Fix race condition in javascript kernel message processing

Because the binary messages are now deserialized using the asynchronous FileReader API, we need to have some way to force the messages to still be processed in the order they are received.  This patch implements a simple processing queue using promises.

IPython/html/static/services/kernels/kernel.js

@@ -1,1052 +1,1056 b''
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     'base/js/namespace',
     'jquery',
     'base/js/utils',
     './comm',
     './serialize',
     'widgets/js/init'
 ], function(IPython, $, utils, comm, serialize, widgetmanager) {
     "use strict";
 
     /**
      * A Kernel class to communicate with the Python kernel. This
      * should generally not be constructed directly, but be created
      * by.  the `Session` object. Once created, this object should be
      * used to communicate with the kernel.
      * 
      * @class Kernel
      * @param {string} kernel_service_url - the URL to access the kernel REST api
      * @param {string} ws_url - the websockets URL
      * @param {Notebook} notebook - notebook object
      * @param {string} name - the kernel type (e.g. python3)
      */
     var Kernel = function (kernel_service_url, ws_url, notebook, name) {
         this.events = notebook.events;
 
         this.id = null;
         this.name = name;
         this.ws = null;
 
         this.kernel_service_url = kernel_service_url;
         this.kernel_url = null;
         this.ws_url = ws_url || IPython.utils.get_body_data("wsUrl");
         if (!this.ws_url) {
             // trailing 's' in https will become wss for secure web sockets
             this.ws_url = location.protocol.replace('http', 'ws') + "//" + location.host;
         }
 
         this.username = "username";
         this.session_id = utils.uuid();
         this._msg_callbacks = {};
+        this._msg_queue = Promise.resolve();
         this.info_reply = {}; // kernel_info_reply stored here after starting
 
         if (typeof(WebSocket) !== 'undefined') {
             this.WebSocket = WebSocket;
         } else if (typeof(MozWebSocket) !== 'undefined') {
             this.WebSocket = MozWebSocket;
         } else {
             alert('Your browser does not have WebSocket support, please try Chrome, Safari or Firefox ≥ 6. Firefox 4 and 5 are also supported by you have to enable WebSockets in about:config.');
         }
         
         this.bind_events();
         this.init_iopub_handlers();
         this.comm_manager = new comm.CommManager(this);
         this.widget_manager = new widgetmanager.WidgetManager(this.comm_manager, notebook);
         
         this.last_msg_id = null;
         this.last_msg_callbacks = {};
 
         this._autorestart_attempt = 0;
         this._reconnect_attempt = 0;
         this.reconnect_limit = 7;
     };
 
     /**
      * @function _get_msg
      */
     Kernel.prototype._get_msg = function (msg_type, content, metadata, buffers) {
         var msg = {
             header : {
                 msg_id : utils.uuid(),
                 username : this.username,
                 session : this.session_id,
                 msg_type : msg_type,
                 version : "5.0"
             },
             metadata : metadata || {},
             content : content,
             buffers : buffers || [],
             parent_header : {}
         };
         return msg;
     };
 
     /**
      * @function bind_events
      */
     Kernel.prototype.bind_events = function () {
         var that = this;
         this.events.on('send_input_reply.Kernel', function(evt, data) { 
             that.send_input_reply(data);
         });
 
         var record_status = function (evt, info) {
             console.log('Kernel: ' + evt.type + ' (' + info.kernel.id + ')');
         };
 
         this.events.on('kernel_created.Kernel', record_status);
         this.events.on('kernel_reconnecting.Kernel', record_status);
         this.events.on('kernel_connected.Kernel', record_status);
         this.events.on('kernel_starting.Kernel', record_status);
         this.events.on('kernel_restarting.Kernel', record_status);
         this.events.on('kernel_autorestarting.Kernel', record_status);
         this.events.on('kernel_interrupting.Kernel', record_status);
         this.events.on('kernel_disconnected.Kernel', record_status);
         // these are commented out because they are triggered a lot, but can
         // be uncommented for debugging purposes
         //this.events.on('kernel_idle.Kernel', record_status);
         //this.events.on('kernel_busy.Kernel', record_status);
         this.events.on('kernel_ready.Kernel', record_status);
         this.events.on('kernel_killed.Kernel', record_status);
         this.events.on('kernel_dead.Kernel', record_status);
 
         this.events.on('kernel_ready.Kernel', function () {
             that._autorestart_attempt = 0;
         });
         this.events.on('kernel_connected.Kernel', function () {
             that._reconnect_attempt = 0;
         });
     };
 
     /**
      * Initialize the iopub handlers.
      *
      * @function init_iopub_handlers
      */
     Kernel.prototype.init_iopub_handlers = function () {
         var output_msg_types = ['stream', 'display_data', 'execute_result', 'error'];
         this._iopub_handlers = {};
         this.register_iopub_handler('status', $.proxy(this._handle_status_message, this));
         this.register_iopub_handler('clear_output', $.proxy(this._handle_clear_output, this));
         this.register_iopub_handler('execute_input', $.proxy(this._handle_input_message, this));
         
         for (var i=0; i < output_msg_types.length; i++) {
             this.register_iopub_handler(output_msg_types[i], $.proxy(this._handle_output_message, this));
         }
     };
 
     /**
      * GET /api/kernels
      *
      * Get the list of running kernels.
      *
      * @function list
      * @param {function} [success] - function executed on ajax success
      * @param {function} [error] - functon executed on ajax error
      */
     Kernel.prototype.list = function (success, error) {
         $.ajax(this.kernel_service_url, {
             processData: false,
             cache: false,
             type: "GET",
             dataType: "json",
             success: success,
             error: this._on_error(error)
         });
     };
 
     /**
      * POST /api/kernels
      *
      * Start a new kernel.
      *
      * In general this shouldn't be used -- the kernel should be
      * started through the session API. If you use this function and
      * are also using the session API then your session and kernel
      * WILL be out of sync!
      *
      * @function start
      * @param {params} [Object] - parameters to include in the query string
      * @param {function} [success] - function executed on ajax success
      * @param {function} [error] - functon executed on ajax error
      */
     Kernel.prototype.start = function (params, success, error) {
         var url = this.kernel_service_url;
         var qs = $.param(params || {}); // query string for sage math stuff
         if (qs !== "") {
             url = url + "?" + qs;
         }
 
         this.events.trigger('kernel_starting.Kernel', {kernel: this});
         var that = this;
         var on_success = function (data, status, xhr) {
             that.events.trigger('kernel_created.Kernel', {kernel: that});
             that._kernel_created(data);
             if (success) {
                 success(data, status, xhr);
             }
         };
 
         $.ajax(url, {
             processData: false,
             cache: false,
             type: "POST",
             data: JSON.stringify({name: this.name}),
             dataType: "json",
             success: this._on_success(on_success),
             error: this._on_error(error)
         });
 
         return url;
     };
 
     /**
      * GET /api/kernels/[:kernel_id]
      *
      * Get information about the kernel.
      *
      * @function get_info
      * @param {function} [success] - function executed on ajax success
      * @param {function} [error] - functon executed on ajax error
      */
     Kernel.prototype.get_info = function (success, error) {
         $.ajax(this.kernel_url, {
             processData: false,
             cache: false,
             type: "GET",
             dataType: "json",
             success: this._on_success(success),
             error: this._on_error(error)
         });
     };
 
     /**
      * DELETE /api/kernels/[:kernel_id]
      *
      * Shutdown the kernel.
      *
      * If you are also using sessions, then this function shoul NOT be
      * used. Instead, use Session.delete. Otherwise, the session and
      * kernel WILL be out of sync.
      *
      * @function kill
      * @param {function} [success] - function executed on ajax success
      * @param {function} [error] - functon executed on ajax error
      */
     Kernel.prototype.kill = function (success, error) {
         this.events.trigger('kernel_killed.Kernel', {kernel: this});
         this._kernel_dead();
         $.ajax(this.kernel_url, {
             processData: false,
             cache: false,
             type: "DELETE",
             dataType: "json",
             success: this._on_success(success),
             error: this._on_error(error)
         });
     };
 
     /**
      * POST /api/kernels/[:kernel_id]/interrupt
      *
      * Interrupt the kernel.
      *
      * @function interrupt
      * @param {function} [success] - function executed on ajax success
      * @param {function} [error] - functon executed on ajax error
      */
     Kernel.prototype.interrupt = function (success, error) {
         this.events.trigger('kernel_interrupting.Kernel', {kernel: this});
 
         var that = this;
         var on_success = function (data, status, xhr) {
             /**
              * get kernel info so we know what state the kernel is in
              */
             that.kernel_info();
             if (success) {
                 success(data, status, xhr);
             }
         };
 
         var url = utils.url_join_encode(this.kernel_url, 'interrupt');
         $.ajax(url, {
             processData: false,
             cache: false,
             type: "POST",
             dataType: "json",
             success: this._on_success(on_success),
             error: this._on_error(error)
         });
     };
 
     Kernel.prototype.restart = function (success, error) {
         /**
          * POST /api/kernels/[:kernel_id]/restart
          *
          * Restart the kernel.
          *
          * @function interrupt
          * @param {function} [success] - function executed on ajax success
          * @param {function} [error] - functon executed on ajax error
          */
         this.events.trigger('kernel_restarting.Kernel', {kernel: this});
         this.stop_channels();
 
         var that = this;
         var on_success = function (data, status, xhr) {
             that.events.trigger('kernel_created.Kernel', {kernel: that});
             that._kernel_created(data);
             if (success) {
                 success(data, status, xhr);
             }
         };
 
         var on_error = function (xhr, status, err) {
             that.events.trigger('kernel_dead.Kernel', {kernel: that});
             that._kernel_dead();
             if (error) {
                 error(xhr, status, err);
             }
         };
 
         var url = utils.url_join_encode(this.kernel_url, 'restart');
         $.ajax(url, {
             processData: false,
             cache: false,
             type: "POST",
             dataType: "json",
             success: this._on_success(on_success),
             error: this._on_error(on_error)
         });
     };
 
     Kernel.prototype.reconnect = function () {
         /**
          * Reconnect to a disconnected kernel. This is not actually a
          * standard HTTP request, but useful function nonetheless for
          * reconnecting to the kernel if the connection is somehow lost.
          *
          * @function reconnect
          */
         if (this.is_connected()) {
             return;
         }
         this._reconnect_attempt = this._reconnect_attempt + 1;
         this.events.trigger('kernel_reconnecting.Kernel', {
             kernel: this,
             attempt: this._reconnect_attempt,
         });
         this.start_channels();
     };
 
     Kernel.prototype._on_success = function (success) {
         /**
          * Handle a successful AJAX request by updating the kernel id and
          * name from the response, and then optionally calling a provided
          * callback.
          *
          * @function _on_success
          * @param {function} success - callback
          */
         var that = this;
         return function (data, status, xhr) {
             if (data) {
                 that.id = data.id;
                 that.name = data.name;
             }
             that.kernel_url = utils.url_join_encode(that.kernel_service_url, that.id);
             if (success) {
                 success(data, status, xhr);
             }
         };
     };
 
     Kernel.prototype._on_error = function (error) {
         /**
          * Handle a failed AJAX request by logging the error message, and
          * then optionally calling a provided callback.
          *
          * @function _on_error
          * @param {function} error - callback
          */
         return function (xhr, status, err) {
             utils.log_ajax_error(xhr, status, err);
             if (error) {
                 error(xhr, status, err);
             }
         };
     };
 
     Kernel.prototype._kernel_created = function (data) {
         /**
          * Perform necessary tasks once the kernel has been started,
          * including actually connecting to the kernel.
          *
          * @function _kernel_created
          * @param {Object} data - information about the kernel including id
          */
         this.id = data.id;
         this.kernel_url = utils.url_join_encode(this.kernel_service_url, this.id);
         this.start_channels();
     };
 
     Kernel.prototype._kernel_connected = function () {
         /**
          * Perform necessary tasks once the connection to the kernel has
          * been established. This includes requesting information about
          * the kernel.
          *
          * @function _kernel_connected
          */
         this.events.trigger('kernel_connected.Kernel', {kernel: this});
         // get kernel info so we know what state the kernel is in
         var that = this;
         this.kernel_info(function (reply) {
             that.info_reply = reply.content;
             that.events.trigger('kernel_ready.Kernel', {kernel: that});
         });
     };
 
     Kernel.prototype._kernel_dead = function () {
         /**
          * Perform necessary tasks after the kernel has died. This closing
          * communication channels to the kernel if they are still somehow
          * open.
          *
          * @function _kernel_dead
          */
         this.stop_channels();
     };
 
     Kernel.prototype.start_channels = function () {
         /**
          * Start the websocket channels.
          * Will stop and restart them if they already exist.
          *
          * @function start_channels
          */
         var that = this;
         this.stop_channels();
         var ws_host_url = this.ws_url + this.kernel_url;
 
         console.log("Starting WebSockets:", ws_host_url);
         
         this.ws = new this.WebSocket([
                 that.ws_url,
                 utils.url_join_encode(that.kernel_url, 'channels'),
                 "?session_id=" + that.session_id
             ].join('')
         );
         
         var already_called_onclose = false; // only alert once
         var ws_closed_early = function(evt){
             if (already_called_onclose){
                 return;
             }
             already_called_onclose = true;
             if ( ! evt.wasClean ){
                 // If the websocket was closed early, that could mean
                 // that the kernel is actually dead. Try getting
                 // information about the kernel from the API call --
                 // if that fails, then assume the kernel is dead,
                 // otherwise just follow the typical websocket closed
                 // protocol.
                 that.get_info(function () {
                     that._ws_closed(ws_host_url, false);
                 }, function () {
                     that.events.trigger('kernel_dead.Kernel', {kernel: that});
                     that._kernel_dead();
                 });
             }
         };
         var ws_closed_late = function(evt){
             if (already_called_onclose){
                 return;
             }
             already_called_onclose = true;
             if ( ! evt.wasClean ){
                 that._ws_closed(ws_host_url, false);
             }
         };
         var ws_error = function(evt){
             if (already_called_onclose){
                 return;
             }
             already_called_onclose = true;
             that._ws_closed(ws_host_url, true);
         };
 
         this.ws.onopen = $.proxy(this._ws_opened, this);
         this.ws.onclose = ws_closed_early;
         this.ws.onerror = ws_error;
         // switch from early-close to late-close message after 1s
         setTimeout(function() {
             if (that.ws !== null) {
                 that.ws.onclose = ws_closed_late;
             }
         }, 1000);
         this.ws.onmessage = $.proxy(this._handle_ws_message, this);
     };
 
     Kernel.prototype._ws_opened = function (evt) {
         /**
          * Handle a websocket entering the open state,
          * signaling that the kernel is connected when websocket is open.
          *
          * @function _ws_opened
          */
         if (this.is_connected()) {
             // all events ready, trigger started event.
             this._kernel_connected();
         }
     };
 
     Kernel.prototype._ws_closed = function(ws_url, error) {
         /**
          * Handle a websocket entering the closed state.  If the websocket
          * was not closed due to an error, try to reconnect to the kernel.
          *
          * @function _ws_closed
          * @param {string} ws_url - the websocket url
          * @param {bool} error - whether the connection was closed due to an error
          */
         this.stop_channels();
 
         this.events.trigger('kernel_disconnected.Kernel', {kernel: this});
         if (error) {
             console.log('WebSocket connection failed: ', ws_url);
             this.events.trigger('kernel_connection_failed.Kernel', {kernel: this, ws_url: ws_url, attempt: this._reconnect_attempt});
         }
         this._schedule_reconnect();
     };
     
     Kernel.prototype._schedule_reconnect = function () {
         /**
          * function to call when kernel connection is lost
          * schedules reconnect, or fires 'connection_dead' if reconnect limit is hit
          */
         if (this._reconnect_attempt < this.reconnect_limit) {
             var timeout = Math.pow(2, this._reconnect_attempt);
             console.log("Connection lost, reconnecting in " + timeout + " seconds.");
             setTimeout($.proxy(this.reconnect, this), 1e3 * timeout);
         } else {
             this.events.trigger('kernel_connection_dead.Kernel', {
                 kernel: this,
                 reconnect_attempt: this._reconnect_attempt,
             });
             console.log("Failed to reconnect, giving up.");
         }
     };
     
     Kernel.prototype.stop_channels = function () {
         /**
          * Close the websocket. After successful close, the value
          * in `this.ws` will be null.
          *
          * @function stop_channels
          */
         var that = this;
         var close = function () {
             if (that.ws && that.ws.readyState === WebSocket.CLOSED) {
                 that.ws = null;
             }
         };
         if (this.ws !== null) {
             if (this.ws.readyState === WebSocket.OPEN) {
                 this.ws.onclose = close;
                 this.ws.close();
             } else {
                 close();
             }
         }
     };
 
     Kernel.prototype.is_connected = function () {
         /**
          * Check whether there is a connection to the kernel. This
          * function only returns true if websocket has been
          * created and has a state of WebSocket.OPEN.
          *
          * @function is_connected
          * @returns {bool} - whether there is a connection
          */
         // if any channel is not ready, then we're not connected
         if (this.ws === null) {
             return false;
         }
         if (this.ws.readyState !== WebSocket.OPEN) {
             return false;
         }
         return true;
     };
 
     Kernel.prototype.is_fully_disconnected = function () {
         /**
          * Check whether the connection to the kernel has been completely
          * severed. This function only returns true if all channel objects
          * are null.
          *
          * @function is_fully_disconnected
          * @returns {bool} - whether the kernel is fully disconnected
          */
         return (this.ws === null);
     };
     
     Kernel.prototype.send_shell_message = function (msg_type, content, callbacks, metadata, buffers) {
         /**
          * Send a message on the Kernel's shell channel
          *
          * @function send_shell_message
          */
         if (!this.is_connected()) {
             throw new Error("kernel is not connected");
         }
         var msg = this._get_msg(msg_type, content, metadata, buffers);
         msg.channel = 'shell';
         this.ws.send(serialize.serialize(msg));
         this.set_callbacks_for_msg(msg.header.msg_id, callbacks);
         return msg.header.msg_id;
     };
 
     Kernel.prototype.kernel_info = function (callback) {
         /**
          * Get kernel info
          *
          * @function kernel_info
          * @param callback {function}
          *
          * When calling this method, pass a callback function that expects one argument.
          * The callback will be passed the complete `kernel_info_reply` message documented
          * [here](http://ipython.org/ipython-doc/dev/development/messaging.html#kernel-info)
          */
         var callbacks;
         if (callback) {
             callbacks = { shell : { reply : callback } };
         }
         return this.send_shell_message("kernel_info_request", {}, callbacks);
     };
 
     Kernel.prototype.inspect = function (code, cursor_pos, callback) {
         /**
          * Get info on an object
          *
          * When calling this method, pass a callback function that expects one argument.
          * The callback will be passed the complete `inspect_reply` message documented
          * [here](http://ipython.org/ipython-doc/dev/development/messaging.html#object-information)
          *
          * @function inspect
          * @param code {string}
          * @param cursor_pos {integer}
          * @param callback {function}
          */
         var callbacks;
         if (callback) {
             callbacks = { shell : { reply : callback } };
         }
         
         var content = {
             code : code,
             cursor_pos : cursor_pos,
             detail_level : 0
         };
         return this.send_shell_message("inspect_request", content, callbacks);
     };
 
     Kernel.prototype.execute = function (code, callbacks, options) {
         /**
          * Execute given code into kernel, and pass result to callback.
          *
          * @async
          * @function execute
          * @param {string} code
          * @param [callbacks] {Object} With the following keys (all optional)
          *      @param callbacks.shell.reply {function}
          *      @param callbacks.shell.payload.[payload_name] {function}
          *      @param callbacks.iopub.output {function}
          *      @param callbacks.iopub.clear_output {function}
          *      @param callbacks.input {function}
          * @param {object} [options]
          *      @param [options.silent=false] {Boolean}
          *      @param [options.user_expressions=empty_dict] {Dict}
          *      @param [options.allow_stdin=false] {Boolean} true|false
          *
          * @example
          *
          * The options object should contain the options for the execute
          * call. Its default values are:
          *
          *      options = {
          *        silent : true,
          *        user_expressions : {},
          *        allow_stdin : false
          *      }
          *
          * When calling this method pass a callbacks structure of the
          * form:
          *
          *      callbacks = {
          *       shell : {
          *         reply : execute_reply_callback,
          *         payload : {
          *           set_next_input : set_next_input_callback,
          *         }
          *       },
          *       iopub : {
          *         output : output_callback,
          *         clear_output : clear_output_callback,
          *       },
          *       input : raw_input_callback
          *      }
          *
          * Each callback will be passed the entire message as a single
          * arugment.  Payload handlers will be passed the corresponding
          * payload and the execute_reply message.
          */
         var content = {
             code : code,
             silent : true,
             store_history : false,
             user_expressions : {},
             allow_stdin : false
         };
         callbacks = callbacks || {};
         if (callbacks.input !== undefined) {
             content.allow_stdin = true;
         }
         $.extend(true, content, options);
         this.events.trigger('execution_request.Kernel', {kernel: this, content: content});
         return this.send_shell_message("execute_request", content, callbacks);
     };
 
     /**
      * When calling this method, pass a function to be called with the
      * `complete_reply` message as its only argument when it arrives.
      *
      * `complete_reply` is documented
      * [here](http://ipython.org/ipython-doc/dev/development/messaging.html#complete)
      *
      * @function complete
      * @param code {string}
      * @param cursor_pos {integer}
      * @param callback {function}
      */
     Kernel.prototype.complete = function (code, cursor_pos, callback) {
         var callbacks;
         if (callback) {
             callbacks = { shell : { reply : callback } };
         }
         var content = {
             code : code,
             cursor_pos : cursor_pos
         };
         return this.send_shell_message("complete_request", content, callbacks);
     };
 
     /**
      * @function send_input_reply
      */
     Kernel.prototype.send_input_reply = function (input) {
         if (!this.is_connected()) {
             throw new Error("kernel is not connected");
         }
         var content = {
             value : input
         };
         this.events.trigger('input_reply.Kernel', {kernel: this, content: content});
         var msg = this._get_msg("input_reply", content);
         msg.channel = 'stdin';
         this.ws.send(serialize.serialize(msg));
         return msg.header.msg_id;
     };
 
     /**
      * @function register_iopub_handler
      */
     Kernel.prototype.register_iopub_handler = function (msg_type, callback) {
         this._iopub_handlers[msg_type] = callback;
     };
 
     /**
      * Get the iopub handler for a specific message type.
      *
      * @function get_iopub_handler
      */
     Kernel.prototype.get_iopub_handler = function (msg_type) {
         return this._iopub_handlers[msg_type];
     };
 
     /**
      * Get callbacks for a specific message.
      *
      * @function get_callbacks_for_msg
      */
     Kernel.prototype.get_callbacks_for_msg = function (msg_id) {
         if (msg_id == this.last_msg_id) {
             return this.last_msg_callbacks;
         } else {
             return this._msg_callbacks[msg_id];
         }
     };
 
     /**
      * Clear callbacks for a specific message.
      *
      * @function clear_callbacks_for_msg
      */
     Kernel.prototype.clear_callbacks_for_msg = function (msg_id) {
         if (this._msg_callbacks[msg_id] !== undefined ) {
             delete this._msg_callbacks[msg_id];
         }
     };
     
     /**
      * @function _finish_shell
      */
     Kernel.prototype._finish_shell = function (msg_id) {
         var callbacks = this._msg_callbacks[msg_id];
         if (callbacks !== undefined) {
             callbacks.shell_done = true;
             if (callbacks.iopub_done) {
                 this.clear_callbacks_for_msg(msg_id);
             }
         }
     };
 
     /**
      * @function _finish_iopub
      */
     Kernel.prototype._finish_iopub = function (msg_id) {
         var callbacks = this._msg_callbacks[msg_id];
         if (callbacks !== undefined) {
             callbacks.iopub_done = true;
             if (callbacks.shell_done) {
                 this.clear_callbacks_for_msg(msg_id);
             }
         }
     };
     
     /**
      * Set callbacks for a particular message.
      * Callbacks should be a struct of the following form:
      * shell : {
      * 
      * }
      *
      * @function set_callbacks_for_msg
      */
     Kernel.prototype.set_callbacks_for_msg = function (msg_id, callbacks) {
         this.last_msg_id = msg_id;
         if (callbacks) {
             // shallow-copy mapping, because we will modify it at the top level
             var cbcopy = this._msg_callbacks[msg_id] = this.last_msg_callbacks = {};
             cbcopy.shell = callbacks.shell;
             cbcopy.iopub = callbacks.iopub;
             cbcopy.input = callbacks.input;
             cbcopy.shell_done = (!callbacks.shell);
             cbcopy.iopub_done = (!callbacks.iopub);
         } else {
             this.last_msg_callbacks = {};
         }
     };
     
     Kernel.prototype._handle_ws_message = function (e) {
-        serialize.deserialize(e.data, $.proxy(this._finish_ws_message, this));
+        this._msg_queue = this._msg_queue.then(function() {
+            return serialize.deserialize(e.data);
+        }).then($.proxy(this._finish_ws_message, this))
+        .catch(utils.reject("Couldn't process kernel message", true));
     };
 
     Kernel.prototype._finish_ws_message = function (msg) {
         switch (msg.channel) {
             case 'shell':
                 this._handle_shell_reply(msg);
                 break;
             case 'iopub':
                 this._handle_iopub_message(msg);
                 break;
             case 'stdin':
                 this._handle_input_request(msg);
                 break;
             default:
                 console.error("unrecognized message channel", msg.channel, msg);
         }
     };
     
     Kernel.prototype._handle_shell_reply = function (reply) {
         this.events.trigger('shell_reply.Kernel', {kernel: this, reply:reply});
         var content = reply.content;
         var metadata = reply.metadata;
         var parent_id = reply.parent_header.msg_id;
         var callbacks = this.get_callbacks_for_msg(parent_id);
         if (!callbacks || !callbacks.shell) {
             return;
         }
         var shell_callbacks = callbacks.shell;
         
         // signal that shell callbacks are done
         this._finish_shell(parent_id);
         
         if (shell_callbacks.reply !== undefined) {
             shell_callbacks.reply(reply);
         }
         if (content.payload && shell_callbacks.payload) {
             this._handle_payloads(content.payload, shell_callbacks.payload, reply);
         }
     };
 
     /**
      * @function _handle_payloads
      */
     Kernel.prototype._handle_payloads = function (payloads, payload_callbacks, msg) {
         var l = payloads.length;
         // Payloads are handled by triggering events because we don't want the Kernel
         // to depend on the Notebook or Pager classes.
         for (var i=0; i<l; i++) {
             var payload = payloads[i];
             var callback = payload_callbacks[payload.source];
             if (callback) {
                 callback(payload, msg);
             }
         }
     };
 
     /**
      * @function _handle_status_message
      */
     Kernel.prototype._handle_status_message = function (msg) {
         var execution_state = msg.content.execution_state;
         var parent_id = msg.parent_header.msg_id;
         
         // dispatch status msg callbacks, if any
         var callbacks = this.get_callbacks_for_msg(parent_id);
         if (callbacks && callbacks.iopub && callbacks.iopub.status) {
             try {
                 callbacks.iopub.status(msg);
             } catch (e) {
                 console.log("Exception in status msg handler", e, e.stack);
             }
         }
         
         if (execution_state === 'busy') {
             this.events.trigger('kernel_busy.Kernel', {kernel: this});
 
         } else if (execution_state === 'idle') {
             // signal that iopub callbacks are (probably) done
             // async output may still arrive,
             // but only for the most recent request
             this._finish_iopub(parent_id);
             
             // trigger status_idle event
             this.events.trigger('kernel_idle.Kernel', {kernel: this});
 
         } else if (execution_state === 'starting') {
             this.events.trigger('kernel_starting.Kernel', {kernel: this});
             var that = this;
             this.kernel_info(function (reply) {
                 that.info_reply = reply.content;
                 that.events.trigger('kernel_ready.Kernel', {kernel: that});
             });
 
         } else if (execution_state === 'restarting') {
             // autorestarting is distinct from restarting,
             // in that it means the kernel died and the server is restarting it.
             // kernel_restarting sets the notification widget,
             // autorestart shows the more prominent dialog.
             this._autorestart_attempt = this._autorestart_attempt + 1;
             this.events.trigger('kernel_restarting.Kernel', {kernel: this});
             this.events.trigger('kernel_autorestarting.Kernel', {kernel: this, attempt: this._autorestart_attempt});
 
         } else if (execution_state === 'dead') {
             this.events.trigger('kernel_dead.Kernel', {kernel: this});
             this._kernel_dead();
         }
     };
     
     /**
      * Handle clear_output message
      *
      * @function _handle_clear_output
      */
     Kernel.prototype._handle_clear_output = function (msg) {
         var callbacks = this.get_callbacks_for_msg(msg.parent_header.msg_id);
         if (!callbacks || !callbacks.iopub) {
             return;
         }
         var callback = callbacks.iopub.clear_output;
         if (callback) {
             callback(msg);
         }
     };
 
     /**
      * handle an output message (execute_result, display_data, etc.)
      *
      * @function _handle_output_message
      */
     Kernel.prototype._handle_output_message = function (msg) {
         var callbacks = this.get_callbacks_for_msg(msg.parent_header.msg_id);
         if (!callbacks || !callbacks.iopub) {
             // The message came from another client. Let the UI decide what to
             // do with it.
             this.events.trigger('received_unsolicited_message.Kernel', msg);
             return;
         }
         var callback = callbacks.iopub.output;
         if (callback) {
             callback(msg);
         }
     };
 
     /**
      * Handle an input message (execute_input).
      *
      * @function _handle_input message
      */
     Kernel.prototype._handle_input_message = function (msg) {
         var callbacks = this.get_callbacks_for_msg(msg.parent_header.msg_id);
         if (!callbacks) {
             // The message came from another client. Let the UI decide what to
             // do with it.
             this.events.trigger('received_unsolicited_message.Kernel', msg);
         }
     };
 
     /**
      * Dispatch IOPub messages to respective handlers. Each message
      * type should have a handler.
      *
      * @function _handle_iopub_message
      */
     Kernel.prototype._handle_iopub_message = function (msg) {
         var handler = this.get_iopub_handler(msg.header.msg_type);
         if (handler !== undefined) {
             handler(msg);
         }
     };
 
     /**
      * @function _handle_input_request
      */
     Kernel.prototype._handle_input_request = function (request) {
         var header = request.header;
         var content = request.content;
         var metadata = request.metadata;
         var msg_type = header.msg_type;
         if (msg_type !== 'input_request') {
             console.log("Invalid input request!", request);
             return;
         }
         var callbacks = this.get_callbacks_for_msg(request.parent_header.msg_id);
         if (callbacks) {
             if (callbacks.input) {
                 callbacks.input(request);
             }
         }
     };
 
     // Backwards compatability.
     IPython.Kernel = Kernel;
 
     return {'Kernel': Kernel};
 });

IPython/html/static/services/kernels/serialize.js

@@ -1,120 +1,123 b''
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     'underscore',
     ], function (_) {
     "use strict";
     
     var _deserialize_array_buffer = function (buf) {
         var data = new DataView(buf);
         // read the header: 1 + nbufs 32b integers
         var nbufs = data.getUint32(0);
         var offsets = [];
         var i;
         for (i = 1; i <= nbufs; i++) {
             offsets.push(data.getUint32(i * 4));
         }
         var json_bytes = new Uint8Array(buf.slice(offsets[0], offsets[1]));
         var msg = JSON.parse(
             (new TextDecoder('utf8')).decode(json_bytes)
         );
         // the remaining chunks are stored as DataViews in msg.buffers
         msg.buffers = [];
         var start, stop;
         for (i = 1; i < nbufs; i++) {
             start = offsets[i];
             stop = offsets[i+1] || buf.byteLength;
             msg.buffers.push(new DataView(buf.slice(start, stop)));
         }
         return msg;
     };
     
-    var _deserialize_binary = function(data, callback) {
+    var _deserialize_binary = function(data) {
         /**
          * deserialize the binary message format
          * callback will be called with a message whose buffers attribute
          * will be an array of DataViews.
          */
         if (data instanceof Blob) {
             // data is Blob, have to deserialize from ArrayBuffer in reader callback
             var reader = new FileReader();
+            var promise = new Promise(function(resolve, reject) {
             reader.onload = function () {
                 var msg = _deserialize_array_buffer(this.result);
-                callback(msg);
+                    resolve(msg);
             };
+            });
             reader.readAsArrayBuffer(data);
+            return promise;
         } else {
             // data is ArrayBuffer, can deserialize directly
             var msg = _deserialize_array_buffer(data);
-            callback(msg);
+            return msg;
         }
     };
 
-    var deserialize = function (data, callback) {
+    var deserialize = function (data) {
         /**
-         * deserialize a message and pass the unpacked message object to callback
+         * deserialize a message and return a promise for the unpacked message
          */
         if (typeof data === "string") {
             // text JSON message
-            callback(JSON.parse(data));
+            return Promise.resolve(JSON.parse(data));
         } else {
             // binary message
-            _deserialize_binary(data, callback);
+            return Promise.resolve(_deserialize_binary(data));
         }
     };
     
     var _serialize_binary = function (msg) {
         /**
          * implement the binary serialization protocol
          * serializes JSON message to ArrayBuffer
          */
         msg = _.clone(msg);
         var offsets = [];
         var buffers = [];
         msg.buffers.map(function (buf) {
             buffers.push(buf);
         });
         delete msg.buffers;
         var json_utf8 = (new TextEncoder('utf8')).encode(JSON.stringify(msg));
         buffers.unshift(json_utf8);
         var nbufs = buffers.length;
         offsets.push(4 * (nbufs + 1));
         var i;
         for (i = 0; i + 1 < buffers.length; i++) {
             offsets.push(offsets[offsets.length-1] + buffers[i].byteLength);
         }
         var msg_buf = new Uint8Array(
             offsets[offsets.length-1] + buffers[buffers.length-1].byteLength
         );
         // use DataView.setUint32 for network byte-order
         var view = new DataView(msg_buf.buffer);
         // write nbufs to first 4 bytes
         view.setUint32(0, nbufs);
         // write offsets to next 4 * nbufs bytes
         for (i = 0; i < offsets.length; i++) {
             view.setUint32(4 * (i+1), offsets[i]);
         }
         // write all the buffers at their respective offsets
         for (i = 0; i < buffers.length; i++) {
             msg_buf.set(new Uint8Array(buffers[i].buffer), offsets[i]);
         }
         
         // return raw ArrayBuffer
         return msg_buf.buffer;
     };
     
     var serialize = function (msg) {
         if (msg.buffers && msg.buffers.length) {
             return _serialize_binary(msg);
         } else {
             return JSON.stringify(msg);
         }
     };
     
     var exports = {
         deserialize : deserialize,
         serialize: serialize
     };
     return exports;
 });