too many clients in postgresql in docker-swarm with spring boot - postgresql

Question

I set up a development environment in docker swarm environment, which consists of 2 nodes, a few networks and a few microservices. Following gives an example how it looks in cluster.
Service Network Node Image Version
nginx reverse proxy backend, frontend node 1 latest stable-alpine
Service A backend, database node 2 8-jre-alpine
Service B backend, database node 2 8-jre-alpine
Service C backend, database node 1 8-jre-alpine
Database postgresql database node 1 latest alpine
Services are spring boot 2.1.7 applications with boot-data-jpa. All the services above contain database connection to postgresql instance. For database I configured only following properties in application.properties:
spring.datasource.url
spring.datasource.username
spring.datasource.password
spring.datasource.driver-class-name
spring.jpa.hibernate.ddl-auto=
spring.jpa.properties.hibernate.jdbc.lob.non_contextual_creation=true
After some time I see that the connection limit in postgresql exceeds, which does not allow to create a new connection.
2019-09-21 13:01:07.031 1 --- [onnection adder] com.zaxxer.hikari.pool.HikariPool : HikariPool-1 - Cannot acquire connection from data source org.postgresql.util.PSQLException: FATAL: sorry, too many clients already
A similar error is shown also when I try to connect over ssh to database.
psql: FATAL: sorry, too many clients already
What I tried till now:
spring.datasource.hikari.leak-detection-threshold=20000
which didnt help.
I found several answers to this problem like:
increase connection limit in postgresql
No I dont want to do this. It is just a temporary solution. It will pollute the connection again but a bit later maybe.
add idle timeout in hikaripCP configuration
Default configuration of hikariCP has already a default value of 10mins, which doesnt help
add max life time to hikariCP configuration
Default configuration of hikariCP has already a default value of 30mins, which doesnt help
reduce number of idle connection in hikariCP configuration
Default configuration of hikariCP has already a default value of 10, which doesnt help
set min idle in hikariCP configuration
Default is 10 and I am fine with it. b
I am expecting a connection around 30 for the services but I find nearly 100 connections. Restarting the services or stopping them does not close the idle connections neither. What are your suggestions? Is it a docker specific problem? Did someone experience the same problem?