工具概述
Greys为一款“事后工具” ，即服务已经上线了，无法再通过打印日志等方式进行埋点分析，此时可以借助此工具，来跟踪代码执行耗时、堆栈运行情况等。使用Greys，我们无需编写 脚步，它是命令交互式的，直接输入命令指定监控的类、方法。
工作原理
（1）基于动态字节码修改技术(Hotswap)来实现运行时 Java 程序的跟踪和替换。
（2）利用了Java SE 6 新特性Instrumentation。
使用场景
（1）分析哪些方法慢，查询具体的故障点
（2）查看方法的参数、返回值
（3）查看对象属性等
# 程序安装
1、在线安装方式（推荐）
[root@testserver ~]# curl -sLk http://ompc.oss.aliyuncs.com/greys/install.sh|bash Tips: 安装成功后，若出现“greys not found, please check your network” ，则需进行本地安装
2、本地安装方式
（1）下载最新版本的Greys
[root@testserver ~]# wget http://ompc.oss.aliyuncs.com/greys/release/greys-stable-bin.zip
（2）解压zip文件后，执行以下命令，即可完成本地安装
[root@testserver ~]# cd greys [root@testserver ~]# sh ./install-local.sh
3、 操作指南
[root@testserver greys]# ./greys.sh 944————>“944 为 jvm的进程号”
如下，执行此命令后，显示greys相关信息：
[root@testserver greys]# ./greys.sh 944 _ ____ ____ _____ _ _ ___ _____ _____ ____ _____ _| |_ ___ ____ _ _ / _ |/ ___) ___ | | | |/___|_____|____ | _ \(____ (_ _) _ \| \| | | | ( (_| | | | ____| |_| |___ | / ___ | | | / ___ | | || |_| | | | | |_| | \___ |_| |_____)\__ (___/ \_____|_| |_\_____| \__)___/|_|_|_|\__ | (_____| (____/ (____/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |v|e|r|s|i|o|n|:|1|.|7|.|6|.|6| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ga?> ga?>
4、常用命令参考
ga?>help +----------+----------------------------------------------------------------------------------+ | sc | Search all the classes loaded by JVM | +----------+----------------------------------------------------------------------------------+ | sm | Search the method of classes loaded by JVM | +----------+----------------------------------------------------------------------------------+ | monitor | Monitor the execution of specified Class and its method | +----------+----------------------------------------------------------------------------------+ | watch | Display the details of specified class and method | +----------+----------------------------------------------------------------------------------+ | tt | Time Tunnel | +----------+----------------------------------------------------------------------------------+ | stack | Display the stack trace of specified class and method | +----------+----------------------------------------------------------------------------------+ | ptrace | Display the detailed thread path stack of specified class and method | +----------+----------------------------------------------------------------------------------+ | js | Enhanced JavaScript | +----------+----------------------------------------------------------------------------------+ | trace | Display the detailed thread stack of specified class and method | +----------+----------------------------------------------------------------------------------+ | session | Display current session information | +----------+----------------------------------------------------------------------------------+ | quit | Quit Greys console | +----------+----------------------------------------------------------------------------------+ | version | Display Greys version | +----------+----------------------------------------------------------------------------------+ | jvm | Display the target JVM information | +----------+----------------------------------------------------------------------------------+ | reset | Reset all the enhanced classes | +----------+----------------------------------------------------------------------------------+ | asm | Display class bytecode by asm format | +----------+----------------------------------------------------------------------------------+ | shutdown | Shut down Greys server and exit the console | +----------+----------------------------------------------------------------------------------+ | help | Display Greys Help | +----------+----------------------------------------------------------------------------------+ | top | Display The Threads Of Top CPU TIME | +----------+----------------------------------------------------------------------------------+
5、具体参考示例
针对help命令行所显示的操作中，若进行相关操作，可通过执行“help arg”命令查询使用方式，例如：help stack/trace/ptrace/tt/monitor
ga?>help stack +---------+----------------------------------------------------------------------------------+ | USAGE | -[En:] class-pattern method-pattern condition-express | | | Display the stack trace of specified class and method | +---------+----------------------------------------------------------------------------------+ | OPTIONS | [E] | Enable regular expression to match (wildcard matching by def | | | | ault) | | | -----------------+-------------------------------------------------------------- | | | [n:] | Threshold of execution times | | | -----------------+-------------------------------------------------------------- | | | class-pattern | Path and classname of Pattern Matching | | | -----------------+-------------------------------------------------------------- | | | method-pattern | Method of Pattern Matching | | | -----------------+-------------------------------------------------------------- | | | condition-expre | Conditional expression by OGNL | | | ss | | | | | FOR EXAMPLE | | | | TRUE : 1==1 | | | | TRUE : true | | | | FALSE : false | | | | TRUE : params.length>=0 | | | | FALSE : 1==2 | | | | | | | | THE STRUCTURE | | | | target : the object | | | | clazz : the object's class | | | | method : the constructor or method | | | | params[0..n] : the parameters of method | | | | returnObj : the returned object of method | | | | throwExp : the throw exception of method | | | | isReturn : the method ended by return | | | | isThrow : the method ended by throwing exception | +---------+----------------------------------------------------------------------------------+ | EXAMPLE | stack -E org\.apache\.commons\.lang\.StringUtils isBlank | | | stack org.apache.commons.lang.StringUtils isBlank | | | stack *StringUtils isBlank | | | stack *StringUtils isBlank 'params[0].length==1' | | | stack *StringUtils isBlank '#cost>100' | +---------+----------------------------------------------------------------------------------+
以Trace命令为例，使用 trace命令 跟踪指定类、方法的执行时间、参数、返回值情况，如下场景：（此处以官网给的参考为主）
场景：跟踪CookieDecoder类中 requestDecode()方法耗时超过500ms 的方法执行情况：
ga?>trace -n 2 com.netease.urs.CookieDecoder requestDecode '#cost>500' ************************************************************************************************************* * -n 2 ：代表只打印2次就退出（防止刷屏，影响性能） * com.netease.urs.CookieDecoder ：监听的类名 * * requestDecode :监听的方法名 * * ‘#cost>500’ : 打印条件为耗时超过 500ms * ************************************************************************************************************* 执行后，会显示：
ga?>trace -n 2 com.netease.urs.CookieDecoder requestDecode '#cost>10' Press Ctrl+D to abort. Affect(class-cnt:1 , method-cnt:2) cost in 262 ms.
代表动态修改了一个类，对两个方法（例如方法重载）进行监控，修改花费262毫秒。 如果出现满足条件的情况，则我们会看到打印结果：
`---+Tracing for : thread_name="http-nio-8003-exec-8" thread_id=0x7a;is_daemon=true;priority=5; `---+[5283,5283ms]com.netease.urs.CookieDecoder:requestDecode() +---[1,0ms]java.lang.System:nanoTime() +---[2,1ms]org.apache.http.client.methods.HttpPost:<init>(@39) +---[2,0ms]java.lang.StringBuffer:<init>(@41) +---[2,0ms]java.lang.StringBuffer:append(@42) +---[2,0ms]java.net.URLEncoder:encode(@43) +---[2,0ms]java.lang.StringBuffer:append(@43) +---[2,0ms]java.lang.StringBuffer:append(@44) +---[2,0ms]java.lang.StringBuffer:append(@45) +---[2,0ms]java.lang.StringBuffer:append(@46) +---[2,0ms]java.lang.StringBuffer:append(@47) +---[2,0ms]java.lang.StringBuffer:append(@48) +---[2,0ms]java.lang.Integer:<init>(@49) +---[2,0ms]java.lang.Integer:<init>(@49) +---[2,0ms]java.lang.reflect.Method:invoke(@49) +---[2,0ms]java.lang.StringBuffer:append(@49) +---[2,0ms]java.lang.StringBuffer:toString(@50) +---[2,0ms]org.apache.http.entity.StringEntity:<init>(@50) +---[2,0ms]org.apache.http.entity.StringEntity:setContentType(@51) +---[2,0ms]org.apache.http.client.methods.HttpPost:setEntity(@52) +---[2,0ms]org.apache.http.client.methods.HttpPost:getParams(@53) +---[2,0ms]org.apache.http.params.HttpParams:setIntParameter(@55) +---[2,0ms]org.apache.http.params.HttpParams:setIntParameter(@58) +---[5282,5280ms]com.netease.urs.http.CustomHttpComponent:execute(@60) +---[5283,0ms]org.apache.http.HttpResponse:getEntity(@61) +---[5283,0ms]org.apache.http.util.EntityUtils:toString(@62) +---[5283,0ms]com.netease.urs.util.LogUtil:debug(@63) +---[5283,0ms]org.apache.http.client.methods.HttpPost:releaseConnection(@71) +---[5283,0ms]java.lang.System:nanoTime(@64) `---[5283,0ms]com.netease.urs.CookieDecoder:$btrace$com$netease$fa$trace$UrsInterfaceCalls$2$requestDecode(@64)
可以看到，主要耗时在
+---[5282,5280ms]com.netease.urs.http.CustomHttpComponent:execute(@60)
退出前可以使用 reset 恢复增强类（即被动态修改的代码）。最后，使用shutdown 关闭greys 并退出即可。
