Apache Tomcat is an open-source HTTP web server developed by the Apache Software Foundation, widely used for serving Java applications across various operating systems. It implements key Java technologies such as Servlet, JavaServer Pages, Java Expression Language, and WebSocket, and consists of components like Catalina, Coyote, Jasper, and Cluster for efficient operation. Monitoring Tomcat's performance is essential, as poor performance impacts end-user experience, and integrating with Datadog allows for comprehensive metric collection and visualization. Datadog pulls metrics into an out-of-the-box dashboard, categorizing them into general, thread pool, servlet, and JSP metrics, offering insights into server resource consumption and performance. For example, metrics like `tomcat.servlet.processing.time` provide critical insights into user experience and infrastructure efficiency. Datadog's integration facilitates quick identification of performance issues and can be easily configured, enhancing the monitoring capabilities for Apache Tomcat users.