When libpq is loaded in the server (libpqwalreceiver, dblink, postgres_fdw), it may use libpq environment variables set in the postmaster environment for connection parameter defaults. I have noticed that this has some confusing effects in our test suites. I wonder if this is a good idea in general.
For example, the TAP test infrastructure sets PGAPPNAME to allow identifying clients in the server log. But this environment variable is also inherited by temporary servers started with pg_ctl and is then in turn used by libpqwalreceiver as the application_name for connecting to remote servers where it then shows up in pg_stat_replication and is relevant for things like synchronous_standby_names. Also, the pg_rewind tests appear to rely implicitly on PGHOST and PGPORT being set in the server environment to find the other node via primary_conninfo. That is easy to fix, but it shows that this kind of thing can creep in unintentionally. I was thinking that maybe we should clear all libpq environment variables in the server, or perhaps have a mode in libpq to ignore all environment variables. Then again, maybe setting something like PGSSLMODE globally in the server could be useful, so just removing everything might not be the right answer. Maybe pg_ctl should have some functionality to clear the environment, and maybe there could be a facility in postgresql.conf to set environment variables. Thoughts? -- Peter Eisentraut http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
