How to resolve java.sql.SQLTransientConnectionException: HikariPool Connection is not available, request timed out after 3600000ms

Jan 27, 2025

1. Introduction

When using the HikariCP connection pool in Spring Boot applications, you might encounter the following error:

INFO   | jvm 1    | 2019/07/15 09:10:00 | java.sql.SQLTransientConnectionException: HikariPool-2 - Connection is not available, request timed out after 3600000ms.
INFO   | jvm 1    | 2019/07/15 09:10:00 |       at com.zaxxer.hikari.pool.HikariPool.createTimeoutException(HikariPool.java:548) ~[HikariCP-2.5.1.jar:na]
INFO   | jvm 1    | 2019/07/15 09:10:00 |       at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:186) ~[HikariCP-2.5.1.jar:na]
INFO   | jvm 1    | 2019/07/15 09:10:00 |       at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:145) ~[HikariCP-2.5.1.jar:na]
INFO   | jvm 1    | 2019/07/15 09:10:00 |       at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:99) ~[HikariCP-2.5.1.jar:na]

2. Environments

Spring Boot 1.x and 2.x

3. The Code

application.properties

spring.datasource.jdbcUrl=jdbc:mysql://10.1.1.8/test
spring.datasource.username=bswen
spring.datasource.driverClassName=com.mysql.jdbc.Driver
spring.datasource.maximumPoolSize=20
spring.datasource.connectionTimeout=3600000
spring.datasource.idleTimeout=600000
spring.datasource.minimumIdle=5
spring.datasource.test-on-borrow=true
spring.datasource.test-while-idle=true
spring.datasource.time-between-eviction-runs-millis=3600000

Here, we configure a HikariCP connection pool with a connection size ranging from 5 to 20.

Spring Boot Command

@Component
public class MyCityCommand2 implements CommandLineRunner {
    private static Logger logger = LoggerFactory.getLogger(MyCityCommand2.class);
    @Autowired
    @Qualifier("cityDao")
    private CityDao cityDao;

    @Override
    public void run(String... strings) throws Exception {
        while(true) {
            Thread.sleep(2000);

            JdbcTemplate jdbcTemplate = cityDao.getJdbcTemplateObject(); // Get a JdbcTemplate
            try {
                // Get metadata from the connection
                String dbName = jdbcTemplate.getDataSource().getConnection().getMetaData().getDatabaseProductName();
                logger.info("dbName:" + dbName);
            } catch (Exception ex) {
                logger.error("", ex);
            } finally {
                // Close the connection
                jdbcTemplate.getDataSource().getConnection().close();
            }
        }
    }
}

Pay attention to the lines:

jdbcTemplate.getDataSource().getConnection().getMetaData().getDatabaseProductName()
jdbcTemplate.getDataSource().getConnection().close()

In this code, we retrieve a connection from the JdbcTemplate’s data source and then close it. However, this can lead to connection leaks because the connection retrieved and the one closed might not be the same.

When running the code, you might encounter the following error:

INFO   | jvm 1    | 2019/07/15 09:10:00 | java.sql.SQLTransientConnectionException: HikariPool-2 - Connection is not available, request timed out after 3600000ms.

4. The Solution

Get and Close Specific Connection

To resolve this issue, ensure that you are closing the same connection you retrieved. Modify the code as follows:

@Override
public void run(String... strings) throws Exception {
    while(true) {
        Thread.sleep(2000);

        JdbcTemplate jdbcTemplate = cityDao.getJdbcTemplateObject();
        try (Connection conn = jdbcTemplate.getDataSource().getConnection()) {
            String dbName = conn.getMetaData().getDatabaseProductName();
            logger.info("dbName:" + dbName);
        }
    }
}

5. Summary

When using a connection pool in Spring Boot applications, it is crucial to manage connections properly to avoid leaks. If you encounter connection timeout issues, check whether you are closing the correct connection. Using try-with-resources can help ensure that connections are closed properly.

Final Words + More Resources

My intention with this article was to help others who might be considering solving such a problem. So I hope that’s been the case here. If you still have any questions, don’t hesitate to ask me by email: Email me

Here are also the most important links from this article along with some further resources that will help you in this scope:

👨‍💻 Spring Boot and HikariCP

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