Contributing to JDK Mission Control

Copyright © 2017, Oracle and/or its affiliates. All rights reserved.
Contributing to Mission Control
The OpenJDK Project
Marcus Hirt
Consulting Member of Technical Staff
OMC
October, 2018

Agenda
• Introduction to JDK Mission Control
• How to Contribute
– Process
– Tools and Techniques
– Resources
• Roadmap
• Q & A
2

Introduction to JMC
3

Introduction to JDK Mission Control
Mission Control is:
• A Production Time Profiling and Diagnostics Tools Suite
– A JMX console
– A visualizer of JDK Flight Recorder data (henceforth ”flight recordings”)
• Extensible with plug-ins
– Joverflow (hprof format dump analyzer)
• A set libraries to parse and analyse flight recordings
• Open Source! (2018-05-03)
4

Copyright © 2017, Oracle and/or its affiliates. All rights reserved. 5
JFR
Recording
Java Mission Control
Local JVM Process
Local JVM Process
Local JVM Process
Local JVM Process
Remote JVM
Processes
JFR
Recording
JFR
Recording

JMC Demos

Where to get JDK Mission Control?
• Release of JDK Mission Control is planned to 2019-01-30
• But OpenJDK 11 contained the first open source version JFR, what to do?
à Working EA builds available here: http://jdk.java.net/jmc/ ß
7

What About the Core Libraries?
Group: org.openjdk.jmc
Artifacts: common,
flightrecorder,
flightrecorder.rules,
flightrecorder.rules.jdk
Version: 7.0.0-SNAPSHOT
8
<dependency>
<groupId>org.openjdk.jmc</groupId>
<artifactId>common</artifactId>
<version>${jmc.version}</version>
</dependency>
<dependency>
<artifactId>flightrecorder</artifactId>
</dependency>
<dependency>
<artifactId>flightrecorder.rules</artifactId>
</dependency>
<dependency>
<artifactId>flightrecorder.rules.jdk</artifactId>
</dependency>

Contributing to OpenJDK JMC
9

Processes
• JMC is an OpenJDK Project
– Follows the same basic processes in terms of roles and responsibilities
– Uses some of the same tools (Mercurial, webrev) for the main source repos
• Branching is slightly different to the JDK project
– Lazy-branching at Ramp Down Phase 2
• Ongoing development takes place in the main-line Mercurial repo
http://hg.openjdk.java.net/jmc/jmc/
10

Experimenting with Development at GitHub
• JMC Flame Chart View in repo at GitHub
– Experiment - development of stand alone functionality at GitHub?
– Later include in main-line?
– Every contribution still requires OCA
11

First Contribution
• To contribute
– Must either sign an OCA (Oracle Contributor Agreement)…
– …or work for a company with a signed OCA
• Find something intersting to work on
– Discuss on the IRC (#jmc at OFTC)
– Join the mailinglist (jmc-dev)
– Search the bug database (JBS, project JMC, label ’polish’ good start)
12

First Contribution
• Discuss the intended change
– E-mail the jmc-dev list with subject <bugid>: <summary> ß preferred
– Discuss on the IRC
• Submit a patch
– The patch must be built and tested (Windows, Linux and Mac) before submission
– When ready, send a message to the jmc-dev
• Subject should be [PATCH] JMC-1234: Bug description
• A description of the change
• The code change (more on this later)
• A unit test, when applicable
13
Continued (1/2)

First Contribution
• Work with your sponsor
– Find a JMC Committer to sponsor your change
– If a JMC Committer is found to sponsor the bug, that Committer will take ownership
of the bug
– The Committer will be responsible for first evaluation of the patch
• Review
– All code entering the JMC project will be reviewed (informal demand)
14
Continued (2/2)

Project Roles
• Becoming a Participant
– Someone who has subscribed to the jmc-dev list
• Participants can:
– Post messages to the dev-list
15
Participant

Project Rules
• Becoming a Contributor
– Sign the OCA (or work for an organization with a signed OCA)
• Contributors can:
– Submit patches to the mailinglist
16
Contributor

Project Roles
• Becoming an Author
– Have at least two sponsored contributions
– Likely to continue contributing in the future
– Any Contributor may request the Author role by contacting the JMC Project Lead
• Author perks
– An OpenJDK username
– Access to cr.openjdk.java.net for publishing patches (webrevs)
17
Author

Project Roles
• Becoming a Committer
– Approved by Lazy Consensus by the project Committers
– As a rough guide, should have contributed 8 significant contributions
– Any Committer can nominate a Contributor or an Author to Committer
• Committer Perks
– Granted right to directly push change sets
18
Committer

Current JMC People
• Lead
– Marcus Hirt
• Reviewers
– Erik Gahlin
– Erik Greijus
– Henrik Dafgård
– Klara Ward
– Ola Westin
– Per Kroon
• Committers
– David Buck
– Guru Hb
– Mario Torre
– Sharath Ballal
• Authors
– Joshua Matsuoka
– Mirosla Wengner
– Tejpal Rebari
– Deepa Avhad
19

Tools
• Mercurial (SCM)
• Maven (3.5.3+)
• JDK 8 (for building the application)
20

Mercurial
• Is not Git…
• …but is similar enough
• Getting the JMC main-line source:
hg clone http://hg.openjdk.java.net/jmc/jmc/
21

Building JMC Core Libraries
• Core built with vanilla Maven
• Either mvn package or mvn install (to fulfil dependencies from other code,
such as the application)
22
>cd core
>mvn install
[INFO] Blah, blah, blah…
[INFO] BUILD SUCCESS
[INFO] ---------------------
[INFO] Total time: 01:12 min
[INFO] ---------------------
>

Building the Application
• The application is built with Maven + Tycho
– Depends on the previously installed core modules
– Requires a local p2 repository to be built and run for the third party dependencies
23
>cd releng/thirdparty
>mvn clean package
>mvn p2:site
>mvn jetty:run
[INFO] Blah, blah, I am Jetty, blah, blah…
[INFO] Started Jetty Server
[INFO] Starting scanner at interval of 60
seconds.
>mvn clean package
[INFO] Downloading The Internet…
[INFO] Resolving ALL the bundles…
[INFO] Blah, blah, blah…
[INFO] BUILD SUCCESS
[INFO] ---------------------
[INFO] Total time: 02:02 min
[INFO] ---------------------
>

Process for a Committer
24
Start Fixing
Bug/Enhancement
• (Discuss on the jmc-
dev list / IRC)
• Assign Bug in JBS
• Set bug to in progress
• (Discuss on the jmc-
dev list / IRC)
Post patch for
review
• ksh /usr/local/bin/webrev.ksh
-> webrev
• mv webrev ../webrevs/JMC-
1234/webrev.01
• rsync -avz JMC-1234
<openjdkid>@cr.openjdk.java.net:~/
• Post request to jmc-dev mailinglist
Push the
changes
• hg commit
(See the
commit
message
template)
• hg push

Roadmap
• JMC 7
– GA release planned for 2019-01-30
– Support for Oracle JDK 7, 8, 9, 10, 11, support for OpenJDK 11
– New contributors, new stand alone release format, new build system (Maven +
Tycho), bug fixes, enhancements…
• JMC 7.1
– GA release planned for 2019-03-19
– Support for JDK 12
– Support for cipher events (visualization/rules)
– Enhancements to the Trace View (filtering, focus on methods etc)
– Improved overview visualization of all threads/events (behave more like 5.x)
25

Roadmap, cont’d
• JMC 7.2
– GA release not decided, but likely September 2019
– JMC BCI agent
– Improved range navigator
– Better UI support for the OldObject sample event.
– FlameChart view (run at https://github.com/thegreystone/jmc-flame-view)
• JMC 8
– Being discussed with the community
26

Support for Cipher
Events
Roadmap
Open Source JMC
Support for JDK11 Core on Maven
Central
Build and Release
updates
Streaming JFR
support?
Tighter IDE
Integration
Data Race
Detection
Flame Chart View
All the Events!
JMC Agent
Improved Thread
Visualization
JMC 7.0.0
(In development)
JMC 7.1.0
JDK 12
JMC 7.2.0
JDK 13
Integrated support
for JMC Agent
Future
On-Line Heap
Analysis
Agent Rules
Engine?
JMC 8.0.0
JDK 14
Differential Analysis Multi Process
Analysis

Safe Harbor Statement
The preceding is intended to outline our general product direction. It is intended for
information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.

Resources
• OpenJDK: http://openjdk.java.net/projects/jmc/
• My blog: http://hirt.se/blog
• Forum: http://oracle.com/missioncontrol (click Discussion)
• IRC: #jmc at OFTC (https://webchat.oftc.net/?nick=&channels=jmc)
• Dev list: http://mail.openjdk.java.net/mailman/listinfo/jmc-dev
• Twitter: @javamissionctrl, @hirt
• EA builds: http://jdk.java.net/jmc/
29

Other JMC-/JFR-related Presentations
Day Time Title Location
Monday 10:30 Contributing to the Mission Control OpenJDK Project MW 2004
Tuesday 11:30 Three Productive Ways to Use Open Source Java Flight Recorder and
Java Mission Control
MW 2024
Tuesday 14:30 Fast and Furious: Java Flight Recorder and Flame Graphs MW 2020
Wednesday 10:30 Production-Time Profiling and Diagnostics on the JVM MW 2004
Wednesday 12:30 OpenJDK Mission Control: The Hands-on-Lab MW 2001A
Wednesday 16:30 Diagnose Your Microservices: OpenTracing/Oracle APM Cloud MW 2011
Thursday 11:00 Getting Started with the (Open Source) JDK Mission Control MW 2014
Thursday 12:30 Flight Recorder in OpenJDK MW 2018
30

Contributing to JDK Mission Control

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