JDK Flight Recorder: Difference between revisions

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{{short description|Production time profiling and diagnostics for OpenJDK}}

'''JDK Flight Recorder''' is an event recorder built into the OpenJDK <ref>{{cite web |title=OpenJDK |url=https://openjdk.org/| accessdate=28 June 2023}}</ref> [[Java virtual machine]]. It can be thoughthought of as the software equivalent of a Data Flight Recorder (Black Box) in a commercial aircraft. It captures information about the [[Java virtual machine|JVM]] itself, and the application running in the JVM. There is a wide variety of data captured, for example method profiling, allocation profiling and garbage collection related events. The '''JDK Flight Recorder''' was designed to minimize the [[Observer effect (information technology)|Observer Effect]] in the profiled system, and is meant to be always on in production systems. The technology was open sourced in 2018.

Analysis and visualization of flight recordings are normally done using [[JDK Mission Control]].

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* Binary representations, no translations back and forth to strings, the buffers are efficiently emitted to disk

* Most events are recorded into thread local native buffers

* On some platforms invariant [[Time Stamp Counter|TSC]] is employed for efficient time stamping

* Integer compression scheme, to keep in-memory and on-file size down

* Since implemented in the JVM, much data is readily available, or emitted at a time when the data is readily available, keeping cost down

If converting a binary recording to JSon[[JSON]], it can easily blow up by two orders of magnitude or more, depending on length and content recorded.

The expected performance overhead of JFR using the default template is less than a percent, and for the profiling template, less than two percent.

==History==

JDK Flight Recorder started out as JRockit Flight Recorder, and was originally used as a means to collect data to be used to improve the JVM itself.<ref>{{cite web |title=JRockit Flight Recorder Runtime Guide |url=https://docs.oracle.com/cd/E15289_01/JRMCF/E15070-10.pdf |accessdate=22 January 2019}}</ref><ref>{{cite book |title=Oracle JRockit: the Definitive Guide |year=2010 |publisher=Packt Pub |isbn=1847198066978-1847198068 |pages=588 |url=https://www.amazon.com/Oracle-JRockit-Definitive-Marcus-Hirt/dp/1847198066}}</ref> After Oracle acquired [[Sun Microsystems]], JRockit Flight Recorder was rebranded Java Flight Recorder.<ref>{{cite web |title=Java Flight Recorder Runtime Guide |url=https://docs.oracle.com/javacomponents/jmc-5-4/jfr-runtime-guide/about.htm#JFRUH170 |accessdate=22 January 2019}}</ref> In 2018 Java Flight Recorder was open sourced and released as part of [[OpenJDK]] 11.<ref>{{cite web |title=JEP 328: Flight Recorder |url=https://openjdk.java.net/jeps/328 |accessdate=22 January 2019}}</ref> When open sourced it was rebranded JDK Flight Recorder, due to Java trademark issues.

==Versions==

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| v2.0 || Oracle JDK 11+, Open JDK 11+, Azul JDK 8 and Azul JDK 11+

|}

==Development==

The development of JDK Flight Recorder is taking place as part of the OpenJDK JDK <ref>{{cite web |title=OpenJDK JDK Project |url=https://openjdk.org/projects/jdk/| accessdate=28 June 2023}}</ref> project on GitHub,<ref>{{cite web |title=GitHub OpenJDK JDK |website=[[GitHub]] |url=https://github.com/openjdk/jdk| accessdate=28 June 2023}}</ref> although most of the public discussions are taking place on the OpenJDK hotspot-jfr-dev <ref>{{cite web |title=hotspot-jfr-dev mailing list |url=https://mail.openjdk.org/pipermail/hotspot-jfr-dev/| accessdate=28 June 2023}}</ref> [[mailing list]].

==See also==

{{Portal|Free and open-source software|Java (programming language)|Computer programming}}

* [[Java platform]]

* [[JDK Mission Control]]

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{{Reflist}}

[[Category:FreeJava (programming language) software]]

==External links==

[[Category:JavaFree computer programming tools]]

[[Category:Free software]]