monitoring and troubleshooting tools...termination of hotspot jvm based java applications...

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Monitoring and Troubleshooting Tools Available in Your Java 9 “bin” Folder

Poonam Parhar Consulting Member of Technical Staff JVM Sustaining Engineer, Oracle


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What is Troubleshooting ?

• Systematic approach to solving problems

• Three simple steps:

1. Understand the problem/error

2. Collect the required diagnostic data

3. Analyze the collected data

• Good Troubleshooting tools are our friends!

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JDK Troubleshooting Tools

• Tools that allow us to

– Monitor Java applications

– Profile Java applications

– Extract useful diagnostic information from Java applications

– Analyze diagnostic data

– Even perform after-the-fact analysis

• Can work locally or remotely

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Agenda

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Tools available in JDK 9 ‘bin’ folder

1. Monitoring Tools

2. Troubleshooting Tools

3. Newly Added Tools

4. Decommissioned Tools


Monitoring Tools

• jconsole - Starts a graphic console to monitor and manage Java applications.

• jps - Experimental: Lists the instrumented Java Virtual Machines (JVMs) on the target system.

• jstat - Experimental: Monitors JVM statistics

• jstatd - Experimental: Monitors JVMs and enables remote monitoring tools to attach to JVMs.

• jmc – Java Mission Control: JMX console, and JFR recording and analysis tool

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Automated Analysis


JConsole

• JConsole is a GUI based monitoring tool for Java applications

• JMX client

• Helps in monitoring and managing

– Java Applications and the JVM

– Live and remote applications

• jconsole executable available in JDK/bin

• Using JConsole locally is not recommended for production environments

• For remote monitoring: com.sun.management.jmxremote.port=portNum

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Java

Ap

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8

JMX Client Application

Inst

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ted

JV

M

JMX

Age

nt

MBean Server

MBean MBean

MBean


jps (experimental) – Java Process Status tool

• Lists the JVMs running on the system

• Obtains processes information from /tmp/hsperfdata_user/<pid> files

• List of the JVMs reported can be limited by the OS level permissions granted to the user

• Can list the JVMs on local or remote hosts

• For remote monitoring ‘jstatd’ should be running on the remote system

• Accepts optional argument <protocol:><//hostname>:[<port>]

• On local hosts, the VM identifier is typically the OS process id of the application

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$ jps -h illegal argument: -h usage: jps [-help] jps [-q] [-mlvV] [<hostid>] Definitions: <hostid>: <hostname>[:<port>] $ jps -m 9848 GCBasher.jar -time:100000000 7084 Jps –m $ jps -l 3056 jdk.jcmd/sun.tools.jps.Jps 9848 GCBasher.jar $ jps -v 6324 Jps -Dapplication.home=d:\Java\jdk-9 -Xms8m -Djdk.module.main=jdk.jcmd 9848 GCBasher.jar C:\Users\pobajaj.ORADEV>jps -q 9876 9848

jps examples


jstat (experimental) – JVM Statistics

• Tool to monitor JVM statistics

• Performance statistics about HotSpot JVM

• Reads information from /tmp/hsperfdata_user/<pid> file

• Accepts various options to print statistics about different components of the JVM

– class, compiler, gc, gccapacity, gccause, gcnew, gcnewcapacity, gcold, gcoldcapacity, gcmetacapacity, gcutil, printcompilation

• For remote monitoring ‘jstatd’ must be running on the remote system

• Accepts optional argument <protocol:><//hostname>:[<port>]

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jstatd (experimental) - jstat Daemon

• Launches an RMI server application that monitors the creation and termination of HotSpot JVM based java applications

• Provides an interface to allow remote monitoring tools to attach to Java virtual machines running on the system.

• Note: There is no encryption or authentication with jstatd

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JMC - Java Mission Control

• Non-intrusive, low-overhead tool to monitor, manage and profile Java applications

• Suitable for production environments

• JMC Tools Chain

– JMX Console • Monitoring and managing live java applications

• JMX MBeans Browser

– Java Flight Recorder • Engine built in the Java Runtime

• Record interesting events at the application and the JVM level

• Compact binary proprietary format

• Tracking events leading up to a problem provides great help in troubleshooting

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JFR in Java 9

• Supported JFR APIs

– We can create our own custom JFR events and record them in the produced recordings

• Performance enhancements in data collection and recording

• Ability to dump recordings even at VM crashes or OOMs

• Improved and new Events (safepoint, codecache, compiler, G1, module)

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JMC in Java 9

• Improved user interface

• Automated analysis of flight recordings

– Provides analysis what could be going wrong with suggestions for solutions and links to documentation

– Based on a set of defined rules

– Custom rules can be added

– Individual rules can be modified or disabled

• Headless automated analysis

• http://hirt.se/blog/

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Monitoring Tools

• jconsole - Starts a graphic console to monitor and manage Java applications.

• jps - Experimental: Lists the instrumented Java Virtual Machines (JVMs) on the target system.

• jstat - Experimental: Monitors JVM statistics

• jstatd - Experimental: Monitors JVMs and enables remote monitoring tools to attach to JVMs.

• jmc – Java Mission Control: JMX console, and JFR recording and analysis tool

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Troubleshooting Tools

• jcmd – Sends diagnostic commands to a running JVM

• jdb – java platform debugger

• jinfo – Experimental: Obtains and updates configuration information

• jmap – Experimental: Can create heap dumps or heap histograms for a java process

• jstack – Experimental: Prints Java thread stack traces for a Java process

• jhsdb – Attaches to a hanging process or a crash dump file for postmortem analysis

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New tool in Java 9

New diagnostic commands

in Java 9


jcmd – Java Command

• Java Diagnostic Command utility

• Utility to send diagnostic commands to a running JVM

• Uses Attach API to execute d-commands (helper routines) in the JVM

• Can be used only on the same local machine as the target JVM

• New diagnostics commands added in Java 9

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jcmd: popular commands

• jcmd <process id/main class> VM.version

• jcmd <process id/main class> VM.system_properties

• jcmd <process id/main class> VM.flags

• jcmd <process id/main class> GC.class_histogram

• jcmd <process id/main class> GC.class_stats

• jcmd <process id/main class> GC.heap_dump filename=heapdump

• jcmd <process id/main class> Thread.print

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jcmd: Java Flight Recordings commands

• jcmd <process id/main class> JFR.start name=MyRecording settings=profile delay=20s duration=2m filename=/tmp/myrecording.jfr

• jcmd <process id/main class> JFR.check

• jcmd <process id/main class> JFR.stop

• jcmd <process id/main class> JFR.dump name=MyRecording filename=/tmp/myrecording.jfr

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jcmd Attach API

Diagnostic Routines

Commands

Output

Local machine


jdb – Java Debugger

• Command-line debugger for Java Class files

• jdb <options> <class> <arguments>

• Uses Java Debug Interface (JDI)

• JDI is a component of Java Platform Debugger Architecture (JPDA)

• Can perform inspection and debugging of a local or remote Java Virtual Machine

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jinfo jmap jstack

Local live process

Core dump file

Remote Debug Server JDK 8 JDK 9

Serviceability Agent

Attach API


jinfo – Java Configuration Information

• Configuration (flags) information of a running Java process

• Can update the manageable flags at runtime

• It can:

– Print the value of a VM flag

– Enable or disable a specified VM flag

– Set the value of a VM flag

– Print VM flags and system properties

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jmap (experimental) – Java Memory Map

• Heap objects information and Heap dumps

• Classloader Statistics

• -clstats <pid>

• Finalization Information

• -finalizerinfo <pid>

• Class Histograms

• -histo[:live] <pid>

• Heap Dumps

• -dump:<dump-options> <pid>

• JDK 9 removed: heap info and shared memory mappings

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jstack (experimental) – Java Stack

• Thread dump

• Deadlock detection

• jstack –l to see the concurrent locks information

• Removed support for –F and –m options

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jcmd – replacement for old tools

jcmd Individual tools Function

jcmd without any argument jps List Java Processes

jcmd with VM.system_properties, VM.flags, VM.set_flag jinfo VM Configuration

jcmd with GC.class_stats, GC.class_histogram, GC.heap_dump, GC.finalizer_info

jmap Generate Heap Dump and Class Histogram, get Class Statistics and Finalization information

jcmd with Thread.print jstack Thread Dump

jcmd PerfCounter.print jstat Print Performance Counters

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jhsdb- Java HotSpot Debugger

• Can be used to launch a postmortem debugger (SA) to analyze core dump files

• Can be used against live java processes too

jhsdb clhsdb [--pid pid | --exe executable --core coredump] jhsdb debugd [options] pid [server-id]|[option] executable core [server-id] jhsdb hsdb [--pid pid | --exe executable --core coredump] jhsdb jstack [--pid pid | --exe executable --core coredump] [options] jhsdb jmap [--pid pid | --exe executable --core coredump] [options] jhsdb jinfo [--pid pid | --exe executable --core coredump] [options] jhsdb jsnap [options] [--pid pid | --exe executable --core coredump]

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jinfo jmap jstack

Local live process

Core dump file

Remote Debug Server JDK 9


Attach API


jhsdb

Local live process

Core dump file

Remote Debug Server JDK 9


Non-cooperative manner


Troubleshooting Tools

• jcmd – Sends diagnostic commands to a running JVM

• jdb – java platform debugger

• jinfo – Experimental: Generates configuration information

• jmap – Experimental: Can create heap dumps or heap histograms for a java process

• jstack – Experimental: Prints Java thread stack traces for a Java process

• jhsdb – Attaches to a hanging process or a crash dump file for postmortem analysis

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Tools Removed in JDK 9

• Java VisualVM

• jhat

• jsadebugd

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Java VisualVM

• Other tools (profiling and live monitoring) available: Java Mission Control, JConsole

• Several Open Source heap dumps analysis tools available

– Eclipse MAT

• Not included with JDK 9

• Open Source Project: https://visualvm.github.io/download.html

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https://visualvm.github.io/download.html


jhat

• Web application that can be launched with the ‘jhat’ command available in the JDK/bin folder

• Enables heap dump analysis by browsing objects in the heap dump using any web browser

– By default the web server is started at port 7000.

• jhat supports a wide range of pre-designed queries and Object Query Language(OQL) to explore the objects in heap dumps

• Several other heap dump analysis tools available

• Removed in JDK 9

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jsadebugd

• Attaches to a Java process or core file and acts as a debug server

• Up until JDK 8, tools such as jstack, jmap, and jinfo could remotely attach to a debug server using Java RMI

• Removed in Java 9

• The debug server can now be launched with ‘jhsdb debugd’

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Summary

• Enhanced Tools

– jcmd – we encourage to use this tool instead of other individual tools

– Java Mission Control

• New Tools – jhsdb for postmortem analysis

• Removed Tools

– Java VisualVM

– jhat

– jsadebugd

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Oracle MOOC: Java Virtual Machine Troubleshooting

• Troubleshooting Memory Problems in Java Applications

• Enrollments still open until Oct 11

• After enrollment ends, 1 week of grace period to finish the quizzes

http://www.oracle.com/goto/jvm

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Stay connected

• Join us: DevOps Corner (Developer Lounge – Moscone West)

• Learn more: openjdk.java.net | wercker.com/java

• Follow: @OpenJDK, @wercker #JavaOne #DevOps

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monitoring and troubleshooting tools...termination of hotspot jvm based java applications...

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