30.6. Monitoring
Because logical replication is based on a similar architecture as physical streaming replication , the monitoring on a publication node is similar to monitoring of a physical replication master (see Section 26.2.5.2 ).
  The monitoring information about subscription is visible in
  
   
    pg_stat_subscription
   
  
  .
   This view contains one row for every subscription worker.  A subscription
   can have zero or more active subscription workers depending on its state.
 
Normally, there is a single apply process running for an enabled subscription. A disabled subscription or a crashed subscription will have zero rows in this view. If the initial data synchronization of any table is in progress, there will be additional workers for the tables being synchronized.