Скачать или смотреть Resolving Tomcat 8.5 Connection Pool Issues After Database Failover

Discover how to tackle the `Tomcat 8.5 Connection Pool` not reconnecting after database failover, utilizing an AWS RDS Proxy for seamless operation.
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Resolving Tomcat 8.5 Connection Pool Issues After Database Failover

In today's world, reliable database connections are crucial for any application, especially when using a connection pool like Tomcat 8.5. A frequent challenge developers face is handling situations where a database failover occurs. Recently, a user experienced a frustrating issue where after a failover, the Tomcat connection pool failed to reconnect to the database, leading to multiple exceptions. Let’s delve into the problem and explore a robust solution.

The Problem: Connection Pool Failover Failure

The user had a Java application running on Tomcat 8.5, utilizing a Multi-AZ AWS RDS MySQL database. Historically, their setup was resilient enough to handle failovers smoothly; connections were restored automatically within a minute after issues arose. However, they encountered a scenario where:

A hardware failure caused the primary database to go offline, leading to a failover.

While connections could be established through a standalone MySQL client post-failover, the application's connection pool continued to fail.

The connection pool repeatedly logged exceptions such as:

[[See Video to Reveal this Text or Code Snippet]]

Despite the availability of the backup database, the application persisted in failing to establish new connections until the entire Tomcat server was restarted. This raised a significant concern about the reliability of the connection pool handling under adverse conditions.

Configuration Snapshot

Understanding the existing configuration is essential to pinpoint issues. Here are key points from the user’s pool configuration:

Initial Size: 5

Max Active Connections: 16

Idle Connections: 5 (min) and 8 (max)

Wait Time for Connection: 10 seconds

Max Connection Age: 10 minutes

Validation Queries: SELECT 1

JDBC URL Parameters: autoreconnect=true&socketTimeout=20000

Observations

Validation Query: This is set to check connection health; it was anticipated that after a failover, this would fail and connections would be discarded.

Max Age: Under normal circumstances, connections would expire after 10 minutes, suggesting that connections should have been replaced if they were still in use.

Yet, despite these measures, the pool remained unresponsive after the relevant failover.

The Solution: Introducing AWS RDS Proxy

After evaluating potential solutions, a noteworthy fix was proposed: adding an AWS RDS Proxy. This proxy acts as an intermediary between the application and the database, skillfully managing connections.

Benefits of Using AWS RDS Proxy

Seamless Failover Handling: The proxy can automatically route traffic to the standby database instance during failover events.

Improved Connection Management: By pooling connections, the proxy reduces overhead and latency related to establishing new connections.

No Code Changes Required: Implementing the proxy meant that the existing application didn't need modifications; the only adjustment was updating to the new proxy endpoint.

Results

The user tested the new setup by simulating database failovers. They noticed:

The application maintained connectivity even during brief outages of up to 20 seconds.

System performance significantly improved with considerably fewer connection-related errors.

Conclusion

Failovers can be daunting, but with careful planning and proper configuration, their impact can be mitigated. For users facing a similar challenge with Tomcat 8.5 Connection Pool, integrating an AWS RDS Proxy could be a game changer. This solution not only stabilizes your application during database disruptions but also enhances overall application reliability without extensive code modifications.

For database administrators