Checking pg_stat_replication

Checking the archive and archive_command is primarily for Point-In-Time-Recovery. If you want to monitor a streaming-based setup, it is advised to keep an eye on a system view called pg_stat_replication. This view contains the following information:

test=# \d pg_stat_replication
          View "pg_catalog.pg_stat_replication"
      Column      |           Type           | Modifiers
 ------------------+--------------------------+-----------
  pid              | integer                  |
  usesysid         | oid                      |
  usename          | name                     |
  application_name | text                     |
  client_addr      | inet                     |
  client_hostname  | text                     |
  client_port      | integer                  |
  backend_start    | timestamp with time zone |
  backend_xmin     | xid                      |
  state            | text                     |
  sent_location    | pg_lsn                   |
 ...