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

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

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

Safe Harbor Statement

The following 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.

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!

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

Agenda

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

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

JMX Client Application

MBean Server

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

$ 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>]

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

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

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)

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/

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

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

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

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

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

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

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

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

jstack (experimental) – Java Stack

• Thread dump

• Deadlock detection

• jstack –l to see the concurrent locks information

• Removed support for –F and –m options

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

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]

jinfo jmap jstack

Local live process

Core dump file

Remote Debug Server JDK 9

Attach API

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

Tools Removed in JDK 9

• Java VisualVM

• jhat

• jsadebugd

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

• 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

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’

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

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

Stay connected

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

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

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

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

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