/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.dfs;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.hadoop.security.UnixUserGroupInformation;
/** Redirect queries about the hosted filesystem to an appropriate datanode.
* @see org.apache.hadoop.dfs.HftpFileSystem
*/
public class FileDataServlet extends DfsServlet {
private static URI createUri(DFSFileInfo i, UnixUserGroupInformation ugi,
ClientProtocol nnproxy) throws IOException, URISyntaxException {
final DatanodeID host = pickSrcDatanode(i, nnproxy);
final String hostname;
if (host instanceof DatanodeInfo) {
hostname = ((DatanodeInfo)host).getHostName();
} else {
hostname = host.getHost();
}
return new URI("http", null, hostname, host.getInfoPort(),
"/streamFile", "filename=" + i.getPath() + "&ugi=" + ugi, null);
}
private final static JspHelper jspHelper = new JspHelper();
/** Select a datanode to service this request.
* Currently, this looks at no more than the first five blocks of a file,
* selecting a datanode randomly from the most represented.
*/
private static DatanodeID pickSrcDatanode(DFSFileInfo i,
ClientProtocol nnproxy) throws IOException {
final LocatedBlocks blks = nnproxy.getBlockLocations(
i.getPath().toUri().getPath(), 0, 1);
if (i.getLen() == 0 || blks.getLocatedBlocks().size() <= 0) {
// pick a random datanode
return jspHelper.randomNode();
}
return jspHelper.bestNode(blks.get(0));
}
/**
* Service a GET request as described below.
* Request:
* {@code
* GET http://<nn>:<port>/data[/<path>] HTTP/1.1
* }
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException {
final UnixUserGroupInformation ugi = getUGI(request);
final ClientProtocol nnproxy = createNameNodeProxy(ugi);
try {
final String path = request.getPathInfo() != null
? request.getPathInfo() : "/";
DFSFileInfo info = nnproxy.getFileInfo(path);
if (!info.isDir()) {
response.sendRedirect(createUri(info, ugi, nnproxy).toURL().toString());
} else {
response.sendError(400, "cat: " + path + ": is a directory");
}
} catch (URISyntaxException e) {
response.getWriter().println(e.toString());
} catch (IOException e) {
response.sendError(400, e.getMessage());
}
}
}