472,353 Members | 1,723 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

Join Bytes to post your question to a community of 472,353 software developers and data experts.

More than 1024 connections from the same c-client


We have an application running on Linux (SuSE 7.2, kernel 2.4.16) that
opens lots of connections to a Postgres database and occasionaly dies
with segfault. Trying to reproduce the crash, I came up with the
following test code:

--------------------- pgsql-test.c ---------------------
#include <stdio.h>
#include <libpq-fe.h>

int main(int argc, char **argv)
PGconn *conn;
int i;

for (i = 0; i < 2048; i++)
conn = PQsetdbLogin("localhost", "5432", NULL, NULL,
"template1", "postgres", NULL);

if (PQstatus(conn) == CONNECTION_BAD)
printf("%5d: Connection to database FAILED\n", i+1);
printf("%5d: Connection to database OK\n", i+1);

if (i > 1010)

// PQfinish(conn);

// sleep(300);
return 0;

The test program segfaults after it opens 1020 connections. Then it has
exactly 1024 open file descriptors, including stdin, stdout, stderr and
a file descriptor on /proc/sys/kernel/shmmax.

The system limits on open file descriptors is set to 65535 (both ulimit
and /proc/sys/fs/file-max). It's not related to the max-backends limit
in postmaster either. The test program crashes even if postmaster is not
running at all.

The program seems to crash when it returns from pqWaitTimed(). As
pqWaitTimed uses select() to poll the file descriptors, I suppose the
crash is related to the limit of 1024 file descriptors that fd_set can hold.

The weird thing is that it's not the select() that segfaults. The
segfault occurs on return from pqWaitTimed(). It is 100% reproduceable
on one machine, but it doesn't crash on another one. GDB can't show a
backtrace from the core file:

(gdb) bt
#0 0x08049ab3 in connectDBComplete ()
Cannot access memory at address 0x1

When stepping through the program in gdb, I can see the "conn" pointer
getting lost after on the 1021st connect when pqWaitTimed() returns. So
it looks like the return stack gets corrupted or something like that.

Can anyone confirm this? Am I missing anything here?

Any idea how to get more than 1024 connections with one backend?

---------------------------(end of broadcast)---------------------------
TIP 4: Don't 'kill -9' the postmaster

Nov 11 '05 #1
0 1130

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

by: mike420 | last post by:
In the context of LATEX, some Pythonista asked what the big successes of Lisp were. I think there were at least three *big* successes. a....
by: Alan Gifford | last post by:
I wrote a program to make sure that new would throw a bad_alloc exception if more memory was requested than was available. On my system, new...
by: Bob Karaban | last post by:
We ran into a problem using VirtualAllocEx and were wondering if anybody has a way around this. We have an executable that stores a hash table in a...
by: dave | last post by:
i suspect i know the answer to this already, but here goes anyway.... i have a table that has field of varchar(2048), which once in a blue moon i...
by: Andreas Muck | last post by:
Hi! We have an application running on Linux (SuSE 7.2, kernel 2.4.16) that opens lots of connections to a Postgres database and occasionaly dies...
by: ultraton | last post by:
While trying to print a report from Access the user receives the following error: Cannot open any more databases. Okay Help Does anyone...
by: RC | last post by:
What would limit the amount of data that can be written to disk in an ASP.NET Web application? I've looked in the application's Web.config and...
by: Edward W. | last post by:
hello, I have this function below which is simple and easy to understand private function ListHeight (byval UserScreenHeight as int) as int if...
by: Johan Johansson (Sweden) | last post by:
I wonder why it is that no more than 10 clients can access a webservice at a time, and how to increase that number. The eleventh client get a...
by: Gellert, Andre | last post by:
Hello, we installed a new Postgres 7.4.0 on a Suse 9 system. This is used as a part of an extranet , based on Apache+PHP and has besides a ldap...
by: Kemmylinns12 | last post by:
Blockchain technology has emerged as a transformative force in the business world, offering unprecedented opportunities for innovation and...
by: Matthew3360 | last post by:
Hi there. I have been struggling to find out how to use a variable as my location in my header redirect function. Here is my code. ...
by: Matthew3360 | last post by:
Hi, I have a python app that i want to be able to get variables from a php page on my webserver. My python app is on my computer. How would I make it...
by: AndyPSV | last post by:
HOW CAN I CREATE AN AI with an .executable file that would suck all files in the folder and on my computerHOW CAN I CREATE AN AI with an .executable...
by: Arjunsri | last post by:
I have a Redshift database that I need to use as an import data source. I have configured the DSN connection using the server, port, database, and...
by: WisdomUfot | last post by:
It's an interesting question you've got about how Gmail hides the HTTP referrer when a link in an email is clicked. While I don't have the specific...
by: Oralloy | last post by:
Hello Folks, I am trying to hook up a CPU which I designed using SystemC to I/O pins on an FPGA. My problem (spelled failure) is with the...
by: Carina712 | last post by:
Setting background colors for Excel documents can help to improve the visual appeal of the document and make it easier to read and understand....
by: BLUEPANDA | last post by:
At BluePanda Dev, we're passionate about building high-quality software and sharing our knowledge with the community. That's why we've created a SaaS...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.