Support connect_query via PGBOUNCER_CONNECT_QUERY

Squashed version of #1 and
heroku#95 to make
patches easier to carry forward.

Author: nixme

README.md

@@ -146,6 +146,7 @@ Some settings are configurable through app config vars at runtime. Refer to the
 - `PGBOUNCER_SERVER_RESET_QUERY` Default is empty when pool mode is transaction, and "DISCARD ALL;" when session.
 - `PGBOUNCER_IGNORE_STARTUP_PARAMETERS` Adds parameters to ignore when pgbouncer is starting. Some postgres libraries, like Go's pq, append this parameter, making it impossible to use this buildpack. Default is empty and the most common ignored parameter is `extra_float_digits`. Multiple parameters can be seperated via commas. Example: `PGBOUNCER_IGNORE_STARTUP_PARAMETERS="extra_float_digits, some_other_param"`
 - `PGBOUNCER_QUERY_WAIT_TIMEOUT` Default is 120 seconds, helps when the server is down or the database rejects connections for any reason. If this is disabled, clients will be queued infinitely.
+- `PGBOUNCER_CONNECT_QUERY` Default is empty. The query to be executed on newly created connections. This is useful for setting things like `statement_timeout`. e.g. `PGBOUNCER_CONNECT_QUERY="set statement_timeout to 10000"`
 
 For more info, see [CONTRIBUTING.md](CONTRIBUTING.md)
 

bin/gen-pgbouncer-conf.sh

@@ -90,7 +90,7 @@ do
 EOFEOF
 
   cat >> "$CONFIG_DIR/pgbouncer.ini" << EOFEOF
-$CLIENT_DB_NAME= host=$DB_HOST dbname=$DB_NAME port=$DB_PORT
+$CLIENT_DB_NAME= host=$DB_HOST dbname=$DB_NAME port=$DB_PORT ${PGBOUNCER_CONNECT_QUERY:+connect_query=\'${PGBOUNCER_CONNECT_QUERY//\'/\'\'}\'}
 EOFEOF
 
   (( n += 1 ))