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/*
* Copyright (C) 2016, Google Inc. and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.internal.ketch;
import static org.eclipse.jgit.internal.ketch.KetchReplica.State.AHEAD;
import static org.eclipse.jgit.internal.ketch.KetchReplica.State.DIVERGENT;
import static org.eclipse.jgit.internal.ketch.KetchReplica.State.LAGGING;
import static org.eclipse.jgit.internal.ketch.KetchReplica.State.UNKNOWN;
import static org.eclipse.jgit.lib.Constants.OBJ_COMMIT;
import java.io.IOException;
import java.util.Collections;
import java.util.Map;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.transport.ReceiveCommand;
/**
* A helper to check if a {@link KetchReplica} is ahead or behind the leader.
*/
class LagCheck implements AutoCloseable {
private final KetchReplica replica;
private final Repository repo;
private RevWalk rw;
private ObjectId remoteId;
LagCheck(KetchReplica replica, Repository repo) {
this.replica = replica;
this.repo = repo;
initRevWalk();
}
private void initRevWalk() {
if (rw != null) {
rw.close();
}
rw = new RevWalk(repo);
rw.setRetainBody(false);
}
/** {@inheritDoc} */
@Override
public void close() {
if (rw != null) {
rw.close();
rw = null;
}
}
ObjectId getRemoteId() {
return remoteId;
}
KetchReplica.State check(ObjectId acceptId, ReceiveCommand acceptCmd) {
remoteId = acceptId;
if (remoteId == null) {
// Nothing advertised by the replica, value is unknown.
return UNKNOWN;
}
if (AnyObjectId.isEqual(remoteId, ObjectId.zeroId())) {
// Replica does not have the txnAccepted reference.
return LAGGING;
}
try {
RevCommit remote;
try {
remote = parseRemoteCommit(acceptCmd.getRefName());
} catch (RefGoneException gone) {
// Replica does not have the txnAccepted reference.
return LAGGING;
} catch (MissingObjectException notFound) {
// Local repository does not know this commit so it cannot
// be including the replica's log.
return DIVERGENT;
}
RevCommit head = rw.parseCommit(acceptCmd.getNewId());
if (rw.isMergedInto(remote, head)) {
return LAGGING;
}
// TODO(sop) Check term to see if my leader was deposed.
if (rw.isMergedInto(head, remote)) {
return AHEAD;
}
return DIVERGENT;
} catch (IOException err) {
KetchReplica.log.error(String.format(
"Cannot compare %s", //$NON-NLS-1$
acceptCmd.getRefName()), err);
return UNKNOWN;
}
}
private RevCommit parseRemoteCommit(String refName)
throws IOException, MissingObjectException, RefGoneException {
try {
return rw.parseCommit(remoteId);
} catch (MissingObjectException notLocal) {
// Fall through and try to acquire the object by fetching it.
}
ReplicaFetchRequest fetch = new ReplicaFetchRequest(
Collections.singleton(refName),
Collections.<ObjectId> emptySet());
try {
replica.blockingFetch(repo, fetch);
} catch (IOException fetchErr) {
KetchReplica.log.error(String.format(
"Cannot fetch %s (%s) from %s", //$NON-NLS-1$
remoteId.abbreviate(8).name(), refName,
replica.describeForLog()), fetchErr);
throw new MissingObjectException(remoteId, OBJ_COMMIT);
}
Map<String, Ref> adv = fetch.getRefs();
if (adv == null) {
throw new MissingObjectException(remoteId, OBJ_COMMIT);
}
Ref ref = adv.get(refName);
if (ref == null || ref.getObjectId() == null) {
throw new RefGoneException();
}
initRevWalk();
remoteId = ref.getObjectId();
return rw.parseCommit(remoteId);
}
private static class RefGoneException extends Exception {
private static final long serialVersionUID = 1L;
}
}
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