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Diffstat (limited to 'browser/components/sessionstore/SessionFile.sys.mjs')
| -rw-r--r-- | browser/components/sessionstore/SessionFile.sys.mjs | 467 |
1 files changed, 467 insertions, 0 deletions
diff --git a/browser/components/sessionstore/SessionFile.sys.mjs b/browser/components/sessionstore/SessionFile.sys.mjs new file mode 100644 index 0000000000..1e5a3bf718 --- /dev/null +++ b/browser/components/sessionstore/SessionFile.sys.mjs @@ -0,0 +1,467 @@ +/* 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/. */ + +/** + * Implementation of all the disk I/O required by the session store. + * This is a private API, meant to be used only by the session store. + * It will change. Do not use it for any other purpose. + * + * Note that this module depends on SessionWriter and that it enqueues its I/O + * requests and never attempts to simultaneously execute two I/O requests on + * the files used by this module from two distinct threads. + * Otherwise, we could encounter bugs, especially under Windows, + * e.g. if a request attempts to write sessionstore.js while + * another attempts to copy that file. + */ + +const lazy = {}; + +ChromeUtils.defineESModuleGetters(lazy, { + RunState: "resource:///modules/sessionstore/RunState.sys.mjs", + SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs", + SessionWriter: "resource:///modules/sessionstore/SessionWriter.sys.mjs", +}); + +const PREF_UPGRADE_BACKUP = "browser.sessionstore.upgradeBackup.latestBuildID"; +const PREF_MAX_UPGRADE_BACKUPS = + "browser.sessionstore.upgradeBackup.maxUpgradeBackups"; + +const PREF_MAX_SERIALIZE_BACK = "browser.sessionstore.max_serialize_back"; +const PREF_MAX_SERIALIZE_FWD = "browser.sessionstore.max_serialize_forward"; + +export var SessionFile = { + /** + * Read the contents of the session file, asynchronously. + */ + read() { + return SessionFileInternal.read(); + }, + /** + * Write the contents of the session file, asynchronously. + * @param aData - May get changed on shutdown. + */ + write(aData) { + return SessionFileInternal.write(aData); + }, + /** + * Wipe the contents of the session file, asynchronously. + */ + wipe() { + return SessionFileInternal.wipe(); + }, + + /** + * Return the paths to the files used to store, backup, etc. + * the state of the file. + */ + get Paths() { + return SessionFileInternal.Paths; + }, +}; + +Object.freeze(SessionFile); + +const profileDir = PathUtils.profileDir; + +var SessionFileInternal = { + Paths: Object.freeze({ + // The path to the latest version of sessionstore written during a clean + // shutdown. After startup, it is renamed `cleanBackup`. + clean: PathUtils.join(profileDir, "sessionstore.jsonlz4"), + + // The path at which we store the previous version of `clean`. Updated + // whenever we successfully load from `clean`. + cleanBackup: PathUtils.join( + profileDir, + "sessionstore-backups", + "previous.jsonlz4" + ), + + // The directory containing all sessionstore backups. + backups: PathUtils.join(profileDir, "sessionstore-backups"), + + // The path to the latest version of the sessionstore written + // during runtime. Generally, this file contains more + // privacy-sensitive information than |clean|, and this file is + // therefore removed during clean shutdown. This file is designed to protect + // against crashes / sudden shutdown. + recovery: PathUtils.join( + profileDir, + "sessionstore-backups", + "recovery.jsonlz4" + ), + + // The path to the previous version of the sessionstore written + // during runtime (e.g. 15 seconds before recovery). In case of a + // clean shutdown, this file is removed. Generally, this file + // contains more privacy-sensitive information than |clean|, and + // this file is therefore removed during clean shutdown. This + // file is designed to protect against crashes that are nasty + // enough to corrupt |recovery|. + recoveryBackup: PathUtils.join( + profileDir, + "sessionstore-backups", + "recovery.baklz4" + ), + + // The path to a backup created during an upgrade of Firefox. + // Having this backup protects the user essentially from bugs in + // Firefox or add-ons, especially for users of Nightly. This file + // does not contain any information more sensitive than |clean|. + upgradeBackupPrefix: PathUtils.join( + profileDir, + "sessionstore-backups", + "upgrade.jsonlz4-" + ), + + // The path to the backup of the version of the session store used + // during the latest upgrade of Firefox. During load/recovery, + // this file should be used if both |path|, |backupPath| and + // |latestStartPath| are absent/incorrect. May be "" if no + // upgrade backup has ever been performed. This file does not + // contain any information more sensitive than |clean|. + get upgradeBackup() { + let latestBackupID = SessionFileInternal.latestUpgradeBackupID; + if (!latestBackupID) { + return ""; + } + return this.upgradeBackupPrefix + latestBackupID; + }, + + // The path to a backup created during an upgrade of Firefox. + // Having this backup protects the user essentially from bugs in + // Firefox, especially for users of Nightly. + get nextUpgradeBackup() { + return this.upgradeBackupPrefix + Services.appinfo.platformBuildID; + }, + + /** + * The order in which to search for a valid sessionstore file. + */ + get loadOrder() { + // If `clean` exists and has been written without corruption during + // the latest shutdown, we need to use it. + // + // Otherwise, `recovery` and `recoveryBackup` represent the most + // recent state of the session store. + // + // Finally, if nothing works, fall back to the last known state + // that can be loaded (`cleanBackup`) or, if available, to the + // backup performed during the latest upgrade. + let order = ["clean", "recovery", "recoveryBackup", "cleanBackup"]; + if (SessionFileInternal.latestUpgradeBackupID) { + // We have an upgradeBackup + order.push("upgradeBackup"); + } + return order; + }, + }), + + // Number of attempted calls to `write`. + // Note that we may have _attempts > _successes + _failures, + // if attempts never complete. + // Used for error reporting. + _attempts: 0, + + // Number of successful calls to `write`. + // Used for error reporting. + _successes: 0, + + // Number of failed calls to `write`. + // Used for error reporting. + _failures: 0, + + // `true` once we have initialized SessionWriter. + _initialized: false, + + // A string that will be set to the session file name part that was read from + // disk. It will be available _after_ a session file read() is done. + _readOrigin: null, + + // `true` if the old, uncompressed, file format was used to read from disk, as + // a fallback mechanism. + _usingOldExtension: false, + + // The ID of the latest version of Gecko for which we have an upgrade backup + // or |undefined| if no upgrade backup was ever written. + get latestUpgradeBackupID() { + try { + return Services.prefs.getCharPref(PREF_UPGRADE_BACKUP); + } catch (ex) { + return undefined; + } + }, + + async _readInternal(useOldExtension) { + let result; + let noFilesFound = true; + this._usingOldExtension = useOldExtension; + + // Attempt to load by order of priority from the various backups + for (let key of this.Paths.loadOrder) { + let corrupted = false; + let exists = true; + try { + let path; + let startMs = Date.now(); + + let options = {}; + if (useOldExtension) { + path = this.Paths[key] + .replace("jsonlz4", "js") + .replace("baklz4", "bak"); + } else { + path = this.Paths[key]; + options.decompress = true; + } + let source = await IOUtils.readUTF8(path, options); + let parsed = JSON.parse(source); + + if (parsed._cachedObjs) { + try { + let cacheMap = new Map(parsed._cachedObjs); + for (let win of parsed.windows.concat( + parsed._closedWindows || [] + )) { + for (let tab of win.tabs.concat(win._closedTabs || [])) { + tab.image = cacheMap.get(tab.image) || tab.image; + } + } + } catch (e) { + // This is temporary code to clean up after the backout of bug + // 1546847. Just in case there are problems in the format of + // the parsed data, continue on. Favicons might be broken, but + // the session will at least be recovered + console.error(e); + } + } + + if ( + !lazy.SessionStore.isFormatVersionCompatible( + parsed.version || [ + "sessionrestore", + 0, + ] /* fallback for old versions*/ + ) + ) { + // Skip sessionstore files that we don't understand. + console.error( + "Cannot extract data from Session Restore file ", + path, + ". Wrong format/version: " + JSON.stringify(parsed.version) + "." + ); + continue; + } + result = { + origin: key, + source, + parsed, + useOldExtension, + }; + Services.telemetry + .getHistogramById("FX_SESSION_RESTORE_CORRUPT_FILE") + .add(false); + Services.telemetry + .getHistogramById("FX_SESSION_RESTORE_READ_FILE_MS") + .add(Date.now() - startMs); + break; + } catch (ex) { + if (DOMException.isInstance(ex) && ex.name == "NotFoundError") { + exists = false; + } else if ( + DOMException.isInstance(ex) && + ex.name == "NotAllowedError" + ) { + // The file might be inaccessible due to wrong permissions + // or similar failures. We'll just count it as "corrupted". + console.error("Could not read session file ", ex); + corrupted = true; + } else if (ex instanceof SyntaxError) { + console.error( + "Corrupt session file (invalid JSON found) ", + ex, + ex.stack + ); + // File is corrupted, try next file + corrupted = true; + } + } finally { + if (exists) { + noFilesFound = false; + Services.telemetry + .getHistogramById("FX_SESSION_RESTORE_CORRUPT_FILE") + .add(corrupted); + } + } + } + return { result, noFilesFound }; + }, + + // Find the correct session file and read it. + async read() { + // Load session files with lz4 compression. + let { result, noFilesFound } = await this._readInternal(false); + if (!result) { + // No result? Probably because of migration, let's + // load uncompressed session files. + let r = await this._readInternal(true); + result = r.result; + } + + // All files are corrupted if files found but none could deliver a result. + let allCorrupt = !noFilesFound && !result; + Services.telemetry + .getHistogramById("FX_SESSION_RESTORE_ALL_FILES_CORRUPT") + .add(allCorrupt); + + if (!result) { + // If everything fails, start with an empty session. + result = { + origin: "empty", + source: "", + parsed: null, + useOldExtension: false, + }; + } + this._readOrigin = result.origin; + + result.noFilesFound = noFilesFound; + + return result; + }, + + // Initialize SessionWriter and return it as a resolved promise. + getWriter() { + if (!this._initialized) { + if (!this._readOrigin) { + return Promise.reject( + "SessionFileInternal.getWriter() called too early! Please read the session file from disk first." + ); + } + + this._initialized = true; + lazy.SessionWriter.init( + this._readOrigin, + this._usingOldExtension, + this.Paths, + { + maxUpgradeBackups: Services.prefs.getIntPref( + PREF_MAX_UPGRADE_BACKUPS, + 3 + ), + maxSerializeBack: Services.prefs.getIntPref( + PREF_MAX_SERIALIZE_BACK, + 10 + ), + maxSerializeForward: Services.prefs.getIntPref( + PREF_MAX_SERIALIZE_FWD, + -1 + ), + } + ); + } + + return Promise.resolve(lazy.SessionWriter); + }, + + write(aData) { + if (lazy.RunState.isClosed) { + return Promise.reject(new Error("SessionFile is closed")); + } + + let isFinalWrite = false; + if (lazy.RunState.isClosing) { + // If shutdown has started, we will want to stop receiving + // write instructions. + isFinalWrite = true; + lazy.RunState.setClosed(); + } + + let performShutdownCleanup = + isFinalWrite && !lazy.SessionStore.willAutoRestore; + + this._attempts++; + let options = { isFinalWrite, performShutdownCleanup }; + let promise = this.getWriter().then(writer => writer.write(aData, options)); + + // Wait until the write is done. + promise = promise.then( + msg => { + // Record how long the write took. + this._recordTelemetry(msg.telemetry); + this._successes++; + if (msg.result.upgradeBackup) { + // We have just completed a backup-on-upgrade, store the information + // in preferences. + Services.prefs.setCharPref( + PREF_UPGRADE_BACKUP, + Services.appinfo.platformBuildID + ); + } + }, + err => { + // Catch and report any errors. + console.error("Could not write session state file ", err, err.stack); + this._failures++; + // By not doing anything special here we ensure that |promise| cannot + // be rejected anymore. The shutdown/cleanup code at the end of the + // function will thus always be executed. + } + ); + + // Ensure that we can write sessionstore.js cleanly before the profile + // becomes unaccessible. + IOUtils.profileBeforeChange.addBlocker( + "SessionFile: Finish writing Session Restore data", + promise, + { + fetchState: () => ({ + options, + attempts: this._attempts, + successes: this._successes, + failures: this._failures, + }), + } + ); + + // This code will always be executed because |promise| can't fail anymore. + // We ensured that by having a reject handler that reports the failure but + // doesn't forward the rejection. + return promise.then(() => { + // Remove the blocker, no matter if writing failed or not. + IOUtils.profileBeforeChange.removeBlocker(promise); + + if (isFinalWrite) { + Services.obs.notifyObservers( + null, + "sessionstore-final-state-write-complete" + ); + } + }); + }, + + async wipe() { + const writer = await this.getWriter(); + await writer.wipe(); + // After a wipe, we need to make sure to re-initialize upon the next read(), + // because the state variables as sent to the writer have changed. + this._initialized = false; + }, + + _recordTelemetry(telemetry) { + for (let id of Object.keys(telemetry)) { + let value = telemetry[id]; + let samples = []; + if (Array.isArray(value)) { + samples.push(...value); + } else { + samples.push(value); + } + let histogram = Services.telemetry.getHistogramById(id); + for (let sample of samples) { + histogram.add(sample); + } + } + }, +}; |