Re: [HACKERS] production server down
Tom Lane wrote: Are you using one of the scripts that does an auto initdb if it doesn't see a valid PGDATA? 11 seconds might be about right for that. One problem with this theory is how come you didn't get screwed during *that* boot cycle. It seems to require assuming that the NFS mount came online just after the initdb finished (else initdb would have overwritten the on-NFS pg_control) but before the regular postmaster started (else this same scenario would have played out then). That's not a very wide window. [followup] We've now had a chance to bring Postgres down and check under the mount point. There *is* indeed a newly initdb'd cluster under there. FWIW the control file is corrupt: # pg_controldata /home/jconway/pgsql/fds/replica/pgdata WARNING: Calculated CRC checksum does not match value stored in file. Either the file is corrupt, or it has a different layout than this program is expecting. The results below are untrustworthy. pg_control version number:72 Catalog version number: 200310211 Database cluster state: in production pg_control last modified: Sat Feb 6 22:28:16 2106 Current log file ID: 0 Next log file segment:10161036 Latest checkpoint location: 0/9AA1B4 Prior checkpoint location:0/9B0B8C Latest checkpoint's REDO location:0/0 Latest checkpoint's UNDO location:C/218 Latest checkpoint's StartUpID:17142 Latest checkpoint's NextXID: 1099443932 Latest checkpoint's NextOID: 8192 Time of latest checkpoint:Wed Apr 8 07:05:36 6325 Database block size: 1 Blocks per segment of large relation: 128 Maximum length of identifiers:67 Maximum number of function arguments: 0 Date/time type storage: floating-point numbers Maximum length of locale name:0 LC_COLLATE: LC_CTYPE: I have a tarred copy of the under-the-mount PGDATA if anyone is interested in examining it. BTW, there was another Postgres cluster on this same server which we had not used since the November 2 reboot -- it was corrupt in pretty much the same way and also had an initdb'd cluster under its mount. So it looks like using an auto initdb startup script is a very bad idea when using an NFS mounted PGDATA. We left the under-mount structure in place and did chown root:root and chmod 000 on it. And, as mentioned in an earlier post, we now rely on the dba to start postgres manually after a server restart. Joe ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [HACKERS] production server down
Michael Fuhr wrote: On Wed, Dec 15, 2004 at 11:41:02AM -0800, Joe Conway wrote: Just wanted to close the loop for the sake of the list archives. With Tom's xlog dump tool I was able (with a bunch of his help off-list) to identify the needed parameters for pg_resetxlog. Running pg_resetxlog got us back a running database. We're now involved in checking the data. Any chance you could write up a summary of the thread: what caused the problem, how you diagnosed it, how you fixed it, and how to avoid it? Might make a useful lessons learned document. Sorry for the delay -- been a busy week. See a summary below. Hope someone finds this useful. Warning -- this is a bit long... --- Background: --- The server in question is an IBM x445, 8-way Xeon, 8 GB RAM. We're running SuSE 9 with the postgresql-7.4.5-36.4 RPM. The database is just over 400GB in size at this point, and resides on a dedicated NFS mounted Network Appliance volume (~6 TB). The server has 2 network interfaces, both gigabit ethernet. One interface (eth0) is dedicated to the NFS mounted storage. It is on a private storage subsystem vlan, running with jumbo frames (9K): # ifconfig eth0 eth0 Link encap:Ethernet HWaddr 00:09:6B:E6:33:B7 [...] UP BROADCAST RUNNING MULTICAST MTU:9000 Metric:1 The data volume is mounted thus: # cat /etc/fstab csddata7-vlan35:/vol/vol0/replica /replica nfs proto=tcp,suid,rw,vers=3,proto=tcp,timeo=600,retrans=2,hard,fg,rsize=8192,wsize=8192 0 0 We have been continuously and aggressively bulk loading parametric data collected from our company's equipment in the field (i.e. in use at our customers) for the past several weeks. This is part of a push to get caught up with available data, after which we expect bulk loading to take a few hours each evening. The server had been up since November 2, 2004. On December 13 the server experienced a complete hang, requiring our unix admin to go into the datacenter and physically cycle power. We don't know the exact cause of that hang, but we have recently experienced a similar hang on two similar servers (both IBM x445, both running SuSE 8.x, one running Oracle 9i, the other an application server). aside In both of those cases we were advised to increase the size of our swap partition -- for some reason either SuSE's installation defaults, or the admin doing the installation (not sure which), had decided that 1GB swap was sufficient for machines with 8GB of RAM. Novell's support advised to increase swap to = physical RAM. We had made that change on the two other servers, but not on the Postgres server because it was busy loading data at the time. We've now made that change, applied all IBM firmware updates, and are waiting to see if the problem repeats. /aside Upon server restart, there was instability noted with the network interfaces, and so they were reset (not exactly sure how the unix admin determined that, but that is what I was told). Unfortunately, the init.d script was in the process of starting postgresql while the eth0 interface (and thus the NFS mount and PGDATA) was unstable. The PostgreSQL Specific Problem: We decided to wait until the 14th before resuming data loading, because the developer who wrote the loading scripts was due back in the office that day after taking vacation. On the 14th, he noted that Postgres was not running, and further, would not start. Here is the snippet from the logs: 2004-12-13 15:05:52 LOG: recycled transaction log file 0165004C 2004-12-13 15:26:01 LOG: recycled transaction log file 0165004D 2004-12-13 16:39:55 LOG: database system was shut down at 2004-11-02 17:05:33 PST 2004-12-13 16:39:55 LOG: checkpoint record is at 0/9B0B8C 2004-12-13 16:39:55 LOG: redo record is at 0/9B0B8C; undo record is at 0/0; shutdown TRUE 2004-12-13 16:39:55 LOG: next transaction ID: 536; next OID: 17142 2004-12-13 16:39:55 LOG: database system is ready 2004-12-14 15:36:20 FATAL: IDENT authentication failed for user colprod 2004-12-14 15:36:58 FATAL: IDENT authentication failed for user colprod 2004-12-14 15:39:26 LOG: received smart shutdown request 2004-12-14 15:39:26 LOG: shutting down 2004-12-14 15:39:28 PANIC: could not open file /replica/pgdata/pg_xlog/ (log file 0, segment 0): No such file or directory 2004-12-14 15:39:28 LOG: shutdown process (PID 23202) was terminated by signal 6 2004-12-14 15:39:39 LOG: database system shutdown was interrupted at 2004-12-14 15:39:26 PST 2004-12-14 15:39:39 LOG: could not open file /replica/pgdata/pg_xlog/ (log file 0, segment 0): No such file or directory 2004-12-14 15:39:39 LOG: invalid primary checkpoint record 2004-12-14 15:39:39 LOG: could not open file /replica/pgdata/pg_xlog/ (log file 0, segment 0): No such file or directory 2004-12-14 15:39:39 LOG:
Re: [HACKERS] production server down
Joe Conway wrote: We then spent most of the next 24 hours reviewing the recovered database. The bulk data loading process was well instrumented, so we knew exactly which data should have been committed prior to the server hang, and which files were inprocess (we had been doing 10 loads in parallel) at the time of the hang. The results of the investigation indicated complete recovery, with no missing or unwanted (i.e. uncommitted records looking committed) data. Good analysis. Seems you were lucky in that only WAL was corrupt and not the heap or index files. -- Bruce Momjian| http://candle.pha.pa.us [EMAIL PROTECTED] | (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 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
Re: [HACKERS] production server down
On Sat, Dec 18, 2004 at 02:28:51PM -0800, Joe Conway wrote: Hi, Apparently, either because of the server hang, or because of the flakey eth0 interface on reboot, pg_control had become corrupt. However, it was not corrupt in the sense that it contained impossibly invalid data. In fact, as pointed out by Alvaro, it had values that all look close to those one would find in a recently initdb'd pg_control file, except the last modified date: I can't help remembering the fact that the init script executes an initdb automatically if it finds an empty data directory (the ones I know of at least -- does the one you are running?). Maybe what happened was that it found the empty mount point, executed an initdb, and then the NFS drive came online. Later, the pg_control file was sync'ed to the empty database settings. It'd be interesting to know if the mount point does have some files on it. These values (from the corrupt pg_control file) are strange: pg_control last modified: Tue Dec 14 15:39:26 2004 Time of latest checkpoint:Tue Nov 2 17:05:32 2004 Maybe the latest checkpoint date has some interesting bit pattern that could explain it somehow. -- Alvaro Herrera ([EMAIL PROTECTED]) El sentido de las cosas no viene de las cosas, sino de las inteligencias que las aplican a sus problemas diarios en busca del progreso. (Ernesto Hernández-Novich) ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
Re: [HACKERS] production server down
Alvaro Herrera wrote: I can't help remembering the fact that the init script executes an initdb automatically if it finds an empty data directory (the ones I know of at least -- does the one you are running?). Maybe what happened was that it found the empty mount point, executed an initdb, and then the NFS drive came online. Later, the pg_control file was sync'ed to the empty database settings. It'd be interesting to know if the mount point does have some files on it. Good point! I'll take a look at the first opportunity. These values (from the corrupt pg_control file) are strange: pg_control last modified: Tue Dec 14 15:39:26 2004 Time of latest checkpoint:Tue Nov 2 17:05:32 2004 Maybe the latest checkpoint date has some interesting bit pattern that could explain it somehow. The last modified corresponds to just prior to the PANIC. See the logs: 2004-12-14 15:39:26 LOG: received smart shutdown request 2004-12-14 15:39:26 LOG: shutting down 2004-12-14 15:39:28 PANIC: could not open file /replica/pgdata/pg_xlog/ (log file 0, segment 0): No such file or directory The Tue Nov 2 17:05:32 2004 seems to be related to the *previous* restart; from /var/log/messages: 8-- ... Nov 2 17:04:20 csdfds1 syslogd 1.4.1: restart. ... Nov 2 17:05:22 csdfds1 su: pam_unix2: session started for user postgres, service su ... Nov 2 17:05:33 csdfds1 su: (to postgres) root on /dev/pts/5 Nov 2 17:05:33 csdfds1 su: pam_unix2: session started for user postgres, service su Nov 2 17:05:33 csdfds1 su: pam_unix2: session finished for user postgres, service su ... 8-- Can you make any sense out of that? Joe ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send unregister YourEmailAddressHere to [EMAIL PROTECTED])
Re: [HACKERS] production server down
Alvaro Herrera [EMAIL PROTECTED] writes: These values (from the corrupt pg_control file) are strange: pg_control last modified: Tue Dec 14 15:39:26 2004 Time of latest checkpoint:Tue Nov 2 17:05:32 2004 The last modified date doesn't prove a lot because it would have been updated when we set the state to shutting down, just before the panic occurred when we noticed there wasn't any WAL segment file where pg_control said there should be one. The latest checkpoint is mighty interesting though. I think Alvaro's idea that this copy of pg_control got created when the NFS mount was offline is a real good theory. However, it would seem that that was quite some time ago (Nov 2 if not earlier), which would suggest that the mount instability problem has been around longer than Joe realizes :-( If the bogus copy is indeed hiding underneath the mount point, then the sequence of events last week is easy to explain: * system boots * NFS mount takes awhile to come online * Postgres starts and reads the bogus pg_control into memory; then it just sits there since they didn't try to start any data loading tasks right away * eventually NFS mount comes online * next day, admin decides to shut down Postgres * Postgres changes last-mod date and state in its in-memory pg_control, and writes it out, overwriting the good copy on the NFS server * Postgres then panics because there's no WAL file where pg_control indicates the shutdown checkpoint WAL record should go * and now we're in the state Joe documented So one thing I'd strongly suggest is stopping Postgres and dismounting the NFS server to see what's under there. If there is a valid-looking PGDATA directory under there, you definitely want to get rid of it to reduce the risk of this happening again. regards, tom lane ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
Re: [HACKERS] production server down
Joe Conway [EMAIL PROTECTED] writes: The Tue Nov 2 17:05:32 2004 seems to be related to the *previous* restart; from /var/log/messages: Nov 2 17:04:20 csdfds1 syslogd 1.4.1: restart. ... Nov 2 17:05:22 csdfds1 su: pam_unix2: session started for user postgres, service su ... Nov 2 17:05:33 csdfds1 su: (to postgres) root on /dev/pts/5 Nov 2 17:05:33 csdfds1 su: pam_unix2: session started for user postgres, service su Nov 2 17:05:33 csdfds1 su: pam_unix2: session finished for user postgres, service su I'm betting that the su at :33 is the invocation of the postmaster. The fact that it took the script 11 seconds to get to that step is suggestive to say the least. Are you using one of the scripts that does an auto initdb if it doesn't see a valid PGDATA? 11 seconds might be about right for that. One problem with this theory is how come you didn't get screwed during *that* boot cycle. It seems to require assuming that the NFS mount came online just after the initdb finished (else initdb would have overwritten the on-NFS pg_control) but before the regular postmaster started (else this same scenario would have played out then). That's not a very wide window. regards, tom lane ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
pg_resetxlog for 8.0 (was Re: [HACKERS] production server down)
Joe Conway [EMAIL PROTECTED] writes: The manpage for pg_resetxlog gives some general idea how it is used, and a way to estimate the next transaction id and wal segment. I had forgotten that that text was in there. It needs to be updated for 8.0 because WAL segment file names are now three-parters. I think there's also a MUST FIX FOR 8.0 to-do item here: there needs to be a way to specify the timeline ID to use. In prior versions we just allowed pg_resetxlog to set startup ID to 1 all the time, because it wasn't really being used for anything. But as of 8.0 that's a significant value and so you'd better be able to set it. What I'm inclined to do is just widen the -l option to take three numbers instead of 2. That will keep it in sync with what people will see when they look at WAL file names. Any objections? regards, tom lane ---(end of broadcast)--- TIP 8: explain analyze is your friend
Re: [HACKERS] production server down
Tom Lane wrote:
I think Alvaro's idea that this copy of pg_control got created when the
NFS mount was offline is a real good theory. However, it would seem
that that was quite some time ago (Nov 2 if not earlier), which would
suggest that the mount instability problem has been around longer than
Joe realizes :-(
I'm starting to wonder if this has somehow happened once or even twice
before, each time the server was restarted. The timing of services
starting on boot might have been biting us all along.
If the bogus copy is indeed hiding underneath the mount point, then the
sequence of events last week is easy to explain:
* system boots
* NFS mount takes awhile to come online
* Postgres starts and reads the bogus pg_control into memory;
then it just sits there since they didn't try to start any
data loading tasks right away
* eventually NFS mount comes online
* next day, admin decides to shut down Postgres
* Postgres changes last-mod date and state in its in-memory
pg_control, and writes it out, overwriting the good copy
on the NFS server
* Postgres then panics because there's no WAL file where
pg_control indicates the shutdown checkpoint WAL record
should go
* and now we're in the state Joe documented
So one thing I'd strongly suggest is stopping Postgres and dismounting
the NFS server to see what's under there. If there is a valid-looking
PGDATA directory under there, you definitely want to get rid of it to
reduce the risk of this happening again.
Perhaps we should purposefully place a root owned placeholder file there
-- that way Postgres would refuse to start at all in this scenario.
BTW, the init script is indeed the one which automatically does initdb:
[...]
case $1 in
start)
touch $LOGFILE
chown postgres:postgres $LOGFILE
chmod 0600 $LOGFILE
if [ ! -f $DATADIR/PG_VERSION ]; then
echo -n Initializing the PostgreSQL database at location
${DATADIR}
LANG_SYSCONFIG=/etc/sysconfig/language
test -f $LANG_SYSCONFIG . $LANG_SYSCONFIG
LANG=${POSTGRES_LANG:-$RC_LANG}
install -d -o postgres -g daemon -m 700 ${DATADIR}
su - postgres -c env -i LANG=$LANG initdb $DATADIR
initlog || rc_failed
[...]
Joe
---(end of broadcast)---
TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
Re: [HACKERS] production server down
Joe Conway wrote: So one thing I'd strongly suggest is stopping Postgres and dismounting the NFS server to see what's under there. If there is a valid-looking PGDATA directory under there, you definitely want to get rid of it to reduce the risk of this happening again. Perhaps we should purposefully place a root owned placeholder file there -- that way Postgres would refuse to start at all in this scenario. BTW, the init script is indeed the one which automatically does initdb: ISTM that this should ideally be a sysconfig setting that is picked up by the init script. In the absence of that, in your case, certainly the root-owned placeholder is a good idea - it seems nicer than disabling on-boot startup altogether if you can avoid that. cheers andrew ---(end of broadcast)--- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
Re: [HACKERS] production server down
Andrew Dunstan wrote: In the absence of that, in your case, certainly the root-owned placeholder is a good idea - it seems nicer than disabling on-boot startup altogether if you can avoid that. I'm pretty well convinced at this point that a start on boot init script is inappropriate when working with NFS attached storage. We really do need to be sure the mount is OK before starting the database. And we have the watchdogs in place, and people on call at all times, specifically to deal with service down events. And while we could always modify the init script to rip out the helpful initdb part, I think the under-the-mount safety file is a must, unless of course someone thinks of an alternate scenario where it will do more harm than good ;-). Joe ---(end of broadcast)--- TIP 8: explain analyze is your friend
Re: [HACKERS] production server down
Tom Lane wrote: My advice is to backup the $PGDATA tree (which you said was in progress), then pg_resetxlog, then cross-check the hell out of the data you see. Only if you can detect some data problems can we guess at something else to do ... Before running pg_resetxlog, a couple of questions: 1. Since it appears that pg_control is suspect, should I force it to be rebuilt, and if so, how? 2. At the end of GuessControlValues is this comment: /* * XXX eventually, should try to grovel through old XLOG to develop * more accurate values for startupid, nextXID, and nextOID. */ What would be involved in doing this, and do you think it would be worth it? Thanks, Joe ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
Re: [HACKERS] production server down
Joe Conway [EMAIL PROTECTED] writes: I don't trust it at all. So does that imply that I should override next transaction id and WAL starting address per the manpage? Yes, override everything there's a switch for. Also check that the other values shown by pg_controldata look reasonable (the locale settings are probably the only ones you might get burned on). What if anything have you got in $PGDATA/pg_xlog? -rw--- 1 postgres postgres 16777216 Dec 13 15:39 01650077 Um. That's so far from the values shown in pg_control that it's not funny. This is 7.4, right? I have a crude xlog dump tool that I'll send you off-list. We should be able to identify the latest checkpoint in the existing XLOG files, and that will give you something to work with. regards, tom lane ---(end of broadcast)--- TIP 8: explain analyze is your friend
Re: [HACKERS] production server down
Tom Lane [EMAIL PROTECTED] writes: The server experienced a hang (as yet unexplained) yesterday and was restarted at 2004-12-13 16:38:49 according to syslog. I'm told by the network admin that there was a problem with the network card on restart, so the nfs mount most probably disappeared and then reappeared underneath a quiescent postgresql at some point between 2004-12-13 16:39:55 and 2004-12-14 15:36:20 (but much closer to the former than the latter). I've always felt that running a database across NFS was a Bad Idea ;-) Well not that I disagree with that sentiment, but NFS was specifically designed to handle this particular scenario. *UNLESS* you use the soft option. As popular as it is, this is precisely the scenario where it causes problems. (The intr option as well, but I don't think that would be relevant for postgres). -- greg ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send unregister YourEmailAddressHere to [EMAIL PROTECTED])
Re: [HACKERS] production server down
Tom Lane wrote: Joe Conway [EMAIL PROTECTED] writes: I don't trust it at all. So does that imply that I should override next transaction id and WAL starting address per the manpage? Yes, override everything there's a switch for. Also check that the other values shown by pg_controldata look reasonable (the locale settings are probably the only ones you might get burned on). OK What if anything have you got in $PGDATA/pg_xlog? -rw--- 1 postgres postgres 16777216 Dec 13 15:39 01650077 Um. That's so far from the values shown in pg_control that it's not funny. This is 7.4, right? Correct. I have a crude xlog dump tool that I'll send you off-list. We should be able to identify the latest checkpoint in the existing XLOG files, and that will give you something to work with. Thanks, Joe ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [HACKERS] production server down
Greg Stark wrote: Tom Lane [EMAIL PROTECTED] writes: I've always felt that running a database across NFS was a Bad Idea ;-) Well not that I disagree with that sentiment, but NFS was specifically designed to handle this particular scenario. *UNLESS* you use the soft option. As popular as it is, this is precisely the scenario where it causes problems. (The intr option as well, but I don't think that would be relevant for postgres). I checked; doesn't seem to be an issue: # cat /etc/fstab csddata7-vlan35:/vol/vol0/replica /replica nfs proto=tcp,suid,rw,vers=3,proto=tcp,timeo=600,retrans=2,hard,fg,rsize=8192,wsize=8192 0 0 I'd be interested in any feedback on the settings. The connection between server and NetApp is on a private vlan on a separate network interface than the rest of the LAN. I'm not positive, but I think we have jumbo frames (9K) enabled on that interface ... looks like we do: # ifconfig eth0 eth0 Link encap:Ethernet HWaddr 00:09:6B:E6:33:B7 [...] UP BROADCAST RUNNING MULTICAST MTU:9000 Metric:1 Thanks, Joe ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [HACKERS] production server down
On Tue, Dec 14, 2004 at 09:22:42PM -0800, Joe Conway wrote: # pg_controldata /replica/pgdata Current log file ID: 0 Next log file segment:1 Latest checkpoint location: 0/9B0B8C Prior checkpoint location:0/9AA1B4 Latest checkpoint's REDO location:0/9B0B8C Latest checkpoint's UNDO location:0/0 Latest checkpoint's StartUpID:12 Latest checkpoint's NextXID: 536 Latest checkpoint's NextOID: 17142 Isn't it strange that these values are so close to the values found in a just-initdb'd cluster? -- Alvaro Herrera ([EMAIL PROTECTED]) Saca el libro que tu religión considere como el indicado para encontrar la oración que traiga paz a tu alma. Luego rebootea el computador y ve si funciona (Carlos Duclós) ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
Re: [HACKERS] production server down
Joe Conway [EMAIL PROTECTED] writes: Before running pg_resetxlog, a couple of questions: 1. Since it appears that pg_control is suspect, should I force it to be rebuilt, and if so, how? pg_resetxlog will rebuild it in any case. However it will re-use the existing contents as much as it can (if you don't use any of the command line options to override values). Given Alvaro's observation that the existing file looks suspiciously close to a freshly-initdb'd one, I don't think you want to trust the existing contents. 2. At the end of GuessControlValues is this comment: /* * XXX eventually, should try to grovel through old XLOG to develop * more accurate values for startupid, nextXID, and nextOID. */ What would be involved in doing this, and do you think it would be worth it? What if anything have you got in $PGDATA/pg_xlog? regards, tom lane ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
Re: [HACKERS] production server down
Tom Lane wrote: pg_resetxlog will rebuild it in any case. However it will re-use the existing contents as much as it can (if you don't use any of the command line options to override values). Given Alvaro's observation that the existing file looks suspiciously close to a freshly-initdb'd one, I don't think you want to trust the existing contents. I don't trust it at all. So does that imply that I should override next transaction id and WAL starting address per the manpage? What if anything have you got in $PGDATA/pg_xlog? # pwd /replica/pgdata/pg_xlog # ll total 688836 drwx-- 2 postgres postgres32768 Dec 13 15:47 . drwx-- 6 postgres postgres 4096 Dec 14 17:45 .. -rw--- 1 postgres postgres 16777216 Dec 13 16:02 0165004E -rw--- 1 postgres postgres 16777216 Dec 13 06:42 0165004F -rw--- 1 postgres postgres 16777216 Dec 13 06:55 01650050 -rw--- 1 postgres postgres 16777216 Dec 13 07:21 01650051 -rw--- 1 postgres postgres 16777216 Dec 13 07:41 01650052 -rw--- 1 postgres postgres 16777216 Dec 13 07:57 01650053 -rw--- 1 postgres postgres 16777216 Dec 13 08:00 01650054 -rw--- 1 postgres postgres 16777216 Dec 13 08:04 01650055 -rw--- 1 postgres postgres 16777216 Dec 13 08:09 01650056 -rw--- 1 postgres postgres 16777216 Dec 13 08:13 01650057 -rw--- 1 postgres postgres 16777216 Dec 13 08:26 01650058 -rw--- 1 postgres postgres 16777216 Dec 13 08:42 01650059 -rw--- 1 postgres postgres 16777216 Dec 13 09:09 0165005A -rw--- 1 postgres postgres 16777216 Dec 13 09:23 0165005B -rw--- 1 postgres postgres 16777216 Dec 13 09:40 0165005C -rw--- 1 postgres postgres 16777216 Dec 13 09:51 0165005D -rw--- 1 postgres postgres 16777216 Dec 13 09:58 0165005E -rw--- 1 postgres postgres 16777216 Dec 13 10:03 0165005F -rw--- 1 postgres postgres 16777216 Dec 13 10:09 01650060 -rw--- 1 postgres postgres 16777216 Dec 13 10:24 01650061 -rw--- 1 postgres postgres 16777216 Dec 13 10:37 01650062 -rw--- 1 postgres postgres 16777216 Dec 13 10:56 01650063 -rw--- 1 postgres postgres 16777216 Dec 13 11:11 01650064 -rw--- 1 postgres postgres 16777216 Dec 13 11:38 01650065 -rw--- 1 postgres postgres 16777216 Dec 13 11:52 01650066 -rw--- 1 postgres postgres 16777216 Dec 13 11:56 01650067 -rw--- 1 postgres postgres 16777216 Dec 13 12:04 01650068 -rw--- 1 postgres postgres 16777216 Dec 13 12:07 01650069 -rw--- 1 postgres postgres 16777216 Dec 13 12:17 0165006A -rw--- 1 postgres postgres 16777216 Dec 13 12:29 0165006B -rw--- 1 postgres postgres 16777216 Dec 13 12:52 0165006C -rw--- 1 postgres postgres 16777216 Dec 13 13:15 0165006D -rw--- 1 postgres postgres 16777216 Dec 13 13:36 0165006E -rw--- 1 postgres postgres 16777216 Dec 13 13:51 0165006F -rw--- 1 postgres postgres 16777216 Dec 13 13:59 01650070 -rw--- 1 postgres postgres 16777216 Dec 13 14:06 01650071 -rw--- 1 postgres postgres 16777216 Dec 13 14:10 01650072 -rw--- 1 postgres postgres 16777216 Dec 13 14:15 01650073 -rw--- 1 postgres postgres 16777216 Dec 13 14:37 01650074 -rw--- 1 postgres postgres 16777216 Dec 13 14:51 01650075 -rw--- 1 postgres postgres 16777216 Dec 13 15:17 01650076 -rw--- 1 postgres postgres 16777216 Dec 13 15:39 01650077 Joe ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
Re: [HACKERS] production server down
Tom Lane wrote: Yes, override everything there's a switch for. Also check that the other values shown by pg_controldata look reasonable (the locale settings are probably the only ones you might get burned on). What if anything have you got in $PGDATA/pg_xlog? -rw--- 1 postgres postgres 16777216 Dec 13 15:39 01650077 Um. That's so far from the values shown in pg_control that it's not funny. This is 7.4, right? I have a crude xlog dump tool that I'll send you off-list. We should be able to identify the latest checkpoint in the existing XLOG files, and that will give you something to work with. Just wanted to close the loop for the sake of the list archives. With Tom's xlog dump tool I was able (with a bunch of his help off-list) to identify the needed parameters for pg_resetxlog. Running pg_resetxlog got us back a running database. We're now involved in checking the data. Thank you to everyone for your help -- especially Tom! Joe ---(end of broadcast)--- TIP 8: explain analyze is your friend
Re: [HACKERS] production server down
On Wed, Dec 15, 2004 at 11:41:02AM -0800, Joe Conway wrote: Just wanted to close the loop for the sake of the list archives. With Tom's xlog dump tool I was able (with a bunch of his help off-list) to identify the needed parameters for pg_resetxlog. Running pg_resetxlog got us back a running database. We're now involved in checking the data. Any chance you could write up a summary of the thread: what caused the problem, how you diagnosed it, how you fixed it, and how to avoid it? Might make a useful lessons learned document. -- Michael Fuhr http://www.fuhr.org/~mfuhr/ ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
[HACKERS] production server down
I've got a down production server (will not restart) with the following tail to its log file: 2004-12-13 15:05:52 LOG: recycled transaction log file 0165004C 2004-12-13 15:26:01 LOG: recycled transaction log file 0165004D 2004-12-13 16:39:55 LOG: database system was shut down at 2004-11-02 17:05:33 PST 2004-12-13 16:39:55 LOG: checkpoint record is at 0/9B0B8C 2004-12-13 16:39:55 LOG: redo record is at 0/9B0B8C; undo record is at 0/0; shutdown TRUE 2004-12-13 16:39:55 LOG: next transaction ID: 536; next OID: 17142 2004-12-13 16:39:55 LOG: database system is ready 2004-12-14 15:36:20 FATAL: IDENT authentication failed for user colprod 2004-12-14 15:36:58 FATAL: IDENT authentication failed for user colprod 2004-12-14 15:39:26 LOG: received smart shutdown request 2004-12-14 15:39:26 LOG: shutting down 2004-12-14 15:39:28 PANIC: could not open file /replica/pgdata/pg_xlog/ (log file 0, segment 0): No such file or directory 2004-12-14 15:39:28 LOG: shutdown process (PID 23202) was terminated by signal 6 2004-12-14 15:39:39 LOG: database system shutdown was interrupted at 2004-12-14 15:39:26 PST 2004-12-14 15:39:39 LOG: could not open file /replica/pgdata/pg_xlog/ (log file 0, segment 0): No such file or directory 2004-12-14 15:39:39 LOG: invalid primary checkpoint record 2004-12-14 15:39:39 LOG: could not open file /replica/pgdata/pg_xlog/ (log file 0, segment 0): No such file or directory 2004-12-14 15:39:39 LOG: invalid secondary checkpoint record 2004-12-14 15:39:39 PANIC: could not locate a valid checkpoint record 2004-12-14 15:39:39 LOG: startup process (PID 23298) was terminated by signal 6 2004-12-14 15:39:39 LOG: aborting startup due to startup process failure This is a SuSE 9, 8-way Xeon IBM x445, with nfs mounted Network Appliance for database storage, postgresql-7.4.5-36.4. The server experienced a hang (as yet unexplained) yesterday and was restarted at 2004-12-13 16:38:49 according to syslog. I'm told by the network admin that there was a problem with the network card on restart, so the nfs mount most probably disappeared and then reappeared underneath a quiescent postgresql at some point between 2004-12-13 16:39:55 and 2004-12-14 15:36:20 (but much closer to the former than the latter). Any help would be much appreciated. Is our only option pg_resetxlog? Thanks, Joe ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send unregister YourEmailAddressHere to [EMAIL PROTECTED])
Re: [HACKERS] production server down
Joe Conway wrote: This is a SuSE 9, 8-way Xeon IBM x445, with nfs mounted Network Appliance for database storage, postgresql-7.4.5-36.4. The server experienced a hang (as yet unexplained) yesterday and was restarted at 2004-12-13 16:38:49 according to syslog. I'm told by the network admin that there was a problem with the network card on restart, so the nfs mount most probably disappeared and then reappeared underneath a quiescent postgresql at some point between 2004-12-13 16:39:55 and 2004-12-14 15:36:20 (but much closer to the former than the latter). Well, my first reaction is that if the file system storage was not always 100% reliable, then there is no way to know the data is correct except by restoring from backup. The startup failure indicates that there were surely storage problems in the past. There is no way to know how far that corrupt goes. You can use pg_resetxlog to clear it out and look to see how accurate it is, but there is no way to be sure. I would back up the file system with the server down in case you want to do some more serious recovery attempts later though. The Freenode IRC channel can probably walk you through more details of the recovery process. -- Bruce Momjian| http://candle.pha.pa.us [EMAIL PROTECTED] | (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 4: Don't 'kill -9' the postmaster
Re: [HACKERS] production server down
Tom Lane wrote: Joe Conway [EMAIL PROTECTED] writes: I've got a down production server (will not restart) with the following tail to its log file: Please show the output of pg_controldata, or a hex dump of pg_control if pg_controldata fails. OK, here it is: # pg_controldata /replica/pgdata pg_control version number:72 Catalog version number: 200310211 Database cluster state: shutting down pg_control last modified: Tue Dec 14 15:39:26 2004 Current log file ID: 0 Next log file segment:1 Latest checkpoint location: 0/9B0B8C Prior checkpoint location:0/9AA1B4 Latest checkpoint's REDO location:0/9B0B8C Latest checkpoint's UNDO location:0/0 Latest checkpoint's StartUpID:12 Latest checkpoint's NextXID: 536 Latest checkpoint's NextOID: 17142 Time of latest checkpoint:Tue Nov 2 17:05:32 2004 Database block size: 8192 Blocks per segment of large relation: 131072 Maximum length of identifiers:64 Maximum number of function arguments: 32 Date/time type storage: 64-bit integers Maximum length of locale name:128 LC_COLLATE: C LC_CTYPE: C Joe ---(end of broadcast)--- TIP 8: explain analyze is your friend
Re: [HACKERS] production server down
Tom Lane wrote: ... pg_control last modified: Tue Dec 14 15:39:26 2004 ... Time of latest checkpoint:Tue Nov 2 17:05:32 2004 [ blink... ] That seems like an unreasonable gap between checkpoints, especially for a production server. Can you see an explanation? Hmmm, this is even more scary. We have two database clusters on this server, one on /replica/pgdata, and one on /production/pgdata (ignore the names -- /replica is actually the production instance at the moment). # pg_controldata /replica/pgdata pg_control version number:72 Catalog version number: 200310211 Database cluster state: shutting down pg_control last modified: Tue Dec 14 15:39:26 2004 Current log file ID: 0 Next log file segment:1 Latest checkpoint location: 0/9B0B8C Prior checkpoint location:0/9AA1B4 Latest checkpoint's REDO location:0/9B0B8C Latest checkpoint's UNDO location:0/0 Latest checkpoint's StartUpID:12 Latest checkpoint's NextXID: 536 Latest checkpoint's NextOID: 17142 Time of latest checkpoint:Tue Nov 2 17:05:32 2004 Database block size: 8192 Blocks per segment of large relation: 131072 Maximum length of identifiers:64 Maximum number of function arguments: 32 Date/time type storage: 64-bit integers Maximum length of locale name:128 LC_COLLATE: C LC_CTYPE: C # pg_controldata /production/pgdata pg_control version number:72 Catalog version number: 200310211 Database cluster state: shutting down pg_control last modified: Tue Nov 2 21:57:49 2004 Current log file ID: 0 Next log file segment:1 Latest checkpoint location: 0/9B0B8C Prior checkpoint location:0/9AA1B4 Latest checkpoint's REDO location:0/9B0B8C Latest checkpoint's UNDO location:0/0 Latest checkpoint's StartUpID:12 Latest checkpoint's NextXID: 536 Latest checkpoint's NextOID: 17142 Time of latest checkpoint:Tue Nov 2 17:05:32 2004 Database block size: 8192 Blocks per segment of large relation: 131072 Maximum length of identifiers:64 Maximum number of function arguments: 32 Date/time type storage: 64-bit integers Maximum length of locale name:128 LC_COLLATE: C LC_CTYPE: C I have no idea how this happened, but those look too similar except for the last modified date. The space used is quite what I'd expect: # du -h --max-depth=1 /replica 403G/replica/pgdata # du -h --max-depth=1 /production 201G/production/pgdata The /production/pgdata cluster has not been in use since Nov 2. But we've been loading data aggressively into /replica/pgdata. Any theories on how we screwed up? Joe ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [HACKERS] production server down
Joe Conway [EMAIL PROTECTED] writes: Any theories on how we screwed up? I hesitate to suggest this, but maybe a cron job blindly copying data from point A to point B? I'm not sure that that could entirely explain the facts. My recollection of the xlog.c logic is that the pg_control file is read into shared memory during postmaster boot, and after that it's write-only: at checkpoint times we update the file image in shared memory and then write it out to pg_control. Offhand my bets would revolve around (a) multiple postmasters trying to run the same PGDATA directory (we have interlocks to protect against this, but I have no faith that they work against an NFS-mounted data directory), or (b) you somehow wiped a PGDATA directory and restored it from backup tapes underneath a running postmaster. regards, tom lane ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
Re: [HACKERS] production server down
Tom Lane wrote: Joe Conway [EMAIL PROTECTED] writes: Any theories on how we screwed up? I hesitate to suggest this, but maybe a cron job blindly copying data from point A to point B? Not likely, but I'll check. Offhand my bets would revolve around (a) multiple postmasters trying to run the same PGDATA directory (we have interlocks to protect against this, but I have no faith that they work against an NFS-mounted data directory) This might be possible I suppose. I know we have two init scripts. Perhaps there is an error in them that caused both postmasters to point to the same place when the server was rebooted. I'll look them over. or (b) you somehow wiped a PGDATA directory and restored it from backup tapes underneath a running postmaster. This seems highly unlikely because our *nix admin would have had to deliberately do it, and I don't think he'd fail to tell me about something like that. But all the same, I'll ask him tomorrow. Assuming the only real problem here is the control data (long shot, I know), and the actual database files and transaction logs are OK, is there any reasonable way to reconstruct the correct contol data? Or is that the point at which you use pg_resetxlog? Joe ---(end of broadcast)--- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
Re: [HACKERS] production server down
Tom Lane wrote: My advice is to backup the $PGDATA tree (which you said was in progress), then pg_resetxlog, then cross-check the hell out of the data you see. Only if you can detect some data problems can we guess at something else to do ... OK. I plan to gather the usual suspects and try to get an accurate picture of the chain of events first thing tomorrow. Then we'll likely proceed as you suggest. Thinking about your comments and reading xlog.c, it almost seems as though the mount points were momentarily reversed between /replica and /production. I.e. that the /production mount point was used near the beginning of StartupXLOG() for ReadControlFile(), and the /replica mount point was used at the end of StartupXLOG() for UpdateControlFile(). But I have no idea how that could happen. Thanks, Joe ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
Re: [HACKERS] production server down
Joe Conway [EMAIL PROTECTED] writes: Assuming the only real problem here is the control data (long shot, I know), and the actual database files and transaction logs are OK, is there any reasonable way to reconstruct the correct contol data? Or is that the point at which you use pg_resetxlog? Well, the problem is that if you can't trust pg_control you don't know what you can trust. My advice is to backup the $PGDATA tree (which you said was in progress), then pg_resetxlog, then cross-check the hell out of the data you see. Only if you can detect some data problems can we guess at something else to do ... regards, tom lane ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
Re: [HACKERS] production server down
Joe Conway [EMAIL PROTECTED] writes: I've got a down production server (will not restart) with the following tail to its log file: Please show the output of pg_controldata, or a hex dump of pg_control if pg_controldata fails. The server experienced a hang (as yet unexplained) yesterday and was restarted at 2004-12-13 16:38:49 according to syslog. I'm told by the network admin that there was a problem with the network card on restart, so the nfs mount most probably disappeared and then reappeared underneath a quiescent postgresql at some point between 2004-12-13 16:39:55 and 2004-12-14 15:36:20 (but much closer to the former than the latter). I've always felt that running a database across NFS was a Bad Idea ;-) Any help would be much appreciated. Is our only option pg_resetxlog? Possibly, but let's try to dig first. I suppose the DB is too large to save an image aside for forensics later? regards, tom lane ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
Re: [HACKERS] production server down
Tom Lane wrote: Joe Conway [EMAIL PROTECTED] writes: I've got a down production server (will not restart) with the following tail to its log file: Please show the output of pg_controldata, or a hex dump of pg_control if pg_controldata fails. OK, will do shortly. The server experienced a hang (as yet unexplained) yesterday and was restarted at 2004-12-13 16:38:49 according to syslog. I'm told by the network admin that there was a problem with the network card on restart, so the nfs mount most probably disappeared and then reappeared underneath a quiescent postgresql at some point between 2004-12-13 16:39:55 and 2004-12-14 15:36:20 (but much closer to the former than the latter). I've always felt that running a database across NFS was a Bad Idea ;-) Yeah, I knew I had that coming :-) Any help would be much appreciated. Is our only option pg_resetxlog? Possibly, but let's try to dig first. I suppose the DB is too large to save an image aside for forensics later? Actually, although the database is about 400 GB, we do have room and are in the process of saving an image now. Joe ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
Re: [HACKERS] production server down
Joe Conway [EMAIL PROTECTED] writes: Tom Lane wrote: Please show the output of pg_controldata, or a hex dump of pg_control if pg_controldata fails. OK, here it is: ... pg_control last modified: Tue Dec 14 15:39:26 2004 ... Time of latest checkpoint:Tue Nov 2 17:05:32 2004 [ blink... ] That seems like an unreasonable gap between checkpoints, especially for a production server. Can you see an explanation? regards, tom lane ---(end of broadcast)--- TIP 3: 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
