sync/protocol/sync.proto

// Copyright (c) 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.
//
// Sync protocol for communication between sync client and server.

// Update proto_value_conversions{.h,.cc,_unittest.cc} if you change
// any fields in this file.

syntax = "proto2";

option optimize_for = LITE_RUNTIME;
option retain_unknown_fields = true;

package sync_pb;

import "app_notification_specifics.proto";
import "app_setting_specifics.proto";
import "app_specifics.proto";
import "autofill_specifics.proto";
import "bookmark_specifics.proto";
import "client_commands.proto";
import "client_debug_info.proto";
import "device_info_specifics.proto";
import "dictionary_specifics.proto";
import "encryption.proto";
import "experiments_specifics.proto";
import "extension_setting_specifics.proto";
import "extension_specifics.proto";
import "favicon_image_specifics.proto";
import "favicon_tracking_specifics.proto";
import "get_updates_caller_info.proto";
import "history_delete_directive_specifics.proto";
import "nigori_specifics.proto";
import "managed_user_setting_specifics.proto";
import "managed_user_specifics.proto";
import "password_specifics.proto";
import "preference_specifics.proto";
import "priority_preference_specifics.proto";
import "search_engine_specifics.proto";
import "session_specifics.proto";
import "sync_enums.proto";
import "synced_notification_specifics.proto";
import "theme_specifics.proto";
import "typed_url_specifics.proto";
import "unique_position.proto";

// Used for inspecting how long we spent performing operations in different
// backends. All times must be in millis.
message ProfilingData {
  optional int64 meta_data_write_time = 1;
  optional int64 file_data_write_time = 2;
  optional int64 user_lookup_time = 3;
  optional int64 meta_data_read_time = 4;
  optional int64 file_data_read_time = 5;
  optional int64 total_request_time = 6;
}

message EntitySpecifics {
  // If a datatype is encrypted, this field will contain the encrypted
  // original EntitySpecifics. The extension for the datatype will continue
  // to exist, but contain only the default values.
  // Note that currently passwords employ their own legacy encryption scheme and
  // do not use this field.
  optional EncryptedData encrypted = 1;

  // To add new datatype-specific fields to the protocol, extend
  // EntitySpecifics.  First, pick a non-colliding tag number by
  // picking a revision number of one of your past commits
  // to src.chromium.org.  Then, in a different protocol buffer
  // definition, define your message type, and add an optional field
  // to the list below using the unique tag value you selected.
  //
  //  optional MyDatatypeSpecifics my_datatype = 32222;
  //
  // where:
  //   - 32222 is the non-colliding tag number you picked earlier.
  //   - MyDatatypeSpecifics is the type (probably a message type defined
  //     in your new .proto file) that you want to associate with each
  //     object of the new datatype.
  //   - my_datatype is the field identifier you'll use to access the
  //     datatype specifics from the code.
  //
  // Server implementations are obligated to preserve the contents of
  // EntitySpecifics when it contains unrecognized fields.  In this
  // way, it is possible to add new datatype fields without having
  // to update the server.
  //
  // Note: The tag selection process is based on legacy versions of the
  // protocol which used protobuf extensions. We have kept the process
  // consistent as the old values cannot change.  The 5+ digit nature of the
  // tags also makes them recognizable (individually and collectively) from
  // noise in logs and debugging contexts, and creating a divergent subset of
  // tags would only make things a bit more confusing.

  optional AutofillSpecifics autofill = 31729;
  optional BookmarkSpecifics bookmark = 32904;
  optional PreferenceSpecifics preference = 37702;
  optional TypedUrlSpecifics typed_url = 40781;
  optional ThemeSpecifics theme = 41210;
  optional AppNotification app_notification = 45184;
  optional PasswordSpecifics password = 45873;
  optional NigoriSpecifics nigori = 47745;
  optional ExtensionSpecifics extension = 48119;
  optional AppSpecifics app = 48364;
  optional SessionSpecifics session = 50119;
  optional AutofillProfileSpecifics autofill_profile = 63951;
  optional SearchEngineSpecifics search_engine = 88610;
  optional ExtensionSettingSpecifics extension_setting = 96159;
  optional AppSettingSpecifics app_setting = 103656;
  optional HistoryDeleteDirectiveSpecifics history_delete_directive = 150251;
  optional SyncedNotificationSpecifics synced_notification = 153108;
  optional DeviceInfoSpecifics device_info = 154522;
  optional ExperimentsSpecifics experiments = 161496;
  optional PriorityPreferenceSpecifics priority_preference = 163425;
  optional DictionarySpecifics dictionary = 170540;
  optional FaviconTrackingSpecifics favicon_tracking = 181534;
  optional FaviconImageSpecifics favicon_image = 182019;
  optional ManagedUserSettingSpecifics managed_user_setting = 186662;
  optional ManagedUserSpecifics managed_user = 194582;
}

message SyncEntity {
  // This item's identifier.  In a commit of a new item, this will be a
  // client-generated ID.  If the commit succeeds, the server will generate
  // a globally unique ID and return it to the committing client in the
  // CommitResponse.EntryResponse.  In the context of a GetUpdatesResponse,
  // |id_string| is always the server generated ID.  The original
  // client-generated ID is preserved in the |originator_client_id| field.
  // Present in both GetUpdatesResponse and CommitMessage.
  optional string id_string = 1;

  // An id referencing this item's parent in the hierarchy.  In a
  // CommitMessage, it is accepted for this to be a client-generated temporary
  // ID if there was a new created item with that ID appearing earlier
  // in the message.  In all other situations, it is a server ID.
  // Present in both GetUpdatesResponse and CommitMessage.
  optional string parent_id_string = 2;

  // old_parent_id is only set in commits and indicates the old server
  // parent(s) to remove. When omitted, the old parent is the same as
  // the new.
  // Present only in CommitMessage.
  optional string old_parent_id = 3;

  // The version of this item -- a monotonically increasing value that is
  // maintained by for each item.  If zero in a CommitMessage, the server
  // will interpret this entity as a newly-created item and generate a
  // new server ID and an initial version number.  If nonzero in a
  // CommitMessage, this item is treated as an update to an existing item, and
  // the server will use |id_string| to locate the item.  Then, if the item's
  // current version on the server does not match |version|, the commit will
  // fail for that item.  The server will not update it, and will return
  // a result code of CONFLICT.  In a GetUpdatesResponse, |version| is
  // always positive and indentifies the revision of the item data being sent
  // to the client.
  // Present in both GetUpdatesResponse and CommitMessage.
  required int64 version = 4;

  // Last modification time (in java time milliseconds)
  // Present in both GetUpdatesResponse and CommitMessage.
  optional int64 mtime = 5;

  // Creation time.
  // Present in both GetUpdatesResponse and CommitMessage.
  optional int64 ctime = 6;

  // The name of this item.
  // Historical note:
  //   Since November 2010, this value is no different from non_unique_name.
  //   Before then, server implementations would maintain a unique-within-parent
  //   value separate from its base, "non-unique" value.  Clients had not
  //   depended on the uniqueness of the property since November 2009; it was
  //   removed from Chromium by http://codereview.chromium.org/371029 .
  // Present in both GetUpdatesResponse and CommitMessage.
  required string name = 7;

  // The name of this item.  Same as |name|.
  // |non_unique_name| should take precedence over the |name| value if both
  // are supplied.  For efficiency, clients and servers should avoid setting
  // this redundant value.
  // Present in both GetUpdatesResponse and CommitMessage.
  optional string non_unique_name = 8;

  // A value from a monotonically increasing sequence that indicates when
  // this item was last updated on the server. This is now equivalent
  // to version. This is now deprecated in favor of version.
  // Present only in GetUpdatesResponse.
  optional int64 sync_timestamp = 9;

  // If present, this tag identifies this item as being a uniquely
  // instanced item.  The server ensures that there is never more
  // than one entity in a user's store with the same tag value.
  // This value is used to identify and find e.g. the "Google Chrome" settings
  // folder without relying on it existing at a particular path, or having
  // a particular name, in the data store.
  //
  // This variant of the tag is created by the server, so clients can't create
  // an item with a tag using this field.
  //
  // Use client_defined_unique_tag if you want to create one from the client.
  //
  // An item can't have both a client_defined_unique_tag and
  // a server_defined_unique_tag.
  //
  // Present only in GetUpdatesResponse.
  optional string server_defined_unique_tag = 10;

  // If this group is present, it implies that this SyncEntity corresponds to
  // a bookmark or a bookmark folder.
  //
  // This group is deprecated; clients should use the bookmark EntitySpecifics
  // protocol buffer extension instead.
  optional group BookmarkData = 11 {
    // We use a required field to differentiate between a bookmark and a
    // bookmark folder.
    // Present in both GetUpdatesMessage and CommitMessage.
    required bool bookmark_folder = 12;

    // For bookmark objects, contains the bookmark's URL.
    // Present in both GetUpdatesResponse and CommitMessage.
    optional string bookmark_url = 13;

    // For bookmark objects, contains the bookmark's favicon. The favicon is
    // represented as a 16X16 PNG image.
    // Present in both GetUpdatesResponse and CommitMessage.
    optional bytes bookmark_favicon = 14;
  }

  // Supplies a numeric position for this item, relative to other items with the
  // same parent.  Deprecated in M26, though clients are still required to set
  // it.
  //
  // Present in both GetUpdatesResponse and CommitMessage.
  //
  // At one point this was used as an alternative / supplement to
  // the deprecated |insert_after_item_id|, but now it, too, has been
  // deprecated.
  //
  // In order to maintain compatibility with older clients, newer clients should
  // still set this field.  Its value should be based on the first 8 bytes of
  // this item's |unique_position|.
  //
  // Nerwer clients must also support the receipt of items that contain
  // |position_in_parent| but no |unique_position|.  They should locally convert
  // the given int64 position to a UniquePosition.
  //
  // The conversion from int64 to UniquePosition is as follows:
  // The int64 value will have its sign bit flipped then placed in big endian
  // order as the first 8 bytes of the UniquePosition.  The subsequent bytes of
  // the UniquePosition will consist of the item's unique suffix.
  //
  // Conversion from UniquePosition to int64 reverses this process: the first 8
  // bytes of the position are to be interpreted as a big endian int64 value
  // with its sign bit flipped.
  optional int64 position_in_parent = 15;

  // Contains the ID of the element (under the same parent) after which this
  // element resides. An empty string indicates that the element is the first
  // element in the parent.  This value is used during commits to specify
  // a relative position for a position change.  In the context of
  // a GetUpdatesMessage, |position_in_parent| is used instead to
  // communicate position.
  //
  // Present only in CommitMessage.
  //
  // This is deprecated.  Clients are allowed to omit this as long as they
  // include |position_in_parent| instead.
  optional string insert_after_item_id = 16;

  // Arbitrary key/value pairs associated with this item.
  // Present in both GetUpdatesResponse and CommitMessage.
  // Deprecated.
  // optional ExtendedAttributes extended_attributes = 17;

  // If true, indicates that this item has been (or should be) deleted.
  // Present in both GetUpdatesResponse and CommitMessage.
  optional bool deleted = 18 [default = false];

  // A GUID that identifies the the sync client who initially committed
  // this entity.  This value corresponds to |cache_guid| in CommitMessage.
  // This field, along with |originator_client_item_id|, can be used to
  // reunite the original with its official committed version in the case
  // where a client does not receive or process the commit response for
  // some reason.
  //
  // Present only in GetUpdatesResponse.
  //
  // This field is also used in determining the unique identifier used in
  // bookmarks' unique_position field.
  optional string originator_cache_guid = 19;

  // The local item id of this entry from the client that initially
  // committed this entity. Typically a negative integer.
  // Present only in GetUpdatesResponse.
  //
  // This field is also used in determinging the unique identifier used in
  // bookmarks' unique_position field.
  optional string originator_client_item_id = 20;

  // Extensible container for datatype-specific data.
  // This became available in version 23 of the protocol.
  optional EntitySpecifics specifics = 21;

  // Indicate whether this is a folder or not. Available in version 23+.
  optional bool folder = 22 [default = false];

  // A client defined unique hash for this entity.
  // Similar to server_defined_unique_tag.
  //
  // When initially committing an entity, a client can request that the entity
  // is unique per that account. To do so, the client should specify a
  // client_defined_unique_tag. At most one entity per tag value may exist.
  // per account. The server will enforce uniqueness on this tag
  // and fail attempts to create duplicates of this tag.
  // Will be returned in any updates for this entity.
  //
  // The difference between server_defined_unique_tag and
  // client_defined_unique_tag is the creator of the entity. Server defined
  // tags are entities created by the server at account creation,
  // while client defined tags are entities created by the client at any time.
  //
  // During GetUpdates, a sync entity update will come back with ONE of:
  // a) Originator and cache id - If client committed the item as non "unique"
  // b) Server tag - If server committed the item as unique
  // c) Client tag - If client committed the item as unique
  //
  // May be present in CommitMessages for the initial creation of an entity.
  // If present in Commit updates for the entity, it will be ignored.
  //
  // Available in version 24+.
  //
  // May be returned in GetUpdatesMessage and sent up in CommitMessage.
  //
  optional string client_defined_unique_tag = 23;

  // This positioning system had a relatively short life.  It was made obsolete
  // by |unique_position| before either the client or server made much of an
  // attempt to support it.  In fact, no client ever read or set this field.
  //
  // Deprecated in M26.
  optional bytes ordinal_in_parent = 24;

  // This is the fourth attempt at positioning.
  //
  // This field is present in both GetUpdatesResponse and CommitMessage, if the
  // item's type requires it and the client that wrote the item supports it (M26
  // or higher).  Clients must also be prepared to handle updates from clients
  // that do not set this field.  See the comments on
  // |server_position_in_parent| for more information on how this is handled.
  //
  // This field will not be set for items whose type ignores positioning.
  // Clients should not attempt to read this field on the receipt of an item of
  // a type that ignores positioning.
  //
  // Refer to its definition in unique_position.proto for more information about
  // its internal representation.
  optional UniquePosition unique_position = 25;
};

// This message contains diagnostic information used to correlate
// commit-related traffic with extensions-related mutations to the
// data models in chromium.  It plays no functional role in
// processing this CommitMessage.
message ChromiumExtensionsActivity {
  // The human-readable ID identifying the extension responsible
  // for the traffic reported in this ChromiumExtensionsActivity.
  optional string extension_id = 1;

  // How many times the extension successfully invoked a write
  // operation through the bookmarks API since the last CommitMessage.
  optional uint32 bookmark_writes_since_last_commit = 2;
};

// Client specific configuration information.
message ClientConfigParams {
  // The set of data types this client has enabled. Note that this does not
  // include proxy types, as they do not have protocol field numbers and are
  // placeholder types that implicitly enable protocol types.
 repeated int32 enabled_type_ids = 1;

 // Whether the PROXY_TABS proxy datatype is enabled on this client.
 optional bool tabs_datatype_enabled = 2;
};

message CommitMessage {
  repeated SyncEntity entries = 1;

  // A GUID that identifies the committing sync client.  This value will be
  // returned as originator_cache_guid for any new items.
  optional string cache_guid = 2;

  repeated ChromiumExtensionsActivity extensions_activity = 3;

  // The configuration of this client at commit time. Used by the server to
  // make commit-time decisions about how to process datatypes that might
  // involve server-side interaction, and e.g require explicit user intent for
  // syncing a particular data type regardless of whether a commit for that
  // datatype is currently being sent up.
  optional ClientConfigParams config_params = 4;
};

// This message communicates additional per-type information related to
// requests with origin GU_TRIGGER.  This message is not relevant when any
// other origin value is used.
// Introduced in M29.
message GetUpdateTriggers {
  // An opaque-to-the-client string of bytes, received through a notification,
  // that the server may interpret as a hint about the location of the latest
  // version of the data for this type.
  //
  // Note that this will eventually replace the 'optional' field of the same
  // name defined in the progress marker, but the client and server should
  // support both until it's safe to deprecate the old one.
  //
  // This field was introduced in M29.
  repeated string notification_hint = 1;

  // This flag is set if the client was forced to drop hints because the number
  // of queued hints exceeded its limit.  The oldest hints will be discarded
  // first.  Introduced in M29.
  optional bool client_dropped_hints = 2;

  // This flag is set if the invalidation server reports that it may have
  // dropped some invalidations at some point.  The client will also drop any
  // locally cached hints that are older than the server-did-drop notification.
  //
  // TODO(sync): Determine the format for this.
  //
  // optional bool server_dropped_hints = 6;

  // This flag is set when the client suspects that its list of invalidation
  // hints may be incomplete.  This may be the case if:
  // - The client is syncing for the first time.
  // - The client has just restarted and it was unable to keep track of
  //   invalidations that were received prior to the restart.
  // - The client's connection to the invalidation server is currently or
  //   was recently broken.
  //
  // It's difficult to provide more details here.  This is implemented by
  // setting the flag to false whenever anything that might adversely affect
  // notifications happens (eg. a crash, restart on a platform that doesn't
  // support invalidation ack-tracking, transient invalidation error) and is
  // unset only after we've experienced one successful sync cycle while
  // notifications were enabled.
  //
  // This flag was introduced in M29.
  optional bool invalidations_out_of_sync = 3;

  // This counts the number of times the syncer has been asked to commit
  // changes for this type since the last successful sync cycle.  The number of
  // nudges may not be related to the actual number of items modified.  It
  // often correlates with the number of user actions, but that's not always
  // the case.
  // Introduced in M29.
  optional int64 local_modification_nudges = 4;

  // This counts the number of times the syncer has been explicitly asked to
  // fetch updates for this type since the last successful sync cycle.  These
  // explicit refresh requests should be relatively rare on most platforms, and
  // associated with user actions.  For example, at the time of this writing
  // the most common (only?) source of refresh requests is when a user opens
  // the new tab page on a platform that does not support sessions
  // invalidations.
  // Introduced in M29.
  optional int64 datatype_refresh_nudges = 5;
}

message DataTypeProgressMarker {
  // An integer identifying the data type whose progress is tracked by this
  // marker.  The legitimate values of this field correspond to the protobuf
  // field numbers of all EntitySpecifics fields supported by the server.
  // These values are externally declared in per-datatype .proto files.
  optional int32 data_type_id = 1;

  // An opaque-to-the-client sequence of bytes that the server may interpret
  // as an indicator of the client's knowledge state.  If this is empty or
  // omitted by the client, it indicates that the client is initiating a
  // a first-time sync of this datatype.  Otherwise, clients must supply a
  // value previously returned by the server in an earlier GetUpdatesResponse.
  // These values are not comparable or generable on the client.
  //
  // The opaque semantics of this field are to afford server implementations
  // some flexibility in implementing progress tracking.  For instance,
  // a server implementation built on top of a distributed storage service --
  // or multiple heterogenous such services -- might need to supply a vector
  // of totally ordered monotonic update timestamps, rather than a single
  // monotonically increasing value.  Other optimizations may also be
  // possible if the server is allowed to embed arbitrary information in
  // the progress token.
  //
  // Server implementations should keep the size of these tokens relatively
  // small, on the order of tens of bytes, and they should remain small
  // regardless of the number of items synchronized.  (A possible bad server
  // implementation would be for progress_token to contain a list of all the
  // items ever sent to the client.  Servers shouldn't do this.)
  optional bytes token = 2;

  // Clients that previously downloaded updates synced using the timestamp based
  // progress tracking mechanism, but which wish to switch over to the opaque
  // token mechanism can set this field in a GetUpdatesMessage.  The server
  // will perform a get updates operation as normal from the indicated
  // timestamp, and return only an opaque progress token.
  optional int64 timestamp_token_for_migration = 3;

  // An opaque-to-the-client string of bytes, received through a notification,
  // that the server may interpret as a hint about the location of the latest
  // version of the data for this type.
  //
  // Deprecated in M29.  We should use the repeated field version in the
  // PerClientTypeState instead.
  optional string notification_hint = 4;

  // This field will be included only in GetUpdates with origin GU_TRIGGER.
  optional GetUpdateTriggers get_update_triggers = 5;
}

message GetUpdatesMessage {
  // Indicates the client's current progress in downloading updates.  A
  // from_timestamp value of zero means that the client is requesting a first-
  // time sync.  After that point, clients should fill in this value with the
  // value returned in the last-seen GetUpdatesResponse.new_timestamp.
  //
  // from_timestamp has been deprecated; clients should use
  // |from_progress_marker| instead, which allows more flexibility.
  optional int64 from_timestamp = 1;

  // Indicates the reason for the GetUpdatesMessage.
  // Deprecated in M29.  We should eventually rely on GetUpdatesOrigin instead.
  // Newer clients will support both systems during the transition period.
  optional GetUpdatesCallerInfo caller_info = 2;

  // Indicates whether related folders should be fetched.
  optional bool fetch_folders = 3 [default = true];

  // The presence of an individual EntitySpecifics field indicates that the
  // client requests sync object types associated with that field.  This
  // determination depends only on the presence of the field, not its
  // contents -- thus clients should send empty messages as the field value.
  // For backwards compatibility only bookmark objects will be sent to the
  // client should requested_types not be present.
  //
  // requested_types may contain multiple EntitySpecifics fields -- in this
  // event, the server will return items of all the indicated types.
  //
  // requested_types has been deprecated; clients should use
  // |from_progress_marker| instead, which allows more flexibility.
  optional EntitySpecifics requested_types = 4;

  // Client-requested limit on the maximum number of updates to return at once.
  // The server may opt to return fewer updates than this amount, but it should
  // not return more.
  optional int32 batch_size = 5;

  // Per-datatype progress marker.  If present, the server will ignore
  // the values of requested_types and from_timestamp, using this instead.
  //
  // With the exception of certain configuration or initial sync requests, the
  // client should include one instance of this field for each enabled data
  // type.
  repeated DataTypeProgressMarker from_progress_marker = 6;

  // Indicates whether the response should be sent in chunks.  This may be
  // needed for devices with limited memory resources.  If true, the response
  // will include one or more ClientToServerResponses, with the frist one
  // containing GetUpdatesMetadataResponse, and the remaining ones, if any,
  // containing GetUpdatesStreamingResponse.  These ClientToServerResponses are
  // delimited by a length prefix, which is encoded as a varint.
  optional bool streaming = 7 [default = false];

  // Whether the client needs the server to provide an encryption key for this
  // account.
  // Note: this should typically only be set on the first GetUpdates a client
  // requests. Clients are expected to persist the encryption key from then on.
  // The allowed frequency for requesting encryption keys is much lower than
  // other datatypes, so repeated usage will likely result in throttling.
  optional bool need_encryption_key = 8 [default = false];

  // Whether to create the mobile bookmarks folder if it's not
  // already created.  Should be set to true only by mobile clients.
  optional bool create_mobile_bookmarks_folder = 1000 [default = false];

  // This value is an udpated version of the GetUpdatesCallerInfo's
  // GetUpdatesSource.  It describes the reason for the GetUpdate request.
  // Introduced in M29.
  optional SyncEnums.GetUpdatesOrigin get_updates_origin = 9;
};

message AuthenticateMessage {
  required string auth_token = 1;
};

// The client must preserve, store, and resend the chip bag with
// every request.  The server depends on the chip bag in order
// to precisely choreograph a client-server state machines.
//
// Because the client stores and sends this data on every request,
// the contents of the chip bag should be kept relatively small.
//
// If the server does not return a chip bag, the client must assume
// that there has been no change to the chip bag.  The client must
// resend the bag of chips it had prior on the next request.
//
// The client must make the chip bag durable if and only if it
// processes the response from the server.
message ChipBag {
  // Server chips are deliberately oqaque, allowing the server
  // to encapsulate its state machine logic.
  optional bytes server_chips = 1;
}

// Information about the syncer's state.
message ClientStatus {
  // Flag to indicate if the client has detected hierarchy conflcits.  The flag
  // is left unset if update application has not been attempted yet.
  //
  // The server should attempt to resolve any hierarchy conflicts when this flag
  // is set.  The client may not assume that any particular action will be
  // taken.  There is no guarantee the problem will be addressed in a reasonable
  // amount of time.
  optional bool hierarchy_conflict_detected = 1;
}

message ClientToServerMessage {
  required string share = 1;
  optional int32 protocol_version = 2 [default = 31];
  enum Contents {
    COMMIT = 1;
    GET_UPDATES = 2;
    AUTHENTICATE = 3;
    CLEAR_DATA = 4;
  }

  required Contents message_contents = 3;
  optional CommitMessage commit = 4;
  optional GetUpdatesMessage get_updates = 5;
  optional AuthenticateMessage authenticate = 6;

  // Request to clear all Chromium data from the server.
  // DEPRECATED - this field was never used in production.
  // optional ClearUserDataMessage clear_user_data = 9;

  optional string store_birthday = 7; // Opaque store ID; if it changes, duck!
  // The client sets this if it detects a sync issue. The server will tell it
  // if it should perform a refresh.
  optional bool sync_problem_detected = 8 [default = false];

  // Client side state information for debugging purpose.
  // This is only sent on the first getupdates of every sync cycle,
  // as an optimization to save bandwidth.
  optional DebugInfo debug_info = 10;

  // Per-client state for use by the server. Sent with every message sent to the
  // server.
  optional ChipBag bag_of_chips = 11;

  // Google API key.
  optional string api_key = 12;

  // Client's self-reported state.
  // The client should set this on every message sent to the server, though its
  // member fields may often be unset.
  optional ClientStatus client_status = 13;

  // The ID that our invalidation client used to identify itself to the server.
  // Sending the ID here allows the server to not send notifications of our own
  // changes to our invalidator.
  optional string invalidator_client_id = 14;
};

message CommitResponse {
  enum ResponseType {
    SUCCESS = 1;
    CONFLICT = 2; // You're out of date; update and check your data
    // TODO(ncarter): What's the difference between RETRY and TRANSIENT_ERROR?
    RETRY = 3; // Someone has a conflicting, non-expired session open
    INVALID_MESSAGE = 4; // What the client sent was invalid, and trying again
                         // won't help.
    OVER_QUOTA = 5; // This operation would put you, or you are, over quota
    TRANSIENT_ERROR = 6; // Something went wrong; try again in a bit
  }
  repeated group EntryResponse = 1 {
    required ResponseType response_type = 2;

    // Sync servers may also return a new ID for an existing item, indicating
    // a new entry's been created to hold the data the client's sending up.
    optional string id_string = 3;

    // should be filled if our parent was assigned a new ID.
    optional string parent_id_string = 4;

    // This value is the same as the position_in_parent value returned within
    // the SyncEntity message in GetUpdatesResponse.  There was a time when the
    // client would attempt to honor this position, but nowadays the server
    // should ensure it is no different from the position_in_parent sent up in
    // the commit request and the client should not read it.
    optional int64 position_in_parent = 5;

    // The item's current version.
    optional int64 version = 6;

    // Allows the server to move-aside an entry as it's being committed.
    // This name is the same as the name field returned within the SyncEntity
    // message in GetUpdatesResponse.
    optional string name = 7;

    // This name is the same as the non_unique_name field returned within the
    // SyncEntity message in GetUpdatesResponse.
    optional string non_unique_name = 8;

    optional string error_message = 9;

    // Last modification time (in java time milliseconds).  Allows the server
    // to override the client-supplied mtime during a commit operation.
    optional int64 mtime = 10;
  }
};

message GetUpdatesResponse {
  // New sync entries that the client should apply.
  repeated SyncEntity entries = 1;

  // If there are more changes on the server that weren't processed during this
  // GetUpdates request, the client should send another GetUpdates request and
  // use new_timestamp as the from_timestamp value within GetUpdatesMessage.
  //
  // This field has been deprecated and will be returned only to clients
  // that set the also-deprecated |from_timestamp| field in the update request.
  // Clients should use |from_progress_marker| and |new_progress_marker|
  // instead.
  optional int64 new_timestamp = 2;

  // DEPRECATED FIELD - server does not set this anymore.
  optional int64 deprecated_newest_timestamp = 3;

  // Approximate count of changes remaining - use this for UI feedback.
  // If present and zero, this estimate is firm: the server has no changes
  // after the current batch.
  optional int64 changes_remaining = 4;

  // Opaque, per-datatype timestamp-like tokens.  A client should use this
  // field in lieu of new_timestamp, which is deprecated in newer versions
  // of the protocol.  Clients should retain and persist the values returned
  // in this field, and present them back to the server to indicate the
  // starting point for future update requests.
  //
  // This will be sent only if the client provided |from_progress_marker|
  // in the update request.
  //
  // The server may provide a new progress marker even if this is the end of
  // the batch, or if there were no new updates on the server; and the client
  // must save these.  If the server does not provide a |new_progress_marker|
  // value for a particular datatype, when the request provided a
  // |from_progress_marker| value for that datatype, the client should
  // interpret this to mean "no change from the previous state" and retain its
  // previous progress-marker value for that datatype.
  //
  // Progress markers in the context of a response will never have the
  // |timestamp_token_for_migration| field set.
  repeated DataTypeProgressMarker new_progress_marker = 5;

  // The current encryption keys associated with this account. Will be set if
  // the GetUpdatesMessage in the request had need_encryption_key == true or
  // the server has updated the set of encryption keys (e.g. due to a key
  // rotation).
  repeated bytes encryption_keys = 6;
};

// The metadata response for GetUpdatesMessage.  This response is sent when
// streaming is set to true in the request.  It is prefixed with a length
// delimiter, which is encoded in varint.
message GetUpdatesMetadataResponse {
  // Approximate count of changes remaining.  Detailed comment is available in
  // GetUpdatesResponse.
  optional int64 changes_remaining = 1;

  // Opaque, per-datatype timestamp-like tokens.  Detailed comment is available
  // in GetUpdatesResponse.
  repeated DataTypeProgressMarker new_progress_marker = 2;
};

// The streaming response message for GetUpdatesMessage.  This message is sent
// when streaming is set to true in the request.  There may be multiple
// GetUpdatesStreamingResponse messages in a response.  This type of messages
// is preceded by GetUpdatesMetadataResponse.  It is prefixed with a length
// delimiter, which is encoded in varint.
message GetUpdatesStreamingResponse {
  // New sync entries that the client should apply.
  repeated SyncEntity entries = 1;
};

// A user-identifying struct.  For a given Google account the email and display
// name can change, but obfuscated_id should be constant.
// The obfuscated id is optional because at least one planned use of the proto
// (sharing) does not require it.
message UserIdentification {
  required string email = 1;  // the user's full primary email address.
  optional string display_name = 2;  // the user's display name.
  optional string obfuscated_id = 3;  // an obfuscated, opaque user id.
};

message AuthenticateResponse {
  // Optional only for backward compatibility.
  optional UserIdentification user = 1;
};

message ThrottleParameters {
  // Deprecated. Remove this from the server side.
  required int32 min_measure_payload_size = 1;
  required double target_utilization = 2;
  required double measure_interval_max = 3;
  required double measure_interval_min = 4;
  required double observation_window = 5;
};

message ClientToServerResponse {
  optional CommitResponse commit = 1;
  optional GetUpdatesResponse get_updates = 2;
  optional AuthenticateResponse authenticate = 3;

  // Up until protocol_version 24, the default was SUCCESS which made it
  // impossible to add new enum values since older clients would parse any
  // out-of-range value as SUCCESS. Starting with 25, unless explicitly set,
  // the error_code will be UNKNOWN so that clients know when they're
  // out-of-date. Note also that when using protocol_version < 25,
  // TRANSIENT_ERROR is not supported. Instead, the server sends back a HTTP
  // 400 error code. This is deprecated now.
  optional SyncEnums.ErrorType error_code = 4 [default = UNKNOWN];
  optional string error_message = 5;

  // Opaque store ID; if it changes, the contents of the client's cache
  // is meaningless to this server.  This happens most typically when
  // you switch from one storage backend instance (say, a test instance)
  // to another (say, the official instance).
  optional string store_birthday = 6;

  optional ClientCommand client_command = 7;
  optional ProfilingData profiling_data = 8;
  // DEPRECATED - this field was never used in production.
  // optional ClearUserDataResponse clear_user_data = 9;
  optional GetUpdatesMetadataResponse stream_metadata = 10;
  // If GetUpdatesStreamingResponse is contained in the ClientToServerResponse,
  // none of the other fields (error_code and etc) will be set.
  optional GetUpdatesStreamingResponse stream_data = 11;

  // The data types whose storage has been migrated.  Present when the value of
  // error_code is MIGRATION_DONE.
  repeated int32 migrated_data_type_id = 12;

  message Error {
    optional SyncEnums.ErrorType error_type = 1 [default = UNKNOWN];
    optional string error_description       = 2;
    optional string url                     = 3;
    optional SyncEnums.Action action        = 4 [default = UNKNOWN_ACTION];

    // Currently only meaningful if |error_type| is throttled. If this field
    // is absent then the whole client (all datatypes) is throttled.
    repeated int32 error_data_type_ids = 5;
  }
  optional Error error = 13;

  // The new per-client state for this client. If set, should be persisted and
  // sent with any subsequent ClientToServerMessages.
  optional ChipBag new_bag_of_chips = 14;
};