AWS RDS PostgreSQL error "remaining connection slots are reserved for non-replication superuser connections"

Question

In the dashboard I see there are currently 22 open connections to the DB instance, blocking new connections with the error:

remaining connection slots are reserved for non-replication superuser connections.

I'm accessing the DB from web service API running on EC2 instance and always keep the best practise of:

Connection connection = DriverManager.getConnection(URL, USER_NAME, PASSWORD);
Class.forName(DB_CLASS);
Statement statement = connection.createStatement();
ResultSet resultSet = statement.executeQuery(SQL_Query_String);
...
resultSet.close();
statement.close();
connection.close();

1. Can I do something else in the code?

2. Should I do something else in the DB management?

3. Is there a way to periodically close connections?

Answer 1

Amazon has to set the number of connections based on each model's right to demand a certain amount of memory and connections

MODEL      max_connections innodb_buffer_pool_size
---------  --------------- -----------------------
t1.micro   34                326107136 (  311M)
m1-small   125              1179648000 ( 1125M,  1.097G)
m1-large   623              5882511360 ( 5610M,  5.479G)
m1-xlarge  1263            11922309120 (11370M, 11.103G)
m2-xlarge  1441            13605273600 (12975M, 12.671G)
m2-2xlarge 2900            27367833600 (26100M, 25.488G)
m2-4xlarge 5816            54892953600 (52350M, 51.123G)

But if you want you can change the max connection size to custom value by

From RDS Console > Parameter Groups > Edit Parameters,

You can change the value of the max_connections parameter to a custom value.

For closing the connections periodically you can setup a cron job some thing like this.

select pg_terminate_backend(procpid)
from pg_stat_activity
where usename = 'yourusername'
 and current_query = '<IDLE>'
 and query_start < current_timestamp - interval '5 minutes';