聊聊springboot的HeapDumpWebEndpoint

序

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

@Configuration
public class HeapDumpWebEndpointAutoConfiguration {

	@Bean
	@ConditionalOnMissingBean
	@ConditionalOnEnabledEndpoint
	public HeapDumpWebEndpoint heapDumpWebEndpoint() {
		return new HeapDumpWebEndpoint();
	}

}

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<Resource> 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();
	}
}

這裏調用的是dumpHeap方法，委託給heapDumper來執行

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 <em>live</em> 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<PlatformManagedObject>) 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);
		}

	}

這裏建立的是HotSpotDiagnosticMXBeanHeapDumper，利用反射調用HotSpotDiagnosticMXBean的dumpHeap方法

TemporaryFileSystemResource

最後經過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;
		}

	}

小結

heapDump的實現是依賴HotSpotDiagnosticMXBean來，若是不存在則報HeapDumperUnavailableException，而後狀態碼返回STATUS_SERVICE_UNAVAILABLE。若是存在則默認dump存活的對象。

doc

• Spring Boot Reference Guide