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");

const IS_CONTENT_PROCESS = (function() {
  // We cannot use Services.appinfo here because in telemetry xpcshell tests,
  // appinfo is initially unavailable, and becomes available only later on.
  let runtime = Cc["@mozilla.org/xre/app-info;1"].getService(Ci.nsIXULRuntime);
  return runtime.processType == Ci.nsIXULRuntime.PROCESS_TYPE_CONTENT;
})();

// When modifying the payload in incompatible ways, please bump this version number
const PAYLOAD_VERSION = 1;

// This is the HG changeset of the Histogram.json file, used to associate
// submitted ping data with its histogram definition (bug 832007)
#expand const HISTOGRAMS_FILE_VERSION = "__HISTOGRAMS_FILE_VERSION__";

const LOGGER_NAME = "Toolkit.Telemetry";
const LOGGER_PREFIX = "TelemetrySession::";

const PREF_BRANCH = "toolkit.telemetry.";
const PREF_SERVER = PREF_BRANCH + "server";
const PREF_ENABLED = PREF_BRANCH + "enabled";
const PREF_PREVIOUS_BUILDID = PREF_BRANCH + "previousBuildID";
const PREF_CACHED_CLIENTID = PREF_BRANCH + "cachedClientID"
const PREF_FHR_UPLOAD_ENABLED = "datareporting.healthreport.uploadEnabled";
const PREF_ASYNC_PLUGIN_INIT = "dom.ipc.plugins.asyncInit";

const MESSAGE_TELEMETRY_PAYLOAD = "Telemetry:Payload";

// Do not gather data more than once a minute
const TELEMETRY_INTERVAL = 60000;
// Delay before intializing telemetry (ms)
const TELEMETRY_DELAY = 60000;
// Delay before initializing telemetry if we're testing (ms)
const TELEMETRY_TEST_DELAY = 100;

// 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.  On the next idle the data is sent.
const IDLE_TIMEOUT_SECONDS = 5 * 60;

var gLastMemoryPoll = null;

let gWasDebuggerAttached = false;

function getLocale() {
  return Cc["@mozilla.org/chrome/chrome-registry;1"].
         getService(Ci.nsIXULChromeRegistry).
         getSelectedLocale('global');
}

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, "ppmm",
                                   "@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, "TelemetryPing",
                                  "resource://gre/modules/TelemetryPing.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "TelemetryFile",
                                  "resource://gre/modules/TelemetryFile.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, "UpdateChannel",
                                  "resource://gre/modules/UpdateChannel.jsm");

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

/**
 * Read current process I/O counters.
 */
let 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)];
  }
};

this.EXPORTED_SYMBOLS = ["TelemetrySession"];

this.TelemetrySession = Object.freeze({
  Constants: Object.freeze({
    PREF_ENABLED: PREF_ENABLED,
    PREF_SERVER: PREF_SERVER,
    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.
   * @returns Object
   */
  getPayload: function(reason) {
    return Impl.getPayload(reason);
  },
  /**
   * Save histograms to a file.
   * Used only for testing purposes.
   *
   * @param {nsIFile} aFile The file to load from.
   */
  testSaveHistograms: function(aFile) {
    return Impl.testSaveHistograms(aFile);
  },
  /**
   * 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);
  },
  /**
   * Load histograms from a file.
   * Used only for testing purposes.
   *
   * @param aFile - File to load from.
   */
  testLoadHistograms: function(aFile) {
    return Impl.testLoadHistograms(aFile);
  },
  /**
   * 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.
   */
  reset: function() {
    this.uninstall();
    return this.setup();
  },
  /**
   * Used only for testing purposes.
   */
  shutdown: function() {
    return Impl.shutdown(true);
  },
  /**
   * Used only for testing purposes.
   */
  setup: function() {
    return Impl.setupChromeProcess(true);
  },
  /**
   * Used only for testing purposes.
   */
  uninstall: function() {
    try {
      Impl.uninstall();
    } catch (ex) {
      // Ignore errors
    }
  },
  /**
   * Send a notification.
   */
  observe: function (aSubject, aTopic, aData) {
    return Impl.observe(aSubject, aTopic, aData);
  },
  /**
   * The client id send with the telemetry ping.
   *
   * @return The client id as string, or null.
   */
   get clientID() {
    return Impl.clientID;
   },
});

let Impl = {
  _histograms: {},
  _initialized: false,
  _log: null,
  _prevValues: {},
  // Generate a unique id once per session so the server can cope with
  // duplicate submissions.
  _uuid: generateUUID(),
  // 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: {},
  _prevSession: null,
  _hasWindowRestoredObserver: false,
  _hasXulWindowVisibleObserver: false,
  _startupIO : {},
  // The previous build ID, if this is the first run with a new build.
  // Undefined if this is not the first run, or the previous build ID is unknown.
  _previousBuildID: undefined,
  // 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: [],

  /**
   * Gets a series of simple measurements (counters). At the moment, this
   * only returns startup data from nsIAppStartup.getStartupInfo().
   *
   * @return simple measurements as a dictionary.
   */
  getSimpleMeasurements: function getSimpleMeasurements(forSavedSession) {
    this._log.trace("getSimpleMeasurements");

    let si = Services.startup.getStartupInfo();

    // Measurements common to chrome and content processes.
    var ret = {
      // uptime in minutes
      uptime: Math.round((new Date() - si.process) / 60000)
    }

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

    if (si.process) {
      for each (let field in 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 (IS_CONTENT_PROCESS) {
      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];

    let hasPingBeenSent = false;
    try {
      hasPingBeenSent = Telemetry.getHistogramById("TELEMETRY_SUCCESS").snapshot().sum > 0;
    } catch(e) {
    }
    if (!forSavedSession || hasPingBeenSent) {
      ret.savedPings = TelemetryFile.pingsLoaded;
    }

    ret.activeTicks = -1;
    if ("@mozilla.org/datareporting/service;1" in Cc) {
      let drs = Cc["@mozilla.org/datareporting/service;1"]
                  .getService(Ci.nsISupports)
                  .wrappedJSObject;

      let sr = drs.getSessionRecorder();
      if (sr) {
        ret.activeTicks = sr.activeTicks;
      }
    }

    ret.pingsOverdue = TelemetryFile.pingsOverdue;
    ret.pingsDiscarded = TelemetryFile.pingsDiscarded;

    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;
   * - log_sum, log_sum_squares: doubles;
   * - 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>,
   *   sum_squares_lo: <sum_squares_lo>,
   *   sum_squares_hi: <sum_squares_hi>,
   *   log_sum: <log_sum>, log_sum_squares: <log_sum_squares>,
   *   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
    };

    if (hgram.histogram_type == Telemetry.HISTOGRAM_EXPONENTIAL) {
      retgram.log_sum = hgram.log_sum;
      retgram.log_sum_squares = hgram.log_sum_squares;
    } else {
      retgram.sum_squares_lo = hgram.sum_squares_lo;
      retgram.sum_squares_hi = hgram.sum_squares_hi;
    }

    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;
  },

  getHistograms: function getHistograms(subsession) {
    this._log.trace("getHistograms");

    let registered =
      Telemetry.registeredHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN, []);
    let hls = subsession ? Telemetry.subsessionHistogramSnapshots : Telemetry.histogramSnapshots;
    let ret = {};

    for (let name of registered) {
      for (let n of [name, "STARTUP_" + name]) {
        if (n in hls) {
          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) {
    this._log.trace("getKeyedHistograms");

    let registered =
      Telemetry.registeredKeyedHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN, []);
    let ret = {};

    for (let id of registered) {
      ret[id] = {};
      let keyed = Telemetry.getKeyedHistogramById(id);
      let snapshot = subsession ? keyed.subsessionSnapshot() : keyed.snapshot();
      for (let key of Object.keys(snapshot)) {
        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);

    let ai = Services.appinfo;
    let ret = {
      reason: reason,
      OS: ai.OS,
      appVersion: ai.version, // TODO: In Environment, but needed for |submissionPath|
      appName: ai.name, // TODO: In Environment, but needed for |submissionPath|
      appBuildID: ai.appBuildID, // TODO: In Environment, but needed for |submissionPath|
      appUpdateChannel: UpdateChannel.get(), // TODO: In Environment, but needed for |submissionPath|
      platformBuildID: ai.platformBuildID,
      revision: HISTOGRAMS_FILE_VERSION,
      asyncPluginInit: Preferences.get(PREF_ASYNC_PLUGIN_INIT, false)
    };

    // In order to share profile data, the appName used for Metro Firefox is "Firefox",
    // (the same as desktop Firefox). We set it to "MetroFirefox" here in order to
    // differentiate telemetry pings sent by desktop vs. metro Firefox.
    if(Services.metro && Services.metro.immersive) {
      ret.appName = "MetroFirefox";
    }

    if (this._previousBuildID) {
      ret.previousBuildID = this._previousBuildID;
    }

    if (this._addons)
      ret.addons = this._addons;

    let flashVersion = this.getFlashVersion();
    if (flashVersion)
      ret.flashVersion = flashVersion;

    return ret;
  },

  /**
   * Pull values from about:memory into corresponding histograms
   */
  gatherMemory: function gatherMemory() {
    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_TelemetryPing.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_TelemetryPing.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", "residentFast");
    b("MEMORY_HEAP_ALLOCATED", "heapAllocated");
    p("MEMORY_HEAP_COMMITTED_UNUSED_RATIO", "heapOverheadRatio");
    b("MEMORY_JS_GC_HEAP", "JSMainRuntimeGCHeap");
    b("MEMORY_JS_MAIN_RUNTIME_TEMPORARY_PEAK", "JSMainRuntimeTemporaryPeak");
    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("MEMORY_EVENTS_VIRTUAL", "lowMemoryEventsVirtual");
    cc("MEMORY_EVENTS_PHYSICAL", "lowMemoryEventsPhysical");
    c("GHOST_WINDOWS", "ghostWindows");
    cc("PAGE_FAULTS_HARD", "pageFaultsHard");

    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 [for (child of this._childTelemetry) child.payload];
  },

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

    let info =
      Telemetry.registeredHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN, []);
    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) {
    const classicReasons = [
      "saved-session",
      "idle-daily",
      "gather-payload",
      "test-ping",
    ];
    const isSubsession = classicReasons.indexOf(reason) == -1;
    this._log.trace("assemblePayloadWithMeasurements - reason: " + reason +
                    ", submitting subsession data: " + isSubsession);

    // Payload common to chrome and content processes.
    let payloadObj = {
      ver: PAYLOAD_VERSION,
      simpleMeasurements: simpleMeasurements,
      histograms: this.getHistograms(isSubsession),
      keyedHistograms: this.getKeyedHistograms(isSubsession),
      chromeHangs: Telemetry.chromeHangs,
      threadHangStats: this.getThreadHangStats(Telemetry.threadHangStats),
      log: TelemetryLog.entries(),
    };

    if (IS_CONTENT_PROCESS) {
      return payloadObj;
    }

    // Additional payload for chrome process.
    payloadObj.info = info;
    payloadObj.slowSQL = Telemetry.slowSQL;
    payloadObj.fileIOReports = Telemetry.fileIOReports;
    payloadObj.lateWrites = Telemetry.lateWrites;
    payloadObj.addonHistograms = this.getAddonHistograms();
    payloadObj.addonDetails = AddonManagerPrivate.getTelemetryDetails();
    payloadObj.UIMeasurements = UITelemetry.getUIMeasurements();

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

    let clientID = TelemetryPing.clientID;
    if (clientID && Preferences.get(PREF_FHR_UPLOAD_ENABLED, false)) {
      payloadObj.clientID = clientID;
    }

    if (this._childTelemetry.length) {
      payloadObj.childPayloads = this.getChildPayloads();
    }
    return payloadObj;
  },

  getSessionPayload: function getSessionPayload(reason) {
    this._log.trace("getSessionPayload - Reason " + reason);
    let measurements = this.getSimpleMeasurements(reason == "saved-session");
    let info = !IS_CONTENT_PROCESS ? this.getMetadata(reason) : null;
    return this.assemblePayloadWithMeasurements(measurements, info, reason);
  },

  assemblePing: function assemblePing(payloadObj, reason) {
    let slug = this._uuid;
    return { slug: slug, reason: reason, payload: payloadObj };
  },

  getSessionPayloadAndSlug: function getSessionPayloadAndSlug(reason) {
    this._log.trace("getSessionPayloadAndSlug - Reason " + reason);
    return this.assemblePing(this.getSessionPayload(reason), reason);
  },

  /**
   * 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();
    return TelemetryPing.send(reason, this.getSessionPayloadAndSlug(reason));
  },

  submissionPath: function submissionPath(ping) {
    let slug;
    if (!ping) {
      slug = this._uuid;
    } else {
      let info = ping.payload.info;
      let pathComponents = [ping.slug, info.reason, info.appName,
                            info.appVersion, info.appUpdateChannel,
                            info.appBuildID];
      slug = pathComponents.join("/");
    }
    return "/submit/telemetry/" + slug;
  },

  attachObservers: function attachObservers() {
    if (!this._initialized)
      return;
    Services.obs.addObserver(this, "cycle-collector-begin", false);
    Services.obs.addObserver(this, "idle-daily", false);
  },

  detachObservers: function detachObservers() {
    if (!this._initialized)
      return;
    Services.obs.removeObserver(this, "idle-daily");
    Services.obs.removeObserver(this, "cycle-collector-begin");
    if (this._isIdleObserver) {
      idleService.removeIdleObserver(this, IDLE_TIMEOUT_SECONDS);
      this._isIdleObserver = false;
    }
  },

  /**
   * Perform telemetry initialization for either chrome or content process.
   */
  enableTelemetryRecording: function enableTelemetryRecording(testing) {

#ifdef MOZILLA_OFFICIAL
    if (!Telemetry.canSend && !testing) {
      // We can't send data; no point in initializing observers etc.
      // Only do this for official builds so that e.g. developer builds
      // still enable Telemetry based on prefs.
      Telemetry.canRecord = false;
      this._log.config("enableTelemetryRecording - Can't send data, disabling Telemetry recording.");
      return false;
    }
#endif

    let enabled = Preferences.get(PREF_ENABLED, false);
    this._server = Preferences.get(PREF_SERVER, undefined);
    if (!enabled) {
      // Turn off local telemetry if telemetry is disabled.
      // This may change once about:telemetry is added.
      Telemetry.canRecord = false;
      this._log.config("enableTelemetryRecording - Telemetry is disabled, turning off Telemetry recording.");
      return false;
    }

    return true;
  },

  /**
   * Initializes telemetry within a timer. If there is no PREF_SERVER set, don't turn on telemetry.
   */
  setupChromeProcess: function setupChromeProcess(testing) {
    if (testing && !this._log) {
      this._log = Log.repository.getLoggerWithMessagePrefix(LOGGER_NAME, LOGGER_PREFIX);
    }

    this._log.trace("setupChromeProcess");

    // 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, undefined);
    let thisBuildID = Services.appinfo.appBuildID;
    // If there is no previousBuildID preference, this._previousBuildID remains
    // undefined so no value is sent in the telemetry metadata.
    if (previousBuildID != thisBuildID) {
      this._previousBuildID = previousBuildID;
      Preferences.set(PREF_PREVIOUS_BUILDID, thisBuildID);
    }

    if (!this.enableTelemetryRecording(testing)) {
      this._log.config("setupChromeProcess - Telemetry recording is disabled, skipping Chrome process setup.");
      return Promise.resolve();
    }

    AsyncShutdown.sendTelemetry.addBlocker(
      "TelemetrySession: shutting down",
      function condition(){
        this.uninstall();
        if (Telemetry.canSend) {
          return this.savePendingPings();
        }
      }.bind(this));

    Services.obs.addObserver(this, "sessionstore-windows-restored", false);
#ifdef MOZ_WIDGET_ANDROID
    Services.obs.addObserver(this, "application-background", false);
#endif
    Services.obs.addObserver(this, "xul-window-visible", false);
    this._hasWindowRestoredObserver = true;
    this._hasXulWindowVisibleObserver = true;

    ppmm.addMessageListener(MESSAGE_TELEMETRY_PAYLOAD, this);

    // Delay full telemetry initialization to give the browser time to
    // run various late initializers. Otherwise our gathered memory
    // footprint and other numbers would be too optimistic.
    let deferred = Promise.defer();
    let delayedTask = new DeferredTask(function* () {
      this._initialized = true;

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

      Telemetry.asyncFetchTelemetryData(function () {});
      deferred.resolve();

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

    delayedTask.arm();
    return deferred.promise;
  },

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

    if (!this.enableTelemetryRecording()) {
      return;
    }

    Services.obs.addObserver(this, "content-child-shutdown", false);

    this.gatherStartupHistograms();

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

      this.attachObservers();
      this.gatherMemory();
    }.bind(this), TELEMETRY_DELAY);

    delayedTask.arm();
  },

  testLoadHistograms: function testLoadHistograms(file) {
    return TelemetryFile.testLoadHistograms(file);
  },

  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:
    {
      let target = message.target;
      for (let child of this._childTelemetry) {
        if (child.source.get() === target) {
          // Update existing telemetry data.
          child.payload = message.data;
          return;
        }
      }
      // Did not find existing child in this._childTelemetry.
      this._childTelemetry.push({
        source: Cu.getWeakReference(target),
        payload: message.data,
      });
      break;
    }
    default:
      throw new Error("Telemetry.receiveMessage: bad message name");
    }
  },

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

  savePendingPings: function savePendingPings() {
    this._log.trace("savePendingPings");
    let sessionPing = this.getSessionPayloadAndSlug("saved-session");
    return TelemetryFile.savePendingPings(sessionPing);
  },

  testSaveHistograms: function testSaveHistograms(file) {
    return TelemetryFile.savePingToFile(this.getSessionPayloadAndSlug("saved-session"),
      file.path, true);
  },

  /**
   * 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;
    }
#ifdef MOZ_WIDGET_ANDROID
    Services.obs.removeObserver(this, "application-background", false);
#endif
  },

  getPayload: function getPayload(reason) {
    this._log.trace("getPayload");
    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);
  },

  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;
  },

  sendIdlePing: function sendIdlePing(aTest) {
    this._log.trace("sendIdlePing");
    if (this._isIdleObserver) {
      idleService.removeIdleObserver(this, IDLE_TIMEOUT_SECONDS);
      this._isIdleObserver = false;
    }
    if (aTest) {
      return this.send("test-ping");
    } else if (Telemetry.canSend) {
      return this.send("idle-daily");
    }
  },

  testPing: function testPing() {
    return this.sendIdlePing(true);
  },

  /**
   * This observer drives telemetry.
   */
  observe: function (aSubject, aTopic, aData) {
    if (!this._log) {
      this._log = Log.repository.getLoggerWithMessagePrefix(LOGGER_NAME, LOGGER_PREFIX);
    }

    this._log.trace("observe - " + aTopic + " notified.");

    switch (aTopic) {
    case "profile-after-change":
      // profile-after-change is only registered for chrome processes.
      return this.setupChromeProcess();
    case "app-startup":
      // app-startup is only registered for content processes.
      return this.setupContentProcess();
    case "content-child-shutdown":
      // content-child-shutdown is only registered for content processes.
      Services.obs.removeObserver(this, "content-child-shutdown");
      this.uninstall();

      if (Telemetry.canSend) {
        this.sendContentProcessPing("saved-session");
      }
      break;
    case "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, since ping will happen soon.
        Services.obs.notifyObservers(null, "gather-telemetry", null);
        // The ping happens at the first idle of length IDLE_TIMEOUT_SECONDS.
        idleService.addIdleObserver(this, IDLE_TIMEOUT_SECONDS);
        this._isIdleObserver = true;
      }).bind(this), Ci.nsIThread.DISPATCH_NORMAL);
      break;
    case "idle":
      this.sendIdlePing(false, this._server);
      break;

#ifdef MOZ_WIDGET_ANDROID
    // 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.
    case "application-background":
      if (Telemetry.canSend) {
        let ping = this.getSessionPayloadAndSlug("saved-session");
        TelemetryFile.savePing(ping, true);
      }
      break;
#endif
    }
  },

  /**
   * This tells TelemetryPing to uninitialize and save any pending pings.
   * @param testing Optional. If true, always saves the ping whether Telemetry
   *                can send pings or not, which is used for testing.
   */
  shutdown: function(testing = false) {
    this.uninstall();
    if (Telemetry.canSend || testing) {
      return this.savePendingPings();
    }
  },
};