Horton

Re: refactoring basebackup.c

Jeevan Ladhe <jeevanladhe.os@gmail.com>

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From: Jeevan Ladhe <jeevanladhe.os@gmail.com>
To: Dipesh Pandit <dipesh.pandit@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>, Justin Pryzby <pryzby@telsasoft.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, "Shinoda, Noriyoshi (PN Japan FSIP)" <noriyoshi.shinoda@hpe.com>, Abhijit Menon-Sen <ams@toroid.org>, Dmitry Dolgov <9erthalion6@gmail.com>, Jeevan Ladhe <jeevan.ladhe@enterprisedb.com>, Mark Dilger <mark.dilger@enterprisedb.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, tushar <tushar.ahuja@enterprisedb.com>
Date: 2022-03-15T10:33:05Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Document BaseBackupSync and BaseBackupWrite wait events.

  2. Support long distance matching for zstd compression

  3. Fix possible NULL-pointer-deference in backup_compression.c.

  4. Allow parallel zstd compression when taking a base backup.

  5. Make PostgreSQL::Test::Cluster::run_log() return a useful value.

  6. Fix a few goofs in new backup compression code.

  7. Replace BASE_BACKUP COMPRESSION_LEVEL option with COMPRESSION_DETAIL.

  8. Add 'basebackup_to_shell' contrib module.

  9. Allow extensions to add new backup targets.

  10. Change HAVE_LIBLZ4 and HAVE_LIBZSTD tests to USE_LZ4 and USE_ZSTD.

  11. pg_basebackup: Clean up some bogus file extension tests.

  12. pg_basebackup: Avoid unclean failure with server-compression and -D -.

  13. Fix LZ4 tests for remaining buffer space.

  14. Add support for zstd base backup compression.

  15. pg_basebackup: Allow client-side LZ4 (de)compression.

  16. Add suport for server-side LZ4 base backup compression.

  17. Add min() and max() aggregates for xid8.

  18. Remove superfluous variable.

  19. pg_basebackup: Cleaner handling when compression is multiply specified.

  20. Allow server-side compression to be used with -Fp.

  21. pg_basebackup: Fix a couple of recently-introduced bugs.

  22. Tidy up a few cosmetic issues related to pg_basebackup.

  23. Server-side gzip compression.

  24. Unbreak pg_basebackup/t/010_pg_basebackup.pl on msys

  25. Suppress variable-set-but-not-used warning from clang 13.

  26. Extend the options of pg_basebackup to control compression

  27. Support base backup targets.

  28. Modify pg_basebackup to use a new COPY subprotocol for base backups.

  29. Document that tar archives are now properly terminated.

  30. Fix thinko in bbsink_throttle_manifest_contents.

  31. Have the server properly terminate tar archives.

  32. Minimal fix for unterminated tar archive problem.

  33. Introduce 'bbstreamer' abstraction to modularize pg_basebackup.

  34. Introduce 'bbsink' abstraction to modularize base backup code.

  35. Refactor basebackup.c's _tarWriteDir() function.

  36. Flexible options for CREATE_REPLICATION_SLOT.

  37. Flexible options for BASE_BACKUP.

Thanks for the patch, Dipesh.
I had a look at the patch and also tried to take the backup. I have
following suggestions and observations:

I get following error at my end:

$ pg_basebackup -D /tmp/zstd_bk -Ft -Xfetch --compress=server-zstd:7@4
pg_basebackup: error: could not initiate base backup: ERROR:  could not
compress data: Unsupported parameter
pg_basebackup: removing data directory "/tmp/zstd_bk"

This is mostly because I have the zstd library version v1.4.4, which
does not have default support for parallel workers. Maybe we should
have a better error, something that is hinting that the parallelism is
not supported by the particular build.

The regression for pg_verifybackup test 008_untar.pl also fails with a
similar error. Here, I think we should have some logic in regression to
skip the test if the parameter is not supported?

+   if (ZSTD_isError(ret))

+       elog(ERROR,

+            "could not compress data: %s",

+            ZSTD_getErrorName(ret));

I think all of this can go on one line, but anyhow we have to improve
the error message here.

Also, just a thought, for the versions where parallelism is not
supported, should we instead just throw a warning and fall back to
non-parallel behavior?

Regards,
Jeevan Ladhe

On Mon, 14 Mar 2022 at 21:41, Dipesh Pandit <dipesh.pandit@gmail.com> wrote:

> Hi,
>
> I tried to implement support for parallel ZSTD compression. The
> library provides an option (ZSTD_c_nbWorkers) to specify the
> number of compression workers. The number of parallel
> workers can be set as part of compression parameter and if this
> option is specified then the library performs parallel compression
> based on the specified number of workers.
>
> User can specify the number of parallel worker as part of
> --compress option by appending an integer value after at sign (@).
> (-Z, --compress=[{client|server}-]{gzip|lz4|zstd}[:LEVEL][@WORKERS])
>
> Please find the attached patch v1 with the above changes.
>
> Note: ZSTD library version 1.5.x supports parallel compression
> by default and if the library version is lower than 1.5.x then
> parallel compression is enabled only the source is compiled with build
> macro ZSTD_MULTITHREAD. If the linked library version doesn't
> support parallel compression then setting the value of parameter
> ZSTD_c_nbWorkers to a value other than 0 will be no-op and
> returns an error.
>
> Thanks,
> Dipesh
>