Re: [HACKERS] panic on 7.3
Rick Gigger [EMAIL PROTECTED] writes: I got this message: 2006-01-20 11:50:51 PANIC: creation of file /var/lib/pgsql/data/ pg_clog/0292 failed: File exists In 7.3. It caused the server to restart. Can anyone tell me what it means? 7.3.what? What file names exist in the pg_clog directory? regards, tom lane ---(end of broadcast)--- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
Re: [HACKERS] panic on 7.3
Postgres version 7.3.4 ... a whole bunch of other files -rw--- 1 postgres postgres 262144 Jan 18 22:42 027D -rw--- 1 postgres postgres 262144 Jan 19 07:38 027E -rw--- 1 postgres postgres 262144 Jan 19 08:25 027F -rw--- 1 postgres postgres 262144 Jan 19 09:07 0280 -rw--- 1 postgres postgres 262144 Jan 19 09:59 0281 -rw--- 1 postgres postgres 262144 Jan 19 11:07 0282 -rw--- 1 postgres postgres 262144 Jan 19 12:22 0283 -rw--- 1 postgres postgres 262144 Jan 19 13:29 0284 -rw--- 1 postgres postgres 262144 Jan 19 14:26 0285 -rw--- 1 postgres postgres 262144 Jan 19 15:58 0286 -rw--- 1 postgres postgres 262144 Jan 19 19:55 0287 -rw--- 1 postgres postgres 262144 Jan 19 23:47 0288 -rw--- 1 postgres postgres 262144 Jan 20 02:35 0289 -rw--- 1 postgres postgres 262144 Jan 20 04:21 028A -rw--- 1 postgres postgres 262144 Jan 20 06:16 028B -rw--- 1 postgres postgres 262144 Jan 20 07:20 028C -rw--- 1 postgres postgres 262144 Jan 20 08:22 028D -rw--- 1 postgres postgres 262144 Jan 20 09:24 028E -rw--- 1 postgres postgres 262144 Jan 20 10:24 028F -rw--- 1 postgres postgres 262144 Jan 20 11:04 0290 -rw--- 1 postgres postgres 262144 Jan 20 11:50 0291 -rw--- 1 postgres postgres 262144 Jan 20 13:27 0292 -rw--- 1 postgres postgres 262144 Jan 20 14:24 0293 -rw--- 1 postgres postgres 262144 Jan 20 14:53 0294 -rw--- 1 postgres postgres 262144 Jan 20 17:10 0295 That is right now. Right after it started up it went up to 0292. There are a lot of files before the ones listed here right now though. Do you need to see their names? On Jan 20, 2006, at 3:58 PM, Tom Lane wrote: Rick Gigger [EMAIL PROTECTED] writes: I got this message: 2006-01-20 11:50:51 PANIC: creation of file /var/lib/pgsql/data/ pg_clog/0292 failed: File exists In 7.3. It caused the server to restart. Can anyone tell me what it means? 7.3.what? What file names exist in the pg_clog directory? regards, tom lane ---(end of broadcast)--- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org
Re: [HACKERS] panic on 7.3
Rick Gigger wrote: Postgres version 7.3.4 ... a whole bunch of other files -rw--- 1 postgres postgres 262144 Jan 18 22:42 027D -rw--- 1 postgres postgres 262144 Jan 19 07:38 027E -rw--- 1 postgres postgres 262144 Jan 19 08:25 027F -rw--- 1 postgres postgres 262144 Jan 19 09:07 0280 -rw--- 1 postgres postgres 262144 Jan 19 09:59 0281 -rw--- 1 postgres postgres 262144 Jan 19 11:07 0282 -rw--- 1 postgres postgres 262144 Jan 19 12:22 0283 -rw--- 1 postgres postgres 262144 Jan 19 13:29 0284 -rw--- 1 postgres postgres 262144 Jan 19 14:26 0285 -rw--- 1 postgres postgres 262144 Jan 19 15:58 0286 -rw--- 1 postgres postgres 262144 Jan 19 19:55 0287 -rw--- 1 postgres postgres 262144 Jan 19 23:47 0288 -rw--- 1 postgres postgres 262144 Jan 20 02:35 0289 -rw--- 1 postgres postgres 262144 Jan 20 04:21 028A -rw--- 1 postgres postgres 262144 Jan 20 06:16 028B -rw--- 1 postgres postgres 262144 Jan 20 07:20 028C -rw--- 1 postgres postgres 262144 Jan 20 08:22 028D -rw--- 1 postgres postgres 262144 Jan 20 09:24 028E -rw--- 1 postgres postgres 262144 Jan 20 10:24 028F -rw--- 1 postgres postgres 262144 Jan 20 11:04 0290 -rw--- 1 postgres postgres 262144 Jan 20 11:50 0291 -rw--- 1 postgres postgres 262144 Jan 20 13:27 0292 -rw--- 1 postgres postgres 262144 Jan 20 14:24 0293 -rw--- 1 postgres postgres 262144 Jan 20 14:53 0294 -rw--- 1 postgres postgres 262144 Jan 20 17:10 0295 That is right now. Right after it started up it went up to 0292. There are a lot of files before the ones listed here right now though. Do you need to see their names? I assume you are missing one of these fixes in 7.3.X current which were done _after_ 7.3.4 was released: * Fix race condition in transaction log management There was a narrow window in which an I/O operation could be initiated for the wrong page, leading to an Assert failure or data corruption. * Repair incorrect order of operations in GetNewTransactionId() This bug could result in failure under out-of-disk-space conditions, including inability to restart even after disk space is freed. --- On Jan 20, 2006, at 3:58 PM, Tom Lane wrote: Rick Gigger [EMAIL PROTECTED] writes: I got this message: 2006-01-20 11:50:51 PANIC: creation of file /var/lib/pgsql/data/ pg_clog/0292 failed: File exists In 7.3. It caused the server to restart. Can anyone tell me what it means? 7.3.what? What file names exist in the pg_clog directory? regards, tom lane ---(end of broadcast)--- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org -- Bruce Momjian| http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup.| Newtown Square, Pennsylvania 19073 ---(end of broadcast)--- TIP 6: explain analyze is your friend
Re: [HACKERS] panic on 7.3
It is the version that shipped with fedora core 1. The version string from psql is (PostgreSQL) 7.3.4-RH. I assume that it must have been the first bug since I had plenty of disk space. On Jan 20, 2006, at 5:35 PM, Bruce Momjian wrote: Rick Gigger wrote: Postgres version 7.3.4 ... a whole bunch of other files -rw--- 1 postgres postgres 262144 Jan 18 22:42 027D -rw--- 1 postgres postgres 262144 Jan 19 07:38 027E -rw--- 1 postgres postgres 262144 Jan 19 08:25 027F -rw--- 1 postgres postgres 262144 Jan 19 09:07 0280 -rw--- 1 postgres postgres 262144 Jan 19 09:59 0281 -rw--- 1 postgres postgres 262144 Jan 19 11:07 0282 -rw--- 1 postgres postgres 262144 Jan 19 12:22 0283 -rw--- 1 postgres postgres 262144 Jan 19 13:29 0284 -rw--- 1 postgres postgres 262144 Jan 19 14:26 0285 -rw--- 1 postgres postgres 262144 Jan 19 15:58 0286 -rw--- 1 postgres postgres 262144 Jan 19 19:55 0287 -rw--- 1 postgres postgres 262144 Jan 19 23:47 0288 -rw--- 1 postgres postgres 262144 Jan 20 02:35 0289 -rw--- 1 postgres postgres 262144 Jan 20 04:21 028A -rw--- 1 postgres postgres 262144 Jan 20 06:16 028B -rw--- 1 postgres postgres 262144 Jan 20 07:20 028C -rw--- 1 postgres postgres 262144 Jan 20 08:22 028D -rw--- 1 postgres postgres 262144 Jan 20 09:24 028E -rw--- 1 postgres postgres 262144 Jan 20 10:24 028F -rw--- 1 postgres postgres 262144 Jan 20 11:04 0290 -rw--- 1 postgres postgres 262144 Jan 20 11:50 0291 -rw--- 1 postgres postgres 262144 Jan 20 13:27 0292 -rw--- 1 postgres postgres 262144 Jan 20 14:24 0293 -rw--- 1 postgres postgres 262144 Jan 20 14:53 0294 -rw--- 1 postgres postgres 262144 Jan 20 17:10 0295 That is right now. Right after it started up it went up to 0292. There are a lot of files before the ones listed here right now though. Do you need to see their names? I assume you are missing one of these fixes in 7.3.X current which were done _after_ 7.3.4 was released: * Fix race condition in transaction log management There was a narrow window in which an I/O operation could be initiated for the wrong page, leading to an Assert failure or data corruption. * Repair incorrect order of operations in GetNewTransactionId() This bug could result in failure under out-of-disk-space conditions, including inability to restart even after disk space is freed. -- - On Jan 20, 2006, at 3:58 PM, Tom Lane wrote: Rick Gigger [EMAIL PROTECTED] writes: I got this message: 2006-01-20 11:50:51 PANIC: creation of file /var/lib/pgsql/data/ pg_clog/0292 failed: File exists In 7.3. It caused the server to restart. Can anyone tell me what it means? 7.3.what? What file names exist in the pg_clog directory? regards, tom lane ---(end of broadcast)--- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org -- Bruce Momjian| http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup.| Newtown Square, Pennsylvania 19073 ---(end of broadcast)--- TIP 6: explain analyze is your friend ---(end of broadcast)--- TIP 6: explain analyze is your friend
Re: [HACKERS] panic on 7.3
Updates for FC1 are available here: http://download.fedoralegacy.org/fedora/1/updates/i386/ they have 7.3.9 dated in March last year. Or grab the source for 7.3.13 and build it yourself. cheers andrew Rick Gigger wrote: It is the version that shipped with fedora core 1. The version string from psql is (PostgreSQL) 7.3.4-RH. I assume that it must have been the first bug since I had plenty of disk space. On Jan 20, 2006, at 5:35 PM, Bruce Momjian wrote: Rick Gigger wrote: Postgres version 7.3.4 ... a whole bunch of other files -rw--- 1 postgres postgres 262144 Jan 18 22:42 027D -rw--- 1 postgres postgres 262144 Jan 19 07:38 027E -rw--- 1 postgres postgres 262144 Jan 19 08:25 027F -rw--- 1 postgres postgres 262144 Jan 19 09:07 0280 -rw--- 1 postgres postgres 262144 Jan 19 09:59 0281 -rw--- 1 postgres postgres 262144 Jan 19 11:07 0282 -rw--- 1 postgres postgres 262144 Jan 19 12:22 0283 -rw--- 1 postgres postgres 262144 Jan 19 13:29 0284 -rw--- 1 postgres postgres 262144 Jan 19 14:26 0285 -rw--- 1 postgres postgres 262144 Jan 19 15:58 0286 -rw--- 1 postgres postgres 262144 Jan 19 19:55 0287 -rw--- 1 postgres postgres 262144 Jan 19 23:47 0288 -rw--- 1 postgres postgres 262144 Jan 20 02:35 0289 -rw--- 1 postgres postgres 262144 Jan 20 04:21 028A -rw--- 1 postgres postgres 262144 Jan 20 06:16 028B -rw--- 1 postgres postgres 262144 Jan 20 07:20 028C -rw--- 1 postgres postgres 262144 Jan 20 08:22 028D -rw--- 1 postgres postgres 262144 Jan 20 09:24 028E -rw--- 1 postgres postgres 262144 Jan 20 10:24 028F -rw--- 1 postgres postgres 262144 Jan 20 11:04 0290 -rw--- 1 postgres postgres 262144 Jan 20 11:50 0291 -rw--- 1 postgres postgres 262144 Jan 20 13:27 0292 -rw--- 1 postgres postgres 262144 Jan 20 14:24 0293 -rw--- 1 postgres postgres 262144 Jan 20 14:53 0294 -rw--- 1 postgres postgres 262144 Jan 20 17:10 0295 That is right now. Right after it started up it went up to 0292. There are a lot of files before the ones listed here right now though. Do you need to see their names? I assume you are missing one of these fixes in 7.3.X current which were done _after_ 7.3.4 was released: * Fix race condition in transaction log management There was a narrow window in which an I/O operation could be initiated for the wrong page, leading to an Assert failure or data corruption. * Repair incorrect order of operations in GetNewTransactionId() This bug could result in failure under out-of-disk-space conditions, including inability to restart even after disk space is freed. -- - On Jan 20, 2006, at 3:58 PM, Tom Lane wrote: Rick Gigger [EMAIL PROTECTED] writes: I got this message: 2006-01-20 11:50:51 PANIC: creation of file /var/lib/pgsql/data/ pg_clog/0292 failed: File exists In 7.3. It caused the server to restart. Can anyone tell me what it means? 7.3.what? What file names exist in the pg_clog directory? regards, tom lane ---(end of broadcast)--- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org -- Bruce Momjian| http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup.| Newtown Square, Pennsylvania 19073 ---(end of broadcast)--- TIP 6: explain analyze is your friend ---(end of broadcast)--- TIP 6: explain analyze is your friend ---(end of broadcast)--- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
Re: [HACKERS] panic on 7.3
Rick Gigger [EMAIL PROTECTED] writes:
Postgres version 7.3.4
You realize of course that that's pretty old ...
That is right now. Right after it started up it went up to 0292.
So it was the latest file eh? I thought maybe you had some problem
with a corrupted XID leading to trying to touch a clog file
out-of-order, but that seems ruled out.
2006-01-20 11:50:51 PANIC: creation of file /var/lib/pgsql/data/
pg_clog/0292 failed: File exists
Digging in the 7.3 sources, it seems that error message could only have
come from here:
fd = BasicOpenFile(path, O_RDWR | PG_BINARY, S_IRUSR | S_IWUSR);
if (fd 0)
{
if (errno != ENOENT)
elog(PANIC, open of %s failed: %m, path);
fd = BasicOpenFile(path, O_RDWR | O_CREAT | O_EXCL | PG_BINARY,
S_IRUSR | S_IWUSR);
if (fd 0)
elog(PANIC, creation of file %s failed: %m, path);
}
AFAICS, it is simply not possible for the second open() to fail with
that errno, *unless* someone else created the same file in the
microseconds between the two open calls.
The code doing this has a lock on the particular clog buffer it's trying
to write out, so no-one else could be trying to write the same buffer;
but now that I look at it, it's entirely legal for someone else to be
trying to write a different clog buffer. This leads to the following
theory:
1. The clog page that would be first in the 0292 segment got created in
clog buffers, but there was no reason to write it out for awhile. (In
normal operation, only a checkpoint would be cause to write out the
frontmost page of clog.)
2. More than 2K transactions elapsed, so the page that would be second
in the 0292 segment also got set up in clog buffers. (Rick, is the load
on your machine such that several thousand transactions might have
elapsed between checkpoints?) Perhaps there were even enough
transactions so that more than two pages were dirty and pending write
in the clog buffers, yet the file hadn't been created yet.
3. Two different backends decided to try to write different clog pages
concurrently. Probably one was writing the frontmost page because it
was doing a checkpoint, and another needed to read in an older clog page
so it had to swap out one of the other dirty buffers.
4. Kaboom.
If this theory is correct, the bug has been there since the clog code
was first written. But the conditions for having it happen are narrow
enough that it's not too surprising we haven't seen it before.
I think that a sufficient fix might just be to remove the O_EXCL flag
from the second open() call --- ie, if someone else creates the file
in this narrow window, it should be considered OK. Comments?
regards, tom lane
---(end of broadcast)---
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Re: [HACKERS] panic on 7.3
I wrote: If this theory is correct, the bug has been there since the clog code was first written. But the conditions for having it happen are narrow enough that it's not too surprising we haven't seen it before. Actually, there seem to be a couple of unresolved bug reports that look like the same thing ... http://archives.postgresql.org/pgsql-hackers/2006-01/msg00216.php http://archives.postgresql.org/pgsql-bugs/2005-12/msg00130.php http://archives.postgresql.org/pgsql-general/2005-10/msg00975.php The spelling of the message has changed since 7.3, but the code behavior is still fundamentally the same. regards, tom lane ---(end of broadcast)--- TIP 6: explain analyze is your friend
Re: [HACKERS] panic on 7.3
Thanks. I'm not quite sure what version I am going to upgrade to yet. Rick On Jan 20, 2006, at 5:59 PM, Andrew Dunstan wrote: Updates for FC1 are available here: http://download.fedoralegacy.org/fedora/1/updates/i386/ they have 7.3.9 dated in March last year. Or grab the source for 7.3.13 and build it yourself. cheers andrew Rick Gigger wrote: It is the version that shipped with fedora core 1. The version string from psql is (PostgreSQL) 7.3.4-RH. I assume that it must have been the first bug since I had plenty of disk space. On Jan 20, 2006, at 5:35 PM, Bruce Momjian wrote: Rick Gigger wrote: Postgres version 7.3.4 ... a whole bunch of other files -rw--- 1 postgres postgres 262144 Jan 18 22:42 027D -rw--- 1 postgres postgres 262144 Jan 19 07:38 027E -rw--- 1 postgres postgres 262144 Jan 19 08:25 027F -rw--- 1 postgres postgres 262144 Jan 19 09:07 0280 -rw--- 1 postgres postgres 262144 Jan 19 09:59 0281 -rw--- 1 postgres postgres 262144 Jan 19 11:07 0282 -rw--- 1 postgres postgres 262144 Jan 19 12:22 0283 -rw--- 1 postgres postgres 262144 Jan 19 13:29 0284 -rw--- 1 postgres postgres 262144 Jan 19 14:26 0285 -rw--- 1 postgres postgres 262144 Jan 19 15:58 0286 -rw--- 1 postgres postgres 262144 Jan 19 19:55 0287 -rw--- 1 postgres postgres 262144 Jan 19 23:47 0288 -rw--- 1 postgres postgres 262144 Jan 20 02:35 0289 -rw--- 1 postgres postgres 262144 Jan 20 04:21 028A -rw--- 1 postgres postgres 262144 Jan 20 06:16 028B -rw--- 1 postgres postgres 262144 Jan 20 07:20 028C -rw--- 1 postgres postgres 262144 Jan 20 08:22 028D -rw--- 1 postgres postgres 262144 Jan 20 09:24 028E -rw--- 1 postgres postgres 262144 Jan 20 10:24 028F -rw--- 1 postgres postgres 262144 Jan 20 11:04 0290 -rw--- 1 postgres postgres 262144 Jan 20 11:50 0291 -rw--- 1 postgres postgres 262144 Jan 20 13:27 0292 -rw--- 1 postgres postgres 262144 Jan 20 14:24 0293 -rw--- 1 postgres postgres 262144 Jan 20 14:53 0294 -rw--- 1 postgres postgres 262144 Jan 20 17:10 0295 That is right now. Right after it started up it went up to 0292. There are a lot of files before the ones listed here right now though. Do you need to see their names? I assume you are missing one of these fixes in 7.3.X current which were done _after_ 7.3.4 was released: * Fix race condition in transaction log management There was a narrow window in which an I/O operation could be initiated for the wrong page, leading to an Assert failure or data corruption. * Repair incorrect order of operations in GetNewTransactionId() This bug could result in failure under out-of-disk-space conditions, including inability to restart even after disk space is freed. -- - On Jan 20, 2006, at 3:58 PM, Tom Lane wrote: Rick Gigger [EMAIL PROTECTED] writes: I got this message: 2006-01-20 11:50:51 PANIC: creation of file /var/lib/pgsql/data/ pg_clog/0292 failed: File exists In 7.3. It caused the server to restart. Can anyone tell me what it means? 7.3.what? What file names exist in the pg_clog directory? regards, tom lane ---(end of broadcast)--- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org -- Bruce Momjian| http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup.| Newtown Square, Pennsylvania 19073 ---(end of broadcast)--- TIP 6: explain analyze is your friend ---(end of broadcast)--- TIP 6: explain analyze is your friend ---(end of broadcast)--- TIP 6: explain analyze is your friend
Re: [HACKERS] panic on 7.3
=Rick Gigger [EMAIL PROTECTED] writes:
Postgres version 7.3.4
You realize of course that that's pretty old ...
Yes. I will be upgrading immediately.
That is right now. Right after it started up it went up to 0292.
So it was the latest file eh? I thought maybe you had some problem
with a corrupted XID leading to trying to touch a clog file
out-of-order, but that seems ruled out.
Well that sounds like a good thing.
2006-01-20 11:50:51 PANIC: creation of file /var/lib/pgsql/data/
pg_clog/0292 failed: File exists
Digging in the 7.3 sources, it seems that error message could only
have
come from here:
fd = BasicOpenFile(path, O_RDWR | PG_BINARY, S_IRUSR | S_IWUSR);
if (fd 0)
{
if (errno != ENOENT)
elog(PANIC, open of %s failed: %m, path);
fd = BasicOpenFile(path, O_RDWR | O_CREAT | O_EXCL |
PG_BINARY,
S_IRUSR | S_IWUSR);
if (fd 0)
elog(PANIC, creation of file %s failed: %m, path);
}
Yes I found that too (on accident with google) but didn't really have
the slightest clue what exactly would have caused it.
AFAICS, it is simply not possible for the second open() to fail with
that errno, *unless* someone else created the same file in the
microseconds between the two open calls.
The code doing this has a lock on the particular clog buffer it's
trying
to write out, so no-one else could be trying to write the same buffer;
but now that I look at it, it's entirely legal for someone else to be
trying to write a different clog buffer. This leads to the following
theory:
1. The clog page that would be first in the 0292 segment got
created in
clog buffers, but there was no reason to write it out for awhile. (In
normal operation, only a checkpoint would be cause to write out the
frontmost page of clog.)
2. More than 2K transactions elapsed, so the page that would be second
in the 0292 segment also got set up in clog buffers. (Rick, is the
load
on your machine such that several thousand transactions might have
elapsed between checkpoints?) Perhaps there were even enough
transactions so that more than two pages were dirty and pending write
in the clog buffers, yet the file hadn't been created yet.
I don't know if 2K could have passed since the last checkpoint. Part
of the reason I haven't upgraded in so long is that it has been
running like champ for about 3 years. Recently though the load on
the site just shot through the roof. Not only am I going to upgrade
the version of postgres but I need to do some major tuning. I am
still using a lot of defaults. I am using the default checkpoint
settings but I am not sure how often they are happening. Actually
now that I think about it I was getting about 400 pages requests /
minute and each of those would have have been doing at least 2
transactions so yes, I guess that is very likely.
3. Two different backends decided to try to write different clog pages
concurrently. Probably one was writing the frontmost page because it
was doing a checkpoint, and another needed to read in an older clog
page
so it had to swap out one of the other dirty buffers.
4. Kaboom.
Yeah Kaboom. It was really bad timing too. :)
If this theory is correct, the bug has been there since the clog code
was first written. But the conditions for having it happen are narrow
enough that it's not too surprising we haven't seen it before.
Wow it's great to be the first.
I think that a sufficient fix might just be to remove the O_EXCL flag
from the second open() call --- ie, if someone else creates the file
in this narrow window, it should be considered OK. Comments?
Well just a little fyi, I don't know if any of this will help but I
was suffering from severe table bloat. The data in my session table
is unfortunately quite large and being updated constantly so the
session table and it's two indexes and especially it's toast table we
impossible to vacuum. Also the vacuum and fsm settings were the
defaults making the problem worse.
regards, tom lane
Thanks so much for the help.
Rick
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Re: [HACKERS] panic on 7.3
On Jan 20, 2006, at 6:02 PM, Tom Lane wrote:
Rick Gigger [EMAIL PROTECTED] writes:
Postgres version 7.3.4
You realize of course that that's pretty old ...
That is right now. Right after it started up it went up to 0292.
So it was the latest file eh? I thought maybe you had some problem
with a corrupted XID leading to trying to touch a clog file
out-of-order, but that seems ruled out.
2006-01-20 11:50:51 PANIC: creation of file /var/lib/pgsql/data/
pg_clog/0292 failed: File exists
Digging in the 7.3 sources, it seems that error message could only
have
come from here:
fd = BasicOpenFile(path, O_RDWR | PG_BINARY, S_IRUSR | S_IWUSR);
if (fd 0)
{
if (errno != ENOENT)
elog(PANIC, open of %s failed: %m, path);
fd = BasicOpenFile(path, O_RDWR | O_CREAT | O_EXCL |
PG_BINARY,
S_IRUSR | S_IWUSR);
if (fd 0)
elog(PANIC, creation of file %s failed: %m, path);
}
AFAICS, it is simply not possible for the second open() to fail with
that errno, *unless* someone else created the same file in the
microseconds between the two open calls.
The code doing this has a lock on the particular clog buffer it's
trying
to write out, so no-one else could be trying to write the same buffer;
but now that I look at it, it's entirely legal for someone else to be
trying to write a different clog buffer. This leads to the following
theory:
1. The clog page that would be first in the 0292 segment got
created in
clog buffers, but there was no reason to write it out for awhile. (In
normal operation, only a checkpoint would be cause to write out the
frontmost page of clog.)
2. More than 2K transactions elapsed, so the page that would be second
in the 0292 segment also got set up in clog buffers. (Rick, is the
load
on your machine such that several thousand transactions might have
elapsed between checkpoints?) Perhaps there were even enough
transactions so that more than two pages were dirty and pending write
in the clog buffers, yet the file hadn't been created yet.
So what I think I'm getting killed on right now are the disk writes.
So I was thinking of changing away from the default checkpoint
settings. My load is going to continue to go up so 2000+
transactions are going to start happening pretty fast. I have lots
of disk space so I was going to increase the time between
checkpoints. Will that increase the chances of this happening again
or was this such a strange freak of nature coincidence that it can't
really even happen again. Also I've decided to upgrade all the way
to the latest 8.1 code.
3. Two different backends decided to try to write different clog pages
concurrently. Probably one was writing the frontmost page because it
was doing a checkpoint, and another needed to read in an older clog
page
so it had to swap out one of the other dirty buffers.
4. Kaboom.
If this theory is correct, the bug has been there since the clog code
was first written. But the conditions for having it happen are narrow
enough that it's not too surprising we haven't seen it before.
I think that a sufficient fix might just be to remove the O_EXCL flag
from the second open() call --- ie, if someone else creates the file
in this narrow window, it should be considered OK. Comments?
regards, tom lane
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match
Re: [HACKERS] panic on 7.3
Rick Gigger [EMAIL PROTECTED] writes: I don't know if 2K could have passed since the last checkpoint. ... now that I think about it I was getting about 400 pages requests / minute and each of those would have have been doing at least 2 transactions so yes, I guess that is very likely. Good, 'cause if you didn't have a couple thousand transactions between checkpoints then we need another theory ;-) You realize of course that that's pretty old ... Yes. I will be upgrading immediately. You'll want to include this patch: http://archives.postgresql.org/pgsql-committers/2006-01/msg00289.php (or see adjacent messages if you plan to move to something newer than 7.3.*). We probably will not put out another set of releases until next month, unless something really big comes along. This one doesn't qualify as really big IMHO, because it's not a PANIC-grade failure in the later branches. But having been burnt once, I'm sure you'll want a patched copy ... regards, tom lane ---(end of broadcast)--- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
Re: [HACKERS] panic on 7.3
Thanks very much! I've decided to go straight to 8.1 though. There are just too many performance improvements at this point that I might regret not having and I don't want to do a dump reload again. I am about to compile it now. If it isn't a panic grade failure in the latest 8.1 code then I'd just assume take the stock release source code. I don't care at all if this kills one connection at the ultra-low frequency with which it occurs but what I can't have is the whole server rebooting itself in the middle of processing hundreds of transactions. Once that happens all of the web clients hang onto their bad connections and then eventually die. Considering that I'm moving to 8.1 and am not too familiar with applying patches am I crazy for just going with the stock 8.1 code? On Jan 20, 2006, at 10:36 PM, Tom Lane wrote: Rick Gigger [EMAIL PROTECTED] writes: I don't know if 2K could have passed since the last checkpoint. ... now that I think about it I was getting about 400 pages requests / minute and each of those would have have been doing at least 2 transactions so yes, I guess that is very likely. Good, 'cause if you didn't have a couple thousand transactions between checkpoints then we need another theory ;-) You realize of course that that's pretty old ... Yes. I will be upgrading immediately. You'll want to include this patch: http://archives.postgresql.org/pgsql-committers/2006-01/msg00289.php (or see adjacent messages if you plan to move to something newer than 7.3.*). We probably will not put out another set of releases until next month, unless something really big comes along. This one doesn't qualify as really big IMHO, because it's not a PANIC-grade failure in the later branches. But having been burnt once, I'm sure you'll want a patched copy ... regards, tom lane ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org
