Greetings, * Ashwin Agrawal (aagra...@pivotal.io) wrote: > On Wed, May 6, 2020 at 3:02 PM Robert Haas <robertmh...@gmail.com> wrote: > > On Wed, May 6, 2020 at 5:48 PM Ashwin Agrawal <aagra...@pivotal.io> wrote: > > > If pg_basebackup is not able to read BLCKSZ content from file, then it > > > just emits a warning "could not verify checksum in file "____" block > > > X: read buffer size X and page size 8192 differ" currently but misses > > > to error with "checksum error occurred". Only if it can read 8192 and > > > checksum mismatch happens will it error in the end. > > > > I don't think it's a good idea to conflate "hey, we can't checksum > > this because the size is strange" with "hey, the checksum didn't > > match". Suppose the a file has 1000 full blocks and a partial block. > > All 1000 blocks have good checksums. With your change, ISTM that we'd > > first emit a warning saying that the checksum couldn't be verified, > > and then we'd emit a second warning saying that there was 1 checksum > > verification failure, which would also be reported to the stats > > system. I don't think that's what we want. > > I feel the intent of reporting "total checksum verification failure" is to > report corruption. Which way is the secondary piece of the puzzle. Not > being able to read checksum itself to verify is also corruption and is > checksum verification failure I think. WARNINGs will provide fine grained > clarity on what type of checksum verification failure it is, so I am not > sure we really need fine grained clarity in "total numbers" to > differentiate these two types.
Are we absolutely sure that there's no way for a partial block to end up being seen by pg_basebackup, which is just doing routine filesystem read() calls, during normal operation though..? Across all platforms? We certainly don't want to end up reporting a false positive by saying that there's been corruption when it was just that the file was getting extended and a read() happened to catch an incomplete write(), or something along those lines. Thanks, Stephen
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