| // Copyright (C) 2010 The Android Open Source Project |
| // |
| // 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 com.google.gerrit.server.git; |
| |
| import static org.eclipse.jgit.lib.RefDatabase.ALL; |
| |
| import com.google.common.collect.Sets; |
| |
| import org.eclipse.jgit.lib.Constants; |
| import org.eclipse.jgit.lib.ObjectId; |
| import org.eclipse.jgit.lib.Ref; |
| import org.eclipse.jgit.revwalk.RevCommit; |
| import org.eclipse.jgit.revwalk.RevWalk; |
| import org.eclipse.jgit.transport.AdvertiseRefsHook; |
| import org.eclipse.jgit.transport.BaseReceivePack; |
| import org.eclipse.jgit.transport.ServiceMayNotContinueException; |
| import org.eclipse.jgit.transport.UploadPack; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import java.io.IOException; |
| import java.util.Collection; |
| import java.util.Collections; |
| import java.util.Map; |
| import java.util.Set; |
| |
| /** |
| * Advertises part of history to git push clients. |
| * <p> |
| * This is a hack to work around the lack of negotiation in the |
| * send-pack/receive-pack wire protocol. |
| * <p> |
| * When the server is frequently advancing master by creating merge commits, the |
| * client may not be able to discover a common ancestor during push. Attempting |
| * to push will re-upload a very large amount of history. This hook hacks in a |
| * fake negotiation replacement by walking history and sending recent commits as |
| * {@code ".have"} lines in the wire protocol, allowing the client to find a |
| * common ancestor. |
| */ |
| public class HackPushNegotiateHook implements AdvertiseRefsHook { |
| private static final Logger log = LoggerFactory |
| .getLogger(HackPushNegotiateHook.class); |
| |
| /** Size of an additional ".have" line. */ |
| private static final int HAVE_LINE_LEN = 4 |
| + Constants.OBJECT_ID_STRING_LENGTH |
| + 1 + 5 + 1; |
| |
| /** |
| * Maximum number of bytes to "waste" in the advertisement with a peek at this |
| * repository's current reachable history. |
| */ |
| private static final int MAX_EXTRA_BYTES = 8192; |
| |
| /** |
| * Number of recent commits to advertise immediately, hoping to show a client |
| * a nearby merge base. |
| */ |
| private static final int BASE_COMMITS = 64; |
| |
| /** Number of commits to skip once base has already been shown. */ |
| private static final int STEP_COMMITS = 16; |
| |
| /** Total number of commits to extract from the history. */ |
| private static final int MAX_HISTORY = MAX_EXTRA_BYTES / HAVE_LINE_LEN; |
| |
| @Override |
| public void advertiseRefs(UploadPack us) { |
| throw new UnsupportedOperationException( |
| "HackPushNegotiateHook cannot be used for UploadPack"); |
| } |
| |
| @Override |
| public void advertiseRefs(BaseReceivePack rp) |
| throws ServiceMayNotContinueException { |
| Map<String, Ref> r = rp.getAdvertisedRefs(); |
| if (r == null) { |
| try { |
| r = rp.getRepository().getRefDatabase().getRefs(ALL); |
| } catch (ServiceMayNotContinueException e) { |
| throw e; |
| } catch (IOException e) { |
| ServiceMayNotContinueException ex = new ServiceMayNotContinueException(); |
| ex.initCause(e); |
| throw ex; |
| } |
| } |
| rp.setAdvertisedRefs(r, history(r.values(), rp)); |
| } |
| |
| private Set<ObjectId> history(Collection<Ref> refs, BaseReceivePack rp) { |
| Set<ObjectId> alreadySending = rp.getAdvertisedObjects(); |
| if (alreadySending.isEmpty()) { |
| alreadySending = idsOf(refs); |
| } |
| |
| int max = MAX_HISTORY - Math.max(0, alreadySending.size() - refs.size()); |
| if (max <= 0) { |
| return Collections.emptySet(); |
| } |
| |
| // Scan history until the advertisement is full. |
| RevWalk rw = rp.getRevWalk(); |
| rw.reset(); |
| try { |
| for (Ref ref : refs) { |
| try { |
| if (ref.getObjectId() != null) { |
| rw.markStart(rw.parseCommit(ref.getObjectId())); |
| } |
| } catch (IOException badCommit) { |
| continue; |
| } |
| } |
| |
| Set<ObjectId> history = Sets.newHashSetWithExpectedSize(max); |
| try { |
| int stepCnt = 0; |
| for (RevCommit c; history.size() < max && (c = rw.next()) != null;) { |
| if (c.getParentCount() <= 1 |
| && !alreadySending.contains(c) |
| && (history.size() < BASE_COMMITS || (++stepCnt % STEP_COMMITS) == 0)) { |
| history.add(c); |
| } |
| } |
| } catch (IOException err) { |
| log.error("error trying to advertise history", err); |
| } |
| return history; |
| } finally { |
| rw.reset(); |
| } |
| } |
| |
| private static Set<ObjectId> idsOf(Collection<Ref> refs) { |
| Set<ObjectId> r = Sets.newHashSetWithExpectedSize(refs.size()); |
| for (Ref ref : refs) { |
| if (ref.getObjectId() != null) { |
| r.add(ref.getObjectId()); |
| } |
| } |
| return r; |
| } |
| } |