Re: [GENERAL] autovacuum holds exclusive lock on table preventing it from to be updated
On Mon, Jun 19, 2017 at 1:53 PM, Dmitry O Litvintsev wrote: > yes, we had to restart database 4 days ago (and vacuum has resumed on start). > I checked the log files and discovered that autovacuum on this table takes > > pages: 0 removed, 14072307 remain > tuples: 43524292 removed, 395006545 remain > buffer usage: -1493114028 hits, 107664973 misses, 30263658 dirtied > avg read rate: 1.604 MB/s, avg write rate: 0.451 MB/s > system usage: CPU 2055.81s/17710.94u sec elapsed 524356.57 sec > > 6 days. So it is perpetually being autovacuumed (which I assumed to be a good > thing) > > Table has 400M entries, 115 GB. > > I will try your suggestions in the test environment. > > Thank you, > Dmitry Once you get this sorted, look into using the checkpostgresql.pl script and a monitoring solution like zabbix or nagios to monitor things like transactions until wraparound etc so you don't wind up back here again. Best of luck in. Note that if you drop the vacuum delay to 0ms the vacuum will probably complete in a few hours tops. -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] autovacuum holds exclusive lock on table preventing it from to be updated
yes, we had to restart database 4 days ago (and vacuum has resumed on start). I checked the log files and discovered that autovacuum on this table takes pages: 0 removed, 14072307 remain tuples: 43524292 removed, 395006545 remain buffer usage: -1493114028 hits, 107664973 misses, 30263658 dirtied avg read rate: 1.604 MB/s, avg write rate: 0.451 MB/s system usage: CPU 2055.81s/17710.94u sec elapsed 524356.57 sec 6 days. So it is perpetually being autovacuumed (which I assumed to be a good thing) Table has 400M entries, 115 GB. I will try your suggestions in the test environment. Thank you, Dmitry From: Jeff Janes Sent: Monday, June 19, 2017 1:16 PM To: Dmitry O Litvintsev Cc: Andreas Kretschmer; pgsql-general@postgresql.org Subject: Re: [GENERAL] autovacuum holds exclusive lock on table preventing it from to be updated On Mon, Jun 19, 2017 at 10:33 AM, Dmitry O Litvintsev mailto:litvi...@fnal.gov>> wrote: Hi Since I have posted this nothing really changed. I am starting to panic (mildly). The source (production) runs : relname | mode | granted | substr| query_start | age +--+-+--+---+ t_inodes_iio_idx | RowExclusiveLock | t | autovacuum: VACUUM ANALYZE public.t_inodes (to prevent wraparound) | 2017-06-15 10:26:18.643209-05 | 4 days 01:58:56.697559 This is close to unreadable. You can use use \x to get output from psql which survives email more readably. Your first report was 6 days ago. Why is the job only 4 days old? Are you frequently restarting your production server, so that the vacuum job never gets a chance to finish? If so, that would explain your predicament. And how big is this table, that it takes at least 4 days to VACUUM? vacuum_cost_delay = 50ms That is a lot. The default value for this is 0. The default value for autovacuum_vacuum_cost_delay is 20, which is usually too high for giant databases. I think you are changing this in the wrong direction. Rather than increase vacuum_cost_delay, you need to decrease autovacuum_vacuum_cost_delay, so that you won't keep having problems in the future. On your test server, change vacuum_cost_delay to zero and then initiate a manual vacuum of the table. It will block on the autovacuum's lock, so then kill the autovacuum (best to have the manual vacuum queued up first, otherwise it will be race between when you start the manual vacuum, and when the autovacuum automatically restarts, to see who gets the lock). See how long it takes this unthrottled vacuum to run, and how much effect the IO it causes has on the performance of other tasks. If acceptable, repeat this on production (although really, I don't that you have much of a choice on whether the effect it is acceptable or not--it needs to be done.) Cheers, Jeff -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] autovacuum holds exclusive lock on table preventing it from to be updated
On Mon, 19 Jun 2017 17:33:23 + Dmitry O Litvintsev wrote: > > The test stand where I was to test schema upgrade is stuck cuz vacuum is > blocking. If you're in "panic mode" I would recommend cancelling the existing vacuum, running your upgrades, then immeditely running VACUUM FREEZE ANALYZE on that table to make up for cancelling the autovacuum. Note that the manual VACUUM may take quite a while, so run it in a screen session or something. Additionally, autovacuum is going to try to relaunch that vacuum pretty aggressively, so you might have to cancel it a few times (using pg_terminate_backend()) before your other processes are able to sneak in ahead of it. Once you're out of panic mode you can take some time to breathe and consider your options for reducing the issue in the future. I have to 2nd Alvaro's comments about the cost delay. Personally, I'd recommend setting vacuum_cost_delay to zero, unless your hardware is crap. In my recent experience, allowing vacuum to run full-bore is less intrustive on a busy database with good hardware than forcing it to take it's time. Unfortunately, changing it now isn't going to speed the current vacuum up any. Another comment: schema changes almost always need exclusive locks on tables that they're modifying. As a result, you really need to plan them out a bit. Anything could block a schema update, even a simple SELECT statement; so it's important to check the health of things before starting. While it's not _generally_ a good practice to interrupt autovacuum, it _can_ be done if the schema upgrade is necessary. Keep in mind that it's just going to start back up again, but hopefully your schema update will be done by then and it can do it's work without interfering with things. Another thing you can do is to monitor the transaction ID values (the Nagios check_postgres has a nice mode for monitoring this) and manually launch a VACUUM FREEZE ahead of autovacuum, so that _you_ can pick the time for it to run and not have it happen to crop up at the worst possible time ;) You might also find that things are easier to deal with if you tweak the autovacuum settings on this table to cause it to be vacuumed more frequently. In my experience, more frequent vacuums that do less work each time often lead to happier databases. See ALTER TABLE and the available settings to tweak autovacuum behavior. -- Bill Moran -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] autovacuum holds exclusive lock on table preventing it from to be updated
On Mon, Jun 19, 2017 at 10:33 AM, Dmitry O Litvintsev wrote: > Hi > > Since I have posted this nothing really changed. I am starting to panic > (mildly). > > The source (production) runs : > > relname | mode | granted | > substr| > query_start | age > +--+ > -+-- > +---+ > t_inodes_iio_idx | RowExclusiveLock | t | > autovacuum: VACUUM ANALYZE public.t_inodes (to prevent wraparound) | > 2017-06-15 10:26:18.643209-05 | 4 days 01:58:56.697559 > This is close to unreadable. You can use use \x to get output from psql which survives email more readably. Your first report was 6 days ago. Why is the job only 4 days old? Are you frequently restarting your production server, so that the vacuum job never gets a chance to finish? If so, that would explain your predicament. And how big is this table, that it takes at least 4 days to VACUUM? vacuum_cost_delay = 50ms > That is a lot. The default value for this is 0. The default value for autovacuum_vacuum_cost_delay is 20, which is usually too high for giant databases. I think you are changing this in the wrong direction. Rather than increase vacuum_cost_delay, you need to decrease autovacuum_vacuum_cost_delay, so that you won't keep having problems in the future. On your test server, change vacuum_cost_delay to zero and then initiate a manual vacuum of the table. It will block on the autovacuum's lock, so then kill the autovacuum (best to have the manual vacuum queued up first, otherwise it will be race between when you start the manual vacuum, and when the autovacuum automatically restarts, to see who gets the lock). See how long it takes this unthrottled vacuum to run, and how much effect the IO it causes has on the performance of other tasks. If acceptable, repeat this on production (although really, I don't that you have much of a choice on whether the effect it is acceptable or not--it needs to be done.) Cheers, Jeff
Re: [GENERAL] autovacuum holds exclusive lock on table preventing it from to be updated
Dmitry O Litvintsev wrote: > Hi > > Since I have posted this nothing really changed. I am starting to panic > (mildly). ... > vacuum_cost_delay = 50ms Most likely, this value is far too high. You're causing autovacuum to sleep for a very long time with this setting. Hard to say for certain without seeing the cost_limit value and the other related parameters, but it's most certainly what's causing you pain. The default of 20ms is already too high for most users. -- Álvaro Herrerahttps://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] autovacuum holds exclusive lock on table preventing it from to be updated
Hi Since I have posted this nothing really changed. I am starting to panic (mildly). The source (production) runs : relname | mode | granted | substr| query_start | age +--+-+--+---+ t_inodes_iio_idx | RowExclusiveLock | t | autovacuum: VACUUM ANALYZE public.t_inodes (to prevent wraparound) | 2017-06-15 10:26:18.643209-05 | 4 days 01:58:56.697559 t_inodes_pkey | RowExclusiveLock | t | autovacuum: VACUUM ANALYZE public.t_inodes (to prevent wraparound) | 2017-06-15 10:26:18.643209-05 | 4 days 01:58:56.697559 | ExclusiveLock| t | autovacuum: VACUUM ANALYZE public.t_inodes (to prevent wraparound) | 2017-06-15 10:26:18.643209-05 | 4 days 01:58:56.697559 t_inodes | ShareUpdateExclusiveLock | t | autovacuum: VACUUM ANALYZE public.t_inodes (to prevent wraparound) | 2017-06-15 10:26:18.643209-05 | 4 days 01:58:56.697559 t_inodes_itype_idx | RowExclusiveLock | t | autovacuum: VACUUM ANALYZE public.t_inodes (to prevent wraparound) | 2017-06-15 10:26:18.643209-05 | 4 days 01:58:56.697559 t_inodes_imtime_idx| RowExclusiveLock | t | autovacuum: VACUUM ANALYZE public.t_inodes (to prevent wraparound) | 2017-06-15 10:26:18.643209-05 | 4 days 01:58:56.697559 Above does not impact production activity a lot. On the test stand (where I pg_basebackupped from production and also upgraded to 9.6) I see: relname | mode | granted | substr | query_start | age ---+--+-++---+ t_inodes | ShareUpdateExclusiveLock | t | autovacuum: VACUUM public.t_inodes (to prevent wraparound) | 2017-06-13 15:27:54.872154-05 | 5 days 20:59:22.769404 t_inodes_itype_idx| RowExclusiveLock | t | autovacuum: VACUUM public.t_inodes (to prevent wraparound) | 2017-06-13 15:27:54.872154-05 | 5 days 20:59:22.769404 t_inodes_imtime_idx | RowExclusiveLock | t | autovacuum: VACUUM public.t_inodes (to prevent wraparound) | 2017-06-13 15:27:54.872154-05 | 5 days 20:59:22.769404 t_inodes_iio_idx | RowExclusiveLock | t | autovacuum: VACUUM public.t_inodes (to prevent wraparound) | 2017-06-13 15:27:54.872154-05 | 5 days 20:59:22.769404 t_inodes_pkey | RowExclusiveLock | t | autovacuum: VACUUM public.t_inodes (to prevent wraparound) | 2017-06-13 15:27:54.872154-05 | 5 days 20:59:22.769404 | ExclusiveLock| t | autovacuum: VACUUM public.t_inodes (to prevent wraparound) | 2017-06-13 15:27:54.872154-05 | 5 days 20:59:22.769404 t_inodes | ShareUpdateExclusiveLock | f | ANALYZE; | 2017-06-13 15:27:59.781285-05 | 5 days 20:59:17.860273 | ExclusiveLock| t | ANALYZE; | 2017-06-13 15:27:59.781285-05 | 5 days 20:59:17.860273 The test stand where I was to test schema upgrade is stuck cuz vacuum is blocking. Production settings follow: version 9.3.9 max_connections = 512 shared_buffers = 8192MB temp_buffers = 1024MB work_mem = 512MB #maintenance_work_mem = 2048MB maintenance_work_mem = 4096MB #increased after 3 days of vacuum analyze running max_stack_depth = 2MB vacuum_cost_delay = 50ms synchronous_commit = off wal_buffers = 245MB wal_writer_delay = 10s checkpoint_segments = 64 checkpoint_completion_target = 0.9 random_page_cost = 2.0 effective_cache_size = 94GB wal_level = hot_standby hot_standby = on archive_mode = on archive_command = '/usr/loca/bin/wal_backup.sh %p %f' max_wal_senders = 4 wal_keep_segments = 1024 max_standby_streaming_delay = 7200s So, the problem : I cannot do schema change until vacuum has finished, and there seems to be no end in sight for vacuum to finish throwing off our software upgrade plans. Anything can be done here? Thanks, Dmitry From: Andreas Kretschmer Sent: Tuesday, June 13, 2017 1:54 PM To: pgsql-general@postgresql.org; Dmitry O Litvintsev; pgsql-general@postgresql.org Subject: Re: [GENERAL] autovacuum holds exclusive lock on table preventing i
Re: [GENERAL] autovacuum holds exclusive lock on table preventing it from to be updated
Am 13. Juni 2017 20:04:04 MESZ schrieb Dmitry O Litvintsev : > >I >wraparound)| 2017- >| t | enstore | autovacuum: VACUUM public.t_inodes (to prevent >wraparound)| 2017-06-13 12:31:04.870064-05 | >00:28:50.276437 | 40672 >chimera | t_inodes | | >ShareUpdateExclusiveLock | t | enstore | autovacuum: VACUUM >public.t_inodes (to prevent wraparound)| 2017-06-13 >12:31:04.870064-05 | 00:28:50.276437 | 40672 > It is a autocacuum to prevent wraparound, you can't stop or avoid that. Regards, Andreas -- Diese Nachricht wurde von meinem Android-Mobiltelefon mit K-9 Mail gesendet. -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general