Here are the the updated patches, taking care of the issues pointed
earlier. This patch adds the following commands (with specified option):
START_BACKUP [LABEL '<label>'] [FAST]
STOP_BACKUP [NOWAIT]
LIST_TABLESPACES [PROGRESS]
LIST_FILES [TABLESPACE]
LIST_WAL_FILES [START_WAL_LOCATION 'X/X'] [END_WAL_LOCATION 'X/X']
SEND_FILES '(' FILE, FILE... ')' [START_WAL_LOCATION 'X/X']
[NOVERIFY_CHECKSUMS]
Parallel backup is not making any use of tablespace map, so I have
removed that option from the above commands. There is a patch pending
to remove the exclusive backup; we can further refactor the do_pg_start_backup
function at that time, to remove the tablespace information and move the
creation of tablespace_map file to the client.
I have disabled the maxrate option for parallel backup. I intend to send
out a separate patch for it. Robert previously suggested to implement
throttling on the client-side. I found the original email thread [1]
where throttling was proposed and added to the server. In that thread,
it was originally implemented on the client-side, but per many suggestions,
it was moved to server-side.
So, I have a few suggestions on how we can implement this:
1- have another option for pg_basebackup (i.e. per-worker-maxrate) where
the user could choose the bandwidth allocation for each worker. This approach
can be implemented on the client-side as well as on the server-side.
2- have the maxrate, be divided among workers equally at first. and the
let the main thread keep adjusting it whenever one of the workers finishes.
I believe this would only be possible if we handle throttling on the client.
Also, as I understand it, implementing this will introduce additional mutex
for handling of bandwidth consumption data so that rate may be adjusted
according to data received by threads.
