Horton

Re: should frontend tools use syncfs() ?

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Justin Pryzby <pryzby@telsasoft.com>, Thomas Munro <thomas.munro@gmail.com>, David Steele <david@pgmasters.net>, Fujii Masao <masao.fujii@oss.nttdata.com>, Bruce Momjian <bruce@momjian.us>, Tom Lane <tgl@sss.pgh.pa.us>, Michael Brown <michael.brown@discourse.org>, pgsql-hackers@postgresql.org
Date: 2023-08-22T01:44:07Z
Lists: pgsql-hackers 
On Tue, Aug 22, 2023 at 08:56:26AM +0900, Michael Paquier wrote:
> --- a/src/include/storage/fd.h
> +++ b/src/include/storage/fd.h
> @@ -43,15 +43,11 @@
>  #ifndef FD_H
>  #define FD_H
>  
> +#ifndef FRONTEND
> +
>  #include <dirent.h>
>  #include <fcntl.h>
>  
> Ugh.  So you need this part because pg_rewind's filemap.c includes
> fd.h, and pg_rewind also needs file_utils.h.  This is not the fault of
> your patch, but this does not make the situation better, either..  It
> looks like we need to think harder about this layer.  An improvement
> would be to split file_utils.c so as its frontend-only code is moved
> to OBJS_FRONTEND in a new file with a new header?  It should be OK to
> keep DataDirSyncMethod in file_utils.h as long as the split is clean.

I'm hoping there's a simpler path forward here.  pg_rewind only needs the
following lines from fd.h:

	/* Filename components */
	#define PG_TEMP_FILES_DIR "pgsql_tmp"
	#define PG_TEMP_FILE_PREFIX "pgsql_tmp"

Maybe we could move these to file_utils.h instead.  WDYT?

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com

Commits

  1. Adjust documentation for syncfs().

  2. Improve the naming in wal_sync_method code.

  3. Allow using syncfs() in frontend utilities.

  4. Add support for syncfs() in frontend support functions.

  5. Make enum for sync methods available to frontend code.

  6. Move PG_TEMP_FILE* macros to file_utils.h.

  7. Change client-side fsync_fname() to report errors fatally