Introduction
Arthas is an open source Java application diagnostic tool developed by Alibaba that can troubleshoot problems online, dynamically track Java code, and monitor JVM status in real time.
Official website:arthas
Quick start
1. Download
wget https://arthas.aliyun.com/arthas-boot.jar2. run
Need to run in an environment where the java program is running
java -jar arthas-boot.jarThe program will display all running Java processes in the system. Arthas assigns a serial number to each process.
[INFO] JAVA_HOME: C:\Program Files\Java\jdk1.8.0_351\jre [INFO] arthas-boot version: 3.7.1 [INFO] Found existing java process, please choose one and input the serial number of the process, eg : 1. Then hit ENTER. * [1]: 9400 .\target\demo-0.0.1-SNAPSHOT.jar [2]: 13964 org.eclipse.equinox.launcher_1.6.500.v20230717-2134.jar [3]: 6796 org.springframework.ide.vscode.boot.app.BootLanguageServerBootAppFind the Java process with the problem from this list and enter the corresponding serial number. For example, here I enter
1and press Enter. Arthas will automatically download the complete package and Attach it to the target process, the output is as follows:[INFO] Start download arthas from remote server: https://arthas.aliyun.com/download/3.7.1?mirror=aliyun [INFO] Download arthas success. [INFO] arthas home: C:\Users\aneasystone\.arthas\lib\3.7.1\arthas [INFO] Try to attach process 9400 [INFO] Attach process 9400 success. [INFO] arthas-client connect 127.0.0.1 3658 ,---. ,------. ,--------.,--. ,--. ,---. ,---. / O \ | .--. ''--. .--'| '--' | / O \ ' .-' | .-. || '--'.' | | | .--. || .-. |`. `-. | | | || |\ \ | | | | | || | | |.-' | `--' `--'`--' '--' `--' `--' `--'`--' `--'`-----' wiki https://arthas.aliyun.com/doc tutorials https://arthas.aliyun.com/doc/arthas-tutorials.html version 3.7.1 main_class pid 9400 time 2023-12-06 07:16:31 [arthas@9400]$
3. View all commands
[arthas@9400]$ help
NAME DESCRIPTION
help Display Arthas Help
auth Authenticates the current session
keymap Display all the available keymap for the specified connection.
sc Search all the classes loaded by JVM
sm Search the method of classes loaded by JVM
classloader Show classloader info
jad Decompile class
getstatic Show the static field of a class
monitor Monitor method execution statistics, e.g. total/success/failure count, average rt, fail rate, etc.
stack Display the stack trace for the specified class and method
thread Display thread info, thread stack
trace Trace the execution time of specified method invocation.
watch Display the input/output parameter, return object, and thrown exception of specified method invocation
tt Time Tunnel
jvm Display the target JVM information
memory Display jvm memory info.
perfcounter Display the perf counter information.
ognl Execute ognl expression.
mc Memory compiler, compiles java files into bytecode and class files in memory.
redefine Redefine classes. @see Instrumentation#redefineClasses(ClassDefinition...)
retransform Retransform classes. @see Instrumentation#retransformClasses(Class...)
dashboard Overview of target jvm's thread, memory, gc, vm, tomcat info.
dump Dump class byte array from JVM
heapdump Heap dump
options View and change various Arthas options
cls Clear the screen
reset Reset all the enhanced classes
version Display Arthas version
session Display current session information
sysprop Display and change the system properties.
sysenv Display the system env.
vmoption Display, and update the vm diagnostic options.
logger Print logger info, and update the logger level
history Display command history
cat Concatenate and print files
base64 Encode and decode using Base64 representation
echo write arguments to the standard output
pwd Return working directory name
mbean Display the mbean information
grep grep command for pipes.
tee tee command for pipes.
profiler Async Profiler. https://github.com/jvm-profiling-tools/async-profiler
vmtool jvm tool
stop Stop/Shutdown Arthas server and exit the console.
JVM related commands
Commands related to class loading, classes, methods
Statistics and observation commands
Linux-like commands
Other commands
These are the main types of commands
JVM related commands
These commands are mainly related to JVM and are used to view or modify JVM related properties, view JVM thread, memory, CPU, GC and other information:
jvm - View current JVM information;
sysenv - View JVM environment variables;
sysprop - View JVM system properties;
vmoption - View or modify JVM diagnostic-related parameters;
memory - View JVM memory information;
heapdump - Exports the heap snapshot of the Java process to a file to facilitate us to analyze the heap memory;
thread - View information about all threads, including thread name, thread group, priority, thread status, CPU usage, stack information, etc.;
dashboard - View the real-time data panel of the current system, including thread, memory, GC and Runtime information; it can be viewed as
thread,memory,jvm,sysenv,syspropA combination of several commands;perfcounter - View the Perf Counter information of the current JVM;
logger - View application log information and support dynamically updating log levels;
mbean - View or monitor MBean information in real time;
vmtool - uses the JVMTI interface to implement functions such as querying memory objects and forcing GC;
Commands related to class loading, classes, methods
These commands are mainly related to class loading, classes or methods, such as searching for classes or class methods in the JVM, viewing static attributes of classes, compiling or decompiling, hot updating classes, etc.:
classloader - View all Classloader information in the JVM;
dump - Export the specified class into
.classbytecode file;jad - Decompile the specified class into Java source code;
mc - memory compiler, compiles Java source code into
.classbytecode files;redefine / retransform - Both commands can hot update loaded classes, but
redefineandjad/ < a i=3> / / / and other commands will conflict, and after The original class cannot be restored, so it is recommended to use the command. For the difference between the Redefine and Retransform mechanisms in the JDK, you can refer to here;watchtracemonitorttredefineretransformsc - Search Class, search for classes in the JVM;
sm - Search Method, search for methods of classes in the JVM;
getstatic - View static properties of a class;
ognl - executes ognl expressions; ognl is very flexible and can implement many functions, such as viewing or modifying system properties above, and viewing static properties of classes can be implemented through ognl;
Statistics and Observations
These commands can count and monitor the execution of class methods, and are a powerful tool for troubleshooting online problems:
monitor - monitor a given class method and count its call times, call time and success rate, etc.;
stack - View the execution call stack of a method;
trace - monitors a given class method and outputs the time it takes to call the method. The difference from
monitoris that it can also track the calling link of the first-level method and Time-consuming, helping to quickly locate performance problems;watch - observe the execution data of the specified method, including the method's input parameters, return value, thrown exceptions, etc.;
tt - Like the
watchcommand,ttcan also observe the execution data of the specified method, butttwill Each execution is recorded, and then each call is investigated and analyzed, so it is called Time Tunnel;reset - The above commands related to statistical observation are implemented through bytecode enhancement technology and will be executed in the specified class. Insert some aspect code into the method, so after the production environment diagnosis is completed, remember to execute the
resetcommand to reset the enhanced class (or execute thestopcommand); a>profiler - Use async-profiler to sample the application and generate a flame graph from the sampling results;
jfr - Dynamically turn on and off JFR recording, and the generated jfr file can be analyzed through JDK Mission Control;
Comparison of Arthas commands and JDK tools
| Arthas command | JDK tools | Compared |
|---|---|---|
sysprop |
jinfo -sysprops |
can view the system properties of the JVM, but sysprop is better than jinfo in that it can also modify the system properties |
vmoption |
jinfo -flag |
can view JVM parameters, but vmoption only displays diagnostic-related parameters, such as HeapDumpOnOutOfMemoryError, PrintGC , etc.< /span> |
memory |
jmap -heap |
can view the memory information of JVM, but memory is displayed in table form to facilitate user reading |
heapdump |
jmap -dump |
You can export the heap memory of the process, but it is simpler to use. |
thread |
jstack |
can list all threads of the JVM, but thread is displayed in table form, which is convenient for users to read, and it also adds the CPU usage function, which allows us to quickly find out the current maximum Busy Thread |
perfcounter |
jcmd PerfCounter.print |
You can view the performance statistics of the JVM process |
classloader |
jmap -clstats |
can view the JVM's Classloader statistics, but the classloader command also supports viewing in the form of a tree. In addition, it also supports viewing the actual URL of each Classloader, finding resources through the Classloader, etc. |
jfr |
jcmd JFR.start |
You can turn on or off JFR recording and generate the jfr file |
Linux-like commands
In addition to the above commands for problem diagnosis, Arthas also provides some Linux-like commands for us to use in the Arthas terminal, such as:
base64 - performs base64 encoding and decoding;
cat - print file contents;
cls - Clear the current screen area;
echo - print parameters;
grep - Search text using strings or regular expressions and output matching lines;
history - output history commands;
pwd - output the current working directory;
tee - reads data from stdin and outputs to stdout and file simultaneously;
wc- Currently only supportswc -l, counting the number of output lines;In addition, Arthas also supports running tasks in the background. Following the related commands in Linux, we can use
&to run tasks in the background and use thejobscolumn Exit all background tasks, useCtrl + Zto pause the task, usebgandfgto move the suspended tasks to the background or foreground to continue running, Usekillto terminate the task. For details, please refer to Arthas background asynchronous tasks.
Other commands
There are also some commands related to Arthas itself, such as viewing Arthas version number, configuration, session and other information:
version - View Arthas version number;
options - View or modify Arthas global configuration;
keymap - View all currently bound shortcut keys, you can customize the shortcut keys through the
~/.arthas/conf/inputrcfile;session - View current session information;
auth - authenticate the current session;
quit - Exit the current Arthas client, other Arthas clients will not be affected;
stop - Close the Arthas server and exit all Arthas clients; this command will reset all enhanced classes (except
redefineclasses);
Troubleshooting ideas
Use watch to monitor method incoming and outgoing parameters and exceptions
Use logger to dynamically update log levels
Use ognl to view system properties and application configurations
Use jad/sc/retransform hot update code
Other usage scenarios
The use of Arthas is very flexible, and sometimes it even has some unexpected functions. In addition to the above usage scenarios, Arthas's Issues also collected some user cases, several of which impressed me deeply and were very inspiring. , for reference.
Use
stackcommand to locate the calling source ofSystem.exit/System.gc:https://github.com/alibaba/arthas/issues/20Use
sc和jadExclusionNoSuchMethodErrorProblem:https://github.com/alibaba/arthas/issues/160Use
redefineto modifyStringBuilder.toString()to locate unknown log sources:https://github.com/alibaba/arthas/issues/263Use
trace javax.servlet.Servlet/Filterto troubleshoot Spring Boot application 404/401 issues:https://github.com/alibaba/arthas/issues/429Use
ttto locate high CPU load issues in Java applications:https://github.com/alibaba/arthas/issues/1202Use
profilerto do complex link analysis and troubleshoot performance issues:https://github.com/alibaba/arthas/issues/1416Use
tracecommand to optimize interface performance ten times:https://github.com/alibaba/arthas/issues/1892
References
Arthas documentation:
https://arthas.aliyun.com/doc/OGNL reference documentation:
https://commons.apache.org/proper/commons-ognl/language-guide.htmlArthas Online Tutorial - Killercoda:
https://killercoda.com/arthas/course/arthas-tutorials-cnredefine VS. retransform：
https://lsieun.github.io/java-agent/s01ch03/redefine-vs-retransform.htmlAlibaba Arthas practice - get the Spring Context and then do whatever you want:
https://github.com/alibaba/arthas/issues/482Arthas user case:
https://github.com/alibaba/arthas/issues?q=label%3Auser-caseOptimize microservice performance using SkyWalking & Arthas:
https://github.com/alibaba/arthas/issues/1653