Re: naming of wal-archives - Mailing list pgsql-general
From | Neil Worden |
---|---|
Subject | Re: naming of wal-archives |
Date | |
Msg-id | CADZZMN-9S3G+iAGTW3hhe3RP-nr_LRCY4jHrx8qi4P=uU0DeNA@mail.gmail.com Whole thread Raw |
In response to | Re: naming of wal-archives (Neil Worden <nworden1234@gmail.com>) |
Responses |
Re: naming of wal-archives
Re: naming of wal-archives |
List | pgsql-general |
Btw, ps shows:
postgres@darkblue:/data/pgdata/pg_xlog$ ps aux | grep post
postgres 11496 0.1 0.9 161018232 3696076 ? S Jan29 2:49 postmaster -i -D /data/pgdata
postgres 11499 0.0 1.6 161097088 6450616 ? Ss Jan29 1:39 postgres: checkpointer process
postgres 11500 0.0 0.3 161095036 1414612 ? Ss Jan29 0:12 postgres: writer process
postgres 11501 0.0 0.0 161095036 17328 ? Ss Jan29 0:05 postgres: wal writer process
postgres 11502 0.0 0.0 161096724 3112 ? Ss Jan29 0:11 postgres: autovacuum launcher process
postgres 11503 0.0 0.0 20136 884 ? Ss Jan29 0:10 postgres: archiver process last was 000000010000006E00000034
postgres 11504 0.0 0.0 20816 1412 ? Ss Jan29 0:53 postgres: stats collector process
postgres 11507 0.0 0.0 161096264 2652 ? Ss Jan29 1:08 postgres: wal sender process postgres 192.168.30.65(45640) streaming 8E/5544E650
postgres 11864 0.0 0.0 161096136 2656 ? Ss Jan29 0:51 postgres: wal sender process postgres 192.168.10.95(37378) streaming 8E/5544E650
...
The archiver process says "last was 000000010000006E00000034" and when i look into my wal-archive-directory i see:
-rw------- 1 postgres postgres 16777216 Jan 31 10:24 000000010000006E00000033
-rw------- 1 postgres postgres 16777216 Jan 31 10:24 000000010000006E00000034
-rw------- 1 postgres postgres 16777216 Jan 29 16:03 000000010000008C0000008E
-rw------- 1 postgres postgres 16777216 Jan 29 16:32 000000010000008C0000008F
The 6E..34 file was just written by the archiver process. But further down at the same time this file was written:
...
-rw------- 1 postgres postgres 16777216 Jan 31 10:24 000000010000008E00000054
which seems to match the position of the streaming wal-senders .
Any ideas ?
Thanks, Neil.
2013/1/31 Neil Worden <nworden1234@gmail.com>
>>> If your command does overwrite, then the server currently emitting the>>> 8D files will become unrecoverable once those files start getting>>> overwritten. If it refuses to overwrite, but returns a zero status,>>> then the server currently emitting 6D would become unrecoverable once>>> it reaches 8D and its "archived" files are not actually being archived>>> but are getting deleted from the local pg_xlog anyway.>>>>>> Would it not be easier to archive the different servers to different>> directories and eliminate the possibility of name collision between servers?>Easier? I would say that that is the only sane way of doing it. I>was pointing out the consequences of messing it up. A proper>archive_command will save you from some self-inflicted disasters, but>that does not mean I'm recommending that you should invite those>disasters on yourself.>If the original author is in a production environment, he desperately>needs to figure out what is going on, especially so if archive_command>is not tested and verified to obey its contract.>Cheers,>JeffThanks for your answers.Yes, we are in a production environment and there are definitely no two masters writing to the wal-archive directory, at least none that i am aware of. And i can assure you that we are not intentionally working on inviting disasters either :-).Point is, the ..6D.. line started showing up exactly after i set up the archive-command (which is btw: archive_command = 'test ! -f /data/backup/walbackup/%f && cp %p /data/backup/walbackup/%f', running on Ubuntu Linux Server)The situation is as follows:All concerned machines are running 9.2.2 64-bit on Ubuntu Linux Server 12.10, installed from source, all following exactly the same procedure. We have a hot-standby running to a different location over a rather thin line running since version 9.1 came out. That workedflawlessly, we only were bitten by autovacuums to prevent XID wraparounds that generated relatively high wal-volume and wewere not sure whether the network connection could keep up with it before deleting wal-files. Since we had to physically transfer a backup once for other reasons, we set wal_keep_segments to 8192 to have enough fallback-time.The total size of the database is currently at 313 GB and we are in the process of rethinking our backup/emergency-strategy (currently daily full dumps + hot-standby for read-only queries in the other location + one hot-standby in the same office).So we set up another machine, intended to become a another hot_standby later, but for now just use it to experiment with pg_receivexlog. Since our current backup-strategy does not allow for PIT-recovery and we have been thinking about wal-archiving all the time, we decided to implement it and thats what we did. Now we have the two "lines" in the archive-directory.Could the the high number of wal_keep_segments have an impact ?Does the fact that there already were a lot of existing wal-files when i set up archiving and the archive-command have an impact ?Jeff, you wrote:>> And how would i restore the needed file names for recovery>> if i decide to keep one base-backup und then a very long chain of wal-files>> ?>There should be no need for that.When you said there would be no need for that, did you mean restoring the files for recovery or keeping a base-backup and the chain of wal-files ?I understand that the archive-command is responsible for not overwriting wal-files. But if that situation occurs, and if i understand you correctly it will, what do i do ?If the wal-archive files will be overwritten at some point in time, how is it possible to only have one single base-backup at time-point t and from then on only store the following wal-files ( however inconvenient that may be ) to be able to restore to any point in time after time t ?Thanks,Neil
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