}
static DatanodeInfo chooseDatanode(final NameNode namenode,
final String path, final HttpOpParam.Op op, final long openOffset,
final long blocksize, final Configuration conf) throws IOException {
final BlockManager bm = namenode.getNamesystem().getBlockManager();
if (op == PutOpParam.Op.CREATE) {
//choose a datanode near to client
final DatanodeDescriptor clientNode = bm.getDatanodeManager(
).getDatanodeByHost(getRemoteAddress());
if (clientNode != null) {
final DatanodeStorageInfo[] storages = bm.getBlockPlacementPolicy()
.chooseTarget(path, 1, clientNode,
new ArrayList<DatanodeStorageInfo>(), false, null, blocksize,
// TODO: get storage type from the file
StorageType.DEFAULT);
if (storages.length > 0) {
return storages[0].getDatanodeDescriptor();
}
}
} else if (op == GetOpParam.Op.OPEN
|| op == GetOpParam.Op.GETFILECHECKSUM
|| op == PostOpParam.Op.APPEND) {
//choose a datanode containing a replica
final NamenodeProtocols np = namenode.getRpcServer();
final HdfsFileStatus status = np.getFileInfo(path);
if (status == null) {
throw new FileNotFoundException("File " + path + " not found.");
}
final long len = status.getLen();
if (op == GetOpParam.Op.OPEN) {
if (openOffset < 0L || (openOffset >= len && len > 0)) {
throw new IOException("Offset=" + openOffset
+ " out of the range [0, " + len + "); " + op + ", path=" + path);
}
}
if (len > 0) {
final long offset = op == GetOpParam.Op.OPEN? openOffset: len - 1;
final LocatedBlocks locations = np.getBlockLocations(path, offset, 1);
final int count = locations.locatedBlockCount();
if (count > 0) {
return JspHelper.bestNode(locations.get(0).getLocations(), false, conf);
}
}
}
return (DatanodeDescriptor)bm.getDatanodeManager().getNetworkTopology(
).chooseRandom(NodeBase.ROOT);
}