org.apache.jackrabbit.oak.plugins.document.mongo.replica.LocalChanges Maven / Gradle / Ivy
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* 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.
*/
package org.apache.jackrabbit.oak.plugins.document.mongo.replica;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import org.apache.jackrabbit.oak.plugins.document.Revision;
import org.apache.jackrabbit.oak.plugins.document.RevisionVector;
import org.apache.jackrabbit.oak.plugins.document.util.Utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* This class maintains a list of local changes (path+local revision timestamp), which
* shouldn't be read from the secondary Mongo, as we are not sure if they have
* been already replicated from primary. Once we get this confidence, the entry
* will be removed from the map.
*/
public class LocalChanges implements ReplicaSetInfoListener {
private static final Logger LOG = LoggerFactory.getLogger(LocalChanges.class);
/**
* How many paths should be stored in the {@link #localChanges} map. If
* there's more paths added (and not removed in the
* {@link #gotRootRevisions(RevisionVector)}), only the latest changed
* revision will be remembered.
*/
private static final int SIZE_LIMIT = 100;
/**
* This map contains document paths and timestamps in which they have been
* changed. Paths in this collection hasn't been replicated to secondary
* instances yet.
*/
final Map localChanges = new HashMap();
/**
* If there's more than {@link #SIZE_LIMIT} paths in the
* {@link #localChanges}, the class will clear the above map and update this
* variable with the timestamp of the last local change. {@code true} will be returned
* for all {@link #mayContainChildrenOf(String)} and {@link #mayContain(String)}
* invocations until this timestamp is replicated to all secondary instances.
*
* This is a safety mechanism, so the {@link #localChanges} won't grow too much.
*/
private volatile long latestChange;
/**
* True if the current Mongo installation is an working replica. Otherwise
* there's no need to store the local changes.
*/
private volatile boolean replicaActive;
private volatile long rootTS;
private final int clusterId;
public LocalChanges(int clusterId) {
this.clusterId = clusterId;
}
public void add(String id, long timestamp) {
long localRootTS = rootTS;
if (localRootTS != 0 && localRootTS > timestamp) {
return;
}
synchronized (this) {
if (latestChange != 0 && latestChange > timestamp) {
return;
}
if (replicaActive) {
localChanges.put(id, timestamp);
if (localChanges.size() >= SIZE_LIMIT) {
localChanges.clear();
latestChange = timestamp;
LOG.debug(
"The local changes count == {}. Clearing the list and switching to the 'latest change' mode: {}",
SIZE_LIMIT, latestChange);
}
} else {
latestChange = timestamp;
}
}
}
/**
* Check if it's possible that the given document hasn't been replicated to
* the secondary yet.
*
* @param documentId
* @return {@code true} if it's possible that the document is still in the
* Mongo replication queue
*/
public boolean mayContain(String documentId) {
if (!replicaActive || latestChange != 0) {
return true;
}
synchronized (this) {
return localChanges.containsKey(documentId);
}
}
/**
* Check if it's possible that the children of the given document hasn't
* been replicated to the secondary yet.
*
* @param parentId
* @return {@code true} if it's possible that the children of given document
* are still in the Mongo replication queue
*/
public boolean mayContainChildrenOf(String parentId) {
if (!replicaActive || latestChange != 0) {
return true;
}
synchronized (this) {
for (String key : localChanges.keySet()) {
if (parentId.equals(Utils.getParentId(key))) {
return true;
}
}
return false;
}
}
@Override
public void gotRootRevisions(RevisionVector rootRevision) {
if (rootRevision == null) {
return;
}
Revision rootRevForLocalInstance = rootRevision.getRevision(clusterId);
if (rootRevForLocalInstance == null) {
return;
}
this.rootTS = rootRevForLocalInstance.getTimestamp();
if (!replicaActive) {
replicaActive = true;
LOG.info("Replica set became active");
}
synchronized (this) {
if (latestChange != 0 && latestChange <= rootTS) {
latestChange = 0;
}
Iterator it = localChanges.values().iterator();
while (it.hasNext()) {
if (it.next() <= rootTS) {
it.remove();
}
}
}
}
}