/*
* Copyright Myrrix Ltd
*
* Licensed 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 net.myrrix.web.servlets;
import java.io.IOException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.mahout.cf.taste.common.NoSuchUserException;
import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.recommender.IDRescorer;
import org.apache.mahout.cf.taste.recommender.RecommendedItem;
import net.myrrix.common.MyrrixRecommender;
import net.myrrix.common.NotReadyException;
import net.myrrix.common.collection.FastIDSet;
import net.myrrix.online.RescorerProvider;
/**
* <p>Responds to a GET request to
* {@code /recommendToMany/[userID1](/[userID2]/...)(?howMany=n)(&considerKnownItems=true|false)(&rescorerParams=...)}
* and in turn calls
* {@link MyrrixRecommender#recommendToMany(long[], int, boolean, IDRescorer)}.
* If {@code howMany} is not specified, defaults to
* {@link AbstractMyrrixServlet#DEFAULT_HOW_MANY}. If {@code considerKnownItems} is not specified,
* it is considered {@code false}.</p>
*
* <p>Unknown user IDs are ignored, unless all are unknown, in which case a
* {@link HttpServletResponse#SC_BAD_REQUEST} status is returned.</p>
*
* <p>Output is in CSV or JSON format. Select output format using the HTTP {@code Accept} header.</p>
*
* <p>CSV output contains one recommendation per line, and each line is of the form {@code itemID, strength},
* like {@code 325, 0.53}. Strength is an opaque indicator of the relative quality of the recommendation.</p>
*
* <p>JSON output is an array of arrays, with each sub-array containing an item ID and strength.
* Example: {@code [[325, 0.53], [98, 0.499]]}.</p>
*
* @author Sean Owen
* @since 1.0
*/
public final class RecommendToManyServlet extends AbstractMyrrixServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
CharSequence pathInfo = request.getPathInfo();
if (pathInfo == null) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, "No path");
return;
}
Iterator<String> pathComponents = SLASH.split(pathInfo).iterator();
FastIDSet userIDSet = new FastIDSet();
try {
while (pathComponents.hasNext()) {
userIDSet.add(Long.parseLong(pathComponents.next()));
}
} catch (NoSuchElementException nsee) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, nsee.toString());
return;
} catch (NumberFormatException nfe) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, nfe.toString());
return;
}
long[] userIDs = userIDSet.toArray();
MyrrixRecommender recommender = getRecommender();
RescorerProvider rescorerProvider = getRescorerProvider();
try {
IDRescorer rescorer = rescorerProvider == null ? null :
rescorerProvider.getRecommendRescorer(userIDs, recommender, getRescorerParams(request));
Iterable<RecommendedItem> recommended =
recommender.recommendToMany(userIDs, getHowMany(request), getConsiderKnownItems(request), rescorer);
output(request, response, recommended);
} catch (NoSuchUserException nsue) {
response.sendError(HttpServletResponse.SC_NOT_FOUND, nsue.toString());
} catch (NotReadyException nre) {
response.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE, nre.toString());
} catch (TasteException te) {
response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, te.toString());
getServletContext().log("Unexpected error in " + getClass().getSimpleName(), te);
} catch (IllegalArgumentException iae) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, iae.toString());
}
}
@Override
protected Long getUnnormalizedPartitionToServe(HttpServletRequest request) {
CharSequence pathInfo = request.getPathInfo();
if (pathInfo == null) {
return null;
}
Iterator<String> pathComponents = SLASH.split(pathInfo).iterator();
long firstUserID;
try {
firstUserID = Long.parseLong(pathComponents.next());
} catch (NoSuchElementException ignored) {
return null;
} catch (NumberFormatException ignored) {
return null;
}
return firstUserID;
// This assumes all users are on one partition. If not, this will later fail anyway with
// NoSuchUserException as the partition for user 1 won't have the others.
}
}