Example usage for org.apache.cassandra.io.compress CompressionMetadata chunkFor

Introduction

In this page you can find the example usage for org.apache.cassandra.io.compress CompressionMetadata chunkFor.

Prototype

public Chunk chunkFor(long position) 

Source Link

Document

Get a chunk of compressed data (offset, length) corresponding to given position

Usage

From source file:com.fullcontact.cassandra.io.compress.CompressedRandomAccessReaderTest.java

License:Apache License

@Test
public void testDataCorruptionDetection() throws IOException {
    String CONTENT = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Etiam vitae.";

    File file = new File("testDataCorruptionDetection");
    file.deleteOnExit();// w  w w.j  a v a 2  s .  c  om

    File metadata = new File(file.getPath() + ".meta");
    metadata.deleteOnExit();

    SSTableMetadata.Collector sstableMetadataCollector = SSTableMetadata.createCollector().replayPosition(null);
    SequentialWriter writer = new CompressedSequentialWriter(file, metadata.getPath(), false,
            new CompressionParameters(SnappyCompressor.instance), sstableMetadataCollector);

    writer.write(CONTENT.getBytes());
    writer.close();

    // open compression metadata and get chunk information
    CompressionMetadata meta = new CompressionMetadata(metadata.getPath(), file.length(), fs);
    CompressionMetadata.Chunk chunk = meta.chunkFor(0);

    RandomAccessReader reader = CompressedRandomAccessReader.open(new Path(file.getPath()), meta, false, fs);
    // read and verify compressed data
    assertEquals(CONTENT, reader.readLine());
    // close reader
    reader.close();

    Random random = new Random();
    RandomAccessFile checksumModifier = null;

    try {
        checksumModifier = new RandomAccessFile(file, "rw");
        byte[] checksum = new byte[4];

        // seek to the end of the compressed chunk
        checksumModifier.seek(chunk.length);
        // read checksum bytes
        checksumModifier.read(checksum);
        // seek back to the chunk end
        checksumModifier.seek(chunk.length);

        // lets modify one byte of the checksum on each iteration
        for (int i = 0; i < checksum.length; i++) {
            checksumModifier.write(random.nextInt());
            checksumModifier.getFD().sync(); // making sure that change was synced with disk

            final RandomAccessReader r = CompressedRandomAccessReader.open(new Path(file.getPath()), meta,
                    false, fs);

            Throwable exception = null;
            try {
                r.readLine();
            } catch (Throwable t) {
                exception = t;
            }
            assertNotNull(exception);
            assertEquals(exception.getClass(), CorruptSSTableException.class);
            assertEquals(exception.getCause().getClass(), CorruptBlockException.class);

            r.close();
        }

        // lets write original checksum and check if we can read data
        updateChecksum(checksumModifier, chunk.length, checksum);

        reader = CompressedRandomAccessReader.open(new Path(file.getPath()), meta, false, fs);
        // read and verify compressed data
        assertEquals(CONTENT, reader.readLine());
        // close reader
        reader.close();
    } finally {
        if (checksumModifier != null)
            checksumModifier.close();
    }
}

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