Whenever I inspect a system, there is a system view I like to inspect first before digging deeper. I am, of course, talking about pg_stat_activity. The idea behind the view is to give you a chance to figure out what is going on right now.
Here is how it works:
test=# \d pg_stat_activity View "pg_catalog.pg_stat_activity" Column | Type |... ------------------+--------------------------+-... datid | oid | ... datname | name | ... pid | integer | ... usesysid | oid | ... usename | name | ... application_name | text | ... client_addr | inet | ... client_hostname | text | ... client_port | integer | ... backend_start | timestamp with time zone | ... xact_start | timestamp with time zone | ... query_start | timestamp with ...