sync: Implement NonBlockingTypeProcessorCore

sync/engine/sync_thread_sync_entity.cc

+// 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/sync_thread_sync_entity.h"
+
+#include "base/logging.h"
+#include "sync/engine/non_blocking_sync_common.h"
+#include "sync/internal_api/public/base/model_type.h"
+#include "sync/syncable/syncable_util.h"
+#include "sync/util/time.h"
+
+namespace syncer {
+
+SyncThreadSyncEntity* SyncThreadSyncEntity::FromServerUpdate(
+    const std::string& id_string,
+    const std::string& client_tag_hash,
+    int64 received_version) {
+  return new SyncThreadSyncEntity(
+      id_string, client_tag_hash, 0, received_version);
+}
+
+SyncThreadSyncEntity* SyncThreadSyncEntity::FromCommitRequest(
+    const std::string& id_string,
+    const std::string& client_tag_hash,
+    int64 sequence_number,
+    int64 base_version,
+    base::Time ctime,
+    base::Time mtime,
+    const std::string& non_unique_name,
+    bool deleted,
+    const sync_pb::EntitySpecifics& specifics) {
+  return new SyncThreadSyncEntity(id_string,
+                                  client_tag_hash,
+                                  0,
+                                  0,
+                                  true,
+                                  sequence_number,
+                                  base_version,
+                                  ctime,
+                                  mtime,
+                                  non_unique_name,
+                                  deleted,
+                                  specifics);
+}
+
+// Constructor that does not set any pending commit fields.
+SyncThreadSyncEntity::SyncThreadSyncEntity(
+    const std::string& id,
+    const std::string& client_tag_hash,
+    int64 highest_commit_response_version,
+    int64 highest_gu_response_version)
+    : id_(id),
+      client_tag_hash_(client_tag_hash),
+      highest_commit_response_version_(highest_commit_response_version),
+      highest_gu_response_version_(highest_gu_response_version),
+      is_commit_pending_(false),
+      sequence_number_(0),
+      base_version_(0),
+      deleted_(false) {
+}
+
+SyncThreadSyncEntity::SyncThreadSyncEntity(
+    const std::string& id,
+    const std::string& client_tag_hash,
+    int64 highest_commit_response_version,
+    int64 highest_gu_response_version,
+    bool is_commit_pending,
+    int64 sequence_number,
+    int64 base_version,
+    base::Time ctime,
+    base::Time mtime,
+    const std::string& non_unique_name,
+    bool deleted,
+    const sync_pb::EntitySpecifics& specifics)
+    : id_(id),
+      client_tag_hash_(client_tag_hash),
+      highest_commit_response_version_(highest_commit_response_version),
+      highest_gu_response_version_(highest_gu_response_version),
+      is_commit_pending_(is_commit_pending),
+      sequence_number_(sequence_number),
+      base_version_(base_version),
+      ctime_(ctime),
+      mtime_(mtime),
+      non_unique_name_(non_unique_name),
+      deleted_(deleted),
+      specifics_(specifics) {
+}
+
+SyncThreadSyncEntity::~SyncThreadSyncEntity() {
+}
+
+bool SyncThreadSyncEntity::IsCommitPending() const {
+  return is_commit_pending_;
+}
+
+void SyncThreadSyncEntity::PrepareCommitProto(
+    sync_pb::SyncEntity* commit_entity,
+    int64* sequence_number) const {
+  // Set ID if we have a server-assigned ID.  Otherwise, it will be up to
+  // our caller to assign a client-unique initial ID.
+  if (base_version_ != kUncommittedVersion) {
+    commit_entity->set_id_string(id_);
+  }
+
+  commit_entity->set_client_defined_unique_tag(client_tag_hash_);
+  commit_entity->set_version(base_version_);
+  commit_entity->set_deleted(deleted_);
+  commit_entity->set_folder(false);
+  commit_entity->set_name(non_unique_name_);
+  if (!deleted_) {
+    commit_entity->set_ctime(TimeToProtoTime(ctime_));
+    commit_entity->set_mtime(TimeToProtoTime(mtime_));
+    commit_entity->mutable_specifics()->CopyFrom(specifics_);
+  }
+
+  *sequence_number = sequence_number_;
+}
+
+void SyncThreadSyncEntity::RequestCommit(
+    const std::string& id,
+    const std::string& client_tag_hash,
+    int64 sequence_number,
+    int64 base_version,
+    base::Time ctime,
+    base::Time mtime,
+    const std::string& non_unique_name,
+    bool deleted,
+    const sync_pb::EntitySpecifics& specifics) {
+  if (base_version < base_version_) {
+    NOTREACHED() << "Base version should never decrease";
+    return;
+  }
+
+  if (sequence_number < sequence_number_) {
+    NOTREACHED() << "Sequence number should never decrease";
+    return;
+  }
+
+  // Update our book-keeping counters.
+  base_version_ = base_version;
+  sequence_number_ = sequence_number;
+
+  // 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.
+  is_commit_pending_ = true;
+  if (IsInConflict()) {
+    ClearPendingCommit();
+    return;
+  }
+
+  // We don't commit deletions of server-unknown items.
+  if (deleted && !IsServerKnown()) {
+    ClearPendingCommit();
+    return;
+  }
+
+  // Otherwise, we should store the data associated with this pending commit
+  // so we're ready to commit at the next possible opportunity.
+
+  // 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_, client_tag_hash);
+
+  // Set the fields for the pending commit.
+  ctime_ = ctime;
+  mtime_ = mtime;
+  non_unique_name_ = non_unique_name;
+  deleted_ = deleted;
+  specifics_ = specifics;
+}
+
+void SyncThreadSyncEntity::ReceiveCommitResponse(const std::string& response_id,
+                                                 int64 response_version,
+                                                 int64 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 should there's no reason why the

[Nicolas Zea, 2014/05/28 23:56:16]

nit: there should there's

[rlarocque, 2014/05/29 20:54:52]

Done.

+  // 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.
+  ClearPendingCommit();
+}
+
+void SyncThreadSyncEntity::ReceiveUpdate(int64 version) {
+  highest_gu_response_version_ =
+      std::max(highest_gu_response_version_, version);
+
+  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.
+    ClearPendingCommit();
+  }
+}
+
+bool SyncThreadSyncEntity::IsInConflict() const {
+  if (!is_commit_pending_)
+    return false;
+
+  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 SyncThreadSyncEntity::IsServerKnown() const {
+  return base_version_ != kUncommittedVersion;
+}
+
+void SyncThreadSyncEntity::ClearPendingCommit() {
+  is_commit_pending_ = false;
+  specifics_.Clear();

[Nicolas Zea, 2014/05/28 23:56:16]

why clear the specific here?

[rlarocque, 2014/05/29 20:54:52]

It's an optimization.  At this point we've given up on the commit, so we don't
need the specifics.  Clearing it might give back a bit of heap memory.

There's no proof that this is a useful optimization, so it is a bit premature. 
I can remove it if you're worried about it.

[Nicolas Zea, 2014/06/02 20:27:17]

Does the protobuf library actually free memory when cleared? I'm not sure. I
suppose it doesn't hurt to do this though. Maybe just comment about the purpose
of this.

[rlarocque, 2014/06/02 21:39:13]

According to the documentation [1], protobufs can hang on to memory even after
they're cleared.  I would hope that they're smart enough to release the multi-kB
favicon specifics objects, but maybe not.  I suppose it can't hurt to try, and I
see no point in keeping around stale specifics.

I added a comment to explain this Clear() is not really necessary, but an
attempt at optimization.

If someone decides they actually care about this, they could always replace the
protobuf member with a scoped_ptr and call reset() here instead.

[1] https://developers.google.com/protocol-buffers/docs/cpptutorial, see section
"Optimization Tips"

+}
+
+}  // namespace syncer