Re: Trap errors from streaming child in pg_basebackup to exit early

On Wed, Sep 1, 2021 at 1:56 PM Daniel Gustafsson <daniel@yesql.se> wrote:
> A v2 with the above fixes is attached.

Thanks for the updated patch. Here are some comments:

1) Do we need to set bgchild = -1 before the exit(1); in the code
below so that we don't kill(bgchild, SIGTERM); unnecessarily in
kill_bgchild_atexit?
+ if (bgchild_exited)
+ {
+ pg_log_error("background WAL receiver terminated unexpectedly");
+ exit(1);
+ }
+

2) Missing "," after "On Windows, we use a ....."
+ * that time. On Windows we use a background thread which can communicate

3) How about "/* Flag to indicate whether or not child process exited
*/" instead of +/* State of child process */?

4) Instead of just exiting from the main pg_basebackup process when
the child WAL receiver dies, can't we think of restarting the child
process, probably with the WAL streaming position where it left off or
stream from the beginning? This way, the work that the main
pg_basebackup has done so far doesn't get wasted. I'm not sure if this
affects the pg_basebackup functionality. We can restart the child
process for 1 or 2 times, if it still dies, we can kill the main
pg_baasebackup process too. Thoughts?

Regards,
Bharath Rupireddy.