When a Java application running on Apache Tomcat becomes slow, starts returning errors, or stops responding, restarting the service is often the easiest option.

But a restart doesn't explain what happened.

The real challenge is identifying whether the problem comes from the JVM, the application, the operating system, the network, or an external dependency.

In this article, we'll walk through a practical workflow for investigating Java and Tomcat issues on a Linux server.

1. Start with the Symptoms

Before changing JVM options or restarting Tomcat, establish what is actually failing.

Is the application completely unavailable, or are requests simply taking longer than usual? Are all endpoints affected, or only a specific operation?…