FileDataServlet.java
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上传日期:2018-01-08
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- /**
- * 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.hdfs.server.namenode;
- import java.io.IOException;
- import java.net.URI;
- import java.net.URISyntaxException;
- import javax.servlet.http.HttpServletRequest;
- import javax.servlet.http.HttpServletResponse;
- import org.apache.hadoop.fs.FileStatus;
- import org.apache.hadoop.hdfs.protocol.ClientProtocol;
- import org.apache.hadoop.hdfs.protocol.DatanodeID;
- import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
- import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
- import org.apache.hadoop.security.UnixUserGroupInformation;
- /** Redirect queries about the hosted filesystem to an appropriate datanode.
- * @see org.apache.hadoop.hdfs.HftpFileSystem
- */
- public class FileDataServlet extends DfsServlet {
- /** Create a redirection URI */
- protected URI createUri(FileStatus i, UnixUserGroupInformation ugi,
- ClientProtocol nnproxy, HttpServletRequest request)
- throws IOException, URISyntaxException {
- String scheme = request.getScheme();
- final DatanodeID host = pickSrcDatanode(i, nnproxy);
- final String hostname;
- if (host instanceof DatanodeInfo) {
- hostname = ((DatanodeInfo)host).getHostName();
- } else {
- hostname = host.getHost();
- }
- return new URI(scheme, null, hostname,
- "https".equals(scheme)
- ? (Integer)getServletContext().getAttribute("datanode.https.port")
- : host.getInfoPort(),
- "/streamFile", "filename=" + i.getPath() + "&ugi=" + ugi, null);
- }
- private static JspHelper jspHelper = null;
- /** 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(FileStatus i,
- ClientProtocol nnproxy) throws IOException {
- // a race condition can happen by initializing a static member this way.
- // A proper fix should make JspHelper a singleton. Since it doesn't affect
- // correctness, we leave it as is for now.
- if (jspHelper == null)
- jspHelper = new JspHelper();
- 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() : "/";
- FileStatus info = nnproxy.getFileInfo(path);
- if ((info != null) && !info.isDir()) {
- response.sendRedirect(createUri(info, ugi, nnproxy,
- request).toURL().toString());
- } else if (info == null){
- response.sendError(400, "cat: File not found " + path);
- } 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());
- }
- }
- }