /* No such file or directory */
exec: errno 11 /* Try again */

>
> The notion of running external programs from a trigger strikes me as a
> really bad idea in any case.  (What happens if the transaction gets
> rolled back later?  You won't be able to undo whatever the external
> program did.)

That's true, and we are aware of this problem. But it is still better to
have the database to do this than a web server.
Would you prefere to use a normal function?

Thanks in advance

    Stefan


> But I don't know any reason why it would work less well
> now than in 7.1.
>
>             regards, tom lane
>
>
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--
-----------------------------
Dr. Stefan Holzheu
Tel.: 0921/55-5720
Fax.: 0921/55-5799
BITOeK Wiss. Sekretariat
Universitaet Bayreuth
D-95440 Bayreuth
-----------------------------

Stefan Holzheu <stefan.holzheu@bitoek.uni-bayreuth.de> writes:
> In 7.1.3 triggers worked fine. With 7.3.2 triggers work in most cases
> but in some cases execution fails at fork or exec.

>> Fails how?  What's the error code exactly?

> fork: errno 2  /* No such file or directory */
> exec: errno 11 /* Try again */

Hmm.  You mean the other way round, I assume, because ENOENT surely
makes no sense for fork().

System resource exhaustion problems, maybe?  EAGAIN for fork() strongly
suggests that.  Perhaps you are running into a ulimit-like limit, such
as max processes per user?  Not sure about ENOENT --- are you giving an
absolute path to locate the program to execute?

            regards, tom lane