/**
* Test that copy on write for blocks works correctly
*
* @throws IOException an exception might be thrown
*/
@Test
public void testCopyOnWrite() throws IOException {
Configuration conf = new HdfsConfiguration();
if (simulatedStorage) {
conf.setBoolean(SimulatedFSDataset.CONFIG_PROPERTY_SIMULATED, true);
}
MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf).build();
FileSystem fs = cluster.getFileSystem();
InetSocketAddress addr = new InetSocketAddress("localhost", cluster.getNameNodePort());
DFSClient client = new DFSClient(addr, conf);
try {
// create a new file, write to it and close it.
//
Path file1 = new Path("/filestatus.dat");
FSDataOutputStream stm = AppendTestUtil.createFile(fs, file1, 1);
writeFile(stm);
stm.close();
// Get a handle to the datanode
DataNode[] dn = cluster.listDataNodes();
assertTrue("There should be only one datanode but found " + dn.length, dn.length == 1);
LocatedBlocks locations =
client.getNamenode().getBlockLocations(file1.toString(), 0, Long.MAX_VALUE);
List<LocatedBlock> blocks = locations.getLocatedBlocks();
FSDataset dataset = (FSDataset) dn[0].data;
//
// Create hard links for a few of the blocks
//
for (int i = 0; i < blocks.size(); i = i + 2) {
ExtendedBlock b = blocks.get(i).getBlock();
File f = dataset.getFile(b.getBlockPoolId(), b.getLocalBlock());
File link = new File(f.toString() + ".link");
System.out.println("Creating hardlink for File " + f + " to " + link);
HardLink.createHardLink(f, link);
}
//
// Detach all blocks. This should remove hardlinks (if any)
//
for (int i = 0; i < blocks.size(); i++) {
ExtendedBlock b = blocks.get(i).getBlock();
System.out.println("testCopyOnWrite detaching block " + b);
assertTrue(
"Detaching block " + b + " should have returned true", dataset.unlinkBlock(b, 1));
}
// Since the blocks were already detached earlier, these calls should
// return false
//
for (int i = 0; i < blocks.size(); i++) {
ExtendedBlock b = blocks.get(i).getBlock();
System.out.println("testCopyOnWrite detaching block " + b);
assertTrue(
"Detaching block " + b + " should have returned false", !dataset.unlinkBlock(b, 1));
}
} finally {
fs.close();
cluster.shutdown();
}
}
