sync: Implement per-type update processing

sync/engine/process_updates_command.cc

Index: sync/engine/process_updates_command.cc
diff --git a/sync/engine/process_updates_command.cc b/sync/engine/process_updates_command.cc
deleted file mode 100644
index d69c1098c6efc0116327ea7ad1c0c10b4c52ba65..0000000000000000000000000000000000000000
--- a/sync/engine/process_updates_command.cc
+++ /dev/null
@@ -1,348 +0,0 @@
-// Copyright 2012 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/process_updates_command.h"
-
-#include <vector>
-
-#include "base/basictypes.h"
-#include "base/location.h"
-#include "sync/engine/syncer.h"
-#include "sync/engine/syncer_proto_util.h"
-#include "sync/engine/syncer_util.h"
-#include "sync/sessions/sync_session.h"
-#include "sync/syncable/directory.h"
-#include "sync/syncable/model_neutral_mutable_entry.h"
-#include "sync/syncable/syncable_model_neutral_write_transaction.h"
-#include "sync/syncable/syncable_proto_util.h"
-#include "sync/syncable/syncable_util.h"
-#include "sync/util/cryptographer.h"
-
-using std::vector;
-
-namespace syncer {
-
-using sessions::SyncSession;
-using sessions::StatusController;
-
-using syncable::GET_BY_ID;
-
-ProcessUpdatesCommand::ProcessUpdatesCommand() {}
-ProcessUpdatesCommand::~ProcessUpdatesCommand() {}
-
-namespace {
-
-// This function attempts to determine whether or not this update is genuinely
-// new, or if it is a reflection of one of our own commits.
-//
-// There is a known inaccuracy in its implementation.  If this update ends up
-// being applied to a local item with a different ID, we will count the change
-// as being a non-reflection update.  Fortunately, the server usually updates
-// our IDs correctly in its commit response, so a new ID during GetUpdate should
-// be rare.
-//
-// The only secnarios I can think of where this might happen are:
-// - We commit a  new item to the server, but we don't persist the
-// server-returned new ID to the database before we shut down.  On the GetUpdate
-// following the next restart, we will receive an update from the server that
-// updates its local ID.
-// - When two attempts to create an item with identical UNIQUE_CLIENT_TAG values
-// collide at the server.  I have seen this in testing.  When it happens, the
-// test server will send one of the clients a response to upate its local ID so
-// that both clients will refer to the item using the same ID going forward.  In
-// this case, we're right to assume that the update is not a reflection.
-//
-// For more information, see FindLocalIdToUpdate().
-bool UpdateContainsNewVersion(syncable::BaseTransaction *trans,
-                              const sync_pb::SyncEntity &update) {
-  int64 existing_version = -1; // The server always sends positive versions.
-  syncable::Entry existing_entry(trans, GET_BY_ID,
-                                 SyncableIdFromProto(update.id_string()));
-  if (existing_entry.good())
-    existing_version = existing_entry.GetBaseVersion();
-
-  if (!existing_entry.good() && update.deleted()) {
-    // There are several possible explanations for this.  The most common cases
-    // will be first time sync and the redelivery of deletions we've already
-    // synced, accepted, and purged from our database.  In either case, the
-    // update is useless to us.  Let's count them all as "not new", even though
-    // that may not always be entirely accurate.
-    return false;
-  }
-
-  if (existing_entry.good() &&
-      !existing_entry.GetUniqueClientTag().empty() &&
-      existing_entry.GetIsDel() &&
-      update.deleted()) {
-    // Unique client tags will have their version set to zero when they're
-    // deleted.  The usual version comparison logic won't be able to detect
-    // reflections of these items.  Instead, we assume any received tombstones
-    // are reflections.  That should be correct most of the time.
-    return false;
-  }
-
-  return existing_version < update.version();
-}
-
-}  // namespace
-
-SyncerError ProcessUpdatesCommand::ExecuteImpl(SyncSession* session) {
-  syncable::Directory* dir = session->context()->directory();
-
-  syncable::ModelNeutralWriteTransaction trans(
-      FROM_HERE, syncable::SYNCER, dir);
-
-  sessions::StatusController* status = session->mutable_status_controller();
-  const sync_pb::GetUpdatesResponse& updates =
-      status->updates_response().get_updates();
-  ModelTypeSet requested_types = GetRoutingInfoTypes(
-      session->context()->routing_info());
-
-  TypeSyncEntityMap updates_by_type;
-
-  PartitionUpdatesByType(updates, &updates_by_type);
-
-  int update_count = updates.entries().size();
-  status->increment_num_updates_downloaded_by(update_count);
-
-  DVLOG(1) << update_count << " entries to verify";
-  for (TypeSyncEntityMap::iterator it = updates_by_type.begin();
-       it != updates_by_type.end(); ++it) {
-    for (SyncEntityList::iterator update_it = it->second.begin();
-         update_it != it->second.end(); ++update_it) {
-      if (!UpdateContainsNewVersion(&trans, **update_it))
-        status->increment_num_reflected_updates_downloaded_by(1);
-      if ((*update_it)->deleted())
-        status->increment_num_tombstone_updates_downloaded_by(1);
-      VerifyResult verify_result = VerifyUpdate(
-          &trans,
-          **update_it,
-          requested_types,
-          session->context()->routing_info());
-      if (verify_result != VERIFY_SUCCESS && verify_result != VERIFY_UNDELETE)
-        continue;
-      ProcessUpdate(**update_it, dir->GetCryptographer(&trans), &trans);
-    }
-  }
-
-  return SYNCER_OK;
-}
-
-void ProcessUpdatesCommand::PartitionUpdatesByType(
-    const sync_pb::GetUpdatesResponse& updates,
-    TypeSyncEntityMap* updates_by_type) {
-  int update_count = updates.entries().size();
-  for (int i = 0; i < update_count; ++i) {
-    const sync_pb::SyncEntity& update = updates.entries(i);
-    ModelType type = GetModelType(update);
-    DCHECK(IsRealDataType(type));
-    (*updates_by_type)[type].push_back(&update);
-  }
-}
-
-namespace {
-
-// In the event that IDs match, but tags differ AttemptReuniteClient tag
-// will have refused to unify the update.
-// We should not attempt to apply it at all since it violates consistency
-// rules.
-VerifyResult VerifyTagConsistency(
-    const sync_pb::SyncEntity& entry,
-    const syncable::ModelNeutralMutableEntry& same_id) {
-  if (entry.has_client_defined_unique_tag() &&
-      entry.client_defined_unique_tag() !=
-          same_id.GetUniqueClientTag()) {
-    return VERIFY_FAIL;
-  }
-  return VERIFY_UNDECIDED;
-}
-
-}  // namespace
-
-VerifyResult ProcessUpdatesCommand::VerifyUpdate(
-    syncable::ModelNeutralWriteTransaction* trans,
-    const sync_pb::SyncEntity& entry,
-    ModelTypeSet requested_types,
-    const ModelSafeRoutingInfo& routes) {
-  syncable::Id id = SyncableIdFromProto(entry.id_string());
-  VerifyResult result = VERIFY_FAIL;
-
-  const bool deleted = entry.has_deleted() && entry.deleted();
-  const bool is_directory = IsFolder(entry);
-  const ModelType model_type = GetModelType(entry);
-
-  if (!id.ServerKnows()) {
-    LOG(ERROR) << "Illegal negative id in received updates";
-    return result;
-  }
-  {
-    const std::string name = SyncerProtoUtil::NameFromSyncEntity(entry);
-    if (name.empty() && !deleted) {
-      LOG(ERROR) << "Zero length name in non-deleted update";
-      return result;
-    }
-  }
-
-  syncable::ModelNeutralMutableEntry same_id(trans, GET_BY_ID, id);
-  result = VerifyNewEntry(entry, &same_id, deleted);
-
-  ModelType placement_type = !deleted ? GetModelType(entry)
-      : same_id.good() ? same_id.GetModelType() : UNSPECIFIED;
-
-  if (VERIFY_UNDECIDED == result) {
-    result = VerifyTagConsistency(entry, same_id);
-  }
-
-  if (VERIFY_UNDECIDED == result) {
-    if (deleted) {
-      // For deletes the server could send tombostones for items that
-      // the client did not request. If so ignore those items.
-      if (IsRealDataType(placement_type) &&
-          !requested_types.Has(placement_type)) {
-        result = VERIFY_SKIP;
-      } else {
-        result = VERIFY_SUCCESS;
-      }
-    }
-  }
-
-  // If we have an existing entry, we check here for updates that break
-  // consistency rules.
-  if (VERIFY_UNDECIDED == result) {
-    result = VerifyUpdateConsistency(trans, entry, deleted,
-                                     is_directory, model_type, &same_id);
-  }
-
-  if (VERIFY_UNDECIDED == result)
-    result = VERIFY_SUCCESS;  // No news is good news.
-
-  return result;  // This might be VERIFY_SUCCESS as well
-}
-
-namespace {
-// Returns true if the entry is still ok to process.
-bool ReverifyEntry(syncable::ModelNeutralWriteTransaction* trans,
-                   const sync_pb::SyncEntity& entry,
-                   syncable::ModelNeutralMutableEntry* same_id) {
-
-  const bool deleted = entry.has_deleted() && entry.deleted();
-  const bool is_directory = IsFolder(entry);
-  const ModelType model_type = GetModelType(entry);
-
-  return VERIFY_SUCCESS == VerifyUpdateConsistency(trans,
-                                                   entry,
-                                                   deleted,
-                                                   is_directory,
-                                                   model_type,
-                                                   same_id);
-}
-}  // namespace
-
-// Process a single update. Will avoid touching global state.
-void ProcessUpdatesCommand::ProcessUpdate(
-    const sync_pb::SyncEntity& update,
-    const Cryptographer* cryptographer,
-    syncable::ModelNeutralWriteTransaction* const trans) {
-  const syncable::Id& server_id = SyncableIdFromProto(update.id_string());
-  const std::string name = SyncerProtoUtil::NameFromSyncEntity(update);
-
-  // Look to see if there's a local item that should recieve this update,
-  // maybe due to a duplicate client tag or a lost commit response.
-  syncable::Id local_id = FindLocalIdToUpdate(trans, update);
-
-  // FindLocalEntryToUpdate has veto power.
-  if (local_id.IsNull()) {
-    return;  // The entry has become irrelevant.
-  }
-
-  CreateNewEntry(trans, local_id);
-
-  // We take a two step approach. First we store the entries data in the
-  // server fields of a local entry and then move the data to the local fields
-  syncable::ModelNeutralMutableEntry target_entry(trans, GET_BY_ID, local_id);
-
-  // We need to run the Verify checks again; the world could have changed
-  // since we last verified.
-  if (!ReverifyEntry(trans, update, &target_entry)) {
-    return;  // The entry has become irrelevant.
-  }
-
-  // If we're repurposing an existing local entry with a new server ID,
-  // change the ID now, after we're sure that the update can succeed.
-  if (local_id != server_id) {
-    DCHECK(!update.deleted());
-    ChangeEntryIDAndUpdateChildren(trans, &target_entry, server_id);
-    // When IDs change, versions become irrelevant.  Forcing BASE_VERSION
-    // to zero would ensure that this update gets applied, but would indicate
-    // creation or undeletion if it were committed that way.  Instead, prefer
-    // forcing BASE_VERSION to entry.version() while also forcing
-    // IS_UNAPPLIED_UPDATE to true.  If the item is UNSYNCED, it's committable
-    // from the new state; it may commit before the conflict resolver gets
-    // a crack at it.
-    if (target_entry.GetIsUnsynced() || target_entry.GetBaseVersion() > 0) {
-      // If either of these conditions are met, then we can expect valid client
-      // fields for this entry.  When BASE_VERSION is positive, consistency is
-      // enforced on the client fields at update-application time.  Otherwise,
-      // we leave the BASE_VERSION field alone; it'll get updated the first time
-      // we successfully apply this update.
-      target_entry.PutBaseVersion(update.version());
-    }
-    // Force application of this update, no matter what.
-    target_entry.PutIsUnappliedUpdate(true);
-  }
-
-  // If this is a newly received undecryptable update, and the only thing that
-  // has changed are the specifics, store the original decryptable specifics,
-  // (on which any current or future local changes are based) before we
-  // overwrite SERVER_SPECIFICS.
-  // MTIME, CTIME, and NON_UNIQUE_NAME are not enforced.
-
-  bool position_matches = false;
-  if (target_entry.ShouldMaintainPosition() && !update.deleted()) {
-    std::string update_tag = GetUniqueBookmarkTagFromUpdate(update);
-    if (UniquePosition::IsValidSuffix(update_tag)) {
-      position_matches = GetUpdatePosition(update, update_tag).Equals(
-          target_entry.GetServerUniquePosition());
-    } else {
-      NOTREACHED();
-    }
-  } else {
-    // If this item doesn't care about positions, then set this flag to true.
-    position_matches = true;
-  }
-
-  if (!update.deleted() && !target_entry.GetServerIsDel() &&
-      (SyncableIdFromProto(update.parent_id_string()) ==
-          target_entry.GetServerParentId()) &&
-      position_matches &&
-      update.has_specifics() && update.specifics().has_encrypted() &&
-      !cryptographer->CanDecrypt(update.specifics().encrypted())) {
-    sync_pb::EntitySpecifics prev_specifics =
-        target_entry.GetServerSpecifics();
-    // We only store the old specifics if they were decryptable and applied and
-    // there is no BASE_SERVER_SPECIFICS already. Else do nothing.
-    if (!target_entry.GetIsUnappliedUpdate() &&
-        !IsRealDataType(GetModelTypeFromSpecifics(
-            target_entry.GetBaseServerSpecifics())) &&
-        (!prev_specifics.has_encrypted() ||
-         cryptographer->CanDecrypt(prev_specifics.encrypted()))) {
-      DVLOG(2) << "Storing previous server specifcs: "
-               << prev_specifics.SerializeAsString();
-      target_entry.PutBaseServerSpecifics(prev_specifics);
-    }
-  } else if (IsRealDataType(GetModelTypeFromSpecifics(
-                 target_entry.GetBaseServerSpecifics()))) {
-    // We have a BASE_SERVER_SPECIFICS, but a subsequent non-specifics-only
-    // change arrived. As a result, we can't use the specifics alone to detect
-    // changes, so we clear BASE_SERVER_SPECIFICS.
-    target_entry.PutBaseServerSpecifics(
-                     sync_pb::EntitySpecifics());
-  }
-
-  UpdateServerFieldsFromUpdate(&target_entry, update, name);
-
-  return;
-}
-
-}  // namespace syncer