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本文主要研究下springboot的HeapDumpWebEndpoint
HeapDumpWebEndpointAutoConfiguration
spring-boot-actuator-autoconfigure-2.0.1.RELEASE-sources.jar!/org/springframework/boot/actuate/autoconfigure/management/HeapDumpWebEndpointAutoConfiguration.java
@Configurationpublic class HeapDumpWebEndpointAutoConfiguration { @Bean @ConditionalOnMissingBean @ConditionalOnEnabledEndpoint public HeapDumpWebEndpoint heapDumpWebEndpoint() { return new HeapDumpWebEndpoint(); }}复制代码 HeapDumpWebEndpoint
spring-boot-actuator-2.0.1.RELEASE-sources.jar!/org/springframework/boot/actuate/management/HeapDumpWebEndpoint.java
@WebEndpoint(id = "heapdump")public class HeapDumpWebEndpoint { private final long timeout; private final Lock lock = new ReentrantLock(); private HeapDumper heapDumper; public HeapDumpWebEndpoint() { this(TimeUnit.SECONDS.toMillis(10)); } protected HeapDumpWebEndpoint(long timeout) { this.timeout = timeout; } @ReadOperation public WebEndpointResponse heapDump(@Nullable Boolean live) { try { if (this.lock.tryLock(this.timeout, TimeUnit.MILLISECONDS)) { try { return new WebEndpointResponse<>( dumpHeap(live == null ? true : live)); } finally { this.lock.unlock(); } } } catch (InterruptedException ex) { Thread.currentThread().interrupt(); } catch (IOException ex) { return new WebEndpointResponse<>( WebEndpointResponse.STATUS_INTERNAL_SERVER_ERROR); } catch (HeapDumperUnavailableException ex) { return new WebEndpointResponse<>( WebEndpointResponse.STATUS_SERVICE_UNAVAILABLE); } return new WebEndpointResponse<>(WebEndpointResponse.STATUS_TOO_MANY_REQUESTS); } private Resource dumpHeap(boolean live) throws IOException, InterruptedException { if (this.heapDumper == null) { this.heapDumper = createHeapDumper(); } File file = createTempFile(live); this.heapDumper.dumpHeap(file, live); return new TemporaryFileSystemResource(file); } private File createTempFile(boolean live) throws IOException { String date = new SimpleDateFormat("yyyy-MM-dd-HH-mm").format(new Date()); File file = File.createTempFile("heapdump" + date + (live ? "-live" : ""), ".hprof"); file.delete(); return file; } /** * Factory method used to create the {@link HeapDumper}. * @return the heap dumper to use * @throws HeapDumperUnavailableException if the heap dumper cannot be created */ protected HeapDumper createHeapDumper() throws HeapDumperUnavailableException { return new HotSpotDiagnosticMXBeanHeapDumper(); }}复制代码 这里调用的是dumpHeap方法，委托给heapDumper来执行
heapDumper
/** * Factory method used to create the {@link HeapDumper}. * @return the heap dumper to use * @throws HeapDumperUnavailableException if the heap dumper cannot be created */ protected HeapDumper createHeapDumper() throws HeapDumperUnavailableException { return new HotSpotDiagnosticMXBeanHeapDumper(); } /** * Strategy interface used to dump the heap to a file. */ @FunctionalInterface protected interface HeapDumper { /** * Dump the current heap to the specified file. * @param file the file to dump the heap to * @param live if only live objects (i.e. objects that are reachable from * others) should be dumped * @throws IOException on IO error * @throws InterruptedException on thread interruption */ void dumpHeap(File file, boolean live) throws IOException, InterruptedException; } /** * {@link HeapDumper} that uses {@code com.sun.management.HotSpotDiagnosticMXBean} * available on Oracle and OpenJDK to dump the heap to a file. */ protected static class HotSpotDiagnosticMXBeanHeapDumper implements HeapDumper { private Object diagnosticMXBean; private Method dumpHeapMethod; @SuppressWarnings("unchecked") protected HotSpotDiagnosticMXBeanHeapDumper() { try { Class diagnosticMXBeanClass = ClassUtils.resolveClassName( "com.sun.management.HotSpotDiagnosticMXBean", null); this.diagnosticMXBean = ManagementFactory.getPlatformMXBean( (Class ) diagnosticMXBeanClass); this.dumpHeapMethod = ReflectionUtils.findMethod(diagnosticMXBeanClass, "dumpHeap", String.class, Boolean.TYPE); } catch (Throwable ex) { throw new HeapDumperUnavailableException( "Unable to locate HotSpotDiagnosticMXBean", ex); } } @Override public void dumpHeap(File file, boolean live) { ReflectionUtils.invokeMethod(this.dumpHeapMethod, this.diagnosticMXBean, file.getAbsolutePath(), live); } }复制代码 这里创建的是HotSpotDiagnosticMXBeanHeapDumper，利用反射调用HotSpotDiagnosticMXBean的dumpHeap方法
TemporaryFileSystemResource
最后通过TemporaryFileSystemResource返回
private static final class TemporaryFileSystemResource extends FileSystemResource { private final Log logger = LogFactory.getLog(getClass()); private TemporaryFileSystemResource(File file) { super(file); } @Override public ReadableByteChannel readableChannel() throws IOException { ReadableByteChannel readableChannel = super.readableChannel(); return new ReadableByteChannel() { @Override public boolean isOpen() { return readableChannel.isOpen(); } @Override public void close() throws IOException { closeThenDeleteFile(readableChannel); } @Override public int read(ByteBuffer dst) throws IOException { return readableChannel.read(dst); } }; } @Override public InputStream getInputStream() throws IOException { return new FilterInputStream(super.getInputStream()) { @Override public void close() throws IOException { closeThenDeleteFile(this.in); } }; } private void closeThenDeleteFile(Closeable closeable) throws IOException { try { closeable.close(); } finally { deleteFile(); } } private void deleteFile() { try { Files.delete(getFile().toPath()); } catch (IOException ex) { TemporaryFileSystemResource.this.logger.warn( "Failed to delete temporary heap dump file '" + getFile() + "'", ex); } } @Override public boolean isFile() { // Prevent zero-copy so we can delete the file on close return false; } }复制代码 小结
heapDump的实现是依赖HotSpotDiagnosticMXBean来，如果不存在则报HeapDumperUnavailableException，然后状态码返回STATUS_SERVICE_UNAVAILABLE。如果存在则默认dump存活的对象。