Logical replication monitoring

Hello PostgreSQL Community!

I configured logical replication for PostgreSQL 10.4 on 2 machines, set
wal_level to logical, created a publication on master node and created a
subscription on standby node according to the PostgreSQL documentation.
Could you please suggest an approach for replication state monitoring.

According to my experience the monitoring of pg_stat_subscription and
pg_publication, pg_replication_slots unfortunately is not enough for this
aim. Moreover standby database does not prohibit write operations by
default and it can lead to some inconsistency between these databases.

For example a chain of queries as
SELECT pg_is_is_recovery(),
SELECT * FROM pg_stat_replication and
SELECT * FROM pg_stat_wal_receiver
provide insight into replication state for hot_standby replication.

So is there a reliable way of replication state monitoring for logical
replication?

Best regards,
Andrei Yahorau