java.lang.OutOfMemoryError：调用 Files.readAllBytes 时直接缓冲内存

我有以下代码，旨在读取目录并将其压缩到 tar.gz 存档中。当我将代码部署到服务器上并使用一批文件对其进行测试时，它在前几个测试批次中工作，但在第 4 或第 5 批次之后，它开始持续给出 java.lang.OutOfMemoryError: Direct buffer memory，即使文件批量大小保持不变，堆空间看起来很好。这是代码：

public static void compressDirectory(String archiveDirectoryToCompress) throws IOException {
Path archiveToCompress = Files.createFile(Paths.get(archiveDirectoryToCompress + ".tar.gz"));

try (GzipCompressorOutputStream gzipCompressorOutputStream = new GzipCompressorOutputStream(
    Files.newOutputStream(archiveToCompress));
     TarArchiveOutputStream tarArchiveOutputStream = new TarArchiveOutputStream(gzipCompressorOutputStream)) {
  Path directory = Paths.get(archiveDirectoryToCompress);
  Files.walk(directory)
      .filter(path -> !Files.isDirectory(path))
      .forEach(path -> {
        String
            stringPath =
            path.toAbsolutePath().toString().replace(directory.toAbsolutePath().toString(), "")
                .replace(path.getFileName().toString(), "");
        TarArchiveEntry tarEntry = new TarArchiveEntry(stringPath + "/" + path.getFileName().toString());
        try {
          byte[] bytes = Files.readAllBytes(path); //It throws the error at this point.
          tarEntry.setSize(bytes.length);
          tarArchiveOutputStream.putArchiveEntry(tarEntry);
          tarArchiveOutputStream.write(bytes);
          tarArchiveOutputStream.closeArchiveEntry();
        } catch (Exception e) {
          LOGGER.error("There was an error while compressing the files", e);
        }
      });
}

}

这是一个例外：

Caused by: java.lang.OutOfMemoryError: Direct buffer memory
    at java.nio.Bits.reserveMemory(Bits.java:658)
    at java.nio.DirectByteBuffer.<init>(DirectByteBuffer.java:123)
    at java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:311)
    at sun.nio.ch.Util.getTemporaryDirectBuffer(Util.java:174)
    at sun.nio.ch.IOUtil.read(IOUtil.java:195)
    at sun.nio.ch.FileChannelImpl.read(FileChannelImpl.java:158)
    at sun.nio.ch.ChannelInputStream.read(ChannelInputStream.java:65)
    at sun.nio.ch.ChannelInputStream.read(ChannelInputStream.java:109)
    at sun.nio.ch.ChannelInputStream.read(ChannelInputStream.java:103)
    at java.nio.file.Files.read(Files.java:3105)
    at java.nio.file.Files.readAllBytes(Files.java:3158)
    at com.ubs.gfs.etd.reporting.otc.trsloader.service.file.GmiEodFileArchiverService.lambda$compressDirectory$4(GmiEodFileArchiverService.java:124)
    at com.ubs.gfs.etd.reporting.otc.trsloader.service.file.GmiEodFileArchiverService$$Lambda$19/183444013.accept(Unknown Source)
    at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
    at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
    at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
    at java.util.Iterator.forEachRemaining(Iterator.java:116)
    at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:512)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:502)
    at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
    at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
    at com.ubs.gfs.etd.reporting.otc.trsloader.service.file.GmiEodFileArchiverService.compressDirectory(GmiEodFileArchiverService.java:117)
    at com.ubs.gfs.etd.reporting.otc.trsloader.service.file.GmiEodFileArchiverService.archiveFiles(GmiEodFileArchiverService.java:66)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.springframework.expression.spel.support.ReflectiveMethodExecutor.execute(ReflectiveMethodExecutor.java:113)
    at org.springframework.expression.spel.ast.MethodReference.getValueInternal(MethodReference.java:102)
    at org.springframework.expression.spel.ast.MethodReference.access$000(MethodReference.java:49)
    at org.springframework.expression.spel.ast.MethodReference$MethodValueRef.getValue(MethodReference.java:347)
    at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:88)
    at org.springframework.expression.spel.ast.SpelNodeImpl.getTypedValue(SpelNodeImpl.java:131)
    at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:330)
    at org.springframework.integration.util.AbstractExpressionEvaluator.evaluateExpression(AbstractExpressionEvaluator.java:166)
    at org.springframework.integration.util.MessagingMethodInvokerHelper.processInternal(MessagingMethodInvokerHelper.java:317)
    ... 93 more

我认为存在缓冲区内存泄漏，因为它在前 4 个测试批次中工作完美，但随后始终给出 java.lang.OutOfMemoryError: Direct buffer memory 错误，但我不知道如何修复它。我在这里看到了使用 Cleaner 方法的潜在解决方案：http://www.java67.com/2014/01/how-to-fix-javalangoufofmemoryerror-direct-byte-buffer-java.html

但我不知道这是否适用于本例。

- - - - - - - - - - - - 编辑 - - - - - - - - - - - -

我找到了另一种关于如何使用 IOUtils 和缓冲输入流压缩文件的方法，并修复了问题，更新了代码：

  public static void compressDirectory(String archiveDirectoryToCompress) throws IOException {
Path archiveToCompress = Files.createFile(Paths.get(archiveDirectoryToCompress + ".tar.gz"));

try (GzipCompressorOutputStream gzipCompressorOutputStream = new GzipCompressorOutputStream(
    Files.newOutputStream(archiveToCompress));
     TarArchiveOutputStream tarArchiveOutputStream = new TarArchiveOutputStream(gzipCompressorOutputStream)) {
  Path directory = Paths.get(archiveDirectoryToCompress);
  Files.walk(directory)
      .filter(path -> !Files.isDirectory(path))
      .forEach(path -> {
        TarArchiveEntry tarEntry = new TarArchiveEntry(path.toFile(),path.getFileName().toString());
        try (BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream(path.toString()))) {
          tarArchiveOutputStream.putArchiveEntry(tarEntry);
          IOUtils.copy(bufferedInputStream, tarArchiveOutputStream);
          tarArchiveOutputStream.closeArchiveEntry();
        } catch (Exception e) {
          LOGGER.error("There was an error while compressing the files", e);
        }
      });
}

}

将文件加载到内存中时，java 使用称为直接内存池的不同非堆池分配一系列 DirectByteBuffer。这些缓冲区还附加了一个 Deallocator 类，负责在不再需要文件时释放该内存。默认情况下，这些释放器在垃圾收集期间运行。

我怀疑正在发生的事情（这是我之前实际看到的）是您的程序没有充分利用堆，并且垃圾收集运行得不够频繁以释放那些 DirectByteBuffer。因此，您可以尝试以下两种方法之一：使用 -XX:MaxDirectMemorySize 增加直接内存池的大小，或者通过调用 System.gc() 定期强制垃圾回收。