Re: WAL-related tools and .paritial WAL file

On Wed, Jul 1, 2015 at 12:39 PM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> WAL-related tools, i.e., pg_archivecleanup, pg_resetxlog and
> pg_xlogdump don't seem to properly handle .paritial WAL file.
> I think that we should fix at least pg_archivecleanup, otherwise,
> in the system using pg_archivecleanup to clean up old archived
> files, the archived .paritial WAL file will never be removed.
> Thought?

+1 to handle it properly in pg_archivecleanup. If people use the
archive cleanup command in recovery.conf and they remove WAL files
before the fork point of promotion they should not see the partial
file as well.

> To make pg_archivecleanup detect .paritial WAL file, I'd like to
> use IsPartialXLogFileName() macro that commit 179cdd0 added.
> Fortunately Michael proposed the patch which makes the macros
> in xlog_internal.h usable in WAL-related tools, and it's better
> to apply the fix based on his patch. So my plan is to apply his
> patch first and then apply the fix to pg_archivecleanup.
> http://www.postgresql.org/message-id/CAB7nPqSiKU+8HjVe_J05btonC5E7kvmRaLpGS6EaEQe=Dy3jnQ@mail.gmail.com

As we already use extensively XLogFromFileName in a couple of frontend
utilies, I suspect that the buildfarm is not going to blow up, but it
is certainly better to have certitude with a full buildfarm cycle
running on it...

> Regarding pg_resetxlog and pg_xlogdump, do we need to change
> also them so that they can handle .paritial file properly?
> pg_resetxlog cannot clean up .partial file even if it should be
> removed. But the remaining .paritial file is harmless and will be
> recycled later by checkpoint, so extra treatment of .paritial
> file in pg_resetxlog may not be necessary. IOW, maybe we can
> document that's the limitation of pg_resetxlog.

I would rather vote for having pg_resetxlog remove the .partial
segment as well. That's a two-liner in KillExistingArchiveStatus and
KillExistingXLOG at quick glance. It looks to me that as pg_resetxlog
is a reset utility, it should do its jib.

> Also regarding pg_xlogdump, we can just document, for example,
> "please get rid of .paritial suffix from the WAL file name if
> you want to dump it by pg_xlogdump".

For pg_xlogdump, I am on board for only documenting the limitation
(renaming the file by yourself) as it is after all only a debug tool.
This would also make fuzzy_open_file more complicated by having to
detect two times more potential grammars... That's a bit crazy for a
very narrow use-case.
--
Michael