JVM Profiler StacktraceCollectorProfiler

开篇

StacktraceCollectorProfiler主要用来采集线程的调用栈，原理是通过ManagementFactory.getThreadMXBean()返回的ThreadMXBean对象来实现。

源码分析

 public void profile() { // 获取此刻所有线程的dump信息 ThreadInfo[] threadInfos = threadMXBean.dumpAllThreads(false, false); if (threadInfos == null) { return; } // 遍历线程信息并处理每个线程 for (ThreadInfo threadInfo : threadInfos) { String threadName = threadInfo.getThreadName(); if (threadName == null) { threadName = ""; } if (!ignoreThreadNamePrefix.isEmpty() && threadName.startsWith(ignoreThreadNamePrefix)) { continue; } // 获取线程的调用栈 StackTraceElement[] stackTraceElements = threadInfo.getStackTrace(); // 创建调用栈对象 Stacktrace stacktrace = new Stacktrace(); stacktrace.setThreadName(threadName); stacktrace.setThreadState(String.valueOf(threadInfo.getThreadState())); // 创建保存调用栈的list int totalLength = 0; List<ClassAndMethod> stack = new ArrayList<>(stackTraceElements.length); // 按照倒序保存调用链，最底层的放在最前面，把最根本的原因发在前面 for (int i = stackTraceElements.length - 1; i >= 0; i--) { StackTraceElement stackTraceElement = stackTraceElements[i]; String className = String.valueOf(stackTraceElement.getClassName()); String methodName = String.valueOf(stackTraceElement.getMethodName()); stack.add(new ClassAndMethod(className, methodName)); totalLength += className.length() + methodName.length(); // 如果长度超出限制，那么就截断 if (totalLength >= Constants.MAX_STRING_LENGTH) { stack.add(new ClassAndMethod("_stack_", "_trimmed_")); break; } } // 反转调用链，把最底层的放在最前面。 ClassAndMethod[] classAndMethodArray = new ClassAndMethod[stack.size()]; for (int i = 0; i < stack.size(); i++) { classAndMethodArray[classAndMethodArray.length - 1 - i] = stack.get(i); } stacktrace.setStack(classAndMethodArray); buffer.appendValue(stacktrace); } } 

采集结果

调用链的反向序列为：

• java.lang.Thread.sleep
• com.uber.profiling.examples.HelloWorldApplication.privateSleepMethod
• com.uber.profiling.examples.HelloWorldApplication.main

{ "stacktrace": ["java.lang.Thread.sleep", "com.uber.profiling.examples.HelloWorldApplication.privateSleepMethod", "com.uber.profiling.examples.HelloWorldApplication.main"], "endEpoch": 1536072801080, "appId": null, "host": "xiaozhideMacBook-Pro.local", "name": "2203@xiaozhideMacBook-Pro.local", "processUuid": "1e580f6e-0493-4e5b-bee2-a61c5f7b097d", "threadState": "TIMED_WAITING", "count": 24, "tag": "mytag", "startEpoch": 1536072796084, "threadName": "main" }