This seems to be good idea to have checks on upper bound for the max_wal_size and min_wal_size. We have seen customers play with these parameters and ran into issues.
It will also be better to consider all the control parameters and have a min/max checks on them as well.
Could you explain why min wal size must be at least twice but not equal to wal_segment_size ?
thanks Rajesh
On Sat, May 21, 2022 at 7:08 PM Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> wrote: > > Hi, > > Currently postgres allows setting any value for max_wal_size or > min_wal_size, not enforcing "at least twice as wal_segment_size" limit > [1]. This isn't a problem if the server continues to run, however, the > server can't come up after a crash or restart or maintenance or > upgrade (goes to a continuous restart loop with FATAL errors [1]). > > How about we add GUC check hooks for both max_wal_size and > min_wal_size where we can either emit ERROR or WARNING if values are > not "at least twice as wal_segment_size"? > > Thoughts? > > [1] > FATAL: "max_wal_size" must be at least twice "wal_segment_size" > FATAL: "min_wal_size" must be at least twice "wal_segment_size" > > [2] > ./initdb -D data > ./pg_ctl -D data -l logfile start > ./psql -c "alter system set max_wal_size='2MB'" postgres > ./psql -c "alter system set min_wal_size='2MB'" postgres > ./psql -c "select pg_reload_conf()" postgres > ./pg_ctl -D data -l logfile restart > > Regards, > Bharath Rupireddy. > >
