Re: naming of wal-archives

Yes, it does indeed interleave and it seems to archive the backlog just
before the files are about to be deleted. That explains it.

Thanks for your help,

Neil

2013/1/31 Jeff Janes <jeff(dot)janes(at)gmail(dot)com>

> On Thu, Jan 31, 2013 at 12:50 AM, Neil Worden <nworden1234(at)gmail(dot)com>
> wrote:
> >
> > 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 worked
> > flawlessly, we only were bitten by autovacuums to prevent XID wraparounds
> > that generated relatively high wal-volume and we
> > were 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.
>
> Ah.
>
> ...
> >
> > 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 ?
>
> Yes. It is doing something like archiving the newly-finished log
> files as they are completed, and interleaving that with working off
> the wal_keep_segments backlog. So everything seems normal. At some
> point they should converge without difficulty.
>
> >
> > 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 ?
>
> No, you need both of those. There should be no need to restore the
> *names* of the files. It sounded like you were planning to invent
> some scheme to rename files and rename them back.
>
> >
> > 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 it attempts to overwrite, refuses and returns with a non-zero
> status, then your server will accumulate unarchived log files in
> pg_xlog and you will get warnings in the log file something like:
>
> LOG: archive command failed with exit code 1
>
> It will keep trying, but of course also keep failing, until you
> manually intervene.
>
> The risks are that pg_xlog might fill up, or that if the hard drive
> that holds pg_xlog crashes you will lose log files that were scheduled
> to have been archived but never made it there.
>
> But, this should be a moot point if you indeed only have one server
> archiving to that directory.
>
> Although this has happened to me a couple times, and I just renamed
> the offending archived file to something else (i.e. add .bak to the
> name) to unblock the process. And then compare to moved file to the
> newly arrived archival of it and verify that they were identical (they
> were). Apparently what happened was that a network glitch caused the
> file copy think it failed when it had not. Then future attempts
> failed because the file already existed.
>
> Cheers,
>
> Jeff
>