gecko-dev/toolkit/components/telemetry/TelemetrySession.jsm

/* -*- js-indent-level: 2; indent-tabs-mode: nil -*- */
/* 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/. */

"use strict";

const Cc = Components.classes;
const Ci = Components.interfaces;
const Cr = Components.results;
const Cu = Components.utils;

Cu.import("resource://gre/modules/debug.js", this);
Cu.import("resource://gre/modules/Log.jsm");
Cu.import("resource://gre/modules/Services.jsm", this);
Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
Cu.import("resource://gre/modules/Promise.jsm", this);
Cu.import("resource://gre/modules/DeferredTask.jsm", this);
Cu.import("resource://gre/modules/Preferences.jsm");
Cu.import("resource://gre/modules/Task.jsm");
Cu.import("resource://gre/modules/Timer.jsm");
Cu.import("resource://gre/modules/TelemetrySend.jsm", this);
Cu.import("resource://gre/modules/TelemetryUtils.jsm", this);
Cu.import("resource://gre/modules/AppConstants.jsm");

const Utils = TelemetryUtils;

const myScope = this;

// When modifying the payload in incompatible ways, please bump this version number
const PAYLOAD_VERSION = 4;
const PING_TYPE_MAIN = "main";
const PING_TYPE_SAVED_SESSION = "saved-session";

const REASON_ABORTED_SESSION = "aborted-session";
const REASON_DAILY = "daily";
const REASON_SAVED_SESSION = "saved-session";
const REASON_GATHER_PAYLOAD = "gather-payload";
const REASON_GATHER_SUBSESSION_PAYLOAD = "gather-subsession-payload";
const REASON_TEST_PING = "test-ping";
const REASON_ENVIRONMENT_CHANGE = "environment-change";
const REASON_SHUTDOWN = "shutdown";

const ENVIRONMENT_CHANGE_LISTENER = "TelemetrySession::onEnvironmentChange";

const MS_IN_ONE_HOUR  = 60 * 60 * 1000;
const MIN_SUBSESSION_LENGTH_MS = Preferences.get("toolkit.telemetry.minSubsessionLength", 10 * 60) * 1000;

const LOGGER_NAME = "Toolkit.Telemetry";
const LOGGER_PREFIX = "TelemetrySession" + (Utils.isContentProcess ? "#content::" : "::");

const PREF_BRANCH = "toolkit.telemetry.";
const PREF_PREVIOUS_BUILDID = PREF_BRANCH + "previousBuildID";
const PREF_FHR_UPLOAD_ENABLED = "datareporting.healthreport.uploadEnabled";
const PREF_ASYNC_PLUGIN_INIT = "dom.ipc.plugins.asyncInit.enabled";
const PREF_UNIFIED = PREF_BRANCH + "unified";


const MESSAGE_TELEMETRY_PAYLOAD = "Telemetry:Payload";
const MESSAGE_TELEMETRY_GET_CHILD_PAYLOAD = "Telemetry:GetChildPayload";
const MESSAGE_TELEMETRY_THREAD_HANGS = "Telemetry:ChildThreadHangs";
const MESSAGE_TELEMETRY_GET_CHILD_THREAD_HANGS = "Telemetry:GetChildThreadHangs";
const MESSAGE_TELEMETRY_USS = "Telemetry:USS";
const MESSAGE_TELEMETRY_GET_CHILD_USS = "Telemetry:GetChildUSS";

const DATAREPORTING_DIRECTORY = "datareporting";
const ABORTED_SESSION_FILE_NAME = "aborted-session-ping";

// Whether the FHR/Telemetry unification features are enabled.
// Changing this pref requires a restart.
const IS_UNIFIED_TELEMETRY = Preferences.get(PREF_UNIFIED, false);

// Maximum number of content payloads that we are willing to store.
const MAX_NUM_CONTENT_PAYLOADS = 10;

// Do not gather data more than once a minute (ms)
const TELEMETRY_INTERVAL = 60 * 1000;
// Delay before intializing telemetry (ms)
const TELEMETRY_DELAY = Preferences.get("toolkit.telemetry.initDelay", 60) * 1000;
// Delay before initializing telemetry if we're testing (ms)
const TELEMETRY_TEST_DELAY = 1;
// Execute a scheduler tick every 5 minutes.
const SCHEDULER_TICK_INTERVAL_MS = Preferences.get("toolkit.telemetry.scheduler.tickInterval", 5 * 60) * 1000;
// When user is idle, execute a scheduler tick every 60 minutes.
const SCHEDULER_TICK_IDLE_INTERVAL_MS = Preferences.get("toolkit.telemetry.scheduler.idleTickInterval", 60 * 60) * 1000;

// The tolerance we have when checking if it's midnight (15 minutes).
const SCHEDULER_MIDNIGHT_TOLERANCE_MS = 15 * 60 * 1000;

// Seconds of idle time before pinging.
// On idle-daily a gather-telemetry notification is fired, during it probes can
// start asynchronous tasks to gather data.
const IDLE_TIMEOUT_SECONDS = Preferences.get("toolkit.telemetry.idleTimeout", 5 * 60);

// The frequency at which we persist session data to the disk to prevent data loss
// in case of aborted sessions (currently 5 minutes).
const ABORTED_SESSION_UPDATE_INTERVAL_MS = 5 * 60 * 1000;

const TOPIC_CYCLE_COLLECTOR_BEGIN = "cycle-collector-begin";

// How long to wait in millis for all the child memory reports to come in
const TOTAL_MEMORY_COLLECTOR_TIMEOUT = 200;

var gLastMemoryPoll = null;

var gWasDebuggerAttached = false;

XPCOMUtils.defineLazyServiceGetter(this, "Telemetry",
                                   "@mozilla.org/base/telemetry;1",
                                   "nsITelemetry");
XPCOMUtils.defineLazyServiceGetter(this, "idleService",
                                   "@mozilla.org/widget/idleservice;1",
                                   "nsIIdleService");
XPCOMUtils.defineLazyServiceGetter(this, "cpmm",
                                   "@mozilla.org/childprocessmessagemanager;1",
                                   "nsIMessageSender");
XPCOMUtils.defineLazyServiceGetter(this, "cpml",
                                   "@mozilla.org/childprocessmessagemanager;1",
                                   "nsIMessageListenerManager");
XPCOMUtils.defineLazyServiceGetter(this, "ppmm",
                                   "@mozilla.org/parentprocessmessagemanager;1",
                                   "nsIMessageBroadcaster");
XPCOMUtils.defineLazyServiceGetter(this, "ppml",
                                   "@mozilla.org/parentprocessmessagemanager;1",
                                   "nsIMessageListenerManager");

XPCOMUtils.defineLazyModuleGetter(this, "AddonManagerPrivate",
                                  "resource://gre/modules/AddonManager.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "AsyncShutdown",
                                  "resource://gre/modules/AsyncShutdown.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "TelemetryController",
                                  "resource://gre/modules/TelemetryController.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "TelemetryStorage",
                                  "resource://gre/modules/TelemetryStorage.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "TelemetryLog",
                                  "resource://gre/modules/TelemetryLog.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "ThirdPartyCookieProbe",
                                  "resource://gre/modules/ThirdPartyCookieProbe.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "UITelemetry",
                                  "resource://gre/modules/UITelemetry.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "TelemetryEnvironment",
                                  "resource://gre/modules/TelemetryEnvironment.jsm");

function generateUUID() {
  let str = Cc["@mozilla.org/uuid-generator;1"].getService(Ci.nsIUUIDGenerator).generateUUID().toString();
  // strip {}
  return str.substring(1, str.length - 1);
}

function getMsSinceProcessStart() {
  try {
    return Telemetry.msSinceProcessStart();
  } catch (ex) {
    // If this fails return a special value.
    return -1;
  }
}

/**
 * This is a policy object used to override behavior for testing.
 */
var Policy = {
  now: () => new Date(),
  monotonicNow: getMsSinceProcessStart,
  generateSessionUUID: () => generateUUID(),
  generateSubsessionUUID: () => generateUUID(),
  setSchedulerTickTimeout: (callback, delayMs) => setTimeout(callback, delayMs),
  clearSchedulerTickTimeout: id => clearTimeout(id),
};

/**
 * Get the ping type based on the payload.
 * @param {Object} aPayload The ping payload.
 * @return {String} A string representing the ping type.
 */
function getPingType(aPayload) {
  // To remain consistent with server-side ping handling, set "saved-session" as the ping
  // type for "saved-session" payload reasons.
  if (aPayload.info.reason == REASON_SAVED_SESSION) {
    return PING_TYPE_SAVED_SESSION;
  }

  return PING_TYPE_MAIN;
}

/**
 * Annotate the current session ID with the crash reporter to map potential
 * crash pings with the related main ping.
 */
function annotateCrashReport(sessionId) {
  try {
    const cr = Cc["@mozilla.org/toolkit/crash-reporter;1"];
    if (cr) {
      cr.getService(Ci.nsICrashReporter).setTelemetrySessionId(sessionId);
    }
  } catch (e) {
    // Ignore errors when crash reporting is disabled
  }
}

/**
 * Read current process I/O counters.
 */
var processInfo = {
  _initialized: false,
  _IO_COUNTERS: null,
  _kernel32: null,
  _GetProcessIoCounters: null,
  _GetCurrentProcess: null,
  getCounters: function() {
    let isWindows = ("@mozilla.org/windows-registry-key;1" in Components.classes);
    if (isWindows)
      return this.getCounters_Windows();
    return null;
  },
  getCounters_Windows: function() {
    if (!this._initialized){
      Cu.import("resource://gre/modules/ctypes.jsm");
      this._IO_COUNTERS = new ctypes.StructType("IO_COUNTERS", [
        {'readOps': ctypes.unsigned_long_long},
        {'writeOps': ctypes.unsigned_long_long},
        {'otherOps': ctypes.unsigned_long_long},
        {'readBytes': ctypes.unsigned_long_long},
        {'writeBytes': ctypes.unsigned_long_long},
        {'otherBytes': ctypes.unsigned_long_long} ]);
      try {
        this._kernel32 = ctypes.open("Kernel32.dll");
        this._GetProcessIoCounters = this._kernel32.declare("GetProcessIoCounters",
          ctypes.winapi_abi,
          ctypes.bool, // return
          ctypes.voidptr_t, // hProcess
          this._IO_COUNTERS.ptr); // lpIoCounters
        this._GetCurrentProcess = this._kernel32.declare("GetCurrentProcess",
          ctypes.winapi_abi,
          ctypes.voidptr_t); // return
        this._initialized = true;
      } catch (err) {
        return null;
      }
    }
    let io = new this._IO_COUNTERS();
    if(!this._GetProcessIoCounters(this._GetCurrentProcess(), io.address()))
      return null;
    return [parseInt(io.readBytes), parseInt(io.writeBytes)];
  }
};

/**
 * TelemetryScheduler contains a single timer driving all regularly-scheduled
 * Telemetry related jobs. Having a single place with this logic simplifies
 * reasoning about scheduling actions in a single place, making it easier to
 * coordinate jobs and coalesce them.
 */
var TelemetryScheduler = {
  _lastDailyPingTime: 0,
  _lastSessionCheckpointTime: 0,

  // For sanity checking.
  _lastAdhocPingTime: 0,
  _lastTickTime: 0,

  _log: null,

  // The timer which drives the scheduler.
  _schedulerTimer: null,
  // The interval used by the scheduler timer.
  _schedulerInterval: 0,
  _shuttingDown: true,
  _isUserIdle: false,

  /**
   * Initialises the scheduler and schedules the first daily/aborted session pings.
   */
  init: function() {
    this._log = Log.repository.getLoggerWithMessagePrefix(LOGGER_NAME, "TelemetryScheduler::");
    this._log.trace("init");
    this._shuttingDown = false;
    this._isUserIdle = false;

    // Initialize the last daily ping and aborted session last due times to the current time.
    // Otherwise, we might end up sending daily pings even if the subsession is not long enough.
    let now = Policy.now();
    this._lastDailyPingTime = now.getTime();
    this._lastSessionCheckpointTime = now.getTime();
    this._rescheduleTimeout();

    idleService.addIdleObserver(this, IDLE_TIMEOUT_SECONDS);
    Services.obs.addObserver(this, "wake_notification", false);
  },

  /**
   * Stops the scheduler.
   */
  shutdown: function() {
    if (this._shuttingDown) {
      if (this._log) {
        this._log.error("shutdown - Already shut down");
      } else {
        Cu.reportError("TelemetryScheduler.shutdown - Already shut down");
      }
      return;
    }

    this._log.trace("shutdown");
    if (this._schedulerTimer) {
      Policy.clearSchedulerTickTimeout(this._schedulerTimer);
      this._schedulerTimer = null;
    }

    idleService.removeIdleObserver(this, IDLE_TIMEOUT_SECONDS);
    Services.obs.removeObserver(this, "wake_notification");

    this._shuttingDown = true;
  },

  _clearTimeout: function() {
    if (this._schedulerTimer) {
      Policy.clearSchedulerTickTimeout(this._schedulerTimer);
    }
  },

  /**
   * Reschedules the tick timer.
   */
  _rescheduleTimeout: function() {
    this._log.trace("_rescheduleTimeout - isUserIdle: " + this._isUserIdle);
    if (this._shuttingDown) {
      this._log.warn("_rescheduleTimeout - already shutdown");
      return;
    }

    this._clearTimeout();

    const now = Policy.now();
    let timeout = SCHEDULER_TICK_INTERVAL_MS;

    // When the user is idle we want to fire the timer less often.
    if (this._isUserIdle) {
      timeout = SCHEDULER_TICK_IDLE_INTERVAL_MS;
      // We need to make sure though that we don't miss sending pings around
      // midnight when we use the longer idle intervals.
      const nextMidnight = Utils.getNextMidnight(now);
      timeout = Math.min(timeout, nextMidnight.getTime() - now.getTime());
    }

    this._log.trace("_rescheduleTimeout - scheduling next tick for " + new Date(now.getTime() + timeout));
    this._schedulerTimer =
      Policy.setSchedulerTickTimeout(() => this._onSchedulerTick(), timeout);
  },

  _sentDailyPingToday: function(nowDate) {
    // This is today's date and also the previous midnight (0:00).
    const todayDate = Utils.truncateToDays(nowDate);
    // We consider a ping sent for today if it occured after or at 00:00 today.
    return (this._lastDailyPingTime >= todayDate.getTime());
  },

  /**
   * Checks if we can send a daily ping or not.
   * @param {Object} nowDate A date object.
   * @return {Boolean} True if we can send the daily ping, false otherwise.
   */
  _isDailyPingDue: function(nowDate) {
    // The daily ping is not due if we already sent one today.
    if (this._sentDailyPingToday(nowDate)) {
      this._log.trace("_isDailyPingDue - already sent one today");
      return false;
    }

    // Avoid overly short sessions.
    const timeSinceLastDaily = nowDate.getTime() - this._lastDailyPingTime;
    if (timeSinceLastDaily < MIN_SUBSESSION_LENGTH_MS) {
      this._log.trace("_isDailyPingDue - delaying daily to keep minimum session length");
      return false;
    }

    this._log.trace("_isDailyPingDue - is due");
    return true;
  },

  /**
   * An helper function to save an aborted-session ping.
   * @param {Number} now The current time, in milliseconds.
   * @param {Object} [competingPayload=null] If we are coalescing the daily and the
   *                 aborted-session pings, this is the payload for the former. Note
   *                 that the reason field of this payload will be changed.
   * @return {Promise} A promise resolved when the ping is saved.
   */
  _saveAbortedPing: function(now, competingPayload=null) {
    this._lastSessionCheckpointTime = now;
    return Impl._saveAbortedSessionPing(competingPayload)
                .catch(e => this._log.error("_saveAbortedPing - Failed", e));
  },

  /**
   * The notifications handler.
   */
  observe: function(aSubject, aTopic, aData) {
    this._log.trace("observe - aTopic: " + aTopic);
    switch(aTopic) {
      case "idle":
        // If the user is idle, increase the tick interval.
        this._isUserIdle = true;
        return this._onSchedulerTick();
        break;
      case "active":
        // User is back to work, restore the original tick interval.
        this._isUserIdle = false;
        return this._onSchedulerTick();
        break;
      case "wake_notification":
        // The machine woke up from sleep, trigger a tick to avoid sessions
        // spanning more than a day.
        // This is needed because sleep time does not count towards timeouts
        // on Mac & Linux - see bug 1262386, bug 1204823 et al.
        return this._onSchedulerTick();
        break;
    }
    return undefined;
  },

  /**
   * Performs a scheduler tick. This function manages Telemetry recurring operations.
   * @return {Promise} A promise, only used when testing, resolved when the scheduled
   *                   operation completes.
   */
  _onSchedulerTick: function() {
    // This call might not be triggered from a timeout. In that case we don't want to
    // leave any previously scheduled timeouts pending.
    this._clearTimeout();

    if (this._shuttingDown) {
      this._log.warn("_onSchedulerTick - already shutdown.");
      return Promise.reject(new Error("Already shutdown."));
    }

    let promise = Promise.resolve();
    try {
      promise = this._schedulerTickLogic();
    } catch (e) {
      Telemetry.getHistogramById("TELEMETRY_SCHEDULER_TICK_EXCEPTION").add(1);
      this._log.error("_onSchedulerTick - There was an exception", e);
    } finally {
      this._rescheduleTimeout();
    }

    // This promise is returned to make testing easier.
    return promise;
  },

  /**
   * Implements the scheduler logic.
   * @return {Promise} Resolved when the scheduled task completes. Only used in tests.
   */
  _schedulerTickLogic: function() {
    this._log.trace("_schedulerTickLogic");

    let nowDate = Policy.now();
    let now = nowDate.getTime();

    if ((now - this._lastTickTime) > (1.1 * SCHEDULER_TICK_INTERVAL_MS) &&
        (this._lastTickTime != 0)) {
      Telemetry.getHistogramById("TELEMETRY_SCHEDULER_WAKEUP").add(1);
      this._log.trace("_schedulerTickLogic - First scheduler tick after sleep.");
    }
    this._lastTickTime = now;

    // Check if the daily ping is due.
    const shouldSendDaily = this._isDailyPingDue(nowDate);

    if (shouldSendDaily) {
      Telemetry.getHistogramById("TELEMETRY_SCHEDULER_SEND_DAILY").add(1);
      this._log.trace("_schedulerTickLogic - Daily ping due.");
      this._lastDailyPingTime = now;
      return Impl._sendDailyPing();
    }

    // Check if the aborted-session ping is due. If a daily ping was saved above, it was
    // already duplicated as an aborted-session ping.
    const isAbortedPingDue =
      (now - this._lastSessionCheckpointTime) >= ABORTED_SESSION_UPDATE_INTERVAL_MS;
    if (isAbortedPingDue) {
      this._log.trace("_schedulerTickLogic - Aborted session ping due.");
      return this._saveAbortedPing(now);
    }

    // No ping is due.
    this._log.trace("_schedulerTickLogic - No ping due.");
    return Promise.resolve();
  },

  /**
   * Update the scheduled pings if some other ping was sent.
   * @param {String} reason The reason of the ping that was sent.
   * @param {Object} [competingPayload=null] The payload of the ping that was sent. The
   *                 reason of this payload will be changed.
   */
  reschedulePings: function(reason, competingPayload = null) {
    if (this._shuttingDown) {
      this._log.error("reschedulePings - already shutdown");
      return;
    }

    this._log.trace("reschedulePings - reason: " + reason);
    let now = Policy.now();
    this._lastAdhocPingTime = now.getTime();
    if (reason == REASON_ENVIRONMENT_CHANGE) {
      // We just generated an environment-changed ping, save it as an aborted session and
      // update the schedules.
      this._saveAbortedPing(now.getTime(), competingPayload);
      // If we're close to midnight, skip today's daily ping and reschedule it for tomorrow.
      let nearestMidnight = Utils.getNearestMidnight(now, SCHEDULER_MIDNIGHT_TOLERANCE_MS);
      if (nearestMidnight) {
        this._lastDailyPingTime = now.getTime();
      }
    }

    this._rescheduleTimeout();
  },
};

this.EXPORTED_SYMBOLS = ["TelemetrySession"];

this.TelemetrySession = Object.freeze({
  Constants: Object.freeze({
    PREF_PREVIOUS_BUILDID: PREF_PREVIOUS_BUILDID,
  }),
  /**
   * Send a ping to a test server. Used only for testing.
   */
  testPing: function() {
    return Impl.testPing();
  },
  /**
   * Returns the current telemetry payload.
   * @param reason Optional, the reason to trigger the payload.
   * @param clearSubsession Optional, whether to clear subsession specific data.
   * @returns Object
   */
  getPayload: function(reason, clearSubsession = false) {
    return Impl.getPayload(reason, clearSubsession);
  },
  /**
   * Asks the content processes to send their payloads.
   * @returns Object
   */
  requestChildPayloads: function() {
    return Impl.requestChildPayloads();
  },
  /**
   * Returns a promise that resolves to an array of thread hang stats from content processes, one entry per process.
   * The structure of each entry is identical to that of "threadHangStats" in nsITelemetry.
   * While thread hang stats are also part of the child payloads, this function is useful for cheaply getting this information,
   * which is useful for realtime hang monitoring.
   * Child processes that do not respond, or spawn/die during execution of this function are excluded from the result.
   * @returns Promise
   */
  getChildThreadHangs: function() {
    return Impl.getChildThreadHangs();
  },
  /**
   * Save the session state to a pending file.
   * Used only for testing purposes.
   */
  testSavePendingPing: function() {
    return Impl.testSavePendingPing();
  },
  /**
   * Collect and store information about startup.
   */
  gatherStartup: function() {
    return Impl.gatherStartup();
  },
  /**
   * Inform the ping which AddOns are installed.
   *
   * @param aAddOns - The AddOns.
   */
  setAddOns: function(aAddOns) {
    return Impl.setAddOns(aAddOns);
  },
  /**
   * Descriptive metadata
   *
   * @param  reason
   *         The reason for the telemetry ping, this will be included in the
   *         returned metadata,
   * @return The metadata as a JS object
   */
  getMetadata: function(reason) {
    return Impl.getMetadata(reason);
  },
  /**
   * Used only for testing purposes.
   */
  testReset: function() {
    Impl._sessionId = null;
    Impl._subsessionId = null;
    Impl._previousSessionId = null;
    Impl._previousSubsessionId = null;
    Impl._subsessionCounter = 0;
    Impl._profileSubsessionCounter = 0;
    Impl._subsessionStartActiveTicks = 0;
    Impl._subsessionStartTimeMonotonic = 0;
    this.testUninstall();
  },
  /**
   * Triggers shutdown of the module.
   */
  shutdown: function() {
    return Impl.shutdownChromeProcess();
  },
  /**
   * Sets up components used in the content process.
   */
  setupContent: function(testing = false) {
    return Impl.setupContentProcess(testing);
  },
  /**
   * Used only for testing purposes.
   */
  testUninstall: function() {
    try {
      Impl.uninstall();
    } catch (ex) {
      // Ignore errors
    }
  },
  /**
   * Lightweight init function, called as soon as Firefox starts.
   */
  earlyInit: function(aTesting = false) {
    return Impl.earlyInit(aTesting);
  },
  /**
   * Does the "heavy" Telemetry initialization later on, so we
   * don't impact startup performance.
   * @return {Promise} Resolved when the initialization completes.
   */
  delayedInit: function() {
    return Impl.delayedInit();
  },
  /**
   * Send a notification.
   */
  observe: function (aSubject, aTopic, aData) {
    return Impl.observe(aSubject, aTopic, aData);
  },
});

var Impl = {
  _histograms: {},
  _initialized: false,
  _logger: null,
  _prevValues: {},
  // Regex that matches histograms we care about during startup.
  // Keep this in sync with gen-histogram-bucket-ranges.py.
  _startupHistogramRegex: /SQLITE|HTTP|SPDY|CACHE|DNS/,
  _slowSQLStartup: {},
  _hasWindowRestoredObserver: false,
  _hasXulWindowVisibleObserver: false,
  _startupIO : {},
  // The previous build ID, if this is the first run with a new build.
  // Null if this is the first run, or the previous build ID is unknown.
  _previousBuildId: null,
  // Telemetry payloads sent by child processes.
  // Each element is in the format {source: <weak-ref>, payload: <object>},
  // where source is a weak reference to the child process,
  // and payload is the telemetry payload from that child process.
  _childTelemetry: [],
  // Thread hangs from child processes.
  // Used for TelemetrySession.getChildThreadHangs(); not sent with Telemetry pings.
  // TelemetrySession.getChildThreadHangs() is used by extensions such as Statuser (https://github.com/chutten/statuser).
  // Each element is in the format {source: <weak-ref>, payload: <object>},
  // where source is a weak reference to the child process,
  // and payload contains the thread hang stats from that child process.
  _childThreadHangs: [],
  // Array of the resolve functions of all the promises that are waiting for the child thread hang stats to arrive, used to resolve all those promises at once.
  _childThreadHangsResolveFunctions: [],
  // Timeout function for child thread hang stats retrieval.
  _childThreadHangsTimeout: null,
  // Unique id that identifies this session so the server can cope with duplicate
  // submissions, orphaning and other oddities. The id is shared across subsessions.
  _sessionId: null,
  // Random subsession id.
  _subsessionId: null,
  // Session id of the previous session, null on first run.
  _previousSessionId: null,
  // Subsession id of the previous subsession (even if it was in a different session),
  // null on first run.
  _previousSubsessionId: null,
  // The running no. of subsessions since the start of the browser session
  _subsessionCounter: 0,
  // The running no. of all subsessions for the whole profile life time
  _profileSubsessionCounter: 0,
  // Date of the last session split
  _subsessionStartDate: null,
  // Start time of the current subsession using a monotonic clock for the subsession
  // length measurements.
  _subsessionStartTimeMonotonic: 0,
  // The active ticks counted when the subsession starts
  _subsessionStartActiveTicks: 0,
  // A task performing delayed initialization of the chrome process
  _delayedInitTask: null,
  // Need a timeout in case children are tardy in giving back their memory reports.
  _totalMemoryTimeout: undefined,
  _testing: false,
  // An accumulator of total memory across all processes. Only valid once the final child reports.
  _totalMemory: null,
  // A Set of outstanding USS report ids
  _childrenToHearFrom: null,
  // monotonically-increasing id for USS reports
  _nextTotalMemoryId: 1,


  get _log() {
    if (!this._logger) {
      this._logger = Log.repository.getLoggerWithMessagePrefix(LOGGER_NAME, LOGGER_PREFIX);
    }
    return this._logger;
  },

  /**
   * Gets a series of simple measurements (counters). At the moment, this
   * only returns startup data from nsIAppStartup.getStartupInfo().
   * @param {Boolean} isSubsession True if this is a subsession, false otherwise.
   * @param {Boolean} clearSubsession True if a new subsession is being started, false otherwise.
   *
   * @return simple measurements as a dictionary.
   */
  getSimpleMeasurements: function getSimpleMeasurements(forSavedSession, isSubsession, clearSubsession) {
    this._log.trace("getSimpleMeasurements");

    let si = Services.startup.getStartupInfo();

    // Measurements common to chrome and content processes.
    let elapsedTime = Date.now() - si.process;
    var ret = {
      totalTime: Math.round(elapsedTime / 1000), // totalTime, in seconds
      uptime: Math.round(elapsedTime / 60000) // uptime in minutes
    }

    // Look for app-specific timestamps
    var appTimestamps = {};
    try {
      let o = {};
      Cu.import("resource://gre/modules/TelemetryTimestamps.jsm", o);
      appTimestamps = o.TelemetryTimestamps.get();
    } catch (ex) {}

    // Only submit this if the extended set is enabled.
    if (!Utils.isContentProcess && Telemetry.canRecordExtended) {
      try {
        ret.addonManager = AddonManagerPrivate.getSimpleMeasures();
        ret.UITelemetry = UITelemetry.getSimpleMeasures();
      } catch (ex) {}
    }

    if (si.process) {
      for (let field of Object.keys(si)) {
        if (field == "process")
          continue;
        ret[field] = si[field] - si.process
      }

      for (let p in appTimestamps) {
        if (!(p in ret) && appTimestamps[p])
          ret[p] = appTimestamps[p] - si.process;
      }
    }

    ret.startupInterrupted = Number(Services.startup.interrupted);

    ret.js = Cu.getJSEngineTelemetryValue();

    let maximalNumberOfConcurrentThreads = Telemetry.maximalNumberOfConcurrentThreads;
    if (maximalNumberOfConcurrentThreads) {
      ret.maximalNumberOfConcurrentThreads = maximalNumberOfConcurrentThreads;
    }

    if (Utils.isContentProcess) {
      return ret;
    }

    // Measurements specific to chrome process

    // Update debuggerAttached flag
    let debugService = Cc["@mozilla.org/xpcom/debug;1"].getService(Ci.nsIDebug2);
    let isDebuggerAttached = debugService.isDebuggerAttached;
    gWasDebuggerAttached = gWasDebuggerAttached || isDebuggerAttached;
    ret.debuggerAttached = Number(gWasDebuggerAttached);

    let shutdownDuration = Telemetry.lastShutdownDuration;
    if (shutdownDuration)
      ret.shutdownDuration = shutdownDuration;

    let failedProfileLockCount = Telemetry.failedProfileLockCount;
    if (failedProfileLockCount)
      ret.failedProfileLockCount = failedProfileLockCount;

    for (let ioCounter in this._startupIO)
      ret[ioCounter] = this._startupIO[ioCounter];

    ret.savedPings = TelemetryStorage.pendingPingCount;

    ret.activeTicks = -1;
    let sr = TelemetryController.getSessionRecorder();
    if (sr) {
      let activeTicks = sr.activeTicks;
      if (isSubsession) {
        activeTicks = sr.activeTicks - this._subsessionStartActiveTicks;
      }

      if (clearSubsession) {
        this._subsessionStartActiveTicks = activeTicks;
      }

      ret.activeTicks = activeTicks;
    }

    ret.pingsOverdue = TelemetrySend.overduePingsCount;

    return ret;
  },

  /**
   * When reflecting a histogram into JS, Telemetry hands us an object
   * with the following properties:
   *
   * - min, max, histogram_type, sum, sum_squares_{lo,hi}: simple integers;
   * - counts: array of counts for histogram buckets;
   * - ranges: array of calculated bucket sizes.
   *
   * This format is not straightforward to read and potentially bulky
   * with lots of zeros in the counts array.  Packing histograms makes
   * raw histograms easier to read and compresses the data a little bit.
   *
   * Returns an object:
   * { range: [min, max], bucket_count: <number of buckets>,
   *   histogram_type: <histogram_type>, sum: <sum>,
   *   values: { bucket1: count1, bucket2: count2, ... } }
   */
  packHistogram: function packHistogram(hgram) {
    let r = hgram.ranges;
    let c = hgram.counts;
    let retgram = {
      range: [r[1], r[r.length - 1]],
      bucket_count: r.length,
      histogram_type: hgram.histogram_type,
      values: {},
      sum: hgram.sum
    };

    let first = true;
    let last = 0;

    for (let i = 0; i < c.length; i++) {
      let value = c[i];
      if (!value)
        continue;

      // add a lower bound
      if (i && first) {
        retgram.values[r[i - 1]] = 0;
      }
      first = false;
      last = i + 1;
      retgram.values[r[i]] = value;
    }

    // add an upper bound
    if (last && last < c.length)
      retgram.values[r[last]] = 0;
    return retgram;
  },

  /**
   * Get the type of the dataset that needs to be collected, based on the preferences.
   * @return {Integer} A value from nsITelemetry.DATASET_*.
   */
  getDatasetType: function() {
    return Telemetry.canRecordExtended ? Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN
                                       : Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTOUT;
  },

  getHistograms: function getHistograms(subsession, clearSubsession) {
    this._log.trace("getHistograms - subsession: " + subsession + ", clearSubsession: " + clearSubsession);

    let registered =
      Telemetry.registeredHistograms(this.getDatasetType(), []);
    let hls = subsession ? Telemetry.snapshotSubsessionHistograms(clearSubsession)
                         : Telemetry.histogramSnapshots;
    let ret = {};

    for (let name of registered) {
      for (let n of [name, "STARTUP_" + name]) {
        if (n in hls) {
          // Omit telemetry test histograms outside of tests.
          if (n.startsWith('TELEMETRY_TEST_') && this._testing == false) {
            this._log.trace("getHistograms - Skipping test histogram: " + n);
          } else {
            ret[n] = this.packHistogram(hls[n]);
          }
        }
      }
    }

    return ret;
  },

  getAddonHistograms: function getAddonHistograms() {
    this._log.trace("getAddonHistograms");

    let ahs = Telemetry.addonHistogramSnapshots;
    let ret = {};

    for (let addonName in ahs) {
      let addonHistograms = ahs[addonName];
      let packedHistograms = {};
      for (let name in addonHistograms) {
        packedHistograms[name] = this.packHistogram(addonHistograms[name]);
      }
      if (Object.keys(packedHistograms).length != 0)
        ret[addonName] = packedHistograms;
    }

    return ret;
  },

  getKeyedHistograms: function(subsession, clearSubsession) {
    this._log.trace("getKeyedHistograms - subsession: " + subsession + ", clearSubsession: " + clearSubsession);

    let registered =
      Telemetry.registeredKeyedHistograms(this.getDatasetType(), []);
    let ret = {};

    for (let id of registered) {
      // Omit telemetry test histograms outside of tests.
      if (id.startsWith('TELEMETRY_TEST_') && this._testing == false) {
        this._log.trace("getKeyedHistograms - Skipping test histogram: " + id);
        continue;
      }
      let keyed = Telemetry.getKeyedHistogramById(id);
      let snapshot = null;
      if (subsession) {
        snapshot = clearSubsession ? keyed.snapshotSubsessionAndClear()
                                   : keyed.subsessionSnapshot();
      } else {
        snapshot = keyed.snapshot();
      }

      let keys = Object.keys(snapshot);
      if (keys.length == 0) {
        // Skip empty keyed histogram.
        continue;
      }

      ret[id] = {};
      for (let key of keys) {
        ret[id][key] = this.packHistogram(snapshot[key]);
      }
    }

    return ret;
  },

  getThreadHangStats: function getThreadHangStats(stats) {
    this._log.trace("getThreadHangStats");

    stats.forEach((thread) => {
      thread.activity = this.packHistogram(thread.activity);
      thread.hangs.forEach((hang) => {
        hang.histogram = this.packHistogram(hang.histogram);
      });
    });
    return stats;
  },

  /**
   * Descriptive metadata
   *
   * @param  reason
   *         The reason for the telemetry ping, this will be included in the
   *         returned metadata,
   * @return The metadata as a JS object
   */
  getMetadata: function getMetadata(reason) {
    this._log.trace("getMetadata - Reason " + reason);

    const sessionStartDate = Utils.toLocalTimeISOString(Utils.truncateToDays(this._sessionStartDate));
    const subsessionStartDate = Utils.toLocalTimeISOString(Utils.truncateToDays(this._subsessionStartDate));
    const monotonicNow = Policy.monotonicNow();

    let ret = {
      reason: reason,
      revision: AppConstants.SOURCE_REVISION_URL,
      asyncPluginInit: Preferences.get(PREF_ASYNC_PLUGIN_INIT, false),

      // Date.getTimezoneOffset() unintuitively returns negative values if we are ahead of
      // UTC and vice versa (e.g. -60 for UTC+1). We invert the sign here.
      timezoneOffset: -this._subsessionStartDate.getTimezoneOffset(),
      previousBuildId: this._previousBuildId,

      sessionId: this._sessionId,
      subsessionId: this._subsessionId,
      previousSessionId: this._previousSessionId,
      previousSubsessionId: this._previousSubsessionId,

      subsessionCounter: this._subsessionCounter,
      profileSubsessionCounter: this._profileSubsessionCounter,

      sessionStartDate: sessionStartDate,
      subsessionStartDate: subsessionStartDate,

      // Compute the session and subsession length in seconds.
      // We use monotonic clocks as Date() is affected by jumping clocks (leading
      // to negative lengths and other issues).
      sessionLength: Math.floor(monotonicNow / 1000),
      subsessionLength:
        Math.floor((monotonicNow - this._subsessionStartTimeMonotonic) / 1000),
    };

    // TODO: Remove this when bug 1201837 lands.
    if (this._addons)
      ret.addons = this._addons;

    // TODO: Remove this when bug 1201837 lands.
    let flashVersion = this.getFlashVersion();
    if (flashVersion)
      ret.flashVersion = flashVersion;

    return ret;
  },

  /**
   * Pull values from about:memory into corresponding histograms
   */
  gatherMemory: function gatherMemory() {
    if (!Telemetry.canRecordExtended) {
      this._log.trace("gatherMemory - Extended data recording disabled, skipping.");
      return;
    }

    this._log.trace("gatherMemory");

    let mgr;
    try {
      mgr = Cc["@mozilla.org/memory-reporter-manager;1"].
            getService(Ci.nsIMemoryReporterManager);
    } catch (e) {
      // OK to skip memory reporters in xpcshell
      return;
    }

    let histogram = Telemetry.getHistogramById("TELEMETRY_MEMORY_REPORTER_MS");
    let startTime = new Date();

    // Get memory measurements from distinguished amount attributes.  We used
    // to measure "explicit" too, but it could cause hangs, and the data was
    // always really noisy anyway.  See bug 859657.
    //
    // test_TelemetryController.js relies on some of these histograms being
    // here.  If you remove any of the following histograms from here, you'll
    // have to modify test_TelemetryController.js:
    //
    //   * MEMORY_JS_GC_HEAP, and
    //   * MEMORY_JS_COMPARTMENTS_SYSTEM.
    //
    // The distinguished amount attribute names don't match the telemetry id
    // names in some cases due to a combination of (a) historical reasons, and
    // (b) the fact that we can't change telemetry id names without breaking
    // data continuity.
    //
    let boundHandleMemoryReport = this.handleMemoryReport.bind(this);
    function h(id, units, amountName) {
      try {
        // If mgr[amountName] throws an exception, just move on -- some amounts
        // aren't available on all platforms.  But if the attribute simply
        // isn't present, that indicates the distinguished amounts have changed
        // and this file hasn't been updated appropriately.
        let amount = mgr[amountName];
        NS_ASSERT(amount !== undefined,
                  "telemetry accessed an unknown distinguished amount");
        boundHandleMemoryReport(id, units, amount);
      } catch (e) {
      }
    }
    let b = (id, n) => h(id, Ci.nsIMemoryReporter.UNITS_BYTES, n);
    let c = (id, n) => h(id, Ci.nsIMemoryReporter.UNITS_COUNT, n);
    let cc= (id, n) => h(id, Ci.nsIMemoryReporter.UNITS_COUNT_CUMULATIVE, n);
    let p = (id, n) => h(id, Ci.nsIMemoryReporter.UNITS_PERCENTAGE, n);

    b("MEMORY_VSIZE", "vsize");
    b("MEMORY_VSIZE_MAX_CONTIGUOUS", "vsizeMaxContiguous");
    b("MEMORY_RESIDENT_FAST", "residentFast");
    b("MEMORY_UNIQUE", "residentUnique");
    b("MEMORY_HEAP_ALLOCATED", "heapAllocated");
    p("MEMORY_HEAP_OVERHEAD_FRACTION", "heapOverheadFraction");
    b("MEMORY_JS_GC_HEAP", "JSMainRuntimeGCHeap");
    c("MEMORY_JS_COMPARTMENTS_SYSTEM", "JSMainRuntimeCompartmentsSystem");
    c("MEMORY_JS_COMPARTMENTS_USER", "JSMainRuntimeCompartmentsUser");
    b("MEMORY_IMAGES_CONTENT_USED_UNCOMPRESSED", "imagesContentUsedUncompressed");
    b("MEMORY_STORAGE_SQLITE", "storageSQLite");
    cc("LOW_MEMORY_EVENTS_VIRTUAL", "lowMemoryEventsVirtual");
    cc("LOW_MEMORY_EVENTS_PHYSICAL", "lowMemoryEventsPhysical");
    c("GHOST_WINDOWS", "ghostWindows");
    cc("PAGE_FAULTS_HARD", "pageFaultsHard");

    if (!Utils.isContentProcess && !this._totalMemoryTimeout) {
      // Only the chrome process should gather total memory
      // total = parent RSS + sum(child USS)
      this._totalMemory = mgr.residentFast;
      if (ppmm.childCount > 1) {
        // Do not report If we time out waiting for the children to call
        this._totalMemoryTimeout = setTimeout(
          () => {
            this._totalMemoryTimeout = undefined;
            this._childrenToHearFrom.clear();
          },
          TOTAL_MEMORY_COLLECTOR_TIMEOUT);
        this._childrenToHearFrom = new Set();
        for (let i = 1; i < ppmm.childCount; i++) {
          ppmm.getChildAt(i).sendAsyncMessage(MESSAGE_TELEMETRY_GET_CHILD_USS, {id: this._nextTotalMemoryId});
          this._childrenToHearFrom.add(this._nextTotalMemoryId);
          this._nextTotalMemoryId++;
        }
      } else {
        boundHandleMemoryReport(
          "MEMORY_TOTAL",
          Ci.nsIMemoryReporter.UNITS_BYTES,
          this._totalMemory);
      }
    }

    histogram.add(new Date() - startTime);
  },

  handleMemoryReport: function(id, units, amount) {
    let val;
    if (units == Ci.nsIMemoryReporter.UNITS_BYTES) {
      val = Math.floor(amount / 1024);
    }
    else if (units == Ci.nsIMemoryReporter.UNITS_PERCENTAGE) {
      // UNITS_PERCENTAGE amounts are 100x greater than their raw value.
      val = Math.floor(amount / 100);
    }
    else if (units == Ci.nsIMemoryReporter.UNITS_COUNT) {
      val = amount;
    }
    else if (units == Ci.nsIMemoryReporter.UNITS_COUNT_CUMULATIVE) {
      // If the reporter gives us a cumulative count, we'll report the
      // difference in its value between now and our previous ping.

      if (!(id in this._prevValues)) {
        // If this is the first time we're reading this reporter, store its
        // current value but don't report it in the telemetry ping, so we
        // ignore the effect startup had on the reporter.
        this._prevValues[id] = amount;
        return;
      }

      val = amount - this._prevValues[id];
      this._prevValues[id] = amount;
    }
    else {
      NS_ASSERT(false, "Can't handle memory reporter with units " + units);
      return;
    }

    let h = this._histograms[id];
    if (!h) {
      h = Telemetry.getHistogramById(id);
      this._histograms[id] = h;
    }
    h.add(val);
  },

  /**
   * Return true if we're interested in having a STARTUP_* histogram for
   * the given histogram name.
   */
  isInterestingStartupHistogram: function isInterestingStartupHistogram(name) {
    return this._startupHistogramRegex.test(name);
  },

  getChildPayloads: function getChildPayloads() {
    return this._childTelemetry.map(child => child.payload);
  },

  /**
   * Make a copy of interesting histograms at startup.
   */
  gatherStartupHistograms: function gatherStartupHistograms() {
    this._log.trace("gatherStartupHistograms");

    let info =
      Telemetry.registeredHistograms(this.getDatasetType(), []);
    let snapshots = Telemetry.histogramSnapshots;
    for (let name of info) {
      // Only duplicate histograms with actual data.
      if (this.isInterestingStartupHistogram(name) && name in snapshots) {
        Telemetry.histogramFrom("STARTUP_" + name, name);
      }
    }
  },

  /**
   * Get the current session's payload using the provided
   * simpleMeasurements and info, which are typically obtained by a call
   * to |this.getSimpleMeasurements| and |this.getMetadata|,
   * respectively.
   */
  assemblePayloadWithMeasurements: function(simpleMeasurements, info, reason, clearSubsession) {
    const isSubsession = IS_UNIFIED_TELEMETRY && !this._isClassicReason(reason);
    clearSubsession = IS_UNIFIED_TELEMETRY && clearSubsession;
    this._log.trace("assemblePayloadWithMeasurements - reason: " + reason +
                    ", submitting subsession data: " + isSubsession);

    // This allows wrapping data retrieval calls in a try-catch block so that
    // failures don't break the rest of the ping assembly.
    const protect = (fn) => {
      try {
        return fn();
      } catch (ex) {
        this._log.error("assemblePayloadWithMeasurements - caught exception", ex);
        return null;
      }
    };

    // Payload common to chrome and content processes.
    let payloadObj = {
      ver: PAYLOAD_VERSION,
      simpleMeasurements: simpleMeasurements,
      histograms: protect(() => this.getHistograms(isSubsession, clearSubsession)),
      keyedHistograms: protect(() => this.getKeyedHistograms(isSubsession, clearSubsession)),
    };

    // Add extended set measurements common to chrome & content processes
    if (Telemetry.canRecordExtended) {
      payloadObj.chromeHangs = protect(() => Telemetry.chromeHangs);
      payloadObj.threadHangStats = protect(() => this.getThreadHangStats(Telemetry.threadHangStats));
      payloadObj.log = protect(() => TelemetryLog.entries());
      payloadObj.webrtc = protect(() => Telemetry.webrtcStats);
    }

    if (Utils.isContentProcess) {
      return payloadObj;
    }

    // Additional payload for chrome process.
    payloadObj.info = info;

    // Add extended set measurements for chrome process.
    if (Telemetry.canRecordExtended) {
      payloadObj.slowSQL = protect(() => Telemetry.slowSQL);
      payloadObj.fileIOReports = protect(() => Telemetry.fileIOReports);
      payloadObj.lateWrites = protect(() => Telemetry.lateWrites);

      // Add the addon histograms if they are present
      let addonHistograms = protect(() => this.getAddonHistograms());
      if (addonHistograms && Object.keys(addonHistograms).length > 0) {
        payloadObj.addonHistograms = addonHistograms;
      }

      payloadObj.addonDetails = protect(() => AddonManagerPrivate.getTelemetryDetails());

      let clearUIsession = !(reason == REASON_GATHER_PAYLOAD || reason == REASON_GATHER_SUBSESSION_PAYLOAD);
      payloadObj.UIMeasurements = protect(() => UITelemetry.getUIMeasurements(clearUIsession));

      if (this._slowSQLStartup &&
          Object.keys(this._slowSQLStartup).length != 0 &&
          (Object.keys(this._slowSQLStartup.mainThread).length ||
           Object.keys(this._slowSQLStartup.otherThreads).length)) {
        payloadObj.slowSQLStartup = this._slowSQLStartup;
      }
    }

    if (this._childTelemetry.length) {
      payloadObj.childPayloads = protect(() => this.getChildPayloads());
    }

    return payloadObj;
  },

  /**
   * Start a new subsession.
   */
  startNewSubsession: function () {
    this._subsessionStartDate = Policy.now();
    this._subsessionStartTimeMonotonic = Policy.monotonicNow();
    this._previousSubsessionId = this._subsessionId;
    this._subsessionId = Policy.generateSubsessionUUID();
    this._subsessionCounter++;
    this._profileSubsessionCounter++;
  },

  getSessionPayload: function getSessionPayload(reason, clearSubsession) {
    this._log.trace("getSessionPayload - reason: " + reason + ", clearSubsession: " + clearSubsession);

    let payload;
    try {
      const isMobile = ["gonk", "android"].includes(AppConstants.platform);
      const isSubsession = isMobile ? false : !this._isClassicReason(reason);

      if (isMobile) {
        clearSubsession = false;
      }

      let measurements =
        this.getSimpleMeasurements(reason == REASON_SAVED_SESSION, isSubsession, clearSubsession);
      let info = !Utils.isContentProcess ? this.getMetadata(reason) : null;
      payload = this.assemblePayloadWithMeasurements(measurements, info, reason, clearSubsession);
    } catch (ex) {
      Telemetry.getHistogramById("TELEMETRY_ASSEMBLE_PAYLOAD_EXCEPTION").add(1);
      throw ex;
    } finally {
      if (!Utils.isContentProcess && clearSubsession) {
        this.startNewSubsession();
        // Persist session data to disk (don't wait until it completes).
        let sessionData = this._getSessionDataObject();
        TelemetryStorage.saveSessionData(sessionData);
      }
    }

    return payload;
  },

  /**
   * Send data to the server. Record success/send-time in histograms
   */
  send: function send(reason) {
    this._log.trace("send - Reason " + reason);
    // populate histograms one last time
    this.gatherMemory();

    const isSubsession = !this._isClassicReason(reason);
    let payload = this.getSessionPayload(reason, isSubsession);
    let options = {
      addClientId: true,
      addEnvironment: true,
    };
    return TelemetryController.submitExternalPing(getPingType(payload), payload, options);
  },

  attachObservers: function attachObservers() {
    if (!this._initialized)
      return;
    Services.obs.addObserver(this, "idle-daily", false);
    if (Telemetry.canRecordExtended) {
      Services.obs.addObserver(this, TOPIC_CYCLE_COLLECTOR_BEGIN, false);
    }
  },

  detachObservers: function detachObservers() {
    if (!this._initialized)
      return;
    Services.obs.removeObserver(this, "idle-daily");
    try {
      // Tests may flip Telemetry.canRecordExtended on and off. Just try to remove this
      // observer and catch if it fails because the observer was not added.
      Services.obs.removeObserver(this, TOPIC_CYCLE_COLLECTOR_BEGIN);
    } catch (e) {
      this._log.warn("detachObservers - Failed to remove " + TOPIC_CYCLE_COLLECTOR_BEGIN, e);
    }
  },

  /**
   * Lightweight init function, called as soon as Firefox starts.
   */
  earlyInit: function(testing) {
    this._log.trace("earlyInit");

    this._initStarted = true;
    this._testing = testing;

    if (this._initialized && !testing) {
      this._log.error("earlyInit - already initialized");
      return;
    }

    if (!Telemetry.canRecordBase && !testing) {
      this._log.config("earlyInit - Telemetry recording is disabled, skipping Chrome process setup.");
      return;
    }

    // Generate a unique id once per session so the server can cope with duplicate
    // submissions, orphaning and other oddities. The id is shared across subsessions.
    this._sessionId = Policy.generateSessionUUID();
    this.startNewSubsession();
    // startNewSubsession sets |_subsessionStartDate| to the current date/time. Use
    // the very same value for |_sessionStartDate|.
    this._sessionStartDate = this._subsessionStartDate;

    annotateCrashReport(this._sessionId);

    // Initialize some probes that are kept in their own modules
    this._thirdPartyCookies = new ThirdPartyCookieProbe();
    this._thirdPartyCookies.init();

    // Record old value and update build ID preference if this is the first
    // run with a new build ID.
    let previousBuildId = Preferences.get(PREF_PREVIOUS_BUILDID, null);
    let thisBuildID = Services.appinfo.appBuildID;
    // If there is no previousBuildId preference, we send null to the server.
    if (previousBuildId != thisBuildID) {
      this._previousBuildId = previousBuildId;
      Preferences.set(PREF_PREVIOUS_BUILDID, thisBuildID);
    }

    Services.obs.addObserver(this, "sessionstore-windows-restored", false);
    if (AppConstants.platform === "android") {
      Services.obs.addObserver(this, "application-background", false);
    }
    Services.obs.addObserver(this, "xul-window-visible", false);
    this._hasWindowRestoredObserver = true;
    this._hasXulWindowVisibleObserver = true;

    ppml.addMessageListener(MESSAGE_TELEMETRY_PAYLOAD, this);
    ppml.addMessageListener(MESSAGE_TELEMETRY_THREAD_HANGS, this);
    ppml.addMessageListener(MESSAGE_TELEMETRY_USS, this);
},

/**
  * Does the "heavy" Telemetry initialization later on, so we
  * don't impact startup performance.
  * @return {Promise} Resolved when the initialization completes.
  */
  delayedInit:function() {
    this._log.trace("delayedInit");

    this._delayedInitTask = Task.spawn(function* () {
      try {
        this._initialized = true;

        yield this._loadSessionData();
        // Update the session data to keep track of new subsessions created before
        // the initialization.
        yield TelemetryStorage.saveSessionData(this._getSessionDataObject());

        this.attachObservers();
        this.gatherMemory();

        Telemetry.asyncFetchTelemetryData(function () {});

        if (IS_UNIFIED_TELEMETRY) {
          // Check for a previously written aborted session ping.
          yield TelemetryController.checkAbortedSessionPing();

          // Write the first aborted-session ping as early as possible. Just do that
          // if we are not testing, since calling Telemetry.reset() will make a previous
          // aborted ping a pending ping.
          if (!this._testing) {
            yield this._saveAbortedSessionPing();
          }

          TelemetryEnvironment.registerChangeListener(ENVIRONMENT_CHANGE_LISTENER,
                                 (reason, data) => this._onEnvironmentChange(reason, data));

          // Start the scheduler.
          // We skip this if unified telemetry is off, so we don't
          // trigger the new unified ping types.
          TelemetryScheduler.init();
        }

        this._delayedInitTask = null;
      } catch (e) {
        this._delayedInitTask = null;
        throw e;
      }
    }.bind(this));

    return this._delayedInitTask;
  },

  /**
   * Initializes telemetry for a content process.
   */
  setupContentProcess: function setupContentProcess(testing) {
    this._log.trace("setupContentProcess");
    this._testing = testing;

    if (!Telemetry.canRecordBase) {
      this._log.trace("setupContentProcess - base recording is disabled, not initializing");
      return;
    }

    Services.obs.addObserver(this, "content-child-shutdown", false);
    cpml.addMessageListener(MESSAGE_TELEMETRY_GET_CHILD_PAYLOAD, this);
    cpml.addMessageListener(MESSAGE_TELEMETRY_GET_CHILD_THREAD_HANGS, this);
    cpml.addMessageListener(MESSAGE_TELEMETRY_GET_CHILD_USS, this);

    this.gatherStartupHistograms();

    let delayedTask = new DeferredTask(function* () {
      this._initialized = true;

      this.attachObservers();
      this.gatherMemory();
    }.bind(this), testing ? TELEMETRY_TEST_DELAY : TELEMETRY_DELAY);

    delayedTask.arm();
  },

  getFlashVersion: function getFlashVersion() {
    this._log.trace("getFlashVersion");
    let host = Cc["@mozilla.org/plugin/host;1"].getService(Ci.nsIPluginHost);
    let tags = host.getPluginTags();

    for (let i = 0; i < tags.length; i++) {
      if (tags[i].name == "Shockwave Flash")
        return tags[i].version;
    }

    return null;
  },

  receiveMessage: function receiveMessage(message) {
    this._log.trace("receiveMessage - Message name " + message.name);
    switch (message.name) {
    case MESSAGE_TELEMETRY_PAYLOAD:
    {
      // In parent process, receive Telemetry payload from child
      let source = message.data.childUUID;
      delete message.data.childUUID;

      for (let child of this._childTelemetry) {
        if (child.source === source) {
          // Update existing telemetry data.
          child.payload = message.data;
          return;
        }
      }
      // Did not find existing child in this._childTelemetry.
      this._childTelemetry.push({
        source: source,
        payload: message.data,
      });

      if (this._childTelemetry.length == MAX_NUM_CONTENT_PAYLOADS + 1) {
        this._childTelemetry.shift();
        Telemetry.getHistogramById("TELEMETRY_DISCARDED_CONTENT_PINGS_COUNT").add();
      }

      break;
    }
    case MESSAGE_TELEMETRY_GET_CHILD_PAYLOAD:
    {
      // In child process, send the requested Telemetry payload
      this.sendContentProcessPing("saved-session");
      break;
    }
    case MESSAGE_TELEMETRY_THREAD_HANGS:
    {
      // Accumulate child thread hang stats from this child
      this._childThreadHangs.push(message.data);

      // Check if we've got data from all the children, accounting for child processes dying
      // if it happens before the last response is received and no new child processes are spawned at the exact same time
      // If that happens, we can resolve the promise earlier rather than having to wait for the timeout to expire
      // Basically, the number of replies is at most the number of messages sent out, this._childCount,
      // and also at most the number of child processes that currently exist
      if (this._childThreadHangs.length === Math.min(this._childCount, ppmm.childCount)) {
        clearTimeout(this._childThreadHangsTimeout);

        // Resolve all the promises that are waiting on these thread hang stats
        // We resolve here instead of rejecting because
        for (let resolve of this._childThreadHangsResolveFunctions) {
          resolve(this._childThreadHangs);
        }
        this._childThreadHangsResolveFunctions = [];
      }

      break;
    }
    case MESSAGE_TELEMETRY_GET_CHILD_THREAD_HANGS:
    {
      // In child process, send the requested child thread hangs
      this.sendContentProcessThreadHangs();
      break;
    }
    case MESSAGE_TELEMETRY_USS:
    {
      // In parent process, receive the USS report from the child
      if (this._totalMemoryTimeout && this._childrenToHearFrom.delete(message.data.id)) {
        this._totalMemory += message.data.bytes;
        if (this._childrenToHearFrom.size == 0) {
          clearTimeout(this._totalMemoryTimeout);
          this._totalMemoryTimeout = undefined;
          this.handleMemoryReport(
            "MEMORY_TOTAL",
            Ci.nsIMemoryReporter.UNITS_BYTES,
            this._totalMemory);
        }
      } else {
        this._log.trace("Child USS report was missed");
      }
      break;
    }
    case MESSAGE_TELEMETRY_GET_CHILD_USS:
    {
      // In child process, send the requested USS report
      this.sendContentProcessUSS(message.data.id);
      break
    }
    default:
      throw new Error("Telemetry.receiveMessage: bad message name");
    }
  },

  _processUUID: generateUUID(),

  sendContentProcessUSS: function sendContentProcessUSS(aMessageId) {
    this._log.trace("sendContentProcessUSS");

    let mgr;
    try {
      mgr = Cc["@mozilla.org/memory-reporter-manager;1"].
            getService(Ci.nsIMemoryReporterManager);
    } catch (e) {
      // OK to skip memory reporters in xpcshell
      return;
    }

    cpmm.sendAsyncMessage(
      MESSAGE_TELEMETRY_USS,
      {bytes: mgr.residentUnique, id: aMessageId}
    );
  },

  sendContentProcessPing: function sendContentProcessPing(reason) {
    this._log.trace("sendContentProcessPing - Reason " + reason);
    const isSubsession = !this._isClassicReason(reason);
    let payload = this.getSessionPayload(reason, isSubsession);
    payload.childUUID = this._processUUID;
    cpmm.sendAsyncMessage(MESSAGE_TELEMETRY_PAYLOAD, payload);
  },

  sendContentProcessThreadHangs: function sendContentProcessThreadHangs() {
    this._log.trace("sendContentProcessThreadHangs");
    let payload = {
      childUUID: this._processUUID,
      hangs: Telemetry.threadHangStats,
    };
    cpmm.sendAsyncMessage(MESSAGE_TELEMETRY_THREAD_HANGS, payload);
  },

   /**
    * Save both the "saved-session" and the "shutdown" pings to disk.
    * This needs to be called after TelemetrySend shuts down otherwise pings
    * would be sent instead of getting persisted to disk.
    */
  saveShutdownPings: function() {
    this._log.trace("saveShutdownPings");

    // We don't wait for "shutdown" pings to be written to disk before gathering the
    // "saved-session" payload. Instead we append the promises to this list and wait
    // on both to be saved after kicking off their collection.
    let p = [];

    if (IS_UNIFIED_TELEMETRY) {
      let shutdownPayload = this.getSessionPayload(REASON_SHUTDOWN, false);

      let options = {
        addClientId: true,
        addEnvironment: true,
      };
      p.push(TelemetryController.submitExternalPing(getPingType(shutdownPayload), shutdownPayload, options)
                                .catch(e => this._log.error("saveShutdownPings - failed to submit shutdown ping", e)));
     }

    // As a temporary measure, we want to submit saved-session too if extended Telemetry is enabled
    // to keep existing performance analysis working.
    if (Telemetry.canRecordExtended) {
      let payload = this.getSessionPayload(REASON_SAVED_SESSION, false);

      let options = {
        addClientId: true,
        addEnvironment: true,
      };
      p.push(TelemetryController.submitExternalPing(getPingType(payload), payload, options)
                                .catch (e => this._log.error("saveShutdownPings - failed to submit saved-session ping", e)));
    }

    // Wait on pings to be saved.
    return Promise.all(p);
  },


  testSavePendingPing: function testSaveHistograms() {
    this._log.trace("testSaveHistograms");
    let payload = this.getSessionPayload(REASON_SAVED_SESSION, false);
    let options = {
      addClientId: true,
      addEnvironment: true,
      overwrite: true,
    };
    return TelemetryController.addPendingPing(getPingType(payload), payload, options);
  },

  /**
   * Remove observers to avoid leaks
   */
  uninstall: function uninstall() {
    this.detachObservers();
    if (this._hasWindowRestoredObserver) {
      Services.obs.removeObserver(this, "sessionstore-windows-restored");
      this._hasWindowRestoredObserver = false;
    }
    if (this._hasXulWindowVisibleObserver) {
      Services.obs.removeObserver(this, "xul-window-visible");
      this._hasXulWindowVisibleObserver = false;
    }
    if (AppConstants.platform === "android") {
      Services.obs.removeObserver(this, "application-background", false);
    }
  },

  getPayload: function getPayload(reason, clearSubsession) {
    this._log.trace("getPayload - clearSubsession: " + clearSubsession);
    reason = reason || REASON_GATHER_PAYLOAD;
    // This function returns the current Telemetry payload to the caller.
    // We only gather startup info once.
    if (Object.keys(this._slowSQLStartup).length == 0) {
      this.gatherStartupHistograms();
      this._slowSQLStartup = Telemetry.slowSQL;
    }
    this.gatherMemory();
    return this.getSessionPayload(reason, clearSubsession);
  },

  requestChildPayloads: function() {
    this._log.trace("requestChildPayloads");
    ppmm.broadcastAsyncMessage(MESSAGE_TELEMETRY_GET_CHILD_PAYLOAD, {});
  },

  getChildThreadHangs: function getChildThreadHangs() {
    return new Promise((resolve) => {
      // Return immediately if there are no child processes to get stats from
      if (ppmm.childCount === 0) {
        resolve([]);
        return;
      }

      // Register our promise so it will be resolved when we receive the child thread hang stats on the parent process
      // The resolve functions will all be called from "receiveMessage" when a MESSAGE_TELEMETRY_THREAD_HANGS message comes in
      this._childThreadHangsResolveFunctions.push((threadHangStats) => {
        let hangs = threadHangStats.map(child => child.hangs);
        return resolve(hangs);
      });

      // If we (the parent) are not currently in the process of requesting child thread hangs, request them
      // If we are, then the resolve function we registered above will receive the results without needing to request them again
      if (this._childThreadHangsResolveFunctions.length === 1) {
        // We have to cache the number of children we send messages to, in case the child count changes while waiting for messages to arrive
        // This handles the case where the child count increases later on, in which case the new processes won't respond since we never sent messages to them
        this._childCount = ppmm.childCount;

        this._childThreadHangs = []; // Clear the child hangs
        for (let i = 0; i < this._childCount; i++) {
          // If a child dies at exactly while we're running this loop, the message sending will fail but we won't get an exception
          // In this case, since we won't know this has happened, we will simply rely on the timeout to handle it
          ppmm.getChildAt(i).sendAsyncMessage(MESSAGE_TELEMETRY_GET_CHILD_THREAD_HANGS);
        }

        // Set up a timeout in case one or more of the content processes never responds
        this._childThreadHangsTimeout = setTimeout(() => {
          // Resolve all the promises that are waiting on these thread hang stats
          // We resolve here instead of rejecting because the purpose of this function is
          // to retrieve the BHR stats from all processes that will give us stats
          // As a result, one process failing simply means it doesn't get included in the result.
          for (let resolve of this._childThreadHangsResolveFunctions) {
            resolve(this._childThreadHangs);
          }
          this._childThreadHangsResolveFunctions = [];
        }, 200);
      }
    });
  },

  gatherStartup: function gatherStartup() {
    this._log.trace("gatherStartup");
    let counters = processInfo.getCounters();
    if (counters) {
      [this._startupIO.startupSessionRestoreReadBytes,
        this._startupIO.startupSessionRestoreWriteBytes] = counters;
    }
    this.gatherStartupHistograms();
    this._slowSQLStartup = Telemetry.slowSQL;
  },

  setAddOns: function setAddOns(aAddOns) {
    this._addons = aAddOns;
  },

  testPing: function testPing() {
    return this.send(REASON_TEST_PING);
  },

  /**
   * This observer drives telemetry.
   */
  observe: function (aSubject, aTopic, aData) {
    // Prevent the cycle collector begin topic from cluttering the log.
    if (aTopic != TOPIC_CYCLE_COLLECTOR_BEGIN) {
      this._log.trace("observe - " + aTopic + " notified.");
    }

    switch (aTopic) {
    case "content-child-shutdown":
      // content-child-shutdown is only registered for content processes.
      Services.obs.removeObserver(this, "content-child-shutdown");
      this.uninstall();

      this.sendContentProcessPing(REASON_SAVED_SESSION);
      break;
    case TOPIC_CYCLE_COLLECTOR_BEGIN:
      let now = new Date();
      if (!gLastMemoryPoll
          || (TELEMETRY_INTERVAL <= now - gLastMemoryPoll)) {
        gLastMemoryPoll = now;
        this.gatherMemory();
      }
      break;
    case "xul-window-visible":
      Services.obs.removeObserver(this, "xul-window-visible");
      this._hasXulWindowVisibleObserver = false;
      var counters = processInfo.getCounters();
      if (counters) {
        [this._startupIO.startupWindowVisibleReadBytes,
          this._startupIO.startupWindowVisibleWriteBytes] = counters;
      }
      break;
    case "sessionstore-windows-restored":
      Services.obs.removeObserver(this, "sessionstore-windows-restored");
      this._hasWindowRestoredObserver = false;
      // Check whether debugger was attached during startup
      let debugService = Cc["@mozilla.org/xpcom/debug;1"].getService(Ci.nsIDebug2);
      gWasDebuggerAttached = debugService.isDebuggerAttached;
      this.gatherStartup();
      break;
    case "idle-daily":
      // Enqueue to main-thread, otherwise components may be inited by the
      // idle-daily category and miss the gather-telemetry notification.
      Services.tm.mainThread.dispatch((function() {
        // Notify that data should be gathered now.
        // TODO: We are keeping this behaviour for now but it will be removed as soon as
        // bug 1127907 lands.
        Services.obs.notifyObservers(null, "gather-telemetry", null);
      }).bind(this), Ci.nsIThread.DISPATCH_NORMAL);
      break;

    case "application-background":
      if (AppConstants.platform !== "android") {
        break;
      }
      // On Android, we can get killed without warning once we are in the background,
      // but we may also submit data and/or come back into the foreground without getting
      // killed. To deal with this, we save the current session data to file when we are
      // put into the background. This handles the following post-backgrounding scenarios:
      // 1) We are killed immediately. In this case the current session data (which we
      //    save to a file) will be loaded and submitted on a future run.
      // 2) We submit the data while in the background, and then are killed. In this case
      //    the file that we saved will be deleted by the usual process in
      //    finishPingRequest after it is submitted.
      // 3) We submit the data, and then come back into the foreground. Same as case (2).
      // 4) We do not submit the data, but come back into the foreground. In this case
      //    we have the option of either deleting the file that we saved (since we will either
      //    send the live data while in the foreground, or create the file again on the next
      //    backgrounding), or not (in which case we will delete it on submit, or overwrite
      //    it on the next backgrounding). Not deleting it is faster, so that's what we do.
      let payload = this.getSessionPayload(REASON_SAVED_SESSION, false);
      let options = {
        addClientId: true,
        addEnvironment: true,
        overwrite: true,
      };
      TelemetryController.addPendingPing(getPingType(payload), payload, options);
      break;
    }
    return undefined;
  },

  /**
   * This tells TelemetrySession to uninitialize and save any pending pings.
   */
  shutdownChromeProcess: function() {
    this._log.trace("shutdownChromeProcess");

    let cleanup = () => {
      if (IS_UNIFIED_TELEMETRY) {
        TelemetryEnvironment.unregisterChangeListener(ENVIRONMENT_CHANGE_LISTENER);
        TelemetryScheduler.shutdown();
      }
      this.uninstall();

      let reset = () => {
        this._initStarted = false;
        this._initialized = false;
      };

      return Task.spawn(function*() {
        yield this.saveShutdownPings();

        if (IS_UNIFIED_TELEMETRY) {
          yield TelemetryController.removeAbortedSessionPing();
        }

        reset();
      }.bind(this));
    };

    // We can be in one the following states here:
    // 1) delayedInit was never called
    // or it was called and
    //   2) _delayedInitTask is running now.
    //   3) _delayedInitTask finished running already.

    // This handles 1).
    if (!this._initStarted) {
      return Promise.resolve();
     }

    // This handles 3).
    if (!this._delayedInitTask) {
      // We already ran the delayed initialization.
      return cleanup();
     }

     // This handles 2).
     return this._delayedInitTask.then(cleanup);
   },

  /**
   * Gather and send a daily ping.
   * @return {Promise} Resolved when the ping is sent.
   */
  _sendDailyPing: function() {
    this._log.trace("_sendDailyPing");
    let payload = this.getSessionPayload(REASON_DAILY, true);

    let options = {
      addClientId: true,
      addEnvironment: true,
    };

    let promise = TelemetryController.submitExternalPing(getPingType(payload), payload, options);

    // Also save the payload as an aborted session. If we delay this, aborted-session can
    // lag behind for the profileSubsessionCounter and other state, complicating analysis.
    if (IS_UNIFIED_TELEMETRY) {
      this._saveAbortedSessionPing(payload)
          .catch(e => this._log.error("_sendDailyPing - Failed to save the aborted session ping", e));
    }

    return promise;
  },

  /** Loads session data from the session data file.
   * @return {Promise<object>} A promise which is resolved with an object when
   *                            loading has completed, with null otherwise.
   */
  _loadSessionData: Task.async(function* () {
    let data = yield TelemetryStorage.loadSessionData();

    if (!data) {
      return null;
    }

    if (!("profileSubsessionCounter" in data) ||
        !(typeof(data.profileSubsessionCounter) == "number") ||
        !("subsessionId" in data) || !("sessionId" in data)) {
      this._log.error("_loadSessionData - session data is invalid");
      Telemetry.getHistogramById("TELEMETRY_SESSIONDATA_FAILED_VALIDATION").add(1);
      return null;
    }

    this._previousSessionId = data.sessionId;
    this._previousSubsessionId = data.subsessionId;
    // Add |_subsessionCounter| to the |_profileSubsessionCounter| to account for
    // new subsession while loading still takes place. This will always be exactly
    // 1 - the current subsessions.
    this._profileSubsessionCounter = data.profileSubsessionCounter +
                                     this._subsessionCounter;
    return data;
  }),

  /**
   * Get the session data object to serialise to disk.
   */
  _getSessionDataObject: function() {
    return {
      sessionId: this._sessionId,
      subsessionId: this._subsessionId,
      profileSubsessionCounter: this._profileSubsessionCounter,
    };
  },

  _onEnvironmentChange: function(reason, oldEnvironment) {
    this._log.trace("_onEnvironmentChange", reason);
    let payload = this.getSessionPayload(REASON_ENVIRONMENT_CHANGE, true);

    TelemetryScheduler.reschedulePings(REASON_ENVIRONMENT_CHANGE, payload);

    let options = {
      addClientId: true,
      addEnvironment: true,
      overrideEnvironment: oldEnvironment,
    };
    TelemetryController.submitExternalPing(getPingType(payload), payload, options);
  },

  _isClassicReason: function(reason) {
    const classicReasons = [
      REASON_SAVED_SESSION,
      REASON_GATHER_PAYLOAD,
      REASON_TEST_PING,
    ];
    return classicReasons.includes(reason);
  },

  /**
   * Get an object describing the current state of this module for AsyncShutdown diagnostics.
   */
  _getState: function() {
    return {
      initialized: this._initialized,
      initStarted: this._initStarted,
      haveDelayedInitTask: !!this._delayedInitTask,
    };
  },

  /**
   * Saves the aborted session ping to disk.
   * @param {Object} [aProvidedPayload=null] A payload object to be used as an aborted
   *                 session ping. The reason of this payload is changed to aborted-session.
   *                 If not provided, a new payload is gathered.
   */
  _saveAbortedSessionPing: function(aProvidedPayload = null) {
    this._log.trace("_saveAbortedSessionPing");

    let payload = null;
    if (aProvidedPayload) {
      payload = Cu.cloneInto(aProvidedPayload, myScope);
      // Overwrite the original reason.
      payload.info.reason = REASON_ABORTED_SESSION;
    } else {
      payload = this.getSessionPayload(REASON_ABORTED_SESSION, false);
    }

    return TelemetryController.saveAbortedSessionPing(payload);
  },
};