Java字节码4-使用Java-Agent实现一个JVM监控工具

我会带着你远行 2022-01-26 08:53 346阅读 0赞

一、概述  
在前面几节当中，我们构造了多个Agent。Agent由于是在main方法之前执行，我们可以做很多事情。   
本节中，我们将使用Agent技术来监控应用程序的JVM内存和GC信息。

二、实现  
1、修改pom.xml  
<dependencies>  
<dependency>  
    <groupId>javassist</groupId>  
    <artifactId>javassist</artifactId>  
    <version>3.12.1.GA</version>  
    <type>jar</type>  
</dependency>  
<dependency>  
    <groupId>net.bytebuddy</groupId>  
    <artifactId>byte-buddy</artifactId>  
    <version>1.5.7</version>  
</dependency>  
<dependency>  
    <groupId>net.bytebuddy</groupId>  
    <artifactId>byte-buddy-agent</artifactId>  
    <version>1.5.7</version>  
</dependency>  
</dependencies>

<build>  
<finalName>my-agent</finalName>  
<plugins>  
    <plugin>  
        <groupId>org.apache.maven.plugins</groupId>  
        <artifactId>maven-jar-plugin</artifactId>  
        <version>2.3.2</version>  
        <configuration>  
            <archive>  
                <index>true</index>  
                <manifestFile>src/main/resources/META-INF/MANIFEST.MF</manifestFile>  
                <manifest>  
                    <addDefaultImplementationEntries/>  
                </manifest>  
            </archive>  
        </configuration>  
    </plugin>

<plugin>  
        <groupId>org.apache.maven.plugins</groupId>  
        <artifactId>maven-shade-plugin</artifactId>  
        <executions>  
            <execution>  
                <phase>package</phase>  
                <goals>  
                    <goal>shade</goal>  
                </goals>  
            </execution>  
        </executions>  
        <configuration>  
            <artifactSet>  
                <includes>  
                    <include>javassist:javassist:jar:</include>  
                    <include>net.bytebuddy:byte-buddy:jar:</include>  
                    <include>net.bytebuddy:byte-buddy-agent:jar:</include>  
                </includes>  
            </artifactSet>  
        </configuration>  
    </plugin>

<plugin>  
        <groupId>org.apache.maven.plugins</groupId>  
        <artifactId>maven-compiler-plugin</artifactId>  
        <configuration>  
            <source>1.7</source>  
            <target>1.7</target>  
        </configuration>  
    </plugin>  
</plugins>  
</build>  
  
2、实现一个Agent  
Agent的构造比较简单，我们只需要在premain方法中，加入一个线程池。其功能是每隔5秒输出一次内存信息和GC信息。

public class MyAgent \{

public static void premain(String agentArgs, Instrumentation inst) \{  
        System.out.println("this is an perform monitor agent.");

Executors.newScheduledThreadPool(1).scheduleAtFixedRate(new Runnable() \{  
            public void run() \{  
                Metric.printMemoryInfo();  
                Metric.printGCInfo();  
            \}  
        \}, 0, 5000, TimeUnit.MILLISECONDS);  
    \}  
\}  
  
3、获取JVM 内存以及GC信息  
public class Metric \{  
    private static final long MB = 1048576L;

public static void printMemoryInfo() \{  
        MemoryMXBean memory = ManagementFactory.getMemoryMXBean();  
        MemoryUsage headMemory = memory.getHeapMemoryUsage();

String info = String.format("\\ninit: %s\\t max: %s\\t used: %s\\t committed: %s\\t use rate: %s\\n",  
                headMemory.getInit() / MB + "MB",  
                headMemory.getMax() / MB + "MB", headMemory.getUsed() / MB + "MB",  
                headMemory.getCommitted() / MB + "MB",  
                headMemory.getUsed() \* 100 / headMemory.getCommitted() + "%"

);

System.out.print(info);

MemoryUsage nonheadMemory = memory.getNonHeapMemoryUsage();

info = String.format("init: %s\\t max: %s\\t used: %s\\t committed: %s\\t use rate: %s\\n",  
                nonheadMemory.getInit() / MB + "MB",  
                nonheadMemory.getMax() / MB + "MB", nonheadMemory.getUsed() / MB + "MB",  
                nonheadMemory.getCommitted() / MB + "MB",  
                nonheadMemory.getUsed() \* 100 / nonheadMemory.getCommitted() + "%"

);  
        System.out.println(info);  
    \}

public static void printGCInfo() \{  
        List<GarbageCollectorMXBean> garbages = ManagementFactory.getGarbageCollectorMXBeans();  
        for (GarbageCollectorMXBean garbage : garbages) \{  
            String info = String.format("name: %s\\t count:%s\\t took:%s\\t pool name:%s",  
                    garbage.getName(),  
                    garbage.getCollectionCount(),  
                    garbage.getCollectionTime(),  
                    Arrays.deepToString(garbage.getMemoryPoolNames()));  
            System.out.println(info);  
        \}  
    \}  
\}  
  
三、运行  
public class AgentTest \{

public static void main(String\[\] args) throws Exception \{  
        boolean is = true;  
        while (is) \{  
            List<Object> list = new ArrayList<Object>();  
            list.add("hello world");  
        \}  
    \}  
\}  
  
运行上述代码时，我们同样加上Agent。-javaagent:./my-agent.jar