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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "sync/engine/entity_tracker.h"
#include <stdint.h>
#include "base/logging.h"
#include "sync/internal_api/public/base/model_type.h"
#include "sync/internal_api/public/non_blocking_sync_common.h"
#include "sync/syncable/syncable_util.h"
#include "sync/util/time.h"
namespace syncer_v2 {
scoped_ptr<EntityTracker> EntityTracker::FromUpdateResponse(
const UpdateResponseData& data) {
return make_scoped_ptr(new EntityTracker(
data.entity->id, data.entity->client_tag_hash, 0, data.response_version));
scoped_ptr<EntityTracker> EntityTracker::FromCommitRequest(
const CommitRequestData& data) {
return make_scoped_ptr(
new EntityTracker(data.entity->id, data.entity->client_tag_hash, 0, 0));
EntityTracker::EntityTracker(const std::string& id,
const std::string& client_tag_hash,
int64_t highest_commit_response_version,
int64_t highest_gu_response_version)
: id_(id),
base_version_(kUncommittedVersion) {}
EntityTracker::~EntityTracker() {}
bool EntityTracker::HasPendingCommit() const {
return !!pending_commit_;
void EntityTracker::PrepareCommitProto(sync_pb::SyncEntity* commit_entity,
int64_t* sequence_number) const {
if (!id_.empty()) {
const EntityData& entity = pending_commit_->entity.value();
DCHECK_EQ(client_tag_hash_, entity.client_tag_hash);
// TODO(stanisc): This doesn't support bookmarks yet.
if (!entity.is_deleted()) {
*sequence_number = sequence_number_;
void EntityTracker::RequestCommit(const CommitRequestData& data) {
DCHECK_GE(data.base_version, base_version_)
<< "Base version should never decrease";
DCHECK_GE(data.sequence_number, sequence_number_)
<< "Sequence number should never decrease";
// Update our book-keeping counters.
base_version_ = data.base_version;
sequence_number_ = data.sequence_number;
// Don't commit deletions of server-unknown items.
if (data.entity->is_deleted() && !IsServerKnown()) {
// We intentionally don't update the id_ here. Good ID values come from the
// server and always pass through the sync thread first. There's no way the
// model thread could have a better ID value than we do.
// This entity is identified by its client tag. That value can never change.
DCHECK_EQ(client_tag_hash_, data.entity->client_tag_hash);
// TODO(stanisc): consider simply copying CommitRequestData instead of
// allocating one dynamically.
pending_commit_.reset(new CommitRequestData(data));
// Do our counter values indicate a conflict? If so, don't commit.
// There's no need to inform the model thread of the conflict. The
// conflicting update has already been posted to its task runner; it will
// figure it out as soon as it runs that task.
// Note that this check must be after pending_commit_ is set.
if (IsInConflict()) {
// Otherwise, keep the data associated with this pending commit
// so it can be committed at the next possible opportunity.
void EntityTracker::ReceiveCommitResponse(const std::string& response_id,
int64_t response_version,
int64_t sequence_number) {
// Commit responses, especially after the first commit, can update our ID.
id_ = response_id;
DCHECK_GT(response_version, highest_commit_response_version_)
<< "Had expected higher response version."
<< " id: " << id_;
// Commits are synchronous, so there's no reason why the sequence numbers
// wouldn't match.
DCHECK_EQ(sequence_number_, sequence_number)
<< "Unexpected sequence number mismatch."
<< " id: " << id_;
highest_commit_response_version_ = response_version;
// Because an in-progress commit blocks the sync thread, we can assume that
// the item we just committed successfully is exactly the one we have now.
// Nothing changed it while the commit was happening. Since we're now in
// sync with the server, we can clear the pending commit.
void EntityTracker::ReceiveUpdate(int64_t version) {
if (version <= highest_gu_response_version_)
highest_gu_response_version_ = version;
// Got an applicable update newer than any pending updates. It must be safe
// to discard the old pending update, if there was one.
if (IsInConflict()) {
// Incoming update clobbers the pending commit on the sync thread.
// The model thread can re-request this commit later if it wants to.
bool EntityTracker::ReceivePendingUpdate(const UpdateResponseData& data) {
if (data.response_version < highest_gu_response_version_)
return false;
highest_gu_response_version_ = data.response_version;
pending_update_.reset(new UpdateResponseData(data));
return true;
bool EntityTracker::HasPendingUpdate() const {
return !!pending_update_;
UpdateResponseData EntityTracker::GetPendingUpdate() const {
return *pending_update_;
void EntityTracker::ClearPendingUpdate() {
bool EntityTracker::IsInConflict() const {
if (!HasPendingCommit())
return false;
if (HasPendingUpdate())
return true;
if (highest_gu_response_version_ <= highest_commit_response_version_) {
// The most recent server state was created in a commit made by this
// client. We're fully up to date, and therefore not in conflict.
return false;
} else {
// The most recent server state was written by someone else.
// Did the model thread have the most up to date version when it issued the
// commit request?
if (base_version_ >= highest_gu_response_version_) {
return false; // Yes.
} else {
return true; // No.
bool EntityTracker::IsServerKnown() const {
return base_version_ != kUncommittedVersion;
void EntityTracker::ClearPendingCommit() {
} // namespace syncer_v2