how to limit the database connection created by spring boot application running microservices

Question

I am working on my school project to make an application with microService architecture (with maven and spring boot JPA) hardware i am using: aws RDS (max DB connection is 66, and this caused my problem) aws ec2-instance free tier I am having 3 microservices: employee,salary and leave. However, with only 3 micro services running, my DB connection reached 40+. I cannot figure out how to limit the number of DB connection a service can create.

After some research i encountered the term "connection pool", so i tried to set up tomcat connection pool.

this is the configuration(i did both for) but it does not work am i right to say that if the configuration is right, my application would only make max 5 active connection?

spring.datasource.tomcat.initial-size=5
spring.datasource.tomcat.max-wait=20000
spring.datasource.tomcat.max-active=5
spring.datasource.tomcat.max-idle=5
spring.datasource.tomcat.min-idle=1
spring.datasource.tomcat.default-auto-commit=true   

this is the code for the query

public interface EmployeeRepository extends JpaRepository<Employee, Integer> {
    @Query(
            value = "select * from itsa.Employee;",
            nativeQuery = true)
    List<Employee> findAllEmployee();

    @Query(
            value = "SELECT * FROM Employee where id = :id",
            nativeQuery = true)
    List<Employee> findEmp(@Param("id") int id);

Answer 1

Default CP in Spring boot is HikariCP. as soon as you include spring-boot-starter-data-jpa in pom.xml, you will have HikariCP configured for you with default values.

if you want you configuration get effective, you need to exclude HikariCP and include tomcat-cp. for this, you need to make below changes to your pom.xml.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
    <exclusions>
        <exclusion>
            <groupId>com.zaxxer</groupId>
            <artifactId>HikariCP</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat-jdbc</artifactId>
    <version>9.0.10</version>
</dependency>

Hope this helps solving your issue.