Horton

Re: backup manifests

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: David Steele <david@pgmasters.net>
Cc: Stephen Frost <sfrost@snowman.net>, Amit Kapila <amit.kapila16@gmail.com>, Suraj Kharage <suraj.kharage@enterprisedb.com>, tushar <tushar.ahuja@enterprisedb.com>, Rajkumar Raghuwanshi <rajkumar.raghuwanshi@enterprisedb.com>, Rushabh Lathia <rushabh.lathia@gmail.com>, Tels <nospam-pg-abuse@bloodgate.com>, Andrew Dunstan <andrew.dunstan@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Jeevan Chalke <jeevan.chalke@enterprisedb.com>, vignesh C <vignesh21@gmail.com>
Date: 2020-03-31T11:57:01Z
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. Try to avoid compiler warnings in optimized builds.

  2. Fix option related issues in pg_verifybackup.

  3. Add index term for backup manifest in documentation.

  4. Code review for backup manifest.

  5. Document the backup manifest file format.

  6. Fix typo in pg_validatebackup documentation.

  7. Exclude backup_manifest file that existed in database, from BASE_BACKUP.

  8. Msys2 tweaks for pg_validatebackup corruption test

  9. Fix resource management bug with replication=database.

  10. Be more careful about time_t vs. pg_time_t in basebackup.c.

  11. pg_validatebackup: Fix 'make clean' to remove tmp_check.

  12. pg_validatebackup: Also use perl2host in TAP tests.

  13. Generate backup manifests for base backups, and validate them.

  14. Add checksum helper functions.

  15. pg_waldump: Add a --quiet option.

  16. Catversion bump for b9b408c48724

  17. pg_basebackup: Refactor code for reading COPY and tar data.

  18. Use a ResourceOwner to track buffer pins in all cases.

  19. Use ARMv8 CRC instructions where available.

  20. Logical replication support for initial data copy

  21. Use Intel SSE 4.2 CRC instructions where available.

  22. Switch to CRC-32C in WAL and other places.

  23. Remove support for 64-bit CRC.

  24. Change CRCs in WAL records from 64bit to 32bit for performance reasons.

On Mon, Mar 30, 2020 at 7:24 PM David Steele <david@pgmasters.net> wrote:
> > I'm confused as to why you're not seeing that. What's the exact
> > sequence of steps?
>
> $ pg_basebackup -D test/backup5 --manifest-checksums=SHA256
>
> $ vi test/backup5/backup_manifest
>      * Add 'X' to the checksum of backup_label
>
> $ pg_validatebackup test/backup5
> pg_validatebackup: fatal: invalid checksum for file "backup_label":
> "a98e9164fd59d498d14cfdf19c67d1c2208a30e7b939d1b4a09f524c7adfc11fX"
>
> No mention of the manifest checksum being invalid.  But if I remove the
> backup label file from the manifest:
>
> pg_validatebackup: fatal: manifest checksum mismatch

Oh, I see what's happening now. If the checksum is not an even-length
string of hexademical characters, it's treated as a syntax error, so
it bails out at that point. Generally, a syntax error in the manifest
file is treated as a fatal error, and you just die right there. You'd
get the same behavior if you had malformed JSON, like a stray { or }
or [ or ] someplace that it doesn't belong according to the rules of
JSON. On the other hand, if you corrupt the checksum by adding AA or
EE or 54 or some other even-length string of hex characters, then you
have (in this code's view) a semantic error rather than a syntax
error, so it will finish loading all the manifest data and then bail
because the checksum doesn't match.

We really can't avoid bailing out early sometimes, because if the file
is totally malformed at the JSON level, there's just no way to
continue. We could cause this particular error to get treated as a
semantic error rather than a syntax error, but I don't really see much
advantage in so doing. This way was easier to code, and I don't think
it really matters which error we find first.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company