Question

首先，我有两个并发运行的进程，它们互为支持。一个进程读取一个简单的flatfile，其中包含由时间戳分隔的数据快照。此应用程序只是打开此文件（没有文件锁定），读取快照并将其放入另一个名为topology.netviz的文件（带文件锁定）。第二个应用程序读取topology.netziv（带文件锁定）并将数据传输到临时文件中，以减少编程在另一个进程之间锁定的延迟。

我的问题很简单：当我在第二个进程中将数据传输到临时文件时，会传输奇怪的字符/损坏的数据。我在下面提供了一些代码，让大家可以了解可能出现的问题。

流程1：

try {
    // Determine if File Exists
    topologyFile = new File(Settings.NODE_TOPOLOGY_PATH);
    if (!topologyFile.exists())
        topologyFile.createNewFile();

    // FileChannel Gives the Ability to Create a File Lock
    FileChannel channel =
        new RandomAccessFile(topologyFile, "rwd").getChannel();

    // Use the FileChannel to Create a Lock on the 'distance.dat' (Blocking Method)
    FileLock lock = channel.lock();

    // Delete Files Contents
    channel.truncate(0);

    // Convert 'data' into ByteBuffer
    ByteBuffer buffer = ByteBuffer.wrap(data);

    // Write 'buffer' to 'channel'
    channel.write(buffer, 0);

    // Release Lock
    lock.release();

    // Close Channel
    channel.close();
}

catch(IOException error)
{
    System.out.println("Topology Thread: FileChannel; I/O Error Occured");
}

catch(NonWritableChannelException error)
{
    System.
        out.println("Topology Thread: FileChannel; File is not Writeable");
}

流程2：

try {
    // Determine if File Exists
    topologyFileTemp = new File("tmp/topology.dat");
    if (topologyFileTemp.exists())
        topologyFileTemp.delete();  // Should Never Occur Unless Program Crashes

    // Recreate 'topologyFileTemp'
    topologyFileTemp = new File("tmp/topology.dat");
    topologyFileTemp.createNewFile();

    // Determine if File Exists
    topologyFile = new File("topology.netviz");
    if (!topologyFile.exists())
        topologyFile.createNewFile();   // Should Never Occur

    // Initialize Data Container from 'topology.netviz' in the Form of Bytes
    ByteBuffer topologyData =
        ByteBuffer.allocate((int)topologyFile.length());

    // FileChannel Gives the Ability to Create a File Lock for 'topology.netviz'
    FileChannel rChannel =
        new RandomAccessFile(topologyFile, "rwd").getChannel();

    // Use the FileChannel to Create a Lock on the 'distance.dat' (Blocking Method)
    FileLock lock = rChannel.lock();

    // Grab Data from 'topology.netviz'
    rChannel.read(topologyData);

    // Release Lock
    lock.release();

    // Close Channel
    rChannel.close();

    // FileChannel Gives the Ability to Create a File Lock for 'tmp/topology.dat'
    FileChannel wChannel =
        new RandomAccessFile(topologyFileTemp, "rw").getChannel();

    // Reset Buffers Position
    topologyData.position(0);

    // Write 'topologyData' to 'tmp/topology.dat'
    wChannel.write(topologyData);

    // Close the file
    wChannel.close();
}

catch(IOException error)
{
    System.out.println("Topology Thread: FileChannel; I/O Error Occured");
}

catch(NonWritableChannelException error)
{
    System.out.
        println("Topology Thread: FileChannel; File is not Writeable");
}

Answer 1

一个潜在的问题是进程＃1在关闭通道之前释放锁。由于关闭通道会刷新未完成的写入，这可能意味着在锁定释放后正在写入数据，这可能会导致损坏。

另一种可能性是字节在写入之前已被破坏......或者编写者和读者使用的格式之间存在不匹配。

Java文件锁定有2个进程

1 个答案: