package org.apache.lucene.replicator.http;
/*
* 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.
*/
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Locale;
import java.util.Map;
import java.util.StringTokenizer;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.http.HttpStatus;
import org.apache.lucene.replicator.Replicator;
import org.apache.lucene.replicator.SessionToken;
/**
* A server-side service for handling replication requests. The service assumes
* requests are sent in the format
* <code>/<context>/<shard>/<action></code> where
* <ul>
* <li>{@code context} is the servlet context, e.g. {@link #REPLICATION_CONTEXT}
* <li>{@code shard} is the ID of the shard, e.g. "s1"
* <li>{@code action} is one of {@link ReplicationAction} values
* </ul>
* For example, to check whether there are revision updates for shard "s1" you
* should send the request: <code>http://host:port/replicate/s1/update</code>.
* <p>
* This service is written like a servlet, and
* {@link #perform(HttpServletRequest, HttpServletResponse)} takes servlet
* request and response accordingly, so it is quite easy to embed in your
* application's servlet.
*
* @lucene.experimental
*/
public class ReplicationService {
/** Actions supported by the {@link ReplicationService}. */
public enum ReplicationAction {
OBTAIN, RELEASE, UPDATE
}
/** The context path for the servlet. */
public static final String REPLICATION_CONTEXT = "/replicate";
/** Request parameter name for providing the revision version. */
public final static String REPLICATE_VERSION_PARAM = "version";
/** Request parameter name for providing a session ID. */
public final static String REPLICATE_SESSION_ID_PARAM = "sessionid";
/** Request parameter name for providing the file's source. */
public final static String REPLICATE_SOURCE_PARAM = "source";
/** Request parameter name for providing the file's name. */
public final static String REPLICATE_FILENAME_PARAM = "filename";
private static final int SHARD_IDX = 0, ACTION_IDX = 1;
private final Map<String,Replicator> replicators;
public ReplicationService(Map<String,Replicator> replicators) {
super();
this.replicators = replicators;
}
/**
* Returns the path elements that were given in the servlet request, excluding
* the servlet's action context.
*/
private String[] getPathElements(HttpServletRequest req) {
String path = req.getServletPath();
String pathInfo = req.getPathInfo();
if (pathInfo != null) {
path += pathInfo;
}
int actionLen = REPLICATION_CONTEXT.length();
int startIdx = actionLen;
if (path.length() > actionLen && path.charAt(actionLen) == '/') {
++startIdx;
}
// split the string on '/' and remove any empty elements. This is better
// than using String.split() since the latter may return empty elements in
// the array
StringTokenizer stok = new StringTokenizer(path.substring(startIdx), "/");
ArrayList<String> elements = new ArrayList<String>();
while (stok.hasMoreTokens()) {
elements.add(stok.nextToken());
}
return elements.toArray(new String[0]);
}
private static String extractRequestParam(HttpServletRequest req, String paramName) throws ServletException {
String param = req.getParameter(paramName);
if (param == null) {
throw new ServletException("Missing mandatory parameter: " + paramName);
}
return param;
}
private static void copy(InputStream in, OutputStream out) throws IOException {
byte[] buf = new byte[16384];
int numRead;
while ((numRead = in.read(buf)) != -1) {
out.write(buf, 0, numRead);
}
}
/** Executes the replication task. */
public void perform(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String[] pathElements = getPathElements(req);
if (pathElements.length != 2) {
throw new ServletException("invalid path, must contain shard ID and action, e.g. */s1/update");
}
final ReplicationAction action;
try {
action = ReplicationAction.valueOf(pathElements[ACTION_IDX].toUpperCase(Locale.ENGLISH));
} catch (IllegalArgumentException e) {
throw new ServletException("Unsupported action provided: " + pathElements[ACTION_IDX]);
}
final Replicator replicator = replicators.get(pathElements[SHARD_IDX]);
if (replicator == null) {
throw new ServletException("unrecognized shard ID " + pathElements[SHARD_IDX]);
}
ServletOutputStream resOut = resp.getOutputStream();
try {
switch (action) {
case OBTAIN:
final String sessionID = extractRequestParam(req, REPLICATE_SESSION_ID_PARAM);
final String fileName = extractRequestParam(req, REPLICATE_FILENAME_PARAM);
final String source = extractRequestParam(req, REPLICATE_SOURCE_PARAM);
InputStream in = replicator.obtainFile(sessionID, source, fileName);
try {
copy(in, resOut);
} finally {
in.close();
}
break;
case RELEASE:
replicator.release(extractRequestParam(req, REPLICATE_SESSION_ID_PARAM));
break;
case UPDATE:
String currVersion = req.getParameter(REPLICATE_VERSION_PARAM);
SessionToken token = replicator.checkForUpdate(currVersion);
if (token == null) {
resOut.write(0); // marker for null token
} else {
resOut.write(1); // marker for null token
token.serialize(new DataOutputStream(resOut));
}
break;
}
} catch (Exception e) {
resp.setStatus(HttpStatus.SC_INTERNAL_SERVER_ERROR); // propagate the failure
try {
/*
* Note: it is assumed that "identified exceptions" are thrown before
* anything was written to the stream.
*/
ObjectOutputStream oos = new ObjectOutputStream(resOut);
oos.writeObject(e);
oos.flush();
} catch (Exception e2) {
throw new IOException("Could not serialize", e2);
}
} finally {
resp.flushBuffer();
}
}
}