1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/browser/components/sessionstore/src/SessionFile.jsm Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,258 @@
1.4 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.5 + * License, v. 2.0. If a copy of the MPL was not distributed with this file,
1.6 + * You can obtain one at http://mozilla.org/MPL/2.0/. */
1.7 +
1.8 +"use strict";
1.9 +
1.10 +this.EXPORTED_SYMBOLS = ["SessionFile"];
1.11 +
1.12 +/**
1.13 + * Implementation of all the disk I/O required by the session store.
1.14 + * This is a private API, meant to be used only by the session store.
1.15 + * It will change. Do not use it for any other purpose.
1.16 + *
1.17 + * Note that this module implicitly depends on one of two things:
1.18 + * 1. either the asynchronous file I/O system enqueues its requests
1.19 + * and never attempts to simultaneously execute two I/O requests on
1.20 + * the files used by this module from two distinct threads; or
1.21 + * 2. the clients of this API are well-behaved and do not place
1.22 + * concurrent requests to the files used by this module.
1.23 + *
1.24 + * Otherwise, we could encounter bugs, especially under Windows,
1.25 + * e.g. if a request attempts to write sessionstore.js while
1.26 + * another attempts to copy that file.
1.27 + *
1.28 + * This implementation uses OS.File, which guarantees property 1.
1.29 + */
1.30 +
1.31 +const Cu = Components.utils;
1.32 +const Cc = Components.classes;
1.33 +const Ci = Components.interfaces;
1.34 +const Cr = Components.results;
1.35 +
1.36 +Cu.import("resource://gre/modules/Services.jsm");
1.37 +Cu.import("resource://gre/modules/XPCOMUtils.jsm");
1.38 +Cu.import("resource://gre/modules/osfile.jsm");
1.39 +Cu.import("resource://gre/modules/osfile/_PromiseWorker.jsm", this);
1.40 +Cu.import("resource://gre/modules/Promise.jsm");
1.41 +Cu.import("resource://gre/modules/AsyncShutdown.jsm");
1.42 +
1.43 +XPCOMUtils.defineLazyModuleGetter(this, "console",
1.44 + "resource://gre/modules/devtools/Console.jsm");
1.45 +XPCOMUtils.defineLazyModuleGetter(this, "TelemetryStopwatch",
1.46 + "resource://gre/modules/TelemetryStopwatch.jsm");
1.47 +XPCOMUtils.defineLazyModuleGetter(this, "Task",
1.48 + "resource://gre/modules/Task.jsm");
1.49 +XPCOMUtils.defineLazyServiceGetter(this, "Telemetry",
1.50 + "@mozilla.org/base/telemetry;1", "nsITelemetry");
1.51 +
1.52 +this.SessionFile = {
1.53 + /**
1.54 + * Read the contents of the session file, asynchronously.
1.55 + */
1.56 + read: function () {
1.57 + return SessionFileInternal.read();
1.58 + },
1.59 + /**
1.60 + * Write the contents of the session file, asynchronously.
1.61 + */
1.62 + write: function (aData) {
1.63 + return SessionFileInternal.write(aData);
1.64 + },
1.65 + /**
1.66 + * Gather telemetry statistics.
1.67 + *
1.68 + *
1.69 + * Most of the work is done off the main thread but there is a main
1.70 + * thread cost involved to send data to the worker thread. This method
1.71 + * should therefore be called only when we know that it will not disrupt
1.72 + * the user's experience, e.g. on idle-daily.
1.73 + *
1.74 + * @return {Promise}
1.75 + * @promise {object} An object holding all the information to be submitted
1.76 + * to Telemetry.
1.77 + */
1.78 + gatherTelemetry: function(aData) {
1.79 + return SessionFileInternal.gatherTelemetry(aData);
1.80 + },
1.81 + /**
1.82 + * Create a backup copy, asynchronously.
1.83 + * This is designed to perform backup on upgrade.
1.84 + */
1.85 + createBackupCopy: function (ext) {
1.86 + return SessionFileInternal.createBackupCopy(ext);
1.87 + },
1.88 + /**
1.89 + * Remove a backup copy, asynchronously.
1.90 + * This is designed to clean up a backup on upgrade.
1.91 + */
1.92 + removeBackupCopy: function (ext) {
1.93 + return SessionFileInternal.removeBackupCopy(ext);
1.94 + },
1.95 + /**
1.96 + * Wipe the contents of the session file, asynchronously.
1.97 + */
1.98 + wipe: function () {
1.99 + SessionFileInternal.wipe();
1.100 + }
1.101 +};
1.102 +
1.103 +Object.freeze(SessionFile);
1.104 +
1.105 +/**
1.106 + * Utilities for dealing with promises and Task.jsm
1.107 + */
1.108 +let SessionFileInternal = {
1.109 + /**
1.110 + * The path to sessionstore.js
1.111 + */
1.112 + path: OS.Path.join(OS.Constants.Path.profileDir, "sessionstore.js"),
1.113 +
1.114 + /**
1.115 + * The path to sessionstore.bak
1.116 + */
1.117 + backupPath: OS.Path.join(OS.Constants.Path.profileDir, "sessionstore.bak"),
1.118 +
1.119 + /**
1.120 + * The promise returned by the latest call to |write|.
1.121 + * We use it to ensure that AsyncShutdown.profileBeforeChange cannot
1.122 + * interrupt a call to |write|.
1.123 + */
1.124 + _latestWrite: null,
1.125 +
1.126 + /**
1.127 + * |true| once we have decided to stop receiving write instructiosn
1.128 + */
1.129 + _isClosed: false,
1.130 +
1.131 + read: function () {
1.132 + // We must initialize the worker during startup so it will be ready to
1.133 + // perform the final write. If shutdown happens soon after startup and
1.134 + // the worker has not started yet we may not write.
1.135 + // See Bug 964531.
1.136 + SessionWorker.post("init");
1.137 +
1.138 + return Task.spawn(function*() {
1.139 + for (let filename of [this.path, this.backupPath]) {
1.140 + try {
1.141 + let startMs = Date.now();
1.142 +
1.143 + let data = yield OS.File.read(filename, { encoding: "utf-8" });
1.144 +
1.145 + Telemetry.getHistogramById("FX_SESSION_RESTORE_READ_FILE_MS")
1.146 + .add(Date.now() - startMs);
1.147 +
1.148 + return data;
1.149 + } catch (ex if ex instanceof OS.File.Error && ex.becauseNoSuchFile) {
1.150 + // Ignore exceptions about non-existent files.
1.151 + }
1.152 + }
1.153 +
1.154 + return "";
1.155 + }.bind(this));
1.156 + },
1.157 +
1.158 + gatherTelemetry: function(aStateString) {
1.159 + return Task.spawn(function() {
1.160 + let msg = yield SessionWorker.post("gatherTelemetry", [aStateString]);
1.161 + this._recordTelemetry(msg.telemetry);
1.162 + throw new Task.Result(msg.telemetry);
1.163 + }.bind(this));
1.164 + },
1.165 +
1.166 + write: function (aData) {
1.167 + if (this._isClosed) {
1.168 + return Promise.reject(new Error("SessionFile is closed"));
1.169 + }
1.170 + let refObj = {};
1.171 +
1.172 + let isFinalWrite = false;
1.173 + if (Services.startup.shuttingDown) {
1.174 + // If shutdown has started, we will want to stop receiving
1.175 + // write instructions.
1.176 + isFinalWrite = this._isClosed = true;
1.177 + }
1.178 +
1.179 + return this._latestWrite = Task.spawn(function task() {
1.180 + TelemetryStopwatch.start("FX_SESSION_RESTORE_WRITE_FILE_LONGEST_OP_MS", refObj);
1.181 +
1.182 + try {
1.183 + let promise = SessionWorker.post("write", [aData]);
1.184 + // At this point, we measure how long we stop the main thread
1.185 + TelemetryStopwatch.finish("FX_SESSION_RESTORE_WRITE_FILE_LONGEST_OP_MS", refObj);
1.186 +
1.187 + // Now wait for the result and record how long the write took
1.188 + let msg = yield promise;
1.189 + this._recordTelemetry(msg.telemetry);
1.190 + } catch (ex) {
1.191 + TelemetryStopwatch.cancel("FX_SESSION_RESTORE_WRITE_FILE_LONGEST_OP_MS", refObj);
1.192 + console.error("Could not write session state file ", this.path, ex);
1.193 + }
1.194 +
1.195 + if (isFinalWrite) {
1.196 + Services.obs.notifyObservers(null, "sessionstore-final-state-write-complete", "");
1.197 + }
1.198 + }.bind(this));
1.199 + },
1.200 +
1.201 + createBackupCopy: function (ext) {
1.202 + return SessionWorker.post("createBackupCopy", [ext]);
1.203 + },
1.204 +
1.205 + removeBackupCopy: function (ext) {
1.206 + return SessionWorker.post("removeBackupCopy", [ext]);
1.207 + },
1.208 +
1.209 + wipe: function () {
1.210 + SessionWorker.post("wipe");
1.211 + },
1.212 +
1.213 + _recordTelemetry: function(telemetry) {
1.214 + for (let id of Object.keys(telemetry)){
1.215 + let value = telemetry[id];
1.216 + let samples = [];
1.217 + if (Array.isArray(value)) {
1.218 + samples.push(...value);
1.219 + } else {
1.220 + samples.push(value);
1.221 + }
1.222 + let histogram = Telemetry.getHistogramById(id);
1.223 + for (let sample of samples) {
1.224 + histogram.add(sample);
1.225 + }
1.226 + }
1.227 + }
1.228 +};
1.229 +
1.230 +// Interface to a dedicated thread handling I/O
1.231 +let SessionWorker = (function () {
1.232 + let worker = new PromiseWorker("resource:///modules/sessionstore/SessionWorker.js",
1.233 + OS.Shared.LOG.bind("SessionWorker"));
1.234 + return {
1.235 + post: function post(...args) {
1.236 + let promise = worker.post.apply(worker, args);
1.237 + return promise.then(
1.238 + null,
1.239 + function onError(error) {
1.240 + // Decode any serialized error
1.241 + if (error instanceof PromiseWorker.WorkerError) {
1.242 + throw OS.File.Error.fromMsg(error.data);
1.243 + }
1.244 + // Extract something meaningful from ErrorEvent
1.245 + if (error instanceof ErrorEvent) {
1.246 + throw new Error(error.message, error.filename, error.lineno);
1.247 + }
1.248 + throw error;
1.249 + }
1.250 + );
1.251 + }
1.252 + };
1.253 +})();
1.254 +
1.255 +// Ensure that we can write sessionstore.js cleanly before the profile
1.256 +// becomes unaccessible.
1.257 +AsyncShutdown.profileBeforeChange.addBlocker(
1.258 + "SessionFile: Finish writing the latest sessionstore.js",
1.259 + function() {
1.260 + return SessionFileInternal._latestWrite;
1.261 + });
