Use pack-*.keep files during fetch and receive-pack to prevent GC

[jgit.git] / org.spearce.jgit / src / org / spearce / jgit / transport / BasePackFetchConnection.java

/*
 * Copyright (C) 2008, Robin Rosenberg <robin.rosenberg@dewire.com>
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Git Development Community nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.spearce.jgit.transport;

import java.io.IOException;
import java.util.Collection;
import java.util.Collections;
import java.util.Date;
import java.util.Set;

import org.spearce.jgit.errors.TransportException;
import org.spearce.jgit.lib.AnyObjectId;
import org.spearce.jgit.lib.MutableObjectId;
import org.spearce.jgit.lib.ObjectId;
import org.spearce.jgit.lib.PackLock;
import org.spearce.jgit.lib.ProgressMonitor;
import org.spearce.jgit.lib.Ref;
import org.spearce.jgit.lib.RepositoryConfig;
import org.spearce.jgit.revwalk.RevCommit;
import org.spearce.jgit.revwalk.RevCommitList;
import org.spearce.jgit.revwalk.RevFlag;
import org.spearce.jgit.revwalk.RevObject;
import org.spearce.jgit.revwalk.RevSort;
import org.spearce.jgit.revwalk.RevWalk;
import org.spearce.jgit.revwalk.filter.CommitTimeRevFilter;
import org.spearce.jgit.revwalk.filter.RevFilter;

/**
 * Fetch implementation using the native Git pack transfer service.
 * <p>
 * This is the canonical implementation for transferring objects from the remote
 * repository to the local repository by talking to the 'git-upload-pack'
 * service. Objects are packed on the remote side into a pack file and then sent
 * down the pipe to us.
 * <p>
 * This connection requires only a bi-directional pipe or socket, and thus is
 * easily wrapped up into a local process pipe, anonymous TCP socket, or a
 * command executed through an SSH tunnel.
 * <p>
 * Concrete implementations should just call
 * {@link #init(java.io.InputStream, java.io.OutputStream)} and
 * {@link #readAdvertisedRefs()} methods in constructor or before any use. They
 * should also handle resources releasing in {@link #close()} method if needed.
 */
abstract class BasePackFetchConnection extends BasePackConnection implements
                FetchConnection {
        /**
         * Maximum number of 'have' lines to send before giving up.
         * <p>
         * During {@link #negotiate(ProgressMonitor)} we send at most this many
         * commits to the remote peer as 'have' lines without an ACK response before
         * we give up.
         */
        private static final int MAX_HAVES = 256;

        protected static final int MAX_CLIENT_BUFFER = MAX_HAVES * 46 + 1024;

        static final String OPTION_INCLUDE_TAG = "include-tag";

        static final String OPTION_MULTI_ACK = "multi_ack";

        static final String OPTION_THIN_PACK = "thin-pack";

        static final String OPTION_SIDE_BAND = "side-band";

        static final String OPTION_SIDE_BAND_64K = "side-band-64k";

        static final String OPTION_OFS_DELTA = "ofs-delta";

        static final String OPTION_SHALLOW = "shallow";

        static final String OPTION_NO_PROGRESS = "no-progress";

        private final RevWalk walk;

        /** All commits that are immediately reachable by a local ref. */
        private RevCommitList<RevCommit> reachableCommits;

        /** Marks an object as having all its dependencies. */
        final RevFlag REACHABLE;

        /** Marks a commit known to both sides of the connection. */
        final RevFlag COMMON;

        /** Marks a commit listed in the advertised refs. */
        final RevFlag ADVERTISED;

        private boolean multiAck;

        private boolean thinPack;

        private boolean sideband;

        private boolean includeTags;

        private boolean allowOfsDelta;

        private String lockMessage;

        private PackLock packLock;

        BasePackFetchConnection(final PackTransport packTransport) {
                super(packTransport);

                final RepositoryConfig cfg = local.getConfig();
                includeTags = transport.getTagOpt() != TagOpt.NO_TAGS;
                thinPack = transport.isFetchThin();
                allowOfsDelta = cfg.getBoolean("repack", "usedeltabaseoffset", true);

                walk = new RevWalk(local);
                reachableCommits = new RevCommitList<RevCommit>();
                REACHABLE = walk.newFlag("REACHABLE");
                COMMON = walk.newFlag("COMMON");
                ADVERTISED = walk.newFlag("ADVERTISED");

                walk.carry(COMMON);
                walk.carry(REACHABLE);
                walk.carry(ADVERTISED);
        }

        public final void fetch(final ProgressMonitor monitor,
                        final Collection<Ref> want, final Set<ObjectId> have)
                        throws TransportException {
                markStartedOperation();
                doFetch(monitor, want, have);
        }

        public boolean didFetchIncludeTags() {
                return false;
        }

        public boolean didFetchTestConnectivity() {
                return false;
        }

        public void setPackLockMessage(final String message) {
                lockMessage = message;
        }

        public Collection<PackLock> getPackLocks() {
                if (packLock != null)
                        return Collections.singleton(packLock);
                return Collections.<PackLock> emptyList();
        }

        protected void doFetch(final ProgressMonitor monitor,
                        final Collection<Ref> want, final Set<ObjectId> have)
                        throws TransportException {
                try {
                        markRefsAdvertised();
                        markReachable(have, maxTimeWanted(want));

                        if (sendWants(want)) {
                                negotiate(monitor);

                                walk.dispose();
                                reachableCommits = null;

                                receivePack(monitor);
                        }
                } catch (CancelledException ce) {
                        close();
                        return; // Caller should test (or just know) this themselves.
                } catch (IOException err) {
                        close();
                        throw new TransportException(err.getMessage(), err);
                } catch (RuntimeException err) {
                        close();
                        throw new TransportException(err.getMessage(), err);
                }
        }

        private int maxTimeWanted(final Collection<Ref> wants) {
                int maxTime = 0;
                for (final Ref r : wants) {
                        try {
                                final RevObject obj = walk.parseAny(r.getObjectId());
                                if (obj instanceof RevCommit) {
                                        final int cTime = ((RevCommit) obj).getCommitTime();
                                        if (maxTime < cTime)
                                                maxTime = cTime;
                                }
                        } catch (IOException error) {
                                // We don't have it, but we want to fetch (thus fixing error).
                        }
                }
                return maxTime;
        }

        private void markReachable(final Set<ObjectId> have, final int maxTime)
                        throws IOException {
                for (final Ref r : local.getAllRefs().values()) {
                        try {
                                final RevCommit o = walk.parseCommit(r.getObjectId());
                                o.add(REACHABLE);
                                reachableCommits.add(o);
                        } catch (IOException readError) {
                                // If we cannot read the value of the ref skip it.
                        }
                }

                for (final ObjectId id : have) {
                        try {
                                final RevCommit o = walk.parseCommit(id);
                                o.add(REACHABLE);
                                reachableCommits.add(o);
                        } catch (IOException readError) {
                                // If we cannot read the value of the ref skip it.
                        }
                }

                if (maxTime > 0) {
                        // Mark reachable commits until we reach maxTime. These may
                        // wind up later matching up against things we want and we
                        // can avoid asking for something we already happen to have.
                        //
                        final Date maxWhen = new Date(maxTime * 1000L);
                        walk.sort(RevSort.COMMIT_TIME_DESC);
                        walk.markStart(reachableCommits);
                        walk.setRevFilter(CommitTimeRevFilter.after(maxWhen));
                        for (;;) {
                                final RevCommit c = walk.next();
                                if (c == null)
                                        break;
                                if (c.has(ADVERTISED) && !c.has(COMMON)) {
                                        // This is actually going to be a common commit, but
                                        // our peer doesn't know that fact yet.
                                        //
                                        c.add(COMMON);
                                        c.carry(COMMON);
                                        reachableCommits.add(c);
                                }
                        }
                }
        }

        private boolean sendWants(final Collection<Ref> want) throws IOException {
                boolean first = true;
                for (final Ref r : want) {
                        try {
                                if (walk.parseAny(r.getObjectId()).has(REACHABLE)) {
                                        // We already have this object. Asking for it is
                                        // not a very good idea.
                                        //
                                        continue;
                                }
                        } catch (IOException err) {
                                // Its OK, we don't have it, but we want to fix that
                                // by fetching the object from the other side.
                        }

                        final StringBuilder line = new StringBuilder(46);
                        line.append("want ");
                        line.append(r.getObjectId().name());
                        if (first) {
                                line.append(enableCapabilities());
                                first = false;
                        }
                        line.append('\n');
                        pckOut.writeString(line.toString());
                }
                pckOut.end();
                outNeedsEnd = false;
                return !first;
        }

        private String enableCapabilities() {
                final StringBuilder line = new StringBuilder();
                if (includeTags)
                        includeTags = wantCapability(line, OPTION_INCLUDE_TAG);
                if (allowOfsDelta)
                        wantCapability(line, OPTION_OFS_DELTA);
                multiAck = wantCapability(line, OPTION_MULTI_ACK);
                if (thinPack)
                        thinPack = wantCapability(line, OPTION_THIN_PACK);
                if (wantCapability(line, OPTION_SIDE_BAND_64K))
                        sideband = true;
                else if (wantCapability(line, OPTION_SIDE_BAND))
                        sideband = true;
                return line.toString();
        }

        private void negotiate(final ProgressMonitor monitor) throws IOException,
                        CancelledException {
                final MutableObjectId ackId = new MutableObjectId();
                int resultsPending = 0;
                int havesSent = 0;
                int havesSinceLastContinue = 0;
                boolean receivedContinue = false;
                boolean receivedAck = false;
                boolean sendHaves = true;

                negotiateBegin();
                while (sendHaves) {
                        final RevCommit c = walk.next();
                        if (c == null)
                                break;

                        pckOut.writeString("have " + c.getId().name() + "\n");
                        havesSent++;
                        havesSinceLastContinue++;

                        if ((31 & havesSent) != 0) {
                                // We group the have lines into blocks of 32, each marked
                                // with a flush (aka end). This one is within a block so
                                // continue with another have line.
                                //
                                continue;
                        }

                        if (monitor.isCancelled())
                                throw new CancelledException();

                        pckOut.end();
                        resultsPending++; // Each end will cause a result to come back.

                        if (havesSent == 32) {
                                // On the first block we race ahead and try to send
                                // more of the second block while waiting for the
                                // remote to respond to our first block request.
                                // This keeps us one block ahead of the peer.
                                //
                                continue;
                        }

                        while (resultsPending > 0) {
                                final PacketLineIn.AckNackResult anr;

                                anr = pckIn.readACK(ackId);
                                resultsPending--;
                                if (anr == PacketLineIn.AckNackResult.NAK) {
                                        // More have lines are necessary to compute the
                                        // pack on the remote side. Keep doing that.
                                        //
                                        break;
                                }

                                if (anr == PacketLineIn.AckNackResult.ACK) {
                                        // The remote side is happy and knows exactly what
                                        // to send us. There is no further negotiation and
                                        // we can break out immediately.
                                        //
                                        multiAck = false;
                                        resultsPending = 0;
                                        receivedAck = true;
                                        sendHaves = false;
                                        break;
                                }

                                if (anr == PacketLineIn.AckNackResult.ACK_CONTINUE) {
                                        // The server knows this commit (ackId). We don't
                                        // need to send any further along its ancestry, but
                                        // we need to continue to talk about other parts of
                                        // our local history.
                                        //
                                        markCommon(walk.parseAny(ackId));
                                        receivedAck = true;
                                        receivedContinue = true;
                                        havesSinceLastContinue = 0;
                                }

                                if (monitor.isCancelled())
                                        throw new CancelledException();
                        }

                        if (receivedContinue && havesSinceLastContinue > MAX_HAVES) {
                                // Our history must be really different from the remote's.
                                // We just sent a whole slew of have lines, and it did not
                                // recognize any of them. Avoid sending our entire history
                                // to them by giving up early.
                                //
                                break;
                        }
                }

                // Tell the remote side we have run out of things to talk about.
                //
                if (monitor.isCancelled())
                        throw new CancelledException();
                pckOut.writeString("done\n");
                pckOut.flush();

                if (!receivedAck) {
                        // Apparently if we have never received an ACK earlier
                        // there is one more result expected from the done we
                        // just sent to the remote.
                        //
                        multiAck = false;
                        resultsPending++;
                }

                while (resultsPending > 0 || multiAck) {
                        final PacketLineIn.AckNackResult anr;

                        anr = pckIn.readACK(ackId);
                        resultsPending--;

                        if (anr == PacketLineIn.AckNackResult.ACK)
                                break; // commit negotiation is finished.

                        if (anr == PacketLineIn.AckNackResult.ACK_CONTINUE) {
                                // There must be a normal ACK following this.
                                //
                                multiAck = true;
                        }

                        if (monitor.isCancelled())
                                throw new CancelledException();
                }
        }

        private void negotiateBegin() throws IOException {
                walk.resetRetain(REACHABLE, ADVERTISED);
                walk.markStart(reachableCommits);
                walk.sort(RevSort.COMMIT_TIME_DESC);
                walk.setRevFilter(new RevFilter() {
                        @Override
                        public RevFilter clone() {
                                return this;
                        }

                        @Override
                        public boolean include(final RevWalk walker, final RevCommit c) {
                                final boolean remoteKnowsIsCommon = c.has(COMMON);
                                if (c.has(ADVERTISED)) {
                                        // Remote advertised this, and we have it, hence common.
                                        // Whether or not the remote knows that fact is tested
                                        // before we added the flag. If the remote doesn't know
                                        // we have to still send them this object.
                                        //
                                        c.add(COMMON);
                                }
                                return !remoteKnowsIsCommon;
                        }
                });
        }

        private void markRefsAdvertised() {
                for (final Ref r : getRefs()) {
                        markAdvertised(r.getObjectId());
                        if (r.getPeeledObjectId() != null)
                                markAdvertised(r.getPeeledObjectId());
                }
        }

        private void markAdvertised(final AnyObjectId id) {
                try {
                        walk.parseAny(id).add(ADVERTISED);
                } catch (IOException readError) {
                        // We probably just do not have this object locally.
                }
        }

        private void markCommon(final RevObject obj) {
                obj.add(COMMON);
                if (obj instanceof RevCommit)
                        ((RevCommit) obj).carry(COMMON);
        }

        private void receivePack(final ProgressMonitor monitor) throws IOException {
                final IndexPack ip;

                ip = IndexPack.create(local, sideband ? pckIn.sideband(monitor) : in);
                ip.setFixThin(thinPack);
                ip.setObjectChecking(transport.isCheckFetchedObjects());
                ip.index(monitor);
                packLock = ip.renameAndOpenPack(lockMessage);
        }

        private static class CancelledException extends Exception {
                private static final long serialVersionUID = 1L;
        }
}