Anyone using Java is familiar with the concept of Java class file. It’s the artifact generated from a Java source file after a successful compilation. A class file contains bytecode (instructions) that is interpreted by a Java Virtual Machine (JVM) during execution. As shown in Figure 1, the bytecodes in a class file follows a strict format described in the JVM specification.

It’s been a while since I wrote anything about Java Virtual Machine (JVM). I have been using Java for quite some time, yet my understanding of the inner workings of JVM seems to fade if I don’t refresh it once in a while. This posting is an attempt to renew my memories while trying to add something new. I plan to post a series of articles exploring different aspects of JVM.

In my last posting, I wrote about a Zuul service becoming unresponsive due to the death of a Log4J thread. Here, I will continue our discussion and try to arrive at a resolution to prevent the reoccurrence of the bug in the future.

Recently, I came across a production issue where a Zuul (Spring Cloud Brixton.SR3) edge service became unresponsive to HTTP requests. Even the health REST endpoint, which provides basic health information, of the affected service failed to respond. The Eureka registry service also advertised the unresponsive service as up. It was a Spring Boot (1.3.4.RELEASE) application with an embedded Jetty (9.3.0.v20150612 ) web container running on Red Hat Linux VM with Oracle JVM (1.8.0_31).

Lately, I am getting a few 'how to do' inquiries on my last Swagger posting. Most questions involve either renaming or sorting REST controllers. I also ran into a few interesting Swagger challenges in the last couple of months. Now that it has been over a year since my lasting posting on Swagger, it is a good time to revisit the subject.