make it easier to run multiple clusters with the same extension installed

[jyn514]

postgres has a plethora of features that can only be tested with multiple clusters, the biggest one being replication. unfortunately, it is not easy to run multiple clusters with pgrx. @workingjubilee suggested setting PGRX_HOME to different values between invocations of pgrx, but that requires rebuilding and reinstalling lots of things. it would be nice to have this as a built-in feature.

i wrote a shell script to work around this in the meantime, which i look forward to burning.

i am so sorry

set -ex

data=$HOME/.pgrx/data-16
conf=$data/postgresql.conf
wal_backup=$(realpath ./wal-archive)
mkdir -p $wal_backup

cargo pgrx stop
rm -r $data ~/.pgrx/16.log standby.log
# recreate default config before we edit it
cargo pgrx start
cargo pgrx stop
# listen_addresses = ""  # already configured to localhost
echo \
"shared_preload_libraries = 'my-extension'
archive_command = 'test ! -f $wal_backup/%f && cp %p $wal_backup/%f'
archive_mode = on
archive_timeout = 5s  # this is unreasonably short, but we only use this database for testing
"  >> $conf

# create standby
rm -rf data-standby
cp -r $data data-standby
touch data-standby/standby.signal
cp $conf data-standby
echo "\
# restore_command = ''
primary_conninfo = 'postgresql://%2Fhome%2Fjyn%2F.pgrx'
port = 28817  # avoid conflicting with the primary
" >> data-standby/postgresql.conf

cargo pgrx stop
$(cargo pgrx info path 16)/bin/pg_ctl stop -D data-standby -o "-c unix_socket_directories=/home/jyn/.pgrx" || true
killall postgres || true # standby
cargo pgrx start  # make sure to do this before starting the standby so we load the right version of the .so
[ -e "/home/jyn/.pgrx/.s.PGSQL.28816" ] || exit 1
trap "cargo pgrx stop" EXIT
$(cargo pgrx info path 16)/bin/pg_ctl start -D data-standby -l standby.log -o "-c unix_socket_directories=/home/jyn/.pgrx"
trap "$(cargo pgrx info path 16)/bin/pg_ctl stop -D data-standby -o '-c unix_socket_directories=/home/jyn/.pgrx' >/dev/null" EXIT

# run queries with $(cargo pgrx info path 16)/bin/psql -p 28817 -d my-extension -h ~/.pgrx