Arthas 是Alibaba开源的Java诊断工具，可以查看Java进程的一些信息，例如运行情况、JVM相关参数、线程等信息，采用命令行交互模式，在Linux用着十分方便。
安装
在Linux系统中，首先创建一个文件下，然后在该文件下执行如下命令：
curl -L https://alibaba.github.io/arthas/install.sh | sh
该命令会下载as.sh脚本，执行该脚本的用户需要和目标进程具有相同的权限。比如以admin用户来执行： sudo su admin && ./as.sh 或 sudo -u admin -EH ./as.sh。 详细的启动脚本说明，请参考这里。 如果attatch不上目标进程，可以查看~/logs/arthas/ 目录下的日志。
启动
接下来就需要执行/as.sh脚本，注意后面传入java 进程id
root@ubuntu:/usr/soft/arthas# ./as.sh 2616
启动画面如下图所示：
查看dashboard
输入dashboard可以查看当前进程的信息、JVM内存使用情况，还可以看到当前操作系统和Java的版本信息
$ dashboard
ID NAME GROUP PRIORI STATE %CPU TIME INTERRU DAEMON
16 nioEventLoopGroup-3-1 system 10 RUNNABL 76 0:0 false false
21 Timer-for-arthas-dash system 10 RUNNABL 23 0:0 false true
12 AsyncAppender-Worker- system 9 WAITING 0 0:0 false true
10 Attach Listener system 9 RUNNABL 0 0:0 false true
9 Common-Cleaner InnocuousThrea 8 TIMED_W 0 0:0 false true
3 Finalizer system 8 WAITING 0 0:0 false true
2 Reference Handler system 10 RUNNABL 0 0:0 false true
4 Signal Dispatcher system 9 RUNNABL 0 0:0 false true
20 as-command-execute-da system 10 TIMED_W 0 0:0 false true
14 job-timeout system 9 TIMED_W 0 0:0 false true
Memory used total max usage GC
heap 18M 39M 233M 7.90% gc.copy.count 24
tenured_gen 16M 27M 161M gc.copy.time(ms) 107
eden_space 2M 11M 64M 4.22% gc.marksweepcompact.c 2
survivor_space 0K 1408K 8256K 0.00% ount
nonheap 23M 27M -1
Runtime
os.name Linux
os.version 4.15.0-29-generic
java.version 10.0.2
java.home /usr/package/jdk-10.0
.2
查看JVM信息
输入JVM参数可以查看JVM相关信息，这对JVM调试有很大帮助。
$ jvm
RUNTIME
----------------------------------------------------------------------------------------
MACHINE-NAME 2616@ubuntu
JVM-START-TIME 2018-09-20 20:19:32
MANAGEMENT-SPEC-VERSION 2.0
SPEC-NAME Java Virtual Machine Specification
SPEC-VENDOR Oracle Corporation
SPEC-VERSION 10
VM-NAME Java HotSpot(TM) 64-Bit Server VM
VM-VENDOR "Oracle Corporation"
VM-VERSION 10.0.2+13
INPUT-ARGUMENTS []
CLASS-PATH .:/usr/package/jdk-10.0.2/lib/
BOOT-CLASS-PATH
LIBRARY-PATH /usr/java/packages/lib:/usr/lib64:/lib64:/lib:/usr/lib
----------------------------------------------------------------------------------------
CLASS-LOADING
----------------------------------------------------------------------------------------
LOADED-CLASS-COUNT 2818
TOTAL-LOADED-CLASS-COUN 2818
T
UNLOADED-CLASS-COUNT 0
IS-VERBOSE false
----------------------------------------------------------------------------------------
COMPILATION
----------------------------------------------------------------------------------------
NAME HotSpot 64-Bit Tiered Compilers
TOTAL-COMPILE-TIME 3875(ms)
----------------------------------------------------------------------------------------
GARBAGE-COLLECTORS
----------------------------------------------------------------------------------------
Copy 25/110(ms)
[count/time]
MarkSweepCompact 2/108(ms)
[count/time]
----------------------------------------------------------------------------------------
MEMORY-MANAGERS
----------------------------------------------------------------------------------------
CodeCacheManager CodeHeap 'non-nmethods'
CodeHeap 'profiled nmethods'
CodeHeap 'non-profiled nmethods'
Metaspace Manager Metaspace
Compressed Class Space
Copy Eden Space
Survivor Space
MarkSweepCompact Eden Space
Survivor Space
Tenured Gen
----------------------------------------------------------------------------------------
MEMORY
----------------------------------------------------------------------------------------
HEAP-MEMORY-USAGE 41689088/16777216/245301248/18364616
[committed/init/max/use
d]
NO-HEAP-MEMORY-USAGE 32047104/7667712/-1/27755016
[committed/init/max/use
d]
PENDING-FINALIZE-COUNT 0
----------------------------------------------------------------------------------------
OPERATING-SYSTEM
----------------------------------------------------------------------------------------
OS Linux
ARCH amd64
PROCESSORS-COUNT 1
LOAD-AVERAGE 0.53
VERSION 4.15.0-29-generic
----------------------------------------------------------------------------------------
THREAD
----------------------------------------------------------------------------------------
COUNT 14
DAEMON-COUNT 8
LIVE-COUNT 15
STARTED-COUNT 17
Affect(row-cnt:0) cost in 42 ms.
class/classloader相关
- sc——查看JVM已加载的类信息
- sm——查看已加载类的方法信息
- dump——dump 已加载类的 byte code 到特定目录
- redefine——加载外部的.class文件，redefine到JVM里
- jad——反编译指定已加载类的源码
- classloader——查看classloader的继承树，urls，类加载信息，使用classloader去getResource
详细参考：