Advanced Usage

Basic

• help - display Arthas help
• cls - clear the screen
• session - display current session information
• reset - reset all the enhanced classes. All enhanced classes will also be reset when Arthas server is closed by shutdown
• version - print the version for the Arthas attached to the current Java process
• history - view command history
• quit/exit - exit the current Arthas session, without effecting other sessions
• shutdown - terminate the Arthas server, all Arthas sessions will be destroyed
• keymap - keymap for Arthas keyboard shortcut

JVM

• dashboard - dashboard for the system’s real-time data
• thread - show java thread information
• jvm - show JVM information
• sysprop - view/modify system properties
• sysenv — view system environment variables
• New! getstatic :clap: - examine class’s static properties

class/classloader

• sc - check the info for the classes loaded by JVM
• sm - check methods info for the loaded classes
• dump - dump the loaded classes in byte code to the specified location
• redefine - load external *.class files and re-define it into JVM
• jad - decompile the specified loaded classes
• classloader - check the inheritance structure, urls, class loading info for the specified class; using classloader to get the url of the resource e.g. java/lang/String.class

monitor/watch/trace - related

Attention: commands here are taking advantage of byte-code-injection, which means we are injecting some aspects into the current classes for monitoring and statistics purpose. Therefore when use it for online troubleshooting in your production environment, you’d better explicitly specify classes/methods/criteria, and remember to remove the injected code by shutdown or reset.

• monitor - monitor method execution statistics
• watch - display the input/output parameter, return object, and thrown exception of specified method invocation
• trace - trace the execution time of specified method invocation
• stack - display the stack trace for the specified class and method
• tt - time tunnel, record the arguments and returned value for the methods and replay

options

• options - check/set Arthas global options

pipe

Arthas provides pipe to process the result returned from commands further, e.g. sm org.apache.log4j.Logger | grep <init>. Commands supported in pipe:

• grep - filter the result with the given keyword
• plaintext - remove the color
• wc - count lines

async in background

async can be handy when a problem is hardly to reproduce in the production environment, e.g. one watch condition may happen only once in one single day.

• job control - use > to redirect result into the log file, use & to put the job to the background. Job keeps running even if the session is disconnected (the session lifecycle is 1 day by default)
• jobs - list all jobs
• kill - forcibly terminate the job
• fg - bring the suspend job to the foreground
• bg - put the job to run in the background

Web Console

Arthas supports living inside a browser. The communication between arthas and browser is via websocket.

• Web Console

Other features

• Async support
• log the output
• batch
• how to use ognl