Monitoring Java applications: Memory usage, threads and other JRE metrics

Monitoring Java applications involves analyzing various metrics within the Java Runtime Environment (JRE) to ensure optimal performance and troubleshoot issues. Key aspects include understanding memory usage by profiling stack and heap memory, which are crucial for preventing memory leaks and unexpected service degradation. The stack handles function calls and local variables, while the heap is used for object allocation, both of which need careful monitoring to avoid issues like OutOfMemoryError. Garbage collection processes, such as the Serial, Parallel, CMS, and G1 collectors, play a vital role in memory management by freeing up unused memory, though they introduce overhead and need configuration based on application requirements. Thread monitoring is essential, especially in a concurrent environment, to manage system resources effectively and prevent performance bottlenecks. The use of tools like Sysdig allows for effective monitoring without direct instrumentation of Java applications, offering insights into kernel metadata and events, which is particularly useful in containerized environments like Docker and Kubernetes. The article highlights the importance of understanding JRE metrics and suggests that further exploration into Java Management Extensions and Managed Beans can enhance observability at the application layer.