From aea2ec25da8b76a1ad8aba4d3ec799498399cf43 Mon Sep 17 00:00:00 2001
From: hengyunabc <hengyunabc@gmail.com>
Date: Wed, 24 Jun 2020 17:59:02 +0800
Subject: [PATCH] Checking if arthas is started via SpyAPI

---
 .../arthas/agent332/AgentBootstrap.java       | 20 ++++++++++++++-
 .../arthas/core/server/ArthasBootstrap.java   | 13 +++++++++-
 spy/src/main/java/java/arthas/SpyAPI.java     | 25 ++++++++++++++++---
 3 files changed, 53 insertions(+), 5 deletions(-)

diff --git a/agent/src/main/java/com/taobao/arthas/agent332/AgentBootstrap.java b/agent/src/main/java/com/taobao/arthas/agent332/AgentBootstrap.java
index 311631fad..34e3c4bb0 100755
--- a/agent/src/main/java/com/taobao/arthas/agent332/AgentBootstrap.java
+++ b/agent/src/main/java/com/taobao/arthas/agent332/AgentBootstrap.java
@@ -1,5 +1,6 @@
 package com.taobao.arthas.agent332;
 
+import java.arthas.SpyAPI;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.PrintStream;
@@ -50,7 +51,13 @@ public class AgentBootstrap {
         }
     }
 
-    // 全局持有classloader用于隔离 Arthas 实现
+    /**
+     * <pre>
+     * 1. 全局持有classloader用于隔离 Arthas 实现，防止多次attach重复初始化
+     * 2. ClassLoader在arthas停止时会被reset
+     * 3. 如果ClassLoader一直没变，则 com.taobao.arthas.core.server.ArthasBootstrap#getInstance 返回结果一直是一样的
+     * </pre>
+     */
     private static volatile ClassLoader arthasClassLoader;
 
     public static void premain(String args, Instrumentation inst) {
@@ -81,6 +88,17 @@ public class AgentBootstrap {
     }
 
     private static synchronized void main(String args, final Instrumentation inst) {
+        // 尝试判断arthas是否已在运行，如果是的话，直接就退出
+        try {
+            Class.forName("java.arthas.SpyAPI"); // 加载不到会抛异常
+            if (SpyAPI.isInited()) {
+                ps.println("Arthas server already stared, skip attach.");
+                ps.flush();
+                return;
+            }
+        } catch (Throwable e) {
+            // ignore
+        }
         try {
             ps.println("Arthas server agent start...");
             // 传递的args参数分两个部分:arthasCoreJar路径和agentArgs, 分别是Agent的JAR包路径和期望传递到服务端的参数
diff --git a/core/src/main/java/com/taobao/arthas/core/server/ArthasBootstrap.java b/core/src/main/java/com/taobao/arthas/core/server/ArthasBootstrap.java
index af0372112..a92290e2f 100644
--- a/core/src/main/java/com/taobao/arthas/core/server/ArthasBootstrap.java
+++ b/core/src/main/java/com/taobao/arthas/core/server/ArthasBootstrap.java
@@ -331,6 +331,12 @@ public class ArthasBootstrap {
             UserStatUtil.setStatUrl(configure.getStatUrl());
             UserStatUtil.arthasStart();
 
+            try {
+                SpyAPI.init();
+            } catch (Throwable e) {
+                // ignore
+            }
+
             logger().info("as-server started in {} ms", System.currentTimeMillis() - start);
         } catch (Throwable e) {
             logger().error("Error during bind to port " + configure.getTelnetPort(), e);
@@ -442,7 +448,12 @@ public class ArthasBootstrap {
      * 清除SpyAPI里的引用
      */
     private void cleanUpSpyReference() {
-        SpyAPI.setNopSpy();
+        try {
+            SpyAPI.setNopSpy();
+            SpyAPI.destroy();
+        } catch (Throwable e) {
+            // ignore
+        }
         // AgentBootstrap.resetArthasClassLoader();
         try {
             Class<?> clazz = ClassLoader.getSystemClassLoader().loadClass("com.taobao.arthas.agent332.AgentBootstrap");
diff --git a/spy/src/main/java/java/arthas/SpyAPI.java b/spy/src/main/java/java/arthas/SpyAPI.java
index 5de04962b..32762def9 100644
--- a/spy/src/main/java/java/arthas/SpyAPI.java
+++ b/spy/src/main/java/java/arthas/SpyAPI.java
@@ -21,8 +21,10 @@ package java.arthas;
  *
  */
 public class SpyAPI {
-    private static final AbstractSpy NOPSPY = new NopSpy();
-    private static volatile AbstractSpy spyInstance = new NopSpy();
+    public static final AbstractSpy NOPSPY = new NopSpy();
+    private static volatile AbstractSpy spyInstance = NOPSPY;
+
+    public static volatile boolean INITED;
 
     public static AbstractSpy getSpy() {
         return spyInstance;
@@ -31,11 +33,28 @@ public class SpyAPI {
     public static void setSpy(AbstractSpy spy) {
         spyInstance = spy;
     }
-    
+
     public static void setNopSpy() {
         setSpy(NOPSPY);
     }
 
+    public static boolean isNopSpy() {
+        return NOPSPY == spyInstance;
+    }
+
+    public static void init() {
+        INITED = true;
+    }
+
+    public static boolean isInited() {
+        return INITED;
+    }
+
+    public static void destroy() {
+        setNopSpy();
+        INITED = false;
+    }
+
     public static void atEnter(Class<?> clazz, String methodInfo, Object target, Object[] args) {
         spyInstance.atEnter(clazz, methodInfo, target, args);
     }