Horton

Re: refactoring basebackup.c

Jeevan Ladhe <jeevan.ladhe@enterprisedb.com>

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From: Jeevan Ladhe <jeevan.ladhe@enterprisedb.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Mark Dilger <mark.dilger@enterprisedb.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, tushar <tushar.ahuja@enterprisedb.com>
Date: 2021-10-29T12:58:24Z
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.

Attachments

Thanks, Robert for the patches.

I tried to take a backup using gzip compression and got a core.

$ pg_basebackup -t server:/tmp/data_gzip -Xnone --server-compression=gzip
NOTICE:  WAL archiving is not enabled; you must ensure that all required
WAL segments are copied through other means to complete the backup
pg_basebackup: error: could not read COPY data: server closed the
connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.

The backtrace:

gdb) bt
#0  0x0000000000000000 in ?? ()
#1  0x0000558264bfc40a in bbsink_cleanup (sink=0x55826684b5f8) at
../../../src/include/replication/basebackup_sink.h:268
#2  0x0000558264bfc838 in bbsink_forward_cleanup (sink=0x55826684b710) at
basebackup_sink.c:124
#3  0x0000558264bf4cab in bbsink_cleanup (sink=0x55826684b710) at
../../../src/include/replication/basebackup_sink.h:268
#4  0x0000558264bf7738 in SendBaseBackup (cmd=0x55826683bd10) at
basebackup.c:1020
#5  0x0000558264c10915 in exec_replication_command (
    cmd_string=0x5582667bc580 "BASE_BACKUP ( LABEL 'pg_basebackup base
backup',  PROGRESS,  MANIFEST 'yes',  TABLESPACE_MAP,  TARGET 'server',
 TARGET_DETAIL '/tmp/data_g
zip',  COMPRESSION 'gzip')") at walsender.c:1731
#6  0x0000558264c8a69b in PostgresMain (dbname=0x5582667e84d8 "",
username=0x5582667e84b8 "hadoop") at postgres.c:4493
#7  0x0000558264bb10a6 in BackendRun (port=0x5582667de160) at
postmaster.c:4560
#8  0x0000558264bb098b in BackendStartup (port=0x5582667de160) at
postmaster.c:4288
#9  0x0000558264bacb55 in ServerLoop () at postmaster.c:1801
#10 0x0000558264bac2ee in PostmasterMain (argc=3, argv=0x5582667b68c0) at
postmaster.c:1473
#11 0x0000558264aa0950 in main (argc=3, argv=0x5582667b68c0) at main.c:198

bbsink_gzip_ops have the cleanup() callback set to NULL, and when the
bbsink_cleanup() callback is triggered, it tries to invoke a function that
is NULL. I think either bbsink_gzip_ops should set the cleanup callback
to bbsink_forward_cleanup or we should be calling the cleanup() callback
from PG_CATCH instead of PG_FINALLY()? But in the latter case, even if
we call from PG_CATCH, it will have a similar problem for gzip and other
sinks which may not need a custom cleanup() callback in case there is any
error before the backup could finish up normally.

I have attached a patch to fix this.

Thoughts?

Regards,
Jeevan Ladhe

On Tue, Oct 26, 2021 at 1:45 AM Robert Haas <robertmhaas@gmail.com> wrote:

> On Fri, Oct 15, 2021 at 8:05 AM Robert Haas <robertmhaas@gmail.com> wrote:
> > > You mean the way gzip allows us to use our own alloc and free functions
> > > by means of providing the function pointers for them. Unfortunately,
> > > no, LZ4 does not have that kind of provision. Maybe that makes a
> > > good proposal for LZ4 library ;-).
> > > I cannot think of another solution to it right away.
> >
> > OK. Will give it some thought.
>
> Here's a new patch set. I've tried adding a "cleanup" callback to the
> bbsink method and ensuring that it gets called even in case of an
> error. The code for that is untested since I have no use for it with
> the existing basebackup sink types, so let me know how it goes when
> you try to use it for LZ4.
>
> I've also added documentation for the new pg_basebackup options in
> this version, and I fixed up a couple of these patches to be
> pgindent-clean when they previously were not.
>
> --
> Robert Haas
> EDB: http://www.enterprisedb.com
>