Ruby blocks... forever

ruby-talk
1

Ruby 1.8.1preview2, running on Debian Linux. Server is WEBrick based,
and the main extensions used are Ruby/ODBC and Ruby/Postgres.

I just tried to put the server in to production (approximately an
exponential increase in users, although it was done at a lower-traffic
time of day) and Ruby decided to hang on me. Here’s the appropriate
line from top:

 PID USER      RSS WCHAN        FLAGS LC STAT %CPU %MEM   TIME

COMMAND
16419 se 15M rt_sigsus 40 0 S 0.0 1.7 24:52 server

Although I’m not sure, I think the WCHAN indicates that the process is
blocked waiting for something to happen. What, I don’t know.

I suspect Ruby/ODBC as the culprit, but here are my questions:

  1. What could cause such a hang? Where should I even begin looking?
  2. The process is still sitting there, doing nothing. Is there any
    more information I can get out of it before I kill it?

Thanks,

Nathaniel

<:((><

2

   16419 se 15M rt_sigsus 40 0 S 0.0 1.7 24:52 server

rt_sigsuspend

to it use pthread ?

Guy Decoux

3

“Nathaniel Talbott” nathaniel@talbott.ws schrieb im Newsbeitrag
news:FCD7172F-2984-11D8-9E0C-000A95CD7A8E@talbott.ws…

Ruby 1.8.1preview2, running on Debian Linux. Server is WEBrick based,
and the main extensions used are Ruby/ODBC and Ruby/Postgres.

I just tried to put the server in to production (approximately an
exponential increase in users, although it was done at a lower-traffic
time of day) and Ruby decided to hang on me. Here’s the appropriate
line from top:

 PID USER      RSS WCHAN        FLAGS LC STAT %CPU %MEM   TIME

COMMAND
16419 se 15M rt_sigsus 40 0 S 0.0 1.7 24:52
server

Although I’m not sure, I think the WCHAN indicates that the process is
blocked waiting for something to happen. What, I don’t know.

I suspect Ruby/ODBC as the culprit, but here are my questions:

  1. What could cause such a hang? Where should I even begin looking?

Database transaction deadlocks

  1. The process is still sitting there, doing nothing. Is there any
    more information I can get out of it before I kill it?

Hm, dunno.

robert
4

I can find no evidence that Ruby/ODBC or FreeTDS (which I’m using
Ruby/ODBC to access) use pthreads, although I admittedly do not know
much about how to look. I have no earthly idea whether Ruby/Postgres
uses pthreads, but I suspect it doesn’t.

Nathaniel

<:((><

···

On Dec 8, 2003, at 08:52, ts wrote:

16419 se 15M rt_sigsus 40 0 S 0.0 1.7 24:52
server

rt_sigsuspend

to it use pthread ?

5

I can find no evidence that Ruby/ODBC or FreeTDS (which I’m using
Ruby/ODBC to access) use pthreads, although I admittedly do not know
much about how to look. I have no earthly idea whether Ruby/Postgres
uses pthreads, but I suspect it doesn’t.

svg% ldd ruby
libpthread.so.0 => /lib/i686/libpthread.so.0 (0x40027000)
libdl.so.2 => /lib/libdl.so.2 (0x40078000)
libcrypt.so.1 => /lib/libcrypt.so.1 (0x4007b000)
libm.so.6 => /lib/i686/libm.so.6 (0x400a8000)
libc.so.6 => /lib/i686/libc.so.6 (0x42000000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
svg%

Guy Decoux

6

OK, it appears that Ruby/ODBC and FreeTDS’s ODBC layer both link to
libpthread (though I don’t really understand why; grepping for pthread
in their source turns up nothing interesting). What does that mean?

Nathaniel

<:((><

···

On Dec 8, 2003, at 09:36, ts wrote:

I can find no evidence that Ruby/ODBC or FreeTDS (which I’m using
Ruby/ODBC to access) use pthreads, although I admittedly do not know
much about how to look. I have no earthly idea whether Ruby/Postgres
uses pthreads, but I suspect it doesn’t.

svg% ldd ruby
libpthread.so.0 => /lib/i686/libpthread.so.0 (0x40027000)
libdl.so.2 => /lib/libdl.so.2 (0x40078000)
libcrypt.so.1 => /lib/libcrypt.so.1 (0x4007b000)
libm.so.6 => /lib/i686/libm.so.6 (0x400a8000)
libc.so.6 => /lib/i686/libc.so.6 (0x42000000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
svg%

7

OK, it appears that Ruby/ODBC and FreeTDS’s ODBC layer both link to
libpthread (though I don’t really understand why; grepping for pthread
in their source turns up nothing interesting). What does that mean?

This mean that it can exist a thread synchronisation problem, and perhaps
it’s best to use the latest CVS version of ruby

Guy Decoux

p.s. : the email address in the Cc: is invalid

8

OK… do I need to use --with-pthread-ext when I build?

Thanks,

Nathaniel

<:((><

···

On Dec 8, 2003, at 10:03, ts wrote:

OK, it appears that Ruby/ODBC and FreeTDS’s ODBC layer both link to
libpthread (though I don’t really understand why; grepping for
pthread
in their source turns up nothing interesting). What does that mean?

This mean that it can exist a thread synchronisation problem, and
perhaps
it’s best to use the latest CVS version of ruby

9

OK... do I need to use --with-pthread-ext when I build?

Probably best but this is the option

   --enable-pthread

Guy Decoux

10

OK.

Now, can you or someone else help me understand what this option
actually does? And why, if it’s such a problem, it hasn’t showed up
before and it isn’t on by default? Was every extension linked to
pthread before doomed to lock up eventually?

Thanks,

Nathaniel

<:((><

···

On Dec 8, 2003, at 10:23, ts wrote:

OK… do I need to use --with-pthread-ext when I build?

Probably best but this is the option

–enable-pthread

11

Now, can you or someone else help me understand what this option
actually does?

it compile ruby with -lpthread to be sure that the thread system is
correctly initialized.

               And why, if it's such a problem, it hasn't showed up
before and it isn't on by default?

If I've well understood : it not by default because it can cause problems
on some architecture (*BSD ???)

                                   Was every extension linked to
pthread before doomed to lock up eventually?

Don't expect that one day I can understand pthread :frowning:

In the distribution of bdbxml, you have

# it's important to have xercesc compiled with -rnone
# (i.e. *without* threads)

because if xerces-c is compiled with pthread you'll see strange problems

Guy Decoux

12

Thanks, Guy, that helps me understand things better.

Nathaniel

<:((><

···

On Dec 8, 2003, at 10:38, ts wrote:

Now, can you or someone else help me understand what this option
actually does?

it compile ruby with -lpthread to be sure that the thread system is
correctly initialized.

           And why, if it's such a problem, it hasn't showed up

before and it isn’t on by default?

If I’ve well understood : it not by default because it can cause
problems
on some architecture (*BSD ???)

                               Was every extension linked to

pthread before doomed to lock up eventually?

Don’t expect that one day I can understand pthread :frowning:

In the distribution of bdbxml, you have

it’s important to have xercesc compiled with -rnone

(i.e. without threads)

because if xerces-c is compiled with pthread you’ll see strange
problems