Postgres raise `remaining connection slots are reserved for non-replication superuser connections` error

The Reporting service raised the following error today:

FATAL: remaining connection slots are reserved for non-replication superuser connections

I check the database activity and relevant configurations via the following commands:

check current using connection number:
select count(1) from pg_stat_activity;

check all the connections(not include current client connection):
select datname, pid, application_name, state from pg_stat_activity; where pid<>pg_backend_pid();

show max connections limit
show max_connections;

show system user reserved connections
show superuser_reserved_connections;

Solutions

1. kill all the idel connection in the database:
   select pg_terminate_backend(pid) from pg_stat_activity where pid<>pg_backend_pid() and state='idle';

2. Modify to increase the max_connections in Postgresql configuration file
   in /var/lib/pgsql/{version}/data/postgresql.conf
   change:
   max_connections = 200 # 100 is default value
   shared_buffers = 50MB # 24 is default value, a reasonable starting value is 25% of the memory in the system

3. Increase the kernel max segment size slightly larger than shared_buffers
   in /etc/sysctl.conf, set:
   kernel.shmmax=62914560 #(60MB)
   this takes effect when postgresql reboot