michael@0: /* -*- Mode: js; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: /**
michael@0:  * Crash Monitor
michael@0:  *
michael@0:  * Monitors execution of a program to detect possible crashes. After
michael@0:  * program termination, the monitor can be queried during the next run
michael@0:  * to determine whether the last run exited cleanly or not.
michael@0:  *
michael@0:  * The monitoring is done by registering and listening for special
michael@0:  * notifications, or checkpoints, known to be sent by the monitored
michael@0:  * program as different stages in the execution are reached. As they
michael@0:  * are observed, these notifications are written asynchronously to a
michael@0:  * checkpoint file.
michael@0:  *
michael@0:  * During next program startup the crash monitor reads the checkpoint
michael@0:  * file from the last session. If notifications are missing, a crash
michael@0:  * has likely happened. By inspecting the notifications present, it is
michael@0:  * possible to determine what stages were reached in the program
michael@0:  * before the crash.
michael@0:  *
michael@0:  * Note that since the file is written asynchronously it is possible
michael@0:  * that a received notification is lost if the program crashes right
michael@0:  * after a checkpoint, but before crash monitor has been able to write
michael@0:  * it to disk. Thus, while the presence of a notification in the
michael@0:  * checkpoint file tells us that the corresponding stage was reached
michael@0:  * during the last run, the absence of a notification after a crash
michael@0:  * does not necessarily tell us that the checkpoint wasn't reached.
michael@0:  */
michael@0: 
michael@0: this.EXPORTED_SYMBOLS = [ "CrashMonitor" ];
michael@0: 
michael@0: const Cu = Components.utils;
michael@0: const Cr = Components.results;
michael@0: 
michael@0: Cu.import("resource://gre/modules/Services.jsm");
michael@0: Cu.import("resource://gre/modules/osfile.jsm");
michael@0: Cu.import("resource://gre/modules/Promise.jsm");
michael@0: Cu.import("resource://gre/modules/Task.jsm");
michael@0: Cu.import("resource://gre/modules/AsyncShutdown.jsm");
michael@0: 
michael@0: const NOTIFICATIONS = [
michael@0:   "final-ui-startup",
michael@0:   "sessionstore-windows-restored",
michael@0:   "quit-application-granted",
michael@0:   "quit-application",
michael@0:   "profile-change-net-teardown",
michael@0:   "profile-change-teardown",
michael@0:   "profile-before-change",
michael@0:   "sessionstore-final-state-write-complete"
michael@0: ];
michael@0: 
michael@0: let CrashMonitorInternal = {
michael@0: 
michael@0:   /**
michael@0:    * Notifications received during the current session.
michael@0:    *
michael@0:    * Object where a property with a value of |true| means that the
michael@0:    * notification of the same name has been received at least once by
michael@0:    * the CrashMonitor during this session. Notifications that have not
michael@0:    * yet been received are not present as properties. |NOTIFICATIONS|
michael@0:    * lists the notifications tracked by the CrashMonitor.
michael@0:    */
michael@0:   checkpoints: {},
michael@0: 
michael@0:   /**
michael@0:    * Notifications received during previous session.
michael@0:    *
michael@0:    * Available after |loadPreviousCheckpoints|. Promise which resolves
michael@0:    * to an object containing a set of properties, where a property
michael@0:    * with a value of |true| means that the notification with the same
michael@0:    * name as the property name was received at least once last
michael@0:    * session.
michael@0:    */
michael@0:   previousCheckpoints: null,
michael@0: 
michael@0:   /* Deferred for AsyncShutdown blocker */
michael@0:   profileBeforeChangeDeferred: Promise.defer(),
michael@0: 
michael@0:   /**
michael@0:    * Path to checkpoint file.
michael@0:    *
michael@0:    * Each time a new notification is received, this file is written to
michael@0:    * disc to reflect the information in |checkpoints|. Although Firefox for
michael@0:    * Desktop and Metro share the same profile, they need to keep record of
michael@0:    * crashes separately.
michael@0:    */
michael@0:   path: (Services.metro && Services.metro.immersive) ?
michael@0:     OS.Path.join(OS.Constants.Path.profileDir, "metro", "sessionCheckpoints.json"):
michael@0:     OS.Path.join(OS.Constants.Path.profileDir, "sessionCheckpoints.json"),
michael@0: 
michael@0:   /**
michael@0:    * Load checkpoints from previous session asynchronously.
michael@0:    *
michael@0:    * @return {Promise} A promise that resolves/rejects once loading is complete
michael@0:    */
michael@0:   loadPreviousCheckpoints: function () {
michael@0:     this.previousCheckpoints = Task.spawn(function*() {
michael@0:       let data;
michael@0:       try {
michael@0:         data = yield OS.File.read(CrashMonitorInternal.path, { encoding: "utf-8" });
michael@0:       } catch (ex if ex instanceof OS.File.Error) {
michael@0:         if (!ex.becauseNoSuchFile) {
michael@0:           Cu.reportError("Error while loading crash monitor data: " + ex.toString());
michael@0:         }
michael@0: 
michael@0:         return null;
michael@0:       }
michael@0: 
michael@0:       let notifications;
michael@0:       try {
michael@0:         notifications = JSON.parse(data);
michael@0:       } catch (ex) {
michael@0:         Cu.reportError("Error while parsing crash monitor data: " + ex);
michael@0:         return null;
michael@0:       }
michael@0: 
michael@0:       return Object.freeze(notifications);
michael@0:     });
michael@0: 
michael@0:     return this.previousCheckpoints;
michael@0:   }
michael@0: };
michael@0: 
michael@0: this.CrashMonitor = {
michael@0: 
michael@0:   /**
michael@0:    * Notifications received during previous session.
michael@0:    *
michael@0:    * Return object containing the set of notifications received last
michael@0:    * session as keys with values set to |true|.
michael@0:    *
michael@0:    * @return {Promise} A promise resolving to previous checkpoints
michael@0:    */
michael@0:   get previousCheckpoints() {
michael@0:     if (!CrashMonitorInternal.initialized) {
michael@0:       throw new Error("CrashMonitor must be initialized before getting previous checkpoints");
michael@0:     }
michael@0: 
michael@0:     return CrashMonitorInternal.previousCheckpoints
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Initialize CrashMonitor.
michael@0:    *
michael@0:    * Should only be called from the CrashMonitor XPCOM component.
michael@0:    *
michael@0:    * @return {Promise}
michael@0:    */
michael@0:   init: function () {
michael@0:     if (CrashMonitorInternal.initialized) {
michael@0:       throw new Error("CrashMonitor.init() must only be called once!");
michael@0:     }
michael@0: 
michael@0:     let promise = CrashMonitorInternal.loadPreviousCheckpoints();
michael@0:     // Add "profile-after-change" to checkpoint as this method is
michael@0:     // called after receiving it
michael@0:     CrashMonitorInternal.checkpoints["profile-after-change"] = true;
michael@0: 
michael@0:     NOTIFICATIONS.forEach(function (aTopic) {
michael@0:       Services.obs.addObserver(this, aTopic, false);
michael@0:     }, this);
michael@0: 
michael@0:     // Add shutdown blocker for profile-before-change
michael@0:     AsyncShutdown.profileBeforeChange.addBlocker(
michael@0:       "CrashMonitor: Writing notifications to file after receiving profile-before-change",
michael@0:       CrashMonitorInternal.profileBeforeChangeDeferred.promise
michael@0:     );
michael@0: 
michael@0:     CrashMonitorInternal.initialized = true;
michael@0:     if (Services.metro && Services.metro.immersive) {
michael@0:       OS.File.makeDir(OS.Path.join(OS.Constants.Path.profileDir, "metro"));
michael@0:     }
michael@0:     return promise;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Handle registered notifications.
michael@0:    *
michael@0:    * Update checkpoint file for every new notification received.
michael@0:    */
michael@0:   observe: function (aSubject, aTopic, aData) {
michael@0:     if (!(aTopic in CrashMonitorInternal.checkpoints)) {
michael@0:       // If this is the first time this notification is received,
michael@0:       // remember it and write it to file
michael@0:       CrashMonitorInternal.checkpoints[aTopic] = true;
michael@0:       Task.spawn(function() {
michael@0:         try {
michael@0:           let data = JSON.stringify(CrashMonitorInternal.checkpoints);
michael@0: 
michael@0:           /* Write to the checkpoint file asynchronously, off the main
michael@0:            * thread, for performance reasons. Note that this means
michael@0:            * that there's not a 100% guarantee that the file will be
michael@0:            * written by the time the notification completes. The
michael@0:            * exception is profile-before-change which has a shutdown
michael@0:            * blocker. */
michael@0:           yield OS.File.writeAtomic(
michael@0:             CrashMonitorInternal.path,
michael@0:             data, {tmpPath: CrashMonitorInternal.path + ".tmp"});
michael@0: 
michael@0:         } finally {
michael@0:           // Resolve promise for blocker
michael@0:           if (aTopic == "profile-before-change") {
michael@0:             CrashMonitorInternal.profileBeforeChangeDeferred.resolve();
michael@0:           }
michael@0:         }
michael@0:       });
michael@0:     }
michael@0: 
michael@0:     if (NOTIFICATIONS.every(elem => elem in CrashMonitorInternal.checkpoints)) {
michael@0:       // All notifications received, unregister observers
michael@0:       NOTIFICATIONS.forEach(function (aTopic) {
michael@0:         Services.obs.removeObserver(this, aTopic);
michael@0:       }, this);
michael@0:     }
michael@0:   }
michael@0: };
michael@0: Object.freeze(this.CrashMonitor);