Java Mission Control &

Java Flight RecorderM. ISURU T. C. PERERA

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@chrishantha

Agenda Tools in Java Development Kit

What is Java Mission Control (JMC)

Java Flight Recorder (JFR)

Demos

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JDK Tools

• Basic Tools (java, javac, jar)

• Security Tools (jarsigner, keytool)

• Java Web Service Tools (wsimport, wsgen)

• Java Troubleshooting, Profiling, Monitoring and Management Tools (jcmd, jconsole, jmc, jvisualvm)

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Image Source:

http://commons.wikimedia.org/wiki/File:Hand_tools.jpg

Java Troubleshooting, Profiling,

Monitoring and Management Tools

jcmd - JVM Diagnostic Commands tool

jconsole - A JMX-compliant graphical tool for monitoring a Java

application

jvisualvm – Provides detailed information about the Java application. It

provides CPU & Memory profiling, heap dump analysis, memory leak

detection etc.

jmc – Tools to monitor and manage Java applications without introducing

performance overhead

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Java Experimental Tools

Monitoring Tools

jps – JVM Process Status Tool

jstat – JVM Statistics Monitoring Tool

Troubleshooting Tools

jmap - Memory Map for Java

jhat - Heap Dump Browser

jstack – Stack Trace for Java

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What is Java Mission Control?

A set of powerful tools running on the Oracle JDK to

monitor and manage Java applications

Free for development use (Oracle Binary Code License)

Available in JDK since Java 7 update 40

Supports Plugins

Two main tools

JMX Console

Java Flight Recorder

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Starting Java Mission Control

Run “jmc” command in $JAVA_HOME/bin

It runs on Eclipse

It can also be installed on your existing Eclipse

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Troubleshooting Tip

If “jmc” crashes with SIGSEGV on Ubuntu, try following

sudo -E sh -c 'echo org.eclipse.swt.browser.DefaultType=mozilla >>

$JAVA_HOME/lib/missioncontrol/configuration/config.ini'

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Java Process Browser

Uses the Java Discovery Protocol (JDP).

Allows to list and connect to both locally and remotely running Java

applications.

JMC provides full secure access with encrypted communication and

configurable user access restrictions.

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JMX Console

A tool for monitoring and managing multiple Oracle JDK instances via JMX

interface

Captures and presents live data about:

Garbage Collection (GC) Pauses

Memory (Heap Usage)

CPU Usage

Other attributes exposes via MBeans

Provides triggers that can monitor MBeans and trigger an action

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JMX Console

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JMX Console Tabs

Overview – Dashboard, Graphs with real-time usage statistics

System – Information about the JVM

Memory – Monitor heap usage, garbage collection & active memory

pools

Threads – Live thread usage by the application

MBean Browser – Access all registered MBeans

Triggers – Manage rules that trigger events

Diagnostic Commands – Execute commands on JVM

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JMX Console Demo

Sample applications from Marcus Hirt’s Tutorials

(http://hirt.se/blog/?p=611)

Demonstrating

CPU Usage viewing in JMC

View deadlocked threads

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Flight Recorder

“Black box” used in aircraft

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Image Source: http://commons.wikimedia.org/wiki/File:Black_box.aeroplane.JPG

Java Flight Recorder

A profiling and event collection framework built into the Oracle JDK

Gather low level information about the JVM and application are behaving

without performance impact (less than 2%)

Always on Profiling in Production Environments

Engine was released with Java 7 update 4

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Data Collection

JFR stores data in a hierarchy of in-memory buffers.

The data is moved to the disk when the buffers are full

Initially the JFR stores data in thread-local buffers. (Improves throughput,

no synchronization for every event)

Once the thread-local buffer has been filled, the data is transferred to a

global buffer. (Requires synchronization)

After the buffers are full, the data is written to the disk

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Data Analysis

JFR Plugin in JMC provides dynamic and in-depth analysis of all collected

JFR data.

JFR enables users to analyze all aspects of a Java application

Can analyze the Code, Memory, Threads, Locks and I/O

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Type of Events in JFR

Instant events – Events with only one time

Requestable events – Events with a user configurable period

Duration events – Event with a start and end time

Timed events – Duration events with a user configurable threshold

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JFR Recoding Types

Time Fixed Recordings

Fixed duration

The recording will be opened automatically in JMC at the end(If the recording

was started by JMC)

Continuous Recordings

No end time

Must be explicitly dumped

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Enabling Java Flight Recorder

The server VM needs to be started with following options

-XX:+UnlockCommercialFeatures -XX:+FlightRecorder

Make sure to use JDK 7u40 or later

For remote monitoring, start with appropriate com.sun.management flags

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Flight Recording from JMC

Right click on JVM and select “Start Flight Recording”

Select the type of recording: Time fixed / Continuous

Select the flight recording template

Modify the event options for the selected flight recording template

(Optional)

Modify the event details (Optional)

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Start Flight Recording Wizard

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Event Options for Profiling

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Event Details for Profiling

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Flight Recording using startup flags

To produce a Flight Recording from the command line, you can use “-

XX:StartFlightRecording” option. For example

-

XX:StartFlightRecording=delay=20s,duration=60s,name=Test,filename=recording.

jfr,settings=profile

Setting are in $JAVA_HOME/jre/lib/jfr

Use following to change log level

-XX:FlightRecorderOptions=loglevel=info

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The Default Recording

Use default recording option to start a continuous recording

-XX:FlightRecorderOptions=defaultrecording=true

Default recording can be dumped on exit

Only the default recording can be used with the dumponexit and

dumponexitpath parameters

-

XX:FlightRecorderOptions=defaultrecording=true,dumponexit=true,dumponexit

path=/tmp/dumponexit.jfr

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Creating Recording with “jcmd”

command

The command “jcmd” can also be used to start flight recording

Start Recording Example:

jcmd <pid> JFR.start delay=20s duration=60s name=MyRecording

filename=/tmp/recording.jfr settings=profile

Check recording

jcmd <pid> JFR.check

Dump Recording

jcmd <pid> JFR.dump filename=/tmp/dump.jfr name=MyRecording

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Analyzing Flight Recordings

JFR runtime engine dumps recorded data to files with *.jfr extension

These binary files can be viewed from JMC client

There are tab groups showing certain aspects of the JVM and the Java

application runtime such as Memory, Threads, I/O etc.

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Analyzing Flight Recordings

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JFR Tab Groups

General – Details of the JVM, the system, and the recording.

Memory - Information about memory & garbage collection.

Code - Information about methods, exceptions, compilations, and class

loading.

Threads - Information about threads and locks.

I/O: Information about file and socket I/O.

System: Information about environment

Events: Information about the event types in the recording

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Operative Set

A global set of events

Events can be added or removed from the context menu

A check box is used to show events in the operative set

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Flight Recording Demo

Time fixed & continuous recordings

Analyzing

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References

Java Mission Control

Marcus Hirt’s Blog

Advanced Java Diagnostics and Monitoring Without Performance Overhead - Oracle Whitepaper

Oracle Java SE Advanced

InfoQ - Mission Control and Flight Recorder on HotSpot JVM

JMC & JFR - Diagnostic Tools

JDK Development Tools

Java Mission Control and Flight Recorder Demo Series

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Thank you!

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