JVM第十五天-JVM调优-arthas的使用
Arthas简介
arthas是啥？ 一款阿里出品的在线JVM监测工具
为什么需要在线排查？
在生产上我们经常会碰到一些不好排查的问题，例如线程安全问题，
用最简单的threaddump或者heapdump不好查到问题原因。
为了排查这些问题，有时我们会临时加一些日志，比如在一些关键的函数里打印出入参，
然后重新打包发布，如果打了日志还是没找到问题，继续加日志，重新打包发布。
对于上线流程复杂而且审核比较严的公司，从改代码到上线需要层层的流转，会大大影响问题排查的进度。
下载和安装
访问 https://github.com/alibaba/arthas
进行jar包的下载安装，这里不进行赘述。
启动
这里还是使用我们上次的案例程序
package com.peng.jvm.gc;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
/**
* 从数据库中读取信用数据，套用模型，并把结果进行记录和传输
*/
public class T15_FullGC_Problem01 {
private static class CardInfo {
BigDecimal price = new BigDecimal(0.0);
String name = "张三";
int age = 5;
Date birthdate = new Date();
public void m() {}
}
private static ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(50,
new ThreadPoolExecutor.DiscardOldestPolicy());
public static void main(String[] args) throws Exception {
executor.setMaximumPoolSize(50);
for (;;){
modelFit();
Thread.sleep(100);
}
}
private static void modelFit(){
List<CardInfo> taskList = getAllCardInfo();
taskList.forEach(info -> {
// do something
executor.scheduleWithFixedDelay(() -> {
//do sth with info
info.m();
}, 2, 3, TimeUnit.SECONDS);
});
}
private static List<CardInfo> getAllCardInfo(){
List<CardInfo> taskList = new ArrayList<>();
for (int i = 0; i < 100; i++) {
CardInfo ci = new CardInfo();
taskList.add(ci);
}
return taskList;
}
}
先启动这个程序：
java -Xms20M -Xmx20M -XX:+UseParallelGC -XX:+HeapDumpOnOutOfMemoryError com.peng.jvm.gc.T15_FullGC_Problem01
接下来移动到arthas根目录，启动arthas：
java -jar arthas-agent.jar
[root@dream01 arthas]# java -jar arthas-agent.jar
arthas-agent.jar中没有主清单属性
[root@dream01 arthas]# java -jar arthas-boot.jar
[INFO] arthas-boot version: 3.1.7
[INFO] Found existing java process, please choose one and hit RETURN.
* [1]: 2169 T15_FullGC_Problem01
此时，可以看到，arthas检测到了所有的java运行程序，其中1号就是我们刚启动的程序。
输入1：
1
[INFO] arthas home: /usr/local/arthas
[INFO] Try to attach process 2363
[INFO] Attach process 2363 success.
[INFO] arthas-client connect 127.0.0.1 3658
,---. ,------. ,--------.,--. ,--. ,---. ,---.
/ O \ | .--. ''--. .--'| '--' | / O \ ' .-'
| .-. || '--'.' | | | .--. || .-. |`. `-.
| | | || |\ \ | | | | | || | | |.-' |
`--' `--'`--' '--' `--' `--' `--'`--' `--'`-----'
wiki https://alibaba.github.io/arthas
tutorials https://alibaba.github.io/arthas/arthas-tutorials
version 3.1.7
pid 2363
time 2020-03-23 00:35:55
此时代表已经成功进入检测我们程序的界面了。
帮助
可以通过help查看有哪些命令
[arthas@2874]$ help
NAME DESCRIPTION
help Display Arthas Help
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
ognl Execute ognl expression.
mc Memory compiler, compiles java files into bytecode and class files in memory.
redefine Redefine classes. @see Instrumentation#redefineClasses(ClassDefinition...)
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
shutdown Shutdown Arthas server and exit the console
stop Stop/Shutdown Arthas server and exit the console. Alias for shutdown.
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
pwd Return working directory name
mbean Display the mbean information
grep grep command for pipes.
profiler Async Profiler. https://github.com/jvm-profiling-tools/async-profiler
常用命令
jvm
打印JVM内的一些基本信息
[arthas@2496]$ jvm
RUNTIME
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
MACHINE-NAME 2496@dream01
JVM-START-TIME 2020-03-23 00:37:11
MANAGEMENT-SPEC-VERSION 1.2
SPEC-NAME Java Virtual Machine Specification
SPEC-VENDOR Oracle Corporation
SPEC-VERSION 1.8
VM-NAME Java HotSpot(TM) 64-Bit Server VM
VM-VENDOR Oracle Corporation
VM-VERSION 25.211-b12
INPUT-ARGUMENTS -Xms20M
-Xmx20M
-XX:+UseParallelGC
-XX:+HeapDumpOnOutOfMemoryError
CLASS-PATH .
BOOT-CLASS-PATH /usr/java/jdk1.8.0_211-amd64/jre/lib/resources.jar:/usr/java/jdk1.8.0_211-amd64/jre/lib/rt.jar:/usr/java/jdk1.8.0_211-amd64/jre/lib/sunrsasign.jar:/usr/java/jdk1.8.0_211-amd64/j
re/lib/jsse.jar:/usr/java/jdk1.8.0_211-amd64/jre/lib/jce.jar:/usr/java/jdk1.8.0_211-amd64/jre/lib/charsets.jar:/usr/java/jdk1.8.0_211-amd64/jre/lib/jfr.jar:/usr/java/jdk1.8.0_21
1-amd64/jre/classes
LIBRARY-PATH /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
CLASS-LOADING
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
LOADED-CLASS-COUNT 2288
TOTAL-LOADED-CLASS-COUNT 2293
UNLOADED-CLASS-COUNT 5
IS-VERBOSE false
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
COMPILATION
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
NAME HotSpot 64-Bit Tiered Compilers
TOTAL-COMPILE-TIME 2130(ms)
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
GARBAGE-COLLECTORS
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
PS Scavenge 37/117(ms)
[count/time]
PS MarkSweep 6/589(ms)
[count/time]
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
MEMORY-MANAGERS
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
CodeCacheManager Code Cache
Metaspace Manager Metaspace
Compressed Class Space
PS Scavenge PS Eden Space
PS Survivor Space
PS MarkSweep PS Eden Space
PS Survivor Space
PS Old Gen
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
MEMORY
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
HEAP-MEMORY-USAGE 19922944(19.00 MiB)/20971520(20.00 MiB)/19922944(19.00 MiB)/17337072(16.53 MiB)
[committed/init/max/used]
NO-HEAP-MEMORY-USAGE 19988480(19.06 MiB)/2555904(2.44 MiB)/-1(-1 B)/19155400(18.27 MiB)
[committed/init/max/used]
PENDING-FINALIZE-COUNT 0
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
OPERATING-SYSTEM
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
OS Linux
ARCH amd64
PROCESSORS-COUNT 1
LOAD-AVERAGE 0.69
VERSION 2.6.32-431.el6.x86_64
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
THREAD
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
COUNT 63
DAEMON-COUNT 7
PEAK-COUNT 63
STARTED-COUNT 64
DEADLOCK-COUNT 0
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
FILE-DESCRIPTOR
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
MAX-FILE-DESCRIPTOR-COUNT 4096
OPEN-FILE-DESCRIPTOR-COUNT 36
Affect(row-cnt:0) cost in 259 ms.
其中的GARBAGE-COLLECTORS 项，可以看到我们使用的垃圾回收器是 PS Scavenge：
GARBAGE-COLLECTORS
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
PS Scavenge 37/117(ms)
[count/time]
PS MarkSweep 6/589(ms)
[count/time]
thread
定位线程问题
thread 线程号，可以看到具体线程内的堆栈调用信息：
[arthas@2874]$ thread 1
"main" Id=1 TIMED_WAITING
at java.lang.Thread.sleep(Native Method)
at T15_FullGC_Problem01.main(T15_FullGC_Problem01.java:32)
Affect(row-cnt:0) cost in 23 ms.
dashboard
类似于top命令，观察系统情况
heapdump
类似于jmap dump，会导出当前的堆存储文件，和jmap dump一样，也是非常影响系统性能的。
以上都是其他工具也能实现的比较通用的功能，接下来说一说arthas比较独有的功能。
jad反编译
可以对该进程内的代码进行反编译。
可用于：
1、动态代理生成类的问题定位
2、第三方的类（观察代码）
3、版本问题（确定自己最新提交的版本是不是被使用）
对Object进行反编译：
[arthas@3142]$ jad java.lang.Object
ClassLoader:
Location:
/*
* Decompiled with CFR.
*/
package java.lang;
public class Object {
static {
Object.registerNatives();
}
protected void finalize() throws Throwable {
}
public final void wait() throws InterruptedException {
this.wait(0L);
}
public final void wait(long l, int n) throws InterruptedException {
if (l < 0L) {
throw new IllegalArgumentException("timeout value is negative");
}
if (n < 0 || n > 999999) {
throw new IllegalArgumentException("nanosecond timeout value out of range");
}
if (n > 0) {
++l;
}
this.wait(l);
}
public final native void wait(long var1) throws InterruptedException;
public boolean equals(Object object) {
return this == object;
}
public String toString() {
return this.getClass().getName() + "@" + Integer.toHexString(this.hashCode());
}
public native int hashCode();
public final native Class<?> getClass();
protected native Object clone() throws CloneNotSupportedException;
public final native void notify();
public final native void notifyAll();
private static native void registerNatives();
}
Affect(row-cnt:1) cost in 423 ms.
redefine 热替换
可以实现类的热替换，但目前有些限制条件：只能改方法实现（方法已经运行完成），不能改方法名， 不能改属性
sc
使用通配符搜索class名称。
watch
watch 让你能方便的观察到指定方法的调用情况。
能观察到的范围为：返回值、抛出异常、入参，通过编写 OGNL 表达式进行对应变量的查看。
没有包含的功能
它没有包含jmap的功能
参考文档
https://www.jianshu.com/p/507f7e0cc3a3