Re: pg_basebackup failed to read a file

On 08/14/2018 11:14 AM, Tom Lane wrote:
> Mike Cardwell <mike(dot)cardwell(at)hardenize(dot)com> writes:
>> pg_basebackup: could not get write-ahead log end position from server:
>> ERROR:  could not open file "./postgresql.conf~": Permission denied
>> Now, I know what this error means. There was a root owned file at
>> "/var/lib/pgsql/10/data/postgresql.conf~" which contained an old
>> version of our postgres config and was not readable by the postgres
>> user. I'll delete this file and try again. However, in the mean time: I
>> feel like it would be useful for pg_basebackup to check that it has
>> read access to all of the existing files in the source directory at the
>> start, before it begins it's copy.
> That seems like a pretty expensive thing to do, if there are lots of
> files ... and you'd still end up failing, so it's not moving the ball
> very far.

Why is checking a bunch of file permissions anywhere close to being as
expensive as transferring 1.5TB over a WAN link?

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