Add m-esr52 at 52.6.0

1 files changed, 782 insertions, 0 deletions

diff --git a/services/sync/modules/engines/clients.js b/services/sync/modules/engines/clients.js
new file mode 100644
index 000000000..3dd679570
--- /dev/null
+++ b/services/sync/modules/engines/clients.js
@@ -0,0 +1,782 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * How does the clients engine work?
+ *
+ * - We use 2 files - commands.json and commands-syncing.json.
+ *
+ * - At sync upload time, we attempt a rename of commands.json to
+ *   commands-syncing.json, and ignore errors (helps for crash during sync!).
+ * - We load commands-syncing.json and stash the contents in
+ *   _currentlySyncingCommands which lives for the duration of the upload process.
+ * - We use _currentlySyncingCommands to build the outgoing records
+ * - Immediately after successful upload, we delete commands-syncing.json from
+ *   disk (and clear _currentlySyncingCommands). We reconcile our local records
+ *   with what we just wrote in the server, and add failed IDs commands
+ *   back in commands.json
+ * - Any time we need to "save" a command for future syncs, we load
+ *   commands.json, update it, and write it back out.
+ */
+
+this.EXPORTED_SYMBOLS = [
+  "ClientEngine",
+  "ClientsRec"
+];
+
+var {classes: Cc, interfaces: Ci, utils: Cu} = Components;
+
+Cu.import("resource://services-common/async.js");
+Cu.import("resource://services-common/stringbundle.js");
+Cu.import("resource://services-sync/constants.js");
+Cu.import("resource://services-sync/engines.js");
+Cu.import("resource://services-sync/record.js");
+Cu.import("resource://services-sync/resource.js");
+Cu.import("resource://services-sync/util.js");
+Cu.import("resource://gre/modules/Services.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "fxAccounts",
+  "resource://gre/modules/FxAccounts.jsm");
+
+const CLIENTS_TTL = 1814400; // 21 days
+const CLIENTS_TTL_REFRESH = 604800; // 7 days
+const STALE_CLIENT_REMOTE_AGE = 604800; // 7 days
+
+const SUPPORTED_PROTOCOL_VERSIONS = ["1.1", "1.5"];
+
+function hasDupeCommand(commands, action) {
+  if (!commands) {
+    return false;
+  }
+  return commands.some(other => other.command == action.command &&
+    Utils.deepEquals(other.args, action.args));
+}
+
+this.ClientsRec = function ClientsRec(collection, id) {
+  CryptoWrapper.call(this, collection, id);
+}
+ClientsRec.prototype = {
+  __proto__: CryptoWrapper.prototype,
+  _logName: "Sync.Record.Clients",
+  ttl: CLIENTS_TTL
+};
+
+Utils.deferGetSet(ClientsRec,
+                  "cleartext",
+                  ["name", "type", "commands",
+                   "version", "protocols",
+                   "formfactor", "os", "appPackage", "application", "device",
+                   "fxaDeviceId"]);
+
+
+this.ClientEngine = function ClientEngine(service) {
+  SyncEngine.call(this, "Clients", service);
+
+  // Reset the last sync timestamp on every startup so that we fetch all clients
+  this.resetLastSync();
+}
+ClientEngine.prototype = {
+  __proto__: SyncEngine.prototype,
+  _storeObj: ClientStore,
+  _recordObj: ClientsRec,
+  _trackerObj: ClientsTracker,
+  allowSkippedRecord: false,
+
+  // Always sync client data as it controls other sync behavior
+  get enabled() {
+    return true;
+  },
+
+  get lastRecordUpload() {
+    return Svc.Prefs.get(this.name + ".lastRecordUpload", 0);
+  },
+  set lastRecordUpload(value) {
+    Svc.Prefs.set(this.name + ".lastRecordUpload", Math.floor(value));
+  },
+
+  get remoteClients() {
+    // return all non-stale clients for external consumption.
+    return Object.values(this._store._remoteClients).filter(v => !v.stale);
+  },
+
+  remoteClientExists(id) {
+    let client = this._store._remoteClients[id];
+    return !!(client && !client.stale);
+  },
+
+  // Aggregate some stats on the composition of clients on this account
+  get stats() {
+    let stats = {
+      hasMobile: this.localType == DEVICE_TYPE_MOBILE,
+      names: [this.localName],
+      numClients: 1,
+    };
+
+    for (let id in this._store._remoteClients) {
+      let {name, type, stale} = this._store._remoteClients[id];
+      if (!stale) {
+        stats.hasMobile = stats.hasMobile || type == DEVICE_TYPE_MOBILE;
+        stats.names.push(name);
+        stats.numClients++;
+      }
+    }
+
+    return stats;
+  },
+
+  /**
+   * Obtain information about device types.
+   *
+   * Returns a Map of device types to integer counts.
+   */
+  get deviceTypes() {
+    let counts = new Map();
+
+    counts.set(this.localType, 1);
+
+    for (let id in this._store._remoteClients) {
+      let record = this._store._remoteClients[id];
+      if (record.stale) {
+        continue; // pretend "stale" records don't exist.
+      }
+      let type = record.type;
+      if (!counts.has(type)) {
+        counts.set(type, 0);
+      }
+
+      counts.set(type, counts.get(type) + 1);
+    }
+
+    return counts;
+  },
+
+  get localID() {
+    // Generate a random GUID id we don't have one
+    let localID = Svc.Prefs.get("client.GUID", "");
+    return localID == "" ? this.localID = Utils.makeGUID() : localID;
+  },
+  set localID(value) {
+    Svc.Prefs.set("client.GUID", value);
+  },
+
+  get brandName() {
+    let brand = new StringBundle("chrome://branding/locale/brand.properties");
+    return brand.get("brandShortName");
+  },
+
+  get localName() {
+    let name = Utils.getDeviceName();
+    // If `getDeviceName` returns the default name, set the pref. FxA registers
+    // the device before syncing, so we don't need to update the registration
+    // in this case.
+    Svc.Prefs.set("client.name", name);
+    return name;
+  },
+  set localName(value) {
+    Svc.Prefs.set("client.name", value);
+    // Update the registration in the background.
+    fxAccounts.updateDeviceRegistration().catch(error => {
+      this._log.warn("failed to update fxa device registration", error);
+    });
+  },
+
+  get localType() {
+    return Utils.getDeviceType();
+  },
+  set localType(value) {
+    Svc.Prefs.set("client.type", value);
+  },
+
+  getClientName(id) {
+    if (id == this.localID) {
+      return this.localName;
+    }
+    let client = this._store._remoteClients[id];
+    return client ? client.name : "";
+  },
+
+  getClientFxaDeviceId(id) {
+    if (this._store._remoteClients[id]) {
+      return this._store._remoteClients[id].fxaDeviceId;
+    }
+    return null;
+  },
+
+  isMobile: function isMobile(id) {
+    if (this._store._remoteClients[id])
+      return this._store._remoteClients[id].type == DEVICE_TYPE_MOBILE;
+    return false;
+  },
+
+  _readCommands() {
+    let cb = Async.makeSpinningCallback();
+    Utils.jsonLoad("commands", this, commands => cb(null, commands));
+    return cb.wait() || {};
+  },
+
+  /**
+   * Low level function, do not use directly (use _addClientCommand instead).
+   */
+  _saveCommands(commands) {
+    let cb = Async.makeSpinningCallback();
+    Utils.jsonSave("commands", this, commands, error => {
+      if (error) {
+        this._log.error("Failed to save JSON outgoing commands", error);
+      }
+      cb();
+    });
+    cb.wait();
+  },
+
+  _prepareCommandsForUpload() {
+    let cb = Async.makeSpinningCallback();
+    Utils.jsonMove("commands", "commands-syncing", this).catch(() => {}) // Ignore errors
+      .then(() => {
+        Utils.jsonLoad("commands-syncing", this, commands => cb(null, commands));
+      });
+    return cb.wait() || {};
+  },
+
+  _deleteUploadedCommands() {
+    delete this._currentlySyncingCommands;
+    Async.promiseSpinningly(
+      Utils.jsonRemove("commands-syncing", this).catch(err => {
+        this._log.error("Failed to delete syncing-commands file", err);
+      })
+    );
+  },
+
+  _addClientCommand(clientId, command) {
+    const allCommands = this._readCommands();
+    const clientCommands = allCommands[clientId] || [];
+    if (hasDupeCommand(clientCommands, command)) {
+      return;
+    }
+    allCommands[clientId] = clientCommands.concat(command);
+    this._saveCommands(allCommands);
+  },
+
+  _syncStartup: function _syncStartup() {
+    // Reupload new client record periodically.
+    if (Date.now() / 1000 - this.lastRecordUpload > CLIENTS_TTL_REFRESH) {
+      this._tracker.addChangedID(this.localID);
+      this.lastRecordUpload = Date.now() / 1000;
+    }
+    SyncEngine.prototype._syncStartup.call(this);
+  },
+
+  _processIncoming() {
+    // Fetch all records from the server.
+    this.lastSync = 0;
+    this._incomingClients = {};
+    try {
+      SyncEngine.prototype._processIncoming.call(this);
+      // Since clients are synced unconditionally, any records in the local store
+      // that don't exist on the server must be for disconnected clients. Remove
+      // them, so that we don't upload records with commands for clients that will
+      // never see them. We also do this to filter out stale clients from the
+      // tabs collection, since showing their list of tabs is confusing.
+      for (let id in this._store._remoteClients) {
+        if (!this._incomingClients[id]) {
+          this._log.info(`Removing local state for deleted client ${id}`);
+          this._removeRemoteClient(id);
+        }
+      }
+      // Bug 1264498: Mobile clients don't remove themselves from the clients
+      // collection when the user disconnects Sync, so we mark as stale clients
+      // with the same name that haven't synced in over a week.
+      // (Note we can't simply delete them, or we re-apply them next sync - see
+      // bug 1287687)
+      delete this._incomingClients[this.localID];
+      let names = new Set([this.localName]);
+      for (let id in this._incomingClients) {
+        let record = this._store._remoteClients[id];
+        if (!names.has(record.name)) {
+          names.add(record.name);
+          continue;
+        }
+        let remoteAge = AsyncResource.serverTime - this._incomingClients[id];
+        if (remoteAge > STALE_CLIENT_REMOTE_AGE) {
+          this._log.info(`Hiding stale client ${id} with age ${remoteAge}`);
+          record.stale = true;
+        }
+      }
+    } finally {
+      this._incomingClients = null;
+    }
+  },
+
+  _uploadOutgoing() {
+    this._currentlySyncingCommands = this._prepareCommandsForUpload();
+    const clientWithPendingCommands = Object.keys(this._currentlySyncingCommands);
+    for (let clientId of clientWithPendingCommands) {
+      if (this._store._remoteClients[clientId] || this.localID == clientId) {
+        this._modified.set(clientId, 0);
+      }
+    }
+    SyncEngine.prototype._uploadOutgoing.call(this);
+  },
+
+  _onRecordsWritten(succeeded, failed) {
+    // Reconcile the status of the local records with what we just wrote on the
+    // server
+    for (let id of succeeded) {
+      const commandChanges = this._currentlySyncingCommands[id];
+      if (id == this.localID) {
+        if (this.localCommands) {
+          this.localCommands = this.localCommands.filter(command => !hasDupeCommand(commandChanges, command));
+        }
+      } else {
+        const clientRecord = this._store._remoteClients[id];
+        if (!commandChanges || !clientRecord) {
+          // should be impossible, else we wouldn't have been writing it.
+          this._log.warn("No command/No record changes for a client we uploaded");
+          continue;
+        }
+        // fixup the client record, so our copy of _remoteClients matches what we uploaded.
+        clientRecord.commands = this._store.createRecord(id);
+        // we could do better and pass the reference to the record we just uploaded,
+        // but this will do for now
+      }
+    }
+
+    // Re-add failed commands
+    for (let id of failed) {
+      const commandChanges = this._currentlySyncingCommands[id];
+      if (!commandChanges) {
+        continue;
+      }
+      this._addClientCommand(id, commandChanges);
+    }
+
+    this._deleteUploadedCommands();
+
+    // Notify other devices that their own client collection changed
+    const idsToNotify = succeeded.reduce((acc, id) => {
+      if (id == this.localID) {
+        return acc;
+      }
+      const fxaDeviceId = this.getClientFxaDeviceId(id);
+      return fxaDeviceId ? acc.concat(fxaDeviceId) : acc;
+    }, []);
+    if (idsToNotify.length > 0) {
+      this._notifyCollectionChanged(idsToNotify);
+    }
+  },
+
+  _notifyCollectionChanged(ids) {
+    const message = {
+      version: 1,
+      command: "sync:collection_changed",
+      data: {
+        collections: ["clients"]
+      }
+    };
+    fxAccounts.notifyDevices(ids, message, NOTIFY_TAB_SENT_TTL_SECS);
+  },
+
+  _syncFinish() {
+    // Record histograms for our device types, and also write them to a pref
+    // so non-histogram telemetry (eg, UITelemetry) has easy access to them.
+    for (let [deviceType, count] of this.deviceTypes) {
+      let hid;
+      let prefName = this.name + ".devices.";
+      switch (deviceType) {
+        case "desktop":
+          hid = "WEAVE_DEVICE_COUNT_DESKTOP";
+          prefName += "desktop";
+          break;
+        case "mobile":
+          hid = "WEAVE_DEVICE_COUNT_MOBILE";
+          prefName += "mobile";
+          break;
+        default:
+          this._log.warn(`Unexpected deviceType "${deviceType}" recording device telemetry.`);
+          continue;
+      }
+      Services.telemetry.getHistogramById(hid).add(count);
+      Svc.Prefs.set(prefName, count);
+    }
+    SyncEngine.prototype._syncFinish.call(this);
+  },
+
+  _reconcile: function _reconcile(item) {
+    // Every incoming record is reconciled, so we use this to track the
+    // contents of the collection on the server.
+    this._incomingClients[item.id] = item.modified;
+
+    if (!this._store.itemExists(item.id)) {
+      return true;
+    }
+    // Clients are synced unconditionally, so we'll always have new records.
+    // Unfortunately, this will cause the scheduler to use the immediate sync
+    // interval for the multi-device case, instead of the active interval. We
+    // work around this by updating the record during reconciliation, and
+    // returning false to indicate that the record doesn't need to be applied
+    // later.
+    this._store.update(item);
+    return false;
+  },
+
+  // Treat reset the same as wiping for locally cached clients
+  _resetClient() {
+    this._wipeClient();
+  },
+
+  _wipeClient: function _wipeClient() {
+    SyncEngine.prototype._resetClient.call(this);
+    delete this.localCommands;
+    this._store.wipe();
+    const logRemoveError = err => this._log.warn("Could not delete json file", err);
+    Async.promiseSpinningly(
+      Utils.jsonRemove("commands", this).catch(logRemoveError)
+        .then(Utils.jsonRemove("commands-syncing", this).catch(logRemoveError))
+    );
+  },
+
+  removeClientData: function removeClientData() {
+    let res = this.service.resource(this.engineURL + "/" + this.localID);
+    res.delete();
+  },
+
+  // Override the default behavior to delete bad records from the server.
+  handleHMACMismatch: function handleHMACMismatch(item, mayRetry) {
+    this._log.debug("Handling HMAC mismatch for " + item.id);
+
+    let base = SyncEngine.prototype.handleHMACMismatch.call(this, item, mayRetry);
+    if (base != SyncEngine.kRecoveryStrategy.error)
+      return base;
+
+    // It's a bad client record. Save it to be deleted at the end of the sync.
+    this._log.debug("Bad client record detected. Scheduling for deletion.");
+    this._deleteId(item.id);
+
+    // Neither try again nor error; we're going to delete it.
+    return SyncEngine.kRecoveryStrategy.ignore;
+  },
+
+  /**
+   * A hash of valid commands that the client knows about. The key is a command
+   * and the value is a hash containing information about the command such as
+   * number of arguments and description.
+   */
+  _commands: {
+    resetAll:    { args: 0, desc: "Clear temporary local data for all engines" },
+    resetEngine: { args: 1, desc: "Clear temporary local data for engine" },
+    wipeAll:     { args: 0, desc: "Delete all client data for all engines" },
+    wipeEngine:  { args: 1, desc: "Delete all client data for engine" },
+    logout:      { args: 0, desc: "Log out client" },
+    displayURI:  { args: 3, desc: "Instruct a client to display a URI" },
+  },
+
+  /**
+   * Sends a command+args pair to a specific client.
+   *
+   * @param command Command string
+   * @param args Array of arguments/data for command
+   * @param clientId Client to send command to
+   */
+  _sendCommandToClient: function sendCommandToClient(command, args, clientId) {
+    this._log.trace("Sending " + command + " to " + clientId);
+
+    let client = this._store._remoteClients[clientId];
+    if (!client) {
+      throw new Error("Unknown remote client ID: '" + clientId + "'.");
+    }
+    if (client.stale) {
+      throw new Error("Stale remote client ID: '" + clientId + "'.");
+    }
+
+    let action = {
+      command: command,
+      args: args,
+    };
+
+    this._log.trace("Client " + clientId + " got a new action: " + [command, args]);
+    this._addClientCommand(clientId, action);
+    this._tracker.addChangedID(clientId);
+  },
+
+  /**
+   * Check if the local client has any remote commands and perform them.
+   *
+   * @return false to abort sync
+   */
+  processIncomingCommands: function processIncomingCommands() {
+    return this._notify("clients:process-commands", "", function() {
+      if (!this.localCommands) {
+        return true;
+      }
+
+      const clearedCommands = this._readCommands()[this.localID];
+      const commands = this.localCommands.filter(command => !hasDupeCommand(clearedCommands, command));
+
+      let URIsToDisplay = [];
+      // Process each command in order.
+      for (let rawCommand of commands) {
+        let {command, args} = rawCommand;
+        this._log.debug("Processing command: " + command + "(" + args + ")");
+
+        let engines = [args[0]];
+        switch (command) {
+          case "resetAll":
+            engines = null;
+            // Fallthrough
+          case "resetEngine":
+            this.service.resetClient(engines);
+            break;
+          case "wipeAll":
+            engines = null;
+            // Fallthrough
+          case "wipeEngine":
+            this.service.wipeClient(engines);
+            break;
+          case "logout":
+            this.service.logout();
+            return false;
+          case "displayURI":
+            let [uri, clientId, title] = args;
+            URIsToDisplay.push({ uri, clientId, title });
+            break;
+          default:
+            this._log.debug("Received an unknown command: " + command);
+            break;
+        }
+        // Add the command to the "cleared" commands list
+        this._addClientCommand(this.localID, rawCommand)
+      }
+      this._tracker.addChangedID(this.localID);
+
+      if (URIsToDisplay.length) {
+        this._handleDisplayURIs(URIsToDisplay);
+      }
+
+      return true;
+    })();
+  },
+
+  /**
+   * Validates and sends a command to a client or all clients.
+   *
+   * Calling this does not actually sync the command data to the server. If the
+   * client already has the command/args pair, it won't receive a duplicate
+   * command.
+   *
+   * @param command
+   *        Command to invoke on remote clients
+   * @param args
+   *        Array of arguments to give to the command
+   * @param clientId
+   *        Client ID to send command to. If undefined, send to all remote
+   *        clients.
+   */
+  sendCommand: function sendCommand(command, args, clientId) {
+    let commandData = this._commands[command];
+    // Don't send commands that we don't know about.
+    if (!commandData) {
+      this._log.error("Unknown command to send: " + command);
+      return;
+    }
+    // Don't send a command with the wrong number of arguments.
+    else if (!args || args.length != commandData.args) {
+      this._log.error("Expected " + commandData.args + " args for '" +
+                      command + "', but got " + args);
+      return;
+    }
+
+    if (clientId) {
+      this._sendCommandToClient(command, args, clientId);
+    } else {
+      for (let [id, record] of Object.entries(this._store._remoteClients)) {
+        if (!record.stale) {
+          this._sendCommandToClient(command, args, id);
+        }
+      }
+    }
+  },
+
+  /**
+   * Send a URI to another client for display.
+   *
+   * A side effect is the score is increased dramatically to incur an
+   * immediate sync.
+   *
+   * If an unknown client ID is specified, sendCommand() will throw an
+   * Error object.
+   *
+   * @param uri
+   *        URI (as a string) to send and display on the remote client
+   * @param clientId
+   *        ID of client to send the command to. If not defined, will be sent
+   *        to all remote clients.
+   * @param title
+   *        Title of the page being sent.
+   */
+  sendURIToClientForDisplay: function sendURIToClientForDisplay(uri, clientId, title) {
+    this._log.info("Sending URI to client: " + uri + " -> " +
+                   clientId + " (" + title + ")");
+    this.sendCommand("displayURI", [uri, this.localID, title], clientId);
+
+    this._tracker.score += SCORE_INCREMENT_XLARGE;
+  },
+
+  /**
+   * Handle a bunch of received 'displayURI' commands.
+   *
+   * Interested parties should observe the "weave:engine:clients:display-uris"
+   * topic. The callback will receive an array as the subject parameter
+   * containing objects with the following keys:
+   *
+   *   uri       URI (string) that is requested for display.
+   *   clientId  ID of client that sent the command.
+   *   title     Title of page that loaded URI (likely) corresponds to.
+   *
+   * The 'data' parameter to the callback will not be defined.
+   *
+   * @param uris
+   *        An array containing URI objects to display
+   * @param uris[].uri
+   *        String URI that was received
+   * @param uris[].clientId
+   *        ID of client that sent URI
+   * @param uris[].title
+   *        String title of page that URI corresponds to. Older clients may not
+   *        send this.
+   */
+  _handleDisplayURIs: function _handleDisplayURIs(uris) {
+    Svc.Obs.notify("weave:engine:clients:display-uris", uris);
+  },
+
+  _removeRemoteClient(id) {
+    delete this._store._remoteClients[id];
+    this._tracker.removeChangedID(id);
+  },
+};
+
+function ClientStore(name, engine) {
+  Store.call(this, name, engine);
+}
+ClientStore.prototype = {
+  __proto__: Store.prototype,
+
+  _remoteClients: {},
+
+  create(record) {
+    this.update(record);
+  },
+
+  update: function update(record) {
+    if (record.id == this.engine.localID) {
+      // Only grab commands from the server; local name/type always wins
+      this.engine.localCommands = record.commands;
+    } else {
+      this._remoteClients[record.id] = record.cleartext;
+    }
+  },
+
+  createRecord: function createRecord(id, collection) {
+    let record = new ClientsRec(collection, id);
+
+    const commandsChanges = this.engine._currentlySyncingCommands ?
+                            this.engine._currentlySyncingCommands[id] :
+                            [];
+
+    // Package the individual components into a record for the local client
+    if (id == this.engine.localID) {
+      let cb = Async.makeSpinningCallback();
+      fxAccounts.getDeviceId().then(id => cb(null, id), cb);
+      try {
+        record.fxaDeviceId = cb.wait();
+      } catch(error) {
+        this._log.warn("failed to get fxa device id", error);
+      }
+      record.name = this.engine.localName;
+      record.type = this.engine.localType;
+      record.version = Services.appinfo.version;
+      record.protocols = SUPPORTED_PROTOCOL_VERSIONS;
+
+      // Substract the commands we recorded that we've already executed
+      if (commandsChanges && commandsChanges.length &&
+          this.engine.localCommands && this.engine.localCommands.length) {
+        record.commands = this.engine.localCommands.filter(command => !hasDupeCommand(commandsChanges, command));
+      }
+
+      // Optional fields.
+      record.os = Services.appinfo.OS;             // "Darwin"
+      record.appPackage = Services.appinfo.ID;
+      record.application = this.engine.brandName   // "Nightly"
+
+      // We can't compute these yet.
+      // record.device = "";            // Bug 1100723
+      // record.formfactor = "";        // Bug 1100722
+    } else {
+      record.cleartext = this._remoteClients[id];
+
+      // Add the commands we have to send
+      if (commandsChanges && commandsChanges.length) {
+        const recordCommands = record.cleartext.commands || [];
+        const newCommands = commandsChanges.filter(command => !hasDupeCommand(recordCommands, command));
+        record.cleartext.commands = recordCommands.concat(newCommands);
+      }
+
+      if (record.cleartext.stale) {
+        // It's almost certainly a logic error for us to upload a record we
+        // consider stale, so make log noise, but still remove the flag.
+        this._log.error(`Preparing to upload record ${id} that we consider stale`);
+        delete record.cleartext.stale;
+      }
+    }
+
+    return record;
+  },
+
+  itemExists(id) {
+    return id in this.getAllIDs();
+  },
+
+  getAllIDs: function getAllIDs() {
+    let ids = {};
+    ids[this.engine.localID] = true;
+    for (let id in this._remoteClients)
+      ids[id] = true;
+    return ids;
+  },
+
+  wipe: function wipe() {
+    this._remoteClients = {};
+  },
+};
+
+function ClientsTracker(name, engine) {
+  Tracker.call(this, name, engine);
+  Svc.Obs.add("weave:engine:start-tracking", this);
+  Svc.Obs.add("weave:engine:stop-tracking", this);
+}
+ClientsTracker.prototype = {
+  __proto__: Tracker.prototype,
+
+  _enabled: false,
+
+  observe: function observe(subject, topic, data) {
+    switch (topic) {
+      case "weave:engine:start-tracking":
+        if (!this._enabled) {
+          Svc.Prefs.observe("client.name", this);
+          this._enabled = true;
+        }
+        break;
+      case "weave:engine:stop-tracking":
+        if (this._enabled) {
+          Svc.Prefs.ignore("client.name", this);
+          this._enabled = false;
+        }
+        break;
+      case "nsPref:changed":
+        this._log.debug("client.name preference changed");
+        this.addChangedID(Svc.Prefs.get("client.GUID"));
+        this.score += SCORE_INCREMENT_XLARGE;
+        break;
+    }
+  }
+};