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/*
* Copyright 2017 Google Inc.
*
* 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.firebase.database.core;
import static com.google.firebase.database.utilities.Utilities.hardAssert;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.annotations.NotNull;
import com.google.firebase.database.annotations.Nullable;
import com.google.firebase.database.collection.LLRBNode;
import com.google.firebase.database.connection.ListenHashProvider;
import com.google.firebase.database.core.operation.AckUserWrite;
import com.google.firebase.database.core.operation.ListenComplete;
import com.google.firebase.database.core.operation.Merge;
import com.google.firebase.database.core.operation.Operation;
import com.google.firebase.database.core.operation.OperationSource;
import com.google.firebase.database.core.operation.Overwrite;
import com.google.firebase.database.core.persistence.PersistenceManager;
import com.google.firebase.database.core.utilities.ImmutableTree;
import com.google.firebase.database.core.view.CacheNode;
import com.google.firebase.database.core.view.Change;
import com.google.firebase.database.core.view.DataEvent;
import com.google.firebase.database.core.view.Event;
import com.google.firebase.database.core.view.QuerySpec;
import com.google.firebase.database.core.view.View;
import com.google.firebase.database.snapshot.ChildKey;
import com.google.firebase.database.snapshot.CompoundHash;
import com.google.firebase.database.snapshot.EmptyNode;
import com.google.firebase.database.snapshot.IndexedNode;
import com.google.firebase.database.snapshot.NamedNode;
import com.google.firebase.database.snapshot.Node;
import com.google.firebase.database.snapshot.RangeMerge;
import com.google.firebase.database.utilities.Clock;
import com.google.firebase.database.utilities.NodeSizeEstimator;
import com.google.firebase.database.utilities.Pair;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.Callable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* SyncTree is the central class for managing event callback registration, data caching, views
* (query processing), and event generation. There are typically two SyncTree instances for each
* Repo, one for the normal Firebase data, and one for the .info data.
*
* It has a number of responsibilities, including: - Tracking all user event callbacks
* (registered via addEventRegistration() and removeEventRegistration()). - Applying and caching
* data changes for user set(), transaction(), and update() calls (applyUserOverwrite(),
* applyUserMerge()). - Applying and caching data changes for server data changes
* (applyServerOverwrite(), applyServerMerge()). - Generating user-facing events for server and user
* changes (all of the apply* methods return the set of events that need to be raised as a result).
* - Maintaining the appropriate set of server listens to ensure we are always subscribed to the
* correct set of paths and queries to satisfy the current set of user event callbacks (listens are
* started/stopped using the provided listenProvider).
*
*
NOTE: Although SyncTree tracks event callbacks and calculates events to raise, the actual
* events are returned to the caller rather than raised synchronously.
*/
public class SyncTree {
// Size after which we start including the compound hash
private static final long SIZE_THRESHOLD_FOR_COMPOUND_HASH = 1024;
private static final Logger logger = LoggerFactory.getLogger(SyncTree.class);
/**
* A tree of all pending user writes (user-initiated set()'s, transaction()'s, update()'s, etc.).
*/
private final WriteTree pendingWriteTree;
private final Map tagToQueryMap;
private final Map queryToTagMap;
private final Set keepSyncedQueries;
private final ListenProvider listenProvider;
private final PersistenceManager persistenceManager;
/** Tree of SyncPoints. There's a SyncPoint at any location that has 1 or more views. */
private ImmutableTree syncPointTree;
/** Static tracker for next query tag. */
private long nextQueryTag = 1L;
public SyncTree(
PersistenceManager persistenceManager, ListenProvider listenProvider) {
this.syncPointTree = ImmutableTree.emptyInstance();
this.pendingWriteTree = new WriteTree();
this.tagToQueryMap = new HashMap<>();
this.queryToTagMap = new HashMap<>();
this.keepSyncedQueries = new HashSet<>();
this.listenProvider = listenProvider;
this.persistenceManager = persistenceManager;
}
public boolean isEmpty() {
return this.syncPointTree.isEmpty();
}
/** Apply the data changes for a user-generated set() or transaction() call. */
public List applyUserOverwrite(
final Path path,
final Node newDataUnresolved,
final Node newData,
final long writeId,
final boolean visible,
final boolean persist) {
hardAssert(visible || !persist, "We shouldn't be persisting non-visible writes.");
return persistenceManager.runInTransaction(
new Callable>() {
@Override
public List call() {
if (persist) {
persistenceManager.saveUserOverwrite(path, newDataUnresolved, writeId);
}
pendingWriteTree.addOverwrite(path, newData, writeId, visible);
if (!visible) {
return Collections.emptyList();
} else {
return applyOperationToSyncPoints(new Overwrite(OperationSource.USER, path, newData));
}
}
});
}
/** Apply the data from a user-generated update() call. */
public List applyUserMerge(
final Path path,
final CompoundWrite unresolvedChildren,
final CompoundWrite children,
final long writeId,
final boolean persist) {
return this.persistenceManager.runInTransaction(
new Callable>() {
@Override
public List call() throws Exception {
if (persist) {
persistenceManager.saveUserMerge(path, unresolvedChildren, writeId);
}
pendingWriteTree.addMerge(path, children, writeId);
return applyOperationToSyncPoints(new Merge(OperationSource.USER, path, children));
}
});
}
/**
* Acknowledge a pending user write that was previously registered with applyUserOverwrite() or
* applyUserMerge().
*/
// TODO[persistence]: Taking a serverClock here is awkward, but server values are awkward. :-(
public List ackUserWrite(
final long writeId, final boolean revert, final boolean persist, final Clock serverClock) {
return this.persistenceManager.runInTransaction(
new Callable>() {
@Override
public List call() {
if (persist) {
persistenceManager.removeUserWrite(writeId);
}
UserWriteRecord write = pendingWriteTree.getWrite(writeId);
boolean needToReevaluate = pendingWriteTree.removeWrite(writeId);
if (write.isVisible()) {
if (!revert) {
Map serverValues = ServerValues.generateServerValues(serverClock);
if (write.isOverwrite()) {
Node resolvedNode =
ServerValues.resolveDeferredValueSnapshot(write.getOverwrite(), serverValues);
persistenceManager.applyUserWriteToServerCache(write.getPath(), resolvedNode);
} else {
CompoundWrite resolvedMerge =
ServerValues.resolveDeferredValueMerge(write.getMerge(), serverValues);
persistenceManager.applyUserWriteToServerCache(write.getPath(), resolvedMerge);
}
}
}
if (!needToReevaluate) {
return Collections.emptyList();
} else {
ImmutableTree affectedTree = ImmutableTree.emptyInstance();
if (write.isOverwrite()) {
affectedTree = affectedTree.set(Path.getEmptyPath(), true);
} else {
for (Map.Entry entry : write.getMerge()) {
affectedTree = affectedTree.set(entry.getKey(), true);
}
}
return applyOperationToSyncPoints(
new AckUserWrite(write.getPath(), affectedTree, revert));
}
}
});
}
/** Removes all local writes. */
public List removeAllWrites() {
return this.persistenceManager.runInTransaction(
new Callable>() {
@Override
public List call() throws Exception {
persistenceManager.removeAllUserWrites();
List purgedWrites = pendingWriteTree.purgeAllWrites();
if (purgedWrites.isEmpty()) {
return Collections.emptyList();
} else {
ImmutableTree affectedTree = new ImmutableTree<>(true);
return applyOperationToSyncPoints(
new AckUserWrite(Path.getEmptyPath(), affectedTree, /*revert=*/ true));
}
}
});
}
/** Apply new server data for the specified path. */
public List applyServerOverwrite(final Path path, final Node newData) {
return persistenceManager.runInTransaction(
new Callable>() {
@Override
public List call() {
persistenceManager.updateServerCache(QuerySpec.defaultQueryAtPath(path), newData);
return applyOperationToSyncPoints(new Overwrite(OperationSource.SERVER, path, newData));
}
});
}
/** Apply new server data to be merged in at the specified path. */
public List applyServerMerge(
final Path path, final Map changedChildren) {
return persistenceManager.runInTransaction(
new Callable>() {
@Override
public List call() {
CompoundWrite merge = CompoundWrite.fromPathMerge(changedChildren);
persistenceManager.updateServerCache(path, merge);
return applyOperationToSyncPoints(new Merge(OperationSource.SERVER, path, merge));
}
});
}
/** Apply a range merge. */
public List applyServerRangeMerges(
final Path path, List rangeMerges) {
SyncPoint syncPoint = syncPointTree.get(path);
if (syncPoint == null) {
// Removed view, so it's safe to just ignore this update
return Collections.emptyList();
} else {
// This could be for any "complete" (unfiltered) view, and if there is more than one
// complete
// view, they should each have the same cache so it doesn't matter which one we use.
View view = syncPoint.getCompleteView();
if (view != null) {
Node serverNode = view.getServerCache();
for (RangeMerge merge : rangeMerges) {
serverNode = merge.applyTo(serverNode);
}
return applyServerOverwrite(path, serverNode);
} else {
// There doesn't exist a view for this update, so it was removed and it's safe to
// just
// ignore this range merge
return Collections.emptyList();
}
}
}
public List applyTaggedRangeMerges(
Path path, List rangeMerges, Tag tag) {
QuerySpec query = queryForTag(tag);
if (query != null) {
assert path.equals(query.getPath());
SyncPoint syncPoint = syncPointTree.get(query.getPath());
assert syncPoint != null : "Missing sync point for query tag that we're tracking";
View view = syncPoint.viewForQuery(query);
assert view != null : "Missing view for query tag that we're tracking";
Node serverNode = view.getServerCache();
for (RangeMerge merge : rangeMerges) {
serverNode = merge.applyTo(serverNode);
}
return this.applyTaggedQueryOverwrite(path, serverNode, tag);
} else {
// We've already removed the query. No big deal, ignore the update
return Collections.emptyList();
}
}
/** Apply a listen complete to a path. */
public List applyListenComplete(final Path path) {
return persistenceManager.runInTransaction(
new Callable>() {
@Override
public List call() {
persistenceManager.setQueryComplete(QuerySpec.defaultQueryAtPath(path));
return applyOperationToSyncPoints(new ListenComplete(OperationSource.SERVER, path));
}
});
}
/** Apply a listen complete to a path. */
public List applyTaggedListenComplete(final Tag tag) {
return persistenceManager.runInTransaction(
new Callable>() {
@Override
public List call() {
QuerySpec query = queryForTag(tag);
if (query != null) {
persistenceManager.setQueryComplete(query);
Operation op =
new ListenComplete(
OperationSource.forServerTaggedQuery(query.getParams()), Path.getEmptyPath());
return applyTaggedOperation(query, op);
} else {
// We've already removed the query. No big deal, ignore the update
return Collections.emptyList();
}
}
});
}
private List applyTaggedOperation(QuerySpec query, Operation operation) {
Path queryPath = query.getPath();
SyncPoint syncPoint = syncPointTree.get(queryPath);
assert syncPoint != null : "Missing sync point for query tag that we're tracking";
WriteTreeRef writesCache = pendingWriteTree.childWrites(queryPath);
return syncPoint.applyOperation(operation, writesCache, /*serverCache*/ null);
}
/** Apply new server data for the specified tagged query. */
public List applyTaggedQueryOverwrite(
final Path path, final Node snap, final Tag tag) {
return persistenceManager.runInTransaction(
new Callable>() {
@Override
public List call() {
QuerySpec query = queryForTag(tag);
if (query != null) {
Path relativePath = Path.getRelative(query.getPath(), path);
QuerySpec queryToOverwrite =
relativePath.isEmpty() ? query : QuerySpec.defaultQueryAtPath(path);
persistenceManager.updateServerCache(queryToOverwrite, snap);
Operation op =
new Overwrite(
OperationSource.forServerTaggedQuery(query.getParams()), relativePath, snap);
return applyTaggedOperation(query, op);
} else {
// Query must have been removed already
return Collections.emptyList();
}
}
});
}
/** Apply server data to be merged in for the specified tagged query. */
public List applyTaggedQueryMerge(
final Path path, final Map changedChildren, final Tag tag) {
return persistenceManager.runInTransaction(
new Callable>() {
@Override
public List call() {
QuerySpec query = queryForTag(tag);
if (query != null) {
Path relativePath = Path.getRelative(query.getPath(), path);
CompoundWrite merge = CompoundWrite.fromPathMerge(changedChildren);
persistenceManager.updateServerCache(path, merge);
Operation op =
new Merge(
OperationSource.forServerTaggedQuery(query.getParams()), relativePath, merge);
return applyTaggedOperation(query, op);
} else {
// We've already removed the query. No big deal, ignore the update
return Collections.emptyList();
}
}
});
}
/** Add an event callback for the specified query. */
public List addEventRegistration(
@NotNull final EventRegistration eventRegistration) {
return persistenceManager.runInTransaction(
new Callable>() {
@Override
public List call() {
final QuerySpec query = eventRegistration.getQuerySpec();
Path path = query.getPath();
Node serverCacheNode = null;
boolean foundAncestorDefaultView = false;
// Any covering writes will necessarily be at the root, so really all we need to find is
// the server cache. Consider optimizing this once there's a better understanding of
// what actual behavior will be.
// for (Map.Entry entry: views.entrySet()) {
{
ImmutableTree tree = syncPointTree;
Path currentPath = path;
while (!tree.isEmpty()) {
SyncPoint currentSyncPoint = tree.getValue();
if (currentSyncPoint != null) {
serverCacheNode =
serverCacheNode != null
? serverCacheNode
: currentSyncPoint.getCompleteServerCache(currentPath);
foundAncestorDefaultView =
foundAncestorDefaultView || currentSyncPoint.hasCompleteView();
}
ChildKey front =
currentPath.isEmpty() ? ChildKey.fromString("") : currentPath.getFront();
tree = tree.getChild(front);
currentPath = currentPath.popFront();
}
}
SyncPoint syncPoint = syncPointTree.get(path);
if (syncPoint == null) {
syncPoint = new SyncPoint(persistenceManager);
syncPointTree = syncPointTree.set(path, syncPoint);
} else {
foundAncestorDefaultView = foundAncestorDefaultView || syncPoint.hasCompleteView();
serverCacheNode =
serverCacheNode != null
? serverCacheNode
: syncPoint.getCompleteServerCache(Path.getEmptyPath());
}
persistenceManager.setQueryActive(query);
CacheNode serverCache;
if (serverCacheNode != null) {
serverCache =
new CacheNode(IndexedNode.from(serverCacheNode, query.getIndex()), true, false);
} else {
// Hit persistence
CacheNode persistentServerCache = persistenceManager.serverCache(query);
if (persistentServerCache.isFullyInitialized()) {
serverCache = persistentServerCache;
} else {
serverCacheNode = EmptyNode.Empty();
ImmutableTree subtree = syncPointTree.subtree(path);
for (Map.Entry> child : subtree.getChildren()) {
SyncPoint childSyncPoint = child.getValue().getValue();
if (childSyncPoint != null) {
Node completeCache = childSyncPoint.getCompleteServerCache(Path.getEmptyPath());
if (completeCache != null) {
serverCacheNode =
serverCacheNode.updateImmediateChild(child.getKey(), completeCache);
}
}
}
// Fill the node with any available children we have
for (NamedNode child : persistentServerCache.getNode()) {
if (!serverCacheNode.hasChild(child.getName())) {
serverCacheNode =
serverCacheNode.updateImmediateChild(child.getName(), child.getNode());
}
}
serverCache =
new CacheNode(
IndexedNode.from(serverCacheNode, query.getIndex()), false, false);
}
}
boolean viewAlreadyExists = syncPoint.viewExistsForQuery(query);
if (!viewAlreadyExists && !query.loadsAllData()) {
// We need to track a tag for this query
assert !queryToTagMap.containsKey(query) : "View does not exist but we have a tag";
Tag tag = getNextQueryTag();
queryToTagMap.put(query, tag);
tagToQueryMap.put(tag, query);
}
WriteTreeRef writesCache = pendingWriteTree.childWrites(path);
List events =
syncPoint.addEventRegistration(eventRegistration, writesCache, serverCache);
if (!viewAlreadyExists && !foundAncestorDefaultView) {
View view = syncPoint.viewForQuery(query);
setupListener(query, view);
}
return events;
}
});
}
/**
* Remove all event callback(s).
*
* If query is the default query, we'll check all queries for the specified eventRegistration.
*/
public List removeAllEventRegistrations(
@NotNull QuerySpec query, @NotNull DatabaseError error) {
return this.removeEventRegistration(query, null, error);
}
/**
* Remove event callback(s).
*
* If query is the default query, we'll check all queries for the specified eventRegistration.
*/
public List removeEventRegistration(@NotNull EventRegistration eventRegistration) {
return this.removeEventRegistration(eventRegistration.getQuerySpec(), eventRegistration, null);
}
private List removeEventRegistration(
@NotNull final QuerySpec query,
@Nullable final EventRegistration eventRegistration,
@Nullable final DatabaseError cancelError) {
return persistenceManager.runInTransaction(
new Callable>() {
@Override
public List call() {
// Find the syncPoint first. Then deal with whether or not it has matching listeners
Path path = query.getPath();
SyncPoint maybeSyncPoint = syncPointTree.get(path);
List cancelEvents = new ArrayList<>();
// A removal on a default query affects all queries at that location. A removal on an
// indexed query, even one without other query constraints, does *not* affect all
// queries at that location. So this check must be for 'default', and not
// loadsAllData().
if (maybeSyncPoint != null
&& (query.isDefault() || maybeSyncPoint.viewExistsForQuery(query))) {
// @type {{removed: !Array., events: !Array.}}
Pair, List> removedAndEvents =
maybeSyncPoint.removeEventRegistration(query, eventRegistration, cancelError);
if (maybeSyncPoint.isEmpty()) {
syncPointTree = syncPointTree.remove(path);
}
List removed = removedAndEvents.getFirst();
cancelEvents = removedAndEvents.getSecond();
// We may have just removed one of many listeners and can short-circuit this whole
// process. We may also not have removed a default listener, in which case all of the
// descendant listeners should already be properly set up.
//
// Since indexed queries can shadow if they don't have other query constraints, check
// for loadsAllData(), instead of isDefault().
boolean removingDefault = false;
for (QuerySpec queryRemoved : removed) {
persistenceManager.setQueryInactive(query);
removingDefault = removingDefault || queryRemoved.loadsAllData();
}
ImmutableTree currentTree = syncPointTree;
boolean covered =
currentTree.getValue() != null && currentTree.getValue().hasCompleteView();
for (ChildKey component : path) {
currentTree = currentTree.getChild(component);
covered =
covered
|| (currentTree.getValue() != null
&& currentTree.getValue().hasCompleteView());
if (covered || currentTree.isEmpty()) {
break;
}
}
if (removingDefault && !covered) {
ImmutableTree subtree = syncPointTree.subtree(path);
// There are potentially child listeners. Determine what if any listens we need to
// send before executing the removal.
if (!subtree.isEmpty()) {
// We need to fold over our subtree and collect the listeners to send
List newViews = collectDistinctViewsForSubTree(subtree);
// Ok, we've collected all the listens we need. Set them up.
for (View view : newViews) {
ListenContainer container = new ListenContainer(view);
QuerySpec newQuery = view.getQuery();
listenProvider.startListening(
queryForListening(newQuery), container.tag, container, container);
}
} else {
// There's nothing below us, so nothing we need to start listening on
}
}
// If we removed anything and we're not covered by a higher up listen, we need to stop
// listening on this query. The above block has us covered in terms of making sure
// we're set up on listens lower in the tree.
// Also, note that if we have a cancelError, it's already been removed at the provider
// level.
if (!covered && !removed.isEmpty() && cancelError == null) {
// If we removed a default, then we weren't listening on any of the other queries
// here. Just cancel the one default. Otherwise, we need to iterate through and
// cancel each individual query
if (removingDefault) {
listenProvider.stopListening(queryForListening(query), null);
} else {
for (QuerySpec queryToRemove : removed) {
Tag tag = tagForQuery(queryToRemove);
assert tag != null;
listenProvider.stopListening(queryForListening(queryToRemove), tag);
}
}
}
// Now, clear all of the tags we're tracking for the removed listens
removeTags(removed);
} else {
// No-op, this listener must've been already removed
}
return cancelEvents;
}
});
}
public void keepSynced(final QuerySpec query, final boolean keep) {
if (keep && !keepSyncedQueries.contains(query)) {
// TODO[persistence]: Find better / more efficient way to do keep-synced listeners.
addEventRegistration(new KeepSyncedEventRegistration(query));
keepSyncedQueries.add(query);
} else if (!keep && keepSyncedQueries.contains(query)) {
removeEventRegistration(new KeepSyncedEventRegistration(query));
keepSyncedQueries.remove(query);
}
}
/**
* This collapses multiple unfiltered views into a single view, since we only need a single
* listener for them.
*/
private List collectDistinctViewsForSubTree(ImmutableTree subtree) {
ArrayList accumulator = new ArrayList<>();
collectDistinctViewsForSubTree(subtree, accumulator);
return accumulator;
}
private void collectDistinctViewsForSubTree(
ImmutableTree subtree, List accumulator) {
SyncPoint maybeSyncPoint = subtree.getValue();
if (maybeSyncPoint != null && maybeSyncPoint.hasCompleteView()) {
accumulator.add(maybeSyncPoint.getCompleteView());
} else {
if (maybeSyncPoint != null) {
accumulator.addAll(maybeSyncPoint.getQueryViews());
}
for (Map.Entry> entry : subtree.getChildren()) {
collectDistinctViewsForSubTree(entry.getValue(), accumulator);
}
}
}
private void removeTags(List queries) {
for (QuerySpec removedQuery : queries) {
if (!removedQuery.loadsAllData()) {
// We should have a tag for this
Tag tag = this.tagForQuery(removedQuery);
assert tag != null;
this.queryToTagMap.remove(removedQuery);
this.tagToQueryMap.remove(tag);
}
}
}
private QuerySpec queryForListening(QuerySpec query) {
if (query.loadsAllData() && !query.isDefault()) {
// We treat queries that load all data as default queries
return QuerySpec.defaultQueryAtPath(query.getPath());
} else {
return query;
}
}
/** For a given new listen, manage the de-duplication of outstanding subscriptions. */
private void setupListener(QuerySpec query, View view) {
Path path = query.getPath();
Tag tag = this.tagForQuery(query);
ListenContainer container = new ListenContainer(view);
this.listenProvider.startListening(queryForListening(query), tag, container, container);
ImmutableTree subtree = this.syncPointTree.subtree(path);
// The root of this subtree has our query. We're here because we definitely need to send a
// listen for that, but we may need to shadow other listens as well.
if (tag != null) {
assert !subtree.getValue().hasCompleteView()
: "If we're adding a query, it shouldn't be shadowed";
} else {
// Shadow everything at or below this location, this is a default listener.
subtree.foreach(
new ImmutableTree.TreeVisitor() {
@Override
public Void onNodeValue(Path relativePath, SyncPoint maybeChildSyncPoint, Void accum) {
if (!relativePath.isEmpty() && maybeChildSyncPoint.hasCompleteView()) {
QuerySpec query = maybeChildSyncPoint.getCompleteView().getQuery();
listenProvider.stopListening(queryForListening(query), tagForQuery(query));
} else {
// No default listener here
for (View syncPointView : maybeChildSyncPoint.getQueryViews()) {
QuerySpec childQuery = syncPointView.getQuery();
listenProvider.stopListening(
queryForListening(childQuery), tagForQuery(childQuery));
}
}
return null;
}
});
}
}
/** Return the query associated with the given tag, if we have one. */
private QuerySpec queryForTag(Tag tag) {
return this.tagToQueryMap.get(tag);
}
/** Return the tag associated with the given query. */
private Tag tagForQuery(QuerySpec query) {
return this.queryToTagMap.get(query);
}
/**
* Returns a complete cache, if we have one, of the data at a particular path. The location must
* have a listener above it, but as this is only used by transaction code, that should always be
* the case anyways.
*
* Note: this method will *include* hidden writes from transaction with applyLocally set to
* false.
*/
public Node calcCompleteEventCache(Path path, List writeIdsToExclude) {
ImmutableTree tree = this.syncPointTree;
SyncPoint currentSyncPoint = tree.getValue();
Node serverCache = null;
Path pathToFollow = path;
Path pathSoFar = Path.getEmptyPath();
do {
ChildKey front = pathToFollow.getFront();
pathToFollow = pathToFollow.popFront();
pathSoFar = pathSoFar.child(front);
Path relativePath = Path.getRelative(pathSoFar, path);
tree = front != null ? tree.getChild(front) : ImmutableTree.emptyInstance();
currentSyncPoint = tree.getValue();
if (currentSyncPoint != null) {
serverCache = currentSyncPoint.getCompleteServerCache(relativePath);
}
} while (!pathToFollow.isEmpty() && serverCache == null);
return this.pendingWriteTree.calcCompleteEventCache(path, serverCache, writeIdsToExclude, true);
}
/** Static accessor for query tags. */
private Tag getNextQueryTag() {
return new Tag(nextQueryTag++);
}
/**
* A helper method that visits all descendant and ancestor SyncPoints, applying the operation.
*
* NOTES: - Descendant SyncPoints will be visited first (since we raise events depth-first).
*
*
- We call applyOperation() on each SyncPoint passing three things: 1. A version of the
* Operation that has been made relative to the SyncPoint location. 2. A WriteTreeRef of any
* writes we have cached at the SyncPoint location. 3. A snapshot Node with cached server data, if
* we have it.
*
*
- We concatenate all of the events returned by each SyncPoint and return the result.
*/
private List applyOperationToSyncPoints(Operation operation) {
return this.applyOperationHelper(
operation,
this.syncPointTree, /* serverCache */
null,
this.pendingWriteTree.childWrites(Path.getEmptyPath()));
}
/** Recursive helper for applyOperationToSyncPoints. */
private List applyOperationHelper(
Operation operation,
ImmutableTree syncPointTree,
Node serverCache,
WriteTreeRef writesCache) {
if (operation.getPath().isEmpty()) {
return this.applyOperationDescendantsHelper(
operation, syncPointTree, serverCache, writesCache);
} else {
SyncPoint syncPoint = syncPointTree.getValue();
// If we don't have cached server data, see if we can get it from this SyncPoint.
if (serverCache == null && syncPoint != null) {
serverCache = syncPoint.getCompleteServerCache(Path.getEmptyPath());
}
List events = new ArrayList<>();
ChildKey childKey = operation.getPath().getFront();
Operation childOperation = operation.operationForChild(childKey);
ImmutableTree childTree = syncPointTree.getChildren().get(childKey);
if (childTree != null && childOperation != null) {
Node childServerCache =
(serverCache != null) ? serverCache.getImmediateChild(childKey) : null;
WriteTreeRef childWritesCache = writesCache.child(childKey);
events.addAll(
this.applyOperationHelper(
childOperation, childTree, childServerCache, childWritesCache));
}
if (syncPoint != null) {
events.addAll(syncPoint.applyOperation(operation, writesCache, serverCache));
}
return events;
}
}
/** Recursive helper for applyOperationToSyncPoints. */
private List applyOperationDescendantsHelper(
final Operation operation,
ImmutableTree syncPointTree,
Node serverCache,
final WriteTreeRef writesCache) {
SyncPoint syncPoint = syncPointTree.getValue();
// If we don't have cached server data, see if we can get it from this SyncPoint.
final Node resolvedServerCache;
if (serverCache == null && syncPoint != null) {
resolvedServerCache = syncPoint.getCompleteServerCache(Path.getEmptyPath());
} else {
resolvedServerCache = serverCache;
}
final List events = new ArrayList<>();
syncPointTree
.getChildren()
.inOrderTraversal(
new LLRBNode.NodeVisitor>() {
@Override
public void visitEntry(ChildKey key, ImmutableTree childTree) {
Node childServerCache = null;
if (resolvedServerCache != null) {
childServerCache = resolvedServerCache.getImmediateChild(key);
}
WriteTreeRef childWritesCache = writesCache.child(key);
Operation childOperation = operation.operationForChild(key);
if (childOperation != null) {
events.addAll(
applyOperationDescendantsHelper(
childOperation, childTree, childServerCache, childWritesCache));
}
}
});
if (syncPoint != null) {
events.addAll(syncPoint.applyOperation(operation, writesCache, resolvedServerCache));
}
return events;
}
// Package private for testing purposes only
ImmutableTree getSyncPointTree() {
return syncPointTree;
}
public interface CompletionListener {
List onListenComplete(DatabaseError error);
}
public interface ListenProvider {
void startListening(
QuerySpec query,
Tag tag,
final ListenHashProvider hash,
final CompletionListener onListenComplete);
void stopListening(QuerySpec query, Tag tag);
}
private static class KeepSyncedEventRegistration extends EventRegistration {
private QuerySpec spec;
public KeepSyncedEventRegistration(@NotNull QuerySpec spec) {
this.spec = spec;
}
@Override
public boolean respondsTo(Event.EventType eventType) {
return false;
}
@Override
public DataEvent createEvent(Change change, QuerySpec query) {
return null;
}
@Override
public void fireEvent(DataEvent dataEvent) {}
@Override
public void fireCancelEvent(DatabaseError error) {}
@Override
public EventRegistration clone(QuerySpec newQuery) {
return new KeepSyncedEventRegistration(newQuery);
}
@Override
public boolean isSameListener(EventRegistration other) {
return other instanceof KeepSyncedEventRegistration;
}
@NotNull
@Override
public QuerySpec getQuerySpec() {
return spec;
}
@Override
public boolean equals(Object other) {
return (other instanceof KeepSyncedEventRegistration
&& ((KeepSyncedEventRegistration) other).spec.equals(spec));
}
@Override
public int hashCode() {
return spec.hashCode();
}
}
private class ListenContainer implements ListenHashProvider, CompletionListener {
private final View view;
private final Tag tag;
public ListenContainer(View view) {
this.view = view;
this.tag = SyncTree.this.tagForQuery(view.getQuery());
}
@Override
public com.google.firebase.database.connection.CompoundHash getCompoundHash() {
CompoundHash hash = CompoundHash.fromNode(view.getServerCache());
List pathPosts = hash.getPosts();
List> posts = new ArrayList<>(pathPosts.size());
for (Path path : pathPosts) {
posts.add(path.asList());
}
return new com.google.firebase.database.connection.CompoundHash(posts, hash.getHashes());
}
@Override
public String getSimpleHash() {
return view.getServerCache().getHash();
}
@Override
public boolean shouldIncludeCompoundHash() {
return NodeSizeEstimator.estimateSerializedNodeSize(view.getServerCache())
> SIZE_THRESHOLD_FOR_COMPOUND_HASH;
}
@Override
public List onListenComplete(DatabaseError error) {
if (error == null) {
QuerySpec query = this.view.getQuery();
if (tag != null) {
return SyncTree.this.applyTaggedListenComplete(tag);
} else {
return SyncTree.this.applyListenComplete(query.getPath());
}
} else {
logger.warn("Listen at {} failed: {}", view.getQuery().getPath(), error);
// If a listen failed, kill all of the listeners here, not just the one that triggered the
// error. Note that this may need to be scoped to just this listener if we change
// permissions on filtered children
return SyncTree.this.removeAllEventRegistrations(view.getQuery(), error);
}
}
}
}