JDK Flight Recorder

How & When to Use JDK Flight Recorder in Production

While it would certainly be useful to record the whole lifetime, this is unpractical, even airplane Flight Data Recorders (and Cockpit Voice Recorders) only keep recent history.

Instead, it’s possible to aim at specific time frames where a recording could be useful.

Control JFR Programmatically

While from JDK 14 events can be consumed on the fly, previous JDK versions (from JDK 11) offer a public API useful enough to control Flight Recorder programmatically or to read events from a JFR file.

Such API facilities are useful especially when combined with other technologies like Spring Actuators. Yet when there’s available integration or when using these integrations is too late, like recording startup, the most actionable way to get recording is from the command line.

Continuous Production Profiling and Diagnostics

I’ve gotten a lot of questions about continuous production profiling lately. Why would anyone want to profile in production, or, if production profiling seems reasonable, why the heck leave it on continuously?

I thought I’d take a few moments and share my take on the problem and the success I’ve seen the past years applying continuous production profiling in systems in the real world.

Profiling these days is no longer limited to high overhead development profilers. The capabilities of the production time profilers are steadily increasing and their value is becoming less controversial, some preferring them for complex applications even during development.

Analyze JFR Recordings

Continuing from part 1, to exploit the recording by analyzing it, we have a tool named jfr that ships with the JDK. On Linux the alternative jdk management may not be aware of jfr, which means you may need to use the full path to this executable.

The first interesting thing to do is to get an overview of the recording, the summary sub-command displays an histogram of the events.

Get Started with JDK Flight Recorder

Java Flight Recorder is the profiler you can use in production, continuously.

Flight Recorder has been available before in the JDK, e.g., it shipped as part of the JDK 8, but to use it, it required that you set specific commercial VM flags to unlock Flight Recorder, this is not anymore necessary from Java 11 onwards.

Introducing JmFrX: A Bridge From JMX to Java Flight Recorder

JmFrX is a small utility which allows you to capture JMX data with Java Flight Recorder.

In this blog post I’m going to explain how to use JmFrX for recording JMX data in your applications, point out some interesting JmFrX implemention details, and lastly will discuss some potential steps for future development of the tool.

Monitoring REST APIs with Custom JDK Flight Recorder Events

The Java Flight Recorder (JFR) is an invaluable tool for gaining deep insights into the performance characteristics of Java applications.

In this blog post, we’re going to explore how custom, application-specific JFR events can be used to monitor a REST API, allowing to track request counts, identify long-running requests, and more.

A Closer Look at JFR Streaming

Since JDK 14, there is a new kid on the block – Java Flight Recorder streaming, which enables developers to subscribe to JFR data.

It is a feature allowing a developer to subscribe to select JFR data and to decide what to do with that data in the host process. JFR events can also be consumed from a separate process by pointing to the file repo of a separate JVM process – the mechanism is the same.