381 lines
11 KiB
JavaScript
381 lines
11 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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/**
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* A worker dedicated to handle I/O for Session Store.
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*/
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"use strict";
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importScripts("resource://gre/modules/osfile.jsm");
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var PromiseWorker = require("resource://gre/modules/workers/PromiseWorker.js");
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var File = OS.File;
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var Encoder = new TextEncoder();
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var Decoder = new TextDecoder();
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var worker = new PromiseWorker.AbstractWorker();
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worker.dispatch = function(method, args = []) {
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return Agent[method](...args);
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};
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worker.postMessage = function(result, ...transfers) {
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self.postMessage(result, ...transfers);
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};
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worker.close = function() {
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self.close();
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};
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self.addEventListener("message", msg => worker.handleMessage(msg));
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// The various possible states
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/**
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* We just started (we haven't written anything to disk yet) from
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* `Paths.clean`. The backup directory may not exist.
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*/
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const STATE_CLEAN = "clean";
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/**
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* We know that `Paths.recovery` is good, either because we just read
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* it (we haven't written anything to disk yet) or because have
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* already written once to `Paths.recovery` during this session.
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* `Paths.clean` is absent or invalid. The backup directory exists.
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*/
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const STATE_RECOVERY = "recovery";
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/**
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* We just started from `Paths.recoverBackupy` (we haven't written
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* anything to disk yet). Both `Paths.clean` and `Paths.recovery` are
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* absent or invalid. The backup directory exists.
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*/
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const STATE_RECOVERY_BACKUP = "recoveryBackup";
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/**
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* We just started from `Paths.upgradeBackup` (we haven't written
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* anything to disk yet). Both `Paths.clean`, `Paths.recovery` and
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* `Paths.recoveryBackup` are absent or invalid. The backup directory
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* exists.
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*/
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const STATE_UPGRADE_BACKUP = "upgradeBackup";
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/**
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* We just started without a valid session store file (we haven't
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* written anything to disk yet). The backup directory may not exist.
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*/
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const STATE_EMPTY = "empty";
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var Agent = {
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// Path to the files used by the SessionWorker
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Paths: null,
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/**
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* The current state of the worker, as one of the following strings:
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* - "permanent", once the first write has been completed;
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* - "empty", before the first write has been completed,
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* if we have started without any sessionstore;
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* - one of "clean", "recovery", "recoveryBackup", "cleanBackup",
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* "upgradeBackup", before the first write has been completed, if
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* we have started by loading the corresponding file.
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*/
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state: null,
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/**
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* Number of old upgrade backups that are being kept
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*/
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maxUpgradeBackups: null,
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/**
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* Initialize (or reinitialize) the worker
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*
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* @param {string} origin Which of sessionstore.js or its backups
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* was used. One of the `STATE_*` constants defined above.
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* @param {object} paths The paths at which to find the various files.
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* @param {object} prefs The preferences the worker needs to known.
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*/
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init(origin, paths, prefs = {}) {
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if (!(origin in paths || origin == STATE_EMPTY)) {
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throw new TypeError("Invalid origin: " + origin);
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}
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// Check that all required preference values were passed.
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for (let pref of ["maxUpgradeBackups", "maxSerializeBack", "maxSerializeForward"]) {
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if (!prefs.hasOwnProperty(pref)) {
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throw new TypeError(`Missing preference value for ${pref}`);
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}
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}
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this.state = origin;
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this.Paths = paths;
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this.maxUpgradeBackups = prefs.maxUpgradeBackups;
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this.maxSerializeBack = prefs.maxSerializeBack;
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this.maxSerializeForward = prefs.maxSerializeForward;
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this.upgradeBackupNeeded = paths.nextUpgradeBackup != paths.upgradeBackup;
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return {result: true};
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},
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/**
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* Write the session to disk.
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* Write the session to disk, performing any necessary backup
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* along the way.
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*
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* @param {object} state The state to write to disk.
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* @param {object} options
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* - performShutdownCleanup If |true|, we should
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* perform shutdown-time cleanup to ensure that private data
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* is not left lying around;
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* - isFinalWrite If |true|, write to Paths.clean instead of
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* Paths.recovery
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*/
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write: function (state, options = {}) {
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let exn;
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let telemetry = {};
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// Cap the number of backward and forward shistory entries on shutdown.
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if (options.isFinalWrite) {
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for (let window of state.windows) {
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for (let tab of window.tabs) {
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let lower = 0;
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let upper = tab.entries.length;
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if (this.maxSerializeBack > -1) {
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lower = Math.max(lower, tab.index - this.maxSerializeBack - 1);
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}
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if (this.maxSerializeForward > -1) {
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upper = Math.min(upper, tab.index + this.maxSerializeForward);
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}
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tab.entries = tab.entries.slice(lower, upper);
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tab.index -= lower;
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}
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}
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}
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let stateString = JSON.stringify(state);
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let data = Encoder.encode(stateString);
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let startWriteMs, stopWriteMs;
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try {
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if (this.state == STATE_CLEAN || this.state == STATE_EMPTY) {
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// The backups directory may not exist yet. In all other cases,
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// we have either already read from or already written to this
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// directory, so we are satisfied that it exists.
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File.makeDir(this.Paths.backups);
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}
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if (this.state == STATE_CLEAN) {
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// Move $Path.clean out of the way, to avoid any ambiguity as
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// to which file is more recent.
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File.move(this.Paths.clean, this.Paths.cleanBackup);
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}
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startWriteMs = Date.now();
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if (options.isFinalWrite) {
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// We are shutting down. At this stage, we know that
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// $Paths.clean is either absent or corrupted. If it was
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// originally present and valid, it has been moved to
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// $Paths.cleanBackup a long time ago. We can therefore write
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// with the guarantees that we erase no important data.
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File.writeAtomic(this.Paths.clean, data, {
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tmpPath: this.Paths.clean + ".tmp"
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});
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} else if (this.state == STATE_RECOVERY) {
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// At this stage, either $Paths.recovery was written >= 15
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// seconds ago during this session or we have just started
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// from $Paths.recovery left from the previous session. Either
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// way, $Paths.recovery is good. We can move $Path.backup to
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// $Path.recoveryBackup without erasing a good file with a bad
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// file.
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File.writeAtomic(this.Paths.recovery, data, {
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tmpPath: this.Paths.recovery + ".tmp",
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backupTo: this.Paths.recoveryBackup
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});
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} else {
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// In other cases, either $Path.recovery is not necessary, or
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// it doesn't exist or it has been corrupted. Regardless,
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// don't backup $Path.recovery.
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File.writeAtomic(this.Paths.recovery, data, {
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tmpPath: this.Paths.recovery + ".tmp"
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});
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}
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stopWriteMs = Date.now();
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} catch (ex) {
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// Don't throw immediately
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exn = exn || ex;
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}
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// If necessary, perform an upgrade backup
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let upgradeBackupComplete = false;
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if (this.upgradeBackupNeeded
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&& (this.state == STATE_CLEAN || this.state == STATE_UPGRADE_BACKUP)) {
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try {
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// If we loaded from `clean`, the file has since then been renamed to `cleanBackup`.
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let path = this.state == STATE_CLEAN ? this.Paths.cleanBackup : this.Paths.upgradeBackup;
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File.copy(path, this.Paths.nextUpgradeBackup);
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this.upgradeBackupNeeded = false;
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upgradeBackupComplete = true;
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} catch (ex) {
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// Don't throw immediately
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exn = exn || ex;
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}
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// Find all backups
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let iterator;
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let backups = []; // array that will contain the paths to all upgrade backup
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let upgradeBackupPrefix = this.Paths.upgradeBackupPrefix; // access for forEach callback
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try {
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iterator = new File.DirectoryIterator(this.Paths.backups);
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iterator.forEach(function (file) {
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if (file.path.startsWith(upgradeBackupPrefix)) {
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backups.push(file.path);
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}
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}, this);
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} catch (ex) {
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// Don't throw immediately
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exn = exn || ex;
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} finally {
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if (iterator) {
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iterator.close();
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}
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}
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// If too many backups exist, delete them
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if (backups.length > this.maxUpgradeBackups) {
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// Use alphanumerical sort since dates are in YYYYMMDDHHMMSS format
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backups.sort().forEach((file, i) => {
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// remove backup file if it is among the first (n-maxUpgradeBackups) files
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if (i < backups.length - this.maxUpgradeBackups) {
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File.remove(file);
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}
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});
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}
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}
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if (options.performShutdownCleanup && !exn) {
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// During shutdown, if auto-restore is disabled, we need to
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// remove possibly sensitive data that has been stored purely
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// for crash recovery. Note that this slightly decreases our
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// ability to recover from OS-level/hardware-level issue.
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// If an exception was raised, we assume that we still need
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// these files.
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File.remove(this.Paths.recoveryBackup);
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File.remove(this.Paths.recovery);
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}
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this.state = STATE_RECOVERY;
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if (exn) {
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throw exn;
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}
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return {
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result: {
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upgradeBackup: upgradeBackupComplete
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},
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telemetry: {
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FX_SESSION_RESTORE_WRITE_FILE_MS: stopWriteMs - startWriteMs,
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FX_SESSION_RESTORE_FILE_SIZE_BYTES: data.byteLength,
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}
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};
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},
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/**
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* Wipes all files holding session data from disk.
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*/
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wipe: function () {
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// Don't stop immediately in case of error.
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let exn = null;
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// Erase main session state file
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try {
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File.remove(this.Paths.clean);
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} catch (ex) {
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// Don't stop immediately.
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exn = exn || ex;
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}
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// Wipe the Session Restore directory
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try {
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this._wipeFromDir(this.Paths.backups, null);
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} catch (ex) {
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exn = exn || ex;
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}
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try {
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File.removeDir(this.Paths.backups);
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} catch (ex) {
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exn = exn || ex;
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}
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// Wipe legacy Ression Restore files from the profile directory
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try {
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this._wipeFromDir(OS.Constants.Path.profileDir, "sessionstore.bak");
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} catch (ex) {
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exn = exn || ex;
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}
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this.state = STATE_EMPTY;
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if (exn) {
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throw exn;
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}
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return { result: true };
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},
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/**
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* Wipe a number of files from a directory.
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*
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* @param {string} path The directory.
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* @param {string|null} prefix If provided, only remove files whose
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* name starts with a specific prefix.
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*/
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_wipeFromDir: function(path, prefix) {
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// Sanity check
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if (typeof prefix == "undefined" || prefix == "") {
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throw new TypeError();
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}
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let exn = null;
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let iterator = new File.DirectoryIterator(path);
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if (!iterator.exists()) {
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return;
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}
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for (let entry in iterator) {
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if (entry.isDir) {
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continue;
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}
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if (!prefix || entry.name.startsWith(prefix)) {
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try {
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File.remove(entry.path);
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} catch (ex) {
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// Don't stop immediately
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exn = exn || ex;
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}
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}
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}
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if (exn) {
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throw exn;
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}
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},
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};
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function isNoSuchFileEx(aReason) {
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return aReason instanceof OS.File.Error && aReason.becauseNoSuchFile;
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}
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/**
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* Estimate the number of bytes that a data structure will use on disk
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* once serialized.
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*/
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function getByteLength(str) {
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return Encoder.encode(JSON.stringify(str)).byteLength;
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}
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