WAL segment system-id does not match archive system-id

[javierwilson]

1. pgBackRest version: 1.25 - 32bit

2. PostgreSQL version: 9.4 - 32bit

3. Operating system/version - if you have more than one server (for example, a database server, a backup host server, one or more standbys), please specify each: Ubuntu 14.03 - 32bit

4. Did you install pgBackRest from source or from a package? apt-get

5. Describe the issue:
   I have the same issue as ERROR [044]: : WAL segment system-id does not match archive system-id  #432
   also running on a 32bit system, the WAL system-id doesn't match the archiive system-id, or so claims pgbackrest.
   I did an hexdump of the WAL file and I can see the system-id is correct, only pgbackrest is usin the wrong offset, the issue gets fixed if I set PG_WAL_SYSTEM_ID_OFFSET_GTE_93 = 16, instead of 20. I wonder is this is something that affects only 32bit systems. See https://github.com/pgbackrest/pgbackrest/blob/master/lib/pgBackRest/Archive/Common.pm#L35

[javierwilson]

Quoting https://wiki.postgresql.org/images/a/af/FOSDEM-2015-New-WAL-format.pdf
the XLogRecord in 9.4 and below uses 32 bytes in total (but 28 on 32-bit systems), 4 bytes less, so it makes sense to lower this to 16 if arch is 32bit. Other messages on postgresql mailing list confirm this.

[dwsteele]

Hi Javier,

You are correct about the alignment being different on 32-bit architectures.

We have tests (https://anonscm.debian.org/cgit/pkg-postgresql/pgbackrest.git/tree/debian/tests/suite) which should run on all architectures. The tests are pretty basic but should have caught this.

Any idea why the tests did not catch this, @disco-stu?

[disco-stu]

The only test we run automatically on i386 (and all other architectures) is "make test" of the libc module. However, that test passes [1].

Unfortunately ci.debian.net (which automatically runs the full suite) doesn't run on architectures others than amd64 [2]. I would like to have autopkg-tests on all architectures, but that's future stuff.

[1] https://buildd.debian.org/status/fetch.php?pkg=pgbackrest&arch=i386&ver=1.25-1&stamp=1509026334&raw=0
[2] https://ci.debian.net/packages/p/pgbackrest/

[dwsteele]

Thank you for the clarification, Adrian! Let me know if there's anything I can do to move the autopkg-tests stuff along. I'm working on getting the bulk of the test suite running without Docker. Currently, only the S3 tests won't run that way.

@javierwilson - did everything work once you made the offset change?

[javierwilson]

Yes it did... pgbackrest working happily. I basically did an hexdump of several WAL files to confirm the system-id

[dwsteele]

Thanks - I will make that change for 1.26, then. Can you run:

perl -V:ivsize

And send me the result? It should be ivsize='4'.

[javierwilson]

$ uname -a
Linux example 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:12 UTC 2014 i686 i686 i686 GNU/Linux

$ perl -V:ivsize
ivsize='8';

shrug

[dwsteele]

How about:

perl -V:ptrsize

[javierwilson]

$ perl -V:ptrsize
ptrsize='4';

that is actually different from other 64bit servers

[dwsteele]

OK - we'll go with that. This next version is the last in the 1.X line (except for bug fixes). Version 2.x will require the C library and then I can push all this logic down into C and pull structures straight from the Postgres source.

Thanks for testing those out for me!

[javierwilson]

cool, thank you for all your work!

[dwsteele]

Fixed at 550d4fb.

[lock]

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