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bef47ff85d
The base backup code has accumulated a healthy number of new features over the years, but it's becoming increasingly difficult to maintain and further enhance that code because there's no real separation of concerns. For example, the code that understands knows the details of how we send data to the client using the libpq protocol is scattered throughout basebackup.c, rather than being centralized in one place. To try to improve this situation, introduce a new 'bbsink' object which acts as a recipient for archives generated during the base backup progress and also for the backup manifest. This commit introduces three types of bbsink: a 'copytblspc' bbsink forwards the backup to the client using one COPY OUT operation per tablespace and another for the manifest, a 'progress' bbsink performs command progress reporting, and a 'throttle' bbsink performs rate-limiting. The 'progress' and 'throttle' bbsink types also forward the data to a successor bbsink; at present, the last bbsink in the chain will always be of type 'copytblspc'. There are plans to add more types of 'bbsink' in future commits. This abstraction is a bit leaky in the case of progress reporting, but this still seems cleaner than what we had before. Patch by me, reviewed and tested by Andres Freund, Sumanta Mukherjee, Dilip Kumar, Suraj Kharage, Dipesh Pandit, Tushar Ahuja, Mark Dilger, and Jeevan Ladhe. Discussion: https://postgr.es/m/CA+TgmoZGwR=ZVWFeecncubEyPdwghnvfkkdBe9BLccLSiqdf9Q@mail.gmail.com Discussion: https://postgr.es/m/CA+TgmoZvqk7UuzxsX1xjJRmMGkqoUGYTZLDCH8SmU1xTPr1Xig@mail.gmail.com