/**
* @license
* Copyright The Closure Library Authors.
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @fileoverview Base WebChannel implementation.
*/
goog.provide('goog.labs.net.webChannel.WebChannelBase');
goog.require('goog.Uri');
goog.require('goog.array');
goog.require('goog.asserts');
goog.require('goog.async.run');
goog.require('goog.collections.maps');
goog.require('goog.json');
goog.require('goog.labs.net.webChannel.Channel');
goog.require('goog.labs.net.webChannel.ChannelRequest');
goog.require('goog.labs.net.webChannel.ConnectionState');
goog.require('goog.labs.net.webChannel.ForwardChannelRequestPool');
goog.require('goog.labs.net.webChannel.WebChannelDebug');
goog.require('goog.labs.net.webChannel.Wire');
goog.require('goog.labs.net.webChannel.WireV8');
goog.require('goog.labs.net.webChannel.environment');
goog.require('goog.labs.net.webChannel.netUtils');
goog.require('goog.labs.net.webChannel.requestStats');
goog.require('goog.net.FetchXmlHttpFactory');
goog.require('goog.net.WebChannel');
goog.require('goog.net.XhrIo');
goog.require('goog.net.XmlHttpFactory');
goog.require('goog.net.rpc.HttpCors');
goog.require('goog.object');
goog.require('goog.string');
goog.require('goog.structs');
goog.scope(function() {
'use strict';
const WebChannel = goog.net.WebChannel;
const ChannelRequest = goog.labs.net.webChannel.ChannelRequest;
const ConnectionState = goog.labs.net.webChannel.ConnectionState;
const ForwardChannelRequestPool =
goog.labs.net.webChannel.ForwardChannelRequestPool;
const WebChannelDebug = goog.labs.net.webChannel.WebChannelDebug;
const Wire = goog.labs.net.webChannel.Wire;
const WireV8 = goog.labs.net.webChannel.WireV8;
const environment = goog.labs.net.webChannel.environment;
const netUtils = goog.labs.net.webChannel.netUtils;
const requestStats = goog.labs.net.webChannel.requestStats;
const httpCors = goog.module.get('goog.net.rpc.HttpCors');
/**
* Gets an internal channel parameter in a type-safe way.
*
* @param {string} paramName the key of the parameter to fetch.
* @param {!T} defaultValue the default value to return
* @param {!goog.net.WebChannel.Options=} options Configuration for the
* WebChannel instance.
* @return {T}
* @template T
*/
function getInternalChannelParam(paramName, defaultValue, options) {
if (!options || !options.internalChannelParams) {
return defaultValue;
}
return /** @type {T} */ (options.internalChannelParams[paramName]) ||
defaultValue;
}
/**
* This WebChannel implementation is branched off goog.net.BrowserChannel
* for now. Ongoing changes to goog.net.BrowserChannel will be back
* ported to this implementation as needed.
*
* @param {!goog.net.WebChannel.Options=} opt_options Configuration for the
* WebChannel instance.
* @param {number=} opt_clientVersion An application-specific version number
* that is sent to the server when connected.
* @param {!ConnectionState=} opt_conn Previously determined connection
* conditions.
* @constructor
* @struct
* @implements {goog.labs.net.webChannel.Channel}
*/
goog.labs.net.webChannel.WebChannelBase = function(
opt_options, opt_clientVersion, opt_conn) {
'use strict';
/**
* The client library version (capabilities).
* @private {number}
*/
this.clientVersion_ = opt_clientVersion || 0;
/**
* The server library version (capabilities).
* @private {number}
*/
this.serverVersion_ = 0;
/**
* An array of queued maps that need to be sent to the server.
* @private {!Array<Wire.QueuedMap>}
*/
this.outgoingMaps_ = [];
/**
* The channel debug used for logging
* @private {!WebChannelDebug}
*/
this.channelDebug_ = new WebChannelDebug();
/**
* Connectivity state.
* @private {!ConnectionState}
*/
this.connState_ = opt_conn || new ConnectionState();
/**
* Extra HTTP headers to add to all the requests sent to the server.
* @private {?Object}
*/
this.extraHeaders_ = null;
/**
* Extra HTTP headers to add to the init request(s) sent to the server.
* @private {?Object}
*/
this.initHeaders_ = null;
/**
* @private {?string} The URL param name to overwrite custom HTTP headers
* to bypass CORS preflight.
*/
this.httpHeadersOverwriteParam_ = null;
/**
* Extra parameters to add to all the requests sent to the server.
* @private {?Object}
*/
this.extraParams_ = null;
/**
* Parameter name for the http session id.
* @private {?string}
*/
this.httpSessionIdParam_ = null;
/**
* The http session id, to be sent with httpSessionIdParam_ with each
* request after the initial handshake.
* @private {?string}
*/
this.httpSessionId_ = null;
/**
* The ChannelRequest object for the backchannel.
* @private {?ChannelRequest}
*/
this.backChannelRequest_ = null;
/**
* The relative path (in the context of the page hosting the browser channel)
* for making requests to the server.
* @private {?string}
*/
this.path_ = null;
/**
* The absolute URI for the forwardchannel request.
* @private {?goog.Uri}
*/
this.forwardChannelUri_ = null;
/**
* The absolute URI for the backchannel request.
* @private {?goog.Uri}
*/
this.backChannelUri_ = null;
/**
* A subdomain prefix for using a subdomain in IE for the backchannel
* requests.
* @private {?string}
*/
this.hostPrefix_ = null;
/**
* Whether we allow the use of a subdomain in IE for the backchannel requests.
* @private {boolean}
*/
this.allowHostPrefix_ = true;
/**
* The next id to use for the RID (request identifier) parameter. This
* identifier uniquely identifies the forward channel request.
* @private {number}
*/
this.nextRid_ = 0;
/**
* The id to use for the next outgoing map. This identifier uniquely
* identifies a sent map.
* @private {number}
*/
this.nextMapId_ = 0;
/**
* Whether to fail forward-channel requests after one try or a few tries.
* @private {boolean}
*/
this.failFast_ = getInternalChannelParam('failFast', false, opt_options);
/**
* The handler that receive callbacks for state changes and data.
* @private {?goog.labs.net.webChannel.WebChannelBase.Handler}
*/
this.handler_ = null;
/**
* Timer identifier for asynchronously making a forward channel request.
* This is set to true if the func is scheduled with async.run, which
* is equivalent to setTimeout(0).
* @private {?number|?boolean}
*/
this.forwardChannelTimerId_ = null;
/**
* Timer identifier for asynchronously making a back channel request.
* @private {?number}
*/
this.backChannelTimerId_ = null;
/**
* Timer identifier for the timer that waits for us to retry the backchannel
* in the case where it is dead and no longer receiving data.
* @private {?number}
*/
this.deadBackChannelTimerId_ = null;
/**
* Whether the client's network conditions can support streamed responses.
* @private {?boolean}
*/
this.enableStreaming_ = null;
/**
* Whether streaming mode is allowed. In certain debugging situations, it's
* useful to disable this.
* @private {boolean}
*/
this.allowStreamingMode_ = true;
/**
* The array identifier of the last array received from the server for the
* backchannel request.
* @private {number}
*/
this.lastArrayId_ = -1;
/**
* The array id of the last array sent by the server that we know about.
* @private {number}
*/
this.lastPostResponseArrayId_ = -1;
/**
* The last status code received.
* @private {number}
*/
this.lastStatusCode_ = -1;
/**
* Number of times we have retried the current forward channel request.
* @private {number}
*/
this.forwardChannelRetryCount_ = 0;
/**
* Number of times in a row that we have retried the current back channel
* request and received no data.
* @private {number}
*/
this.backChannelRetryCount_ = 0;
/**
* The attempt id for the current back channel request. Starts at 1 and
* increments for each reconnect. The server uses this to log if our
* connection is flaky or not.
* @private {number}
*/
this.backChannelAttemptId_ = 0;
/**
* The base part of the time before firing next retry request. Default is 5
* seconds. Note that a random delay is added (see {@link retryDelaySeedMs_})
* for all retries, and linear backoff is applied to the sum for subsequent
* retries.
* @private {number}
*/
this.baseRetryDelayMs_ =
getInternalChannelParam('baseRetryDelayMs', 5 * 1000, opt_options);
/**
* A random time between 0 and this number of MS is added to the
* {@link baseRetryDelayMs_}. Default is 10 seconds.
* @private {number}
*/
this.retryDelaySeedMs_ =
getInternalChannelParam('retryDelaySeedMs', 10 * 1000, opt_options);
/**
* Maximum number of attempts to connect to the server for forward channel
* requests. Defaults to 2.
* @private {number}
*/
this.forwardChannelMaxRetries_ =
getInternalChannelParam('forwardChannelMaxRetries', 2, opt_options);
/**
* The timeout in milliseconds for a forward channel request. Defaults to 20
* seconds. Note that part of this timeout can be randomized.
* @private {number}
*/
this.forwardChannelRequestTimeoutMs_ = getInternalChannelParam(
'forwardChannelRequestTimeoutMs', 20 * 1000, opt_options);
/**
* The custom factory used to create XMLHttpRequest objects.
* @private {!goog.net.XmlHttpFactory | undefined}
*/
this.xmlHttpFactory_ =
(opt_options && opt_options.xmlHttpFactory) || undefined;
/**
* Whether or not this channel uses WHATWG Fetch/streams.
* @private {boolean}
*/
this.usesFetchStreams_ =
(opt_options && opt_options.useFetchStreams) || false;
/**
* The timeout in milliseconds for a back channel request. Defaults to using
* the timeout configured in ChannelRequest (45s). If server-side
* keepaliveInterval is known to the client, set the backchannel request
* timeout to 1.5 * keepaliveInterval (ms).
*
* @private {number|undefined}
*/
this.backChannelRequestTimeoutMs_ = undefined;
/**
* A throttle time in ms for readystatechange events for the backchannel.
* Useful for throttling when ready state is INTERACTIVE (partial data).
*
* This throttle is useful if the server sends large data chunks down the
* backchannel. It prevents examining XHR partial data on every readystate
* change event. This is useful because large chunks can trigger hundreds
* of readystatechange events, each of which takes ~5ms or so to handle,
* in turn making the UI unresponsive for a significant period.
*
* If set to zero no throttle is used.
* @private {number}
*/
this.readyStateChangeThrottleMs_ = 0;
/**
* Whether cross origin requests are supported for the channel.
*
* See {@link goog.net.XhrIo#setWithCredentials}.
* @private {boolean}
*/
this.supportsCrossDomainXhrs_ =
(opt_options && opt_options.supportsCrossDomainXhr) || false;
/**
* The current session id.
* @private {string}
*/
this.sid_ = '';
/**
* The current ChannelRequest pool for the forward channel.
* @private {!ForwardChannelRequestPool}
*/
this.forwardChannelRequestPool_ = new ForwardChannelRequestPool(
opt_options && opt_options.concurrentRequestLimit);
/**
* The V8 codec.
* @private {!WireV8}
*/
this.wireCodec_ = new WireV8();
/**
* Whether to turn on the fast handshake behavior.
*
* @private {boolean}
*/
this.fastHandshake_ = (opt_options && opt_options.fastHandshake) || false;
/**
* Whether to signal to the server to enable blocking handshake.
*
* @private {boolean}
*/
this.blockingHandshake_ =
(opt_options && opt_options.blockingHandshake) || false;
if (opt_options && opt_options.disableRedact) {
this.channelDebug_.disableRedact();
}
if (opt_options && opt_options.forceLongPolling) {
this.allowStreamingMode_ = false;
}
/**
* Whether to detect buffering proxies.
*
* fastHandshake + detectBufferingProxy are yet to be implemented.
*
* @private {boolean}
*/
this.detectBufferingProxy_ =
(!this.fastHandshake_ && this.allowStreamingMode_ && opt_options &&
opt_options.detectBufferingProxy) ||
false;
/**
* Callback when all the pending client-sent messages have been flushed.
*
* @private {function()|undefined}
*/
this.forwardChannelFlushedCallback_ = undefined;
/**
* TODO(user): move all backchannel states to its own class similar to
* forwardchannelrequestpool.js and log more stats.
*
* The estimated handshake RTT (ms) as measured from when the handshake
* request is sent and when the handshake response headers are received.
* If the value is 0, the RTT is unknown.
*
* @private {number}
*/
this.handshakeRttMs_ = 0;
/**
* If BP detection is done or still in progress.
* Should only be checked when detectBufferingProxy is turned on.
* @private {boolean}
*/
this.bpDetectionDone_ = false;
/**
* The timer for detecting buffering proxy. This needs be reset with each
* backchannel request. If this is not null, bpDetectionDone_ == false.
* @private {?number}
*/
this.bpDetectionTimerId_ = null;
/***
* Whether to attempt Chrome Origin Trials as part of the handshake.
* @private {boolean}
*/
this.enableOriginTrials_ =
!opt_options || opt_options.enableOriginTrials !== false;
};
const WebChannelBase = goog.labs.net.webChannel.WebChannelBase;
/**
* The channel version that we negotiated with the server for this session.
* Starts out as the version we request, and then is changed to the negotiated
* version after the initial open.
* @private {number}
*/
WebChannelBase.prototype.channelVersion_ = Wire.LATEST_CHANNEL_VERSION;
/**
* Enum type for the channel state machine.
* @enum {number}
*/
WebChannelBase.State = {
/** The channel is closed. */
CLOSED: 0,
/** The channel has been initialized but hasn't yet initiated a connection. */
INIT: 1,
/** The channel is in the process of opening a connection to the server. */
OPENING: 2,
/** The channel is open. */
OPENED: 3
};
/**
* The current state of the WebChannel.
* @private {!WebChannelBase.State}
*/
WebChannelBase.prototype.state_ = WebChannelBase.State.INIT;
/**
* The timeout in milliseconds for a forward channel request.
* @type {number}
*/
WebChannelBase.FORWARD_CHANNEL_RETRY_TIMEOUT = 20 * 1000;
/**
* Maximum number of attempts to connect to the server for back channel
* requests.
* @type {number}
*/
WebChannelBase.BACK_CHANNEL_MAX_RETRIES = 3;
/**
* A number in MS of how long we guess the maxmium amount of time a round trip
* to the server should take. In the future this could be substituted with a
* real measurement of the RTT.
* @type {number}
*/
WebChannelBase.RTT_ESTIMATE = 3 * 1000;
/**
* When retrying for an inactive channel, we will multiply the total delay by
* this number.
* @type {number}
*/
WebChannelBase.INACTIVE_CHANNEL_RETRY_FACTOR = 2;
/**
* Enum type for identifying an error.
* @enum {number}
*/
WebChannelBase.Error = {
/** Value that indicates no error has occurred. */
OK: 0,
/** An error due to a request failing. */
REQUEST_FAILED: 2,
/** An error due to the user being logged out. */
LOGGED_OUT: 4,
/** An error due to server response which contains no data. */
NO_DATA: 5,
/** An error due to a server response indicating an unknown session id */
UNKNOWN_SESSION_ID: 6,
/** An error due to a server response requesting to stop the channel. */
STOP: 7,
/** A general network error. */
NETWORK: 8,
/** An error due to bad data being returned from the server. */
BAD_DATA: 10,
/** An error due to a response that is not parsable. */
BAD_RESPONSE: 11
};
/**
* Internal enum type for the two channel types.
* @enum {number}
* @private
*/
WebChannelBase.ChannelType_ = {
FORWARD_CHANNEL: 1,
BACK_CHANNEL: 2
};
/**
* The maximum number of maps that can be sent in one POST. Should match
* MAX_MAPS_PER_REQUEST on the server code.
* @type {number}
* @private
*/
WebChannelBase.MAX_MAPS_PER_REQUEST_ = 1000;
/**
* The maximum number of utf-8 chars that can be sent in one GET to enable 0-RTT
* handshake.
*
* @const @private {number}
*/
WebChannelBase.MAX_CHARS_PER_GET_ = 4 * 1024;
/**
* A guess at a cutoff at which to no longer assume the backchannel is dead
* when we are slow to receive data. Number in bytes.
*
* Assumption: The worst bandwidth we work on is 50 kilobits/sec
* 50kbits/sec * (1 byte / 8 bits) * 6 sec dead backchannel timeout
* @type {number}
*/
WebChannelBase.OUTSTANDING_DATA_BACKCHANNEL_RETRY_CUTOFF = 37500;
/**
* @return {number} The server version or 0 if undefined
*/
WebChannelBase.prototype.getServerVersion = function() {
'use strict';
return this.serverVersion_;
};
/**
* @return {!ForwardChannelRequestPool} The forward channel request pool.
*/
WebChannelBase.prototype.getForwardChannelRequestPool = function() {
'use strict';
return this.forwardChannelRequestPool_;
};
/**
* @return {!Object} The codec object.
*/
WebChannelBase.prototype.getWireCodec = function() {
'use strict';
return this.wireCodec_;
};
/**
* Returns the logger.
*
* @return {!WebChannelDebug} The channel debug object.
*/
WebChannelBase.prototype.getChannelDebug = function() {
'use strict';
return this.channelDebug_;
};
/**
* Sets the logger.
*
* @param {!WebChannelDebug} channelDebug The channel debug object.
*/
WebChannelBase.prototype.setChannelDebug = function(channelDebug) {
'use strict';
this.channelDebug_ = channelDebug;
};
/**
* Starts the channel. This initiates connections to the server.
*
* @param {string} channelPath The path for the channel connection.
* @param {!Object=} opt_extraParams Extra parameter keys and values to add to
* the requests.
* @param {string=} opt_oldSessionId Session ID from a previous session.
* @param {number=} opt_oldArrayId The last array ID from a previous session.
*/
WebChannelBase.prototype.connect = function(
channelPath, opt_extraParams, opt_oldSessionId, opt_oldArrayId) {
'use strict';
this.channelDebug_.debug('connect()');
this.startOriginTrials_(channelPath);
requestStats.notifyStatEvent(requestStats.Stat.CONNECT_ATTEMPT);
this.path_ = channelPath;
this.extraParams_ = opt_extraParams || {};
// Attach parameters about the previous session if reconnecting.
if (opt_oldSessionId && opt_oldArrayId !== undefined) {
this.extraParams_['OSID'] = opt_oldSessionId;
this.extraParams_['OAID'] = opt_oldArrayId;
}
this.enableStreaming_ = this.allowStreamingMode_;
this.connectChannel_();
};
/**
* Disconnects and closes the channel.
*/
WebChannelBase.prototype.disconnect = function() {
'use strict';
this.channelDebug_.debug('disconnect()');
this.cancelRequests_();
if (this.state_ == WebChannelBase.State.OPENED) {
const rid = this.nextRid_++;
const uri = this.forwardChannelUri_.clone();
uri.setParameterValue('SID', this.sid_);
uri.setParameterValue('RID', rid);
uri.setParameterValue('TYPE', 'terminate');
// Add the reconnect parameters.
this.addAdditionalParams_(uri);
const request = ChannelRequest.createChannelRequest(
this, this.channelDebug_, this.sid_, rid);
request.sendCloseRequest(uri);
}
this.onClose_();
};
/**
* Returns the session id of the channel. Only available after the
* channel has been opened.
* @return {string} Session ID.
*/
WebChannelBase.prototype.getSessionId = function() {
'use strict';
return this.sid_;
};
/**
* Starts the connection.
* @private
*/
WebChannelBase.prototype.connectChannel_ = function() {
'use strict';
this.channelDebug_.debug('connectChannel_()');
this.ensureInState_(WebChannelBase.State.INIT, WebChannelBase.State.CLOSED);
this.forwardChannelUri_ =
this.getForwardChannelUri(/** @type {string} */ (this.path_));
this.ensureForwardChannel_();
};
/**
* Starts the Origin Trials.
* @param {string} channelPath The path for the channel connection.
* @private
*/
WebChannelBase.prototype.startOriginTrials_ = function(channelPath) {
'use strict';
if (!this.enableOriginTrials_) {
return;
}
this.channelDebug_.info('Origin Trials enabled.');
goog.async.run(goog.bind(this.runOriginTrials_, this, channelPath));
};
/**
* Runs the Origin Trials.
* @param {string} channelPath The path for the channel connection.
* @private
*/
WebChannelBase.prototype.runOriginTrials_ = function(channelPath) {
'use strict';
try {
// Since startOriginTrials might throw exceptions asynchronously, we should
// capture it in promise-catch.
environment.startOriginTrials(channelPath, e => {
this.channelDebug_.dumpException(
/** @type {?Error} */ (e), 'Error in running origin trials');
});
this.channelDebug_.info('Origin Trials invoked: ' + channelPath);
} catch (e) {
this.channelDebug_.dumpException(e, 'Error in running origin trials');
}
};
/**
* Cancels backchannel request.
* @private
*/
WebChannelBase.prototype.cancelBackChannelRequest_ = function() {
'use strict';
if (this.backChannelRequest_) {
this.clearBpDetectionTimer_();
this.backChannelRequest_.cancel();
this.backChannelRequest_ = null;
}
};
/**
* Cancels all outstanding requests.
* @private
*/
WebChannelBase.prototype.cancelRequests_ = function() {
'use strict';
this.cancelBackChannelRequest_();
if (this.backChannelTimerId_) {
goog.global.clearTimeout(this.backChannelTimerId_);
this.backChannelTimerId_ = null;
}
this.clearDeadBackchannelTimer_();
this.forwardChannelRequestPool_.cancel();
if (this.forwardChannelTimerId_) {
this.clearForwardChannelTimer_();
}
};
/**
* Clears the forward channel timer.
* @private
*/
WebChannelBase.prototype.clearForwardChannelTimer_ = function() {
'use strict';
if (typeof this.forwardChannelTimerId_ === 'number') {
goog.global.clearTimeout(this.forwardChannelTimerId_);
}
this.forwardChannelTimerId_ = null;
};
/**
* Returns the extra HTTP headers to add to all the requests sent to the server.
*
* @return {Object} The HTTP headers, or null.
*/
WebChannelBase.prototype.getExtraHeaders = function() {
'use strict';
return this.extraHeaders_;
};
/**
* Sets extra HTTP headers to add to all the requests sent to the server.
*
* @param {Object} extraHeaders The HTTP headers, or null.
*/
WebChannelBase.prototype.setExtraHeaders = function(extraHeaders) {
'use strict';
this.extraHeaders_ = extraHeaders;
};
/**
* Returns the extra HTTP headers to add to the init requests
* sent to the server.
*
* @return {Object} The HTTP headers, or null.
*/
WebChannelBase.prototype.getInitHeaders = function() {
'use strict';
return this.initHeaders_;
};
/**
* Sets extra HTTP headers to add to the init requests sent to the server.
*
* @param {Object} initHeaders The HTTP headers, or null.
*/
WebChannelBase.prototype.setInitHeaders = function(initHeaders) {
'use strict';
this.initHeaders_ = initHeaders;
};
/**
* Sets the URL param name to overwrite custom HTTP headers.
*
* @param {string} httpHeadersOverwriteParam The URL param name.
*/
WebChannelBase.prototype.setHttpHeadersOverwriteParam = function(
httpHeadersOverwriteParam) {
'use strict';
this.httpHeadersOverwriteParam_ = httpHeadersOverwriteParam;
};
/**
* @override
*/
WebChannelBase.prototype.setHttpSessionIdParam = function(httpSessionIdParam) {
'use strict';
this.httpSessionIdParam_ = httpSessionIdParam;
};
/**
* @override
*/
WebChannelBase.prototype.getHttpSessionIdParam = function() {
'use strict';
return this.httpSessionIdParam_;
};
/**
* @override
*/
WebChannelBase.prototype.setHttpSessionId = function(httpSessionId) {
'use strict';
this.httpSessionId_ = httpSessionId;
};
/**
* @override
*/
WebChannelBase.prototype.getHttpSessionId = function() {
'use strict';
return this.httpSessionId_;
};
/**
* Sets the throttle for handling onreadystatechange events for the request.
*
* @param {number} throttle The throttle in ms. A value of zero indicates
* no throttle.
*/
WebChannelBase.prototype.setReadyStateChangeThrottle = function(throttle) {
'use strict';
this.readyStateChangeThrottleMs_ = throttle;
};
/**
* Sets whether cross origin requests are supported for the channel.
*
* Setting this allows the creation of requests to secondary domains and
* sends XHRs with the CORS withCredentials bit set to true.
*
* In order for cross-origin requests to work, the server will also need to set
* CORS response headers as per:
* https://developer.mozilla.org/en-US/docs/HTTP_access_control
*
* See {@link goog.net.XhrIo#setWithCredentials}.
* @param {boolean} supportCrossDomain Whether cross domain XHRs are supported.
*/
WebChannelBase.prototype.setSupportsCrossDomainXhrs = function(
supportCrossDomain) {
'use strict';
this.supportsCrossDomainXhrs_ = supportCrossDomain;
};
/**
* Returns the handler used for channel callback events.
*
* @return {WebChannelBase.Handler} The handler.
*/
WebChannelBase.prototype.getHandler = function() {
'use strict';
return this.handler_;
};
/**
* Sets the handler used for channel callback events.
* @param {WebChannelBase.Handler} handler The handler to set.
*/
WebChannelBase.prototype.setHandler = function(handler) {
'use strict';
this.handler_ = handler;
};
/**
* Returns whether the channel allows the use of a subdomain. There may be
* cases where this isn't allowed.
* @return {boolean} Whether a host prefix is allowed.
*/
WebChannelBase.prototype.getAllowHostPrefix = function() {
'use strict';
return this.allowHostPrefix_;
};
/**
* Sets whether the channel allows the use of a subdomain. There may be cases
* where this isn't allowed, for example, logging in with troutboard where
* using a subdomain causes Apache to force the user to authenticate twice.
* @param {boolean} allowHostPrefix Whether a host prefix is allowed.
*/
WebChannelBase.prototype.setAllowHostPrefix = function(allowHostPrefix) {
'use strict';
this.allowHostPrefix_ = allowHostPrefix;
};
/**
* Returns whether the channel is buffered or not. This may be
* queried in the WebChannelBase.okToMakeRequest() callback.
*
* @return {boolean} Whether the channel is buffered.
*/
WebChannelBase.prototype.isBuffered = function() {
'use strict';
return !this.enableStreaming_;
};
/**
* Returns whether streaming mode is allowed. In certain debugging situations,
* it's useful for the application to have a way to disable streaming mode for a
* user.
* @return {boolean} Whether streaming mode is allowed.
*/
WebChannelBase.prototype.getAllowStreamingMode = function() {
'use strict';
return this.allowStreamingMode_;
};
/**
* Sets whether streaming mode is allowed. In certain debugging situations, it's
* useful for the application to have a way to disable streaming mode for a
* user.
* @param {boolean} allowStreamingMode Whether streaming mode is allowed.
*/
WebChannelBase.prototype.setAllowStreamingMode = function(allowStreamingMode) {
'use strict';
this.allowStreamingMode_ = allowStreamingMode;
};
/**
* Sends a request to the server. The format of the request is a Map data
* structure of key/value pairs. These maps are then encoded in a format
* suitable for the wire and then reconstituted as a Map data structure that
* the server can process.
* @param {!Object|!goog.collections.maps.MapLike} map The map to send.
* @param {!Object=} opt_context The context associated with the map.
*/
WebChannelBase.prototype.sendMap = function(map, opt_context) {
'use strict';
goog.asserts.assert(
this.state_ != WebChannelBase.State.CLOSED,
'Invalid operation: sending map when state is closed');
// We can only send 1000 maps per POST, but typically we should never have
// that much to send, so warn if we exceed that (we still send all the maps).
if (this.outgoingMaps_.length == WebChannelBase.MAX_MAPS_PER_REQUEST_) {
// severe() is temporary so that we get these uploaded and can figure out
// what's causing them. Afterwards can change to warning().
this.channelDebug_.severe(function() {
'use strict';
return 'Already have ' + WebChannelBase.MAX_MAPS_PER_REQUEST_ +
' queued maps upon queueing ' + goog.json.serialize(map);
});
}
this.outgoingMaps_.push(
new Wire.QueuedMap(this.nextMapId_++, map, opt_context));
// Messages need be buffered during OPENING to avoid server-side race
if (this.state_ == WebChannelBase.State.OPENED) {
this.ensureForwardChannel_();
}
};
/**
* When set to true, this changes the behavior of the forward channel so it
* will not retry requests; it will fail after one network failure, and if
* there was already one network failure, the request will fail immediately.
* @param {boolean} failFast Whether or not to fail fast.
*/
WebChannelBase.prototype.setFailFast = function(failFast) {
'use strict';
this.failFast_ = failFast;
this.channelDebug_.info('setFailFast: ' + failFast);
if ((this.forwardChannelRequestPool_.hasPendingRequest() ||
this.forwardChannelTimerId_) &&
this.forwardChannelRetryCount_ > this.getForwardChannelMaxRetries()) {
const self = this;
this.channelDebug_.info(function() {
'use strict';
return 'Retry count ' + self.forwardChannelRetryCount_ +
' > new maxRetries ' + self.getForwardChannelMaxRetries() +
'. Fail immediately!';
});
if (!this.forwardChannelRequestPool_.forceComplete(
goog.bind(this.onRequestComplete, this))) {
// i.e., this.forwardChannelTimerId_
this.clearForwardChannelTimer_();
// The error code from the last failed request is gone, so just use a
// generic one.
this.signalError_(WebChannelBase.Error.REQUEST_FAILED);
}
}
};
/**
* @return {number} The max number of forward-channel retries, which will be 0
* in fail-fast mode.
*/
WebChannelBase.prototype.getForwardChannelMaxRetries = function() {
'use strict';
return this.failFast_ ? 0 : this.forwardChannelMaxRetries_;
};
/**
* Sets the maximum number of attempts to connect to the server for forward
* channel requests.
* @param {number} retries The maximum number of attempts.
*/
WebChannelBase.prototype.setForwardChannelMaxRetries = function(retries) {
'use strict';
this.forwardChannelMaxRetries_ = retries;
};
/**
* Sets the timeout for a forward channel request.
* @param {number} timeoutMs The timeout in milliseconds.
*/
WebChannelBase.prototype.setForwardChannelRequestTimeout = function(timeoutMs) {
'use strict';
this.forwardChannelRequestTimeoutMs_ = timeoutMs;
};
/**
* @return {number} The max number of back-channel retries, which is a constant.
*/
WebChannelBase.prototype.getBackChannelMaxRetries = function() {
'use strict';
// Back-channel retries is a constant.
return WebChannelBase.BACK_CHANNEL_MAX_RETRIES;
};
/**
* @override
*/
WebChannelBase.prototype.isClosed = function() {
'use strict';
return this.state_ == WebChannelBase.State.CLOSED;
};
/**
* Returns the channel state.
* @return {WebChannelBase.State} The current state of the channel.
*/
WebChannelBase.prototype.getState = function() {
'use strict';
return this.state_;
};
/**
* Return the last status code received for a request.
* @return {number} The last status code received for a request.
*/
WebChannelBase.prototype.getLastStatusCode = function() {
'use strict';
return this.lastStatusCode_;
};
/**
* @return {number} The last array id received.
*/
WebChannelBase.prototype.getLastArrayId = function() {
'use strict';
return this.lastArrayId_;
};
/**
* Returns whether there are outstanding requests servicing the channel.
* @return {boolean} true if there are outstanding requests.
*/
WebChannelBase.prototype.hasOutstandingRequests = function() {
'use strict';
return this.getOutstandingRequests_() != 0;
};
/**
* Returns the number of outstanding requests.
* @return {number} The number of outstanding requests to the server.
* @private
*/
WebChannelBase.prototype.getOutstandingRequests_ = function() {
'use strict';
let count = 0;
if (this.backChannelRequest_) {
count++;
}
count += this.forwardChannelRequestPool_.getRequestCount();
return count;
};
/**
* Ensures that a forward channel request is scheduled.
* @private
*/
WebChannelBase.prototype.ensureForwardChannel_ = function() {
'use strict';
if (this.forwardChannelRequestPool_.isFull()) {
// enough connection in process - no need to start a new request
return;
}
if (this.forwardChannelTimerId_) {
// no need to start a new request - one is already scheduled
return;
}
// Use async.run instead of setTimeout(0) to avoid the 1s message delay
// from chrome/firefox background tabs
this.forwardChannelTimerId_ = true;
goog.async.run(this.onStartForwardChannelTimer_, this);
this.forwardChannelRetryCount_ = 0;
};
/**
* Schedules a forward-channel retry for the specified request, unless the max
* retries has been reached.
* @param {!ChannelRequest} request The failed request to retry.
* @return {boolean} true iff a retry was scheduled.
* @private
*/
WebChannelBase.prototype.maybeRetryForwardChannel_ = function(request) {
'use strict';
if (this.forwardChannelRequestPool_.getRequestCount() >=
this.forwardChannelRequestPool_.getMaxSize() -
(this.forwardChannelTimerId_ ? 1 : 0)) {
// Should be impossible to be called in this state.
this.channelDebug_.severe('Unexpected retry request is scheduled.');
return false;
}
if (this.forwardChannelTimerId_) {
this.channelDebug_.debug(
'Use the retry request that is already scheduled.');
this.outgoingMaps_ =
request.getPendingMessages().concat(this.outgoingMaps_);
return true;
}
// No retry for open_() and fail-fast
if (this.state_ == WebChannelBase.State.INIT ||
this.state_ == WebChannelBase.State.OPENING ||
(this.forwardChannelRetryCount_ >= this.getForwardChannelMaxRetries())) {
return false;
}
this.channelDebug_.debug('Going to retry POST');
this.forwardChannelTimerId_ = requestStats.setTimeout(
goog.bind(this.onStartForwardChannelTimer_, this, request),
this.getRetryTime_(this.forwardChannelRetryCount_));
this.forwardChannelRetryCount_++;
return true;
};
/**
* Timer callback for ensureForwardChannel
* @param {ChannelRequest=} opt_retryRequest A failed request
* to retry.
* @private
*/
WebChannelBase.prototype.onStartForwardChannelTimer_ = function(
opt_retryRequest) {
'use strict';
// null is possible if scheduled with async.run
if (this.forwardChannelTimerId_) {
this.forwardChannelTimerId_ = null;
this.startForwardChannel_(opt_retryRequest);
}
};
/**
* Begins a new forward channel operation to the server.
* @param {ChannelRequest=} opt_retryRequest A failed request to retry.
* @private
*/
WebChannelBase.prototype.startForwardChannel_ = function(opt_retryRequest) {
'use strict';
this.channelDebug_.debug('startForwardChannel_');
if (!this.okToMakeRequest_()) {
return; // channel is cancelled
} else if (this.state_ == WebChannelBase.State.INIT) {
if (opt_retryRequest) {
this.channelDebug_.severe('Not supposed to retry the open');
return;
}
this.open_();
this.state_ = WebChannelBase.State.OPENING;
} else if (this.state_ == WebChannelBase.State.OPENED) {
if (opt_retryRequest) {
this.makeForwardChannelRequest_(opt_retryRequest);
return;
}
if (this.outgoingMaps_.length == 0) {
this.channelDebug_.debug(
'startForwardChannel_ returned: ' +
'nothing to send');
// no need to start a new forward channel request
return;
}
if (this.forwardChannelRequestPool_.isFull()) {
// Should be impossible to be called in this state.
this.channelDebug_.severe(
'startForwardChannel_ returned: ' +
'connection already in progress');
return;
}
this.makeForwardChannelRequest_();
this.channelDebug_.debug('startForwardChannel_ finished, sent request');
}
};
/**
* Establishes a new channel session with the server.
* @private
*/
WebChannelBase.prototype.open_ = function() {
'use strict';
this.channelDebug_.debug('open_()');
this.nextRid_ = Math.floor(Math.random() * 100000);
const rid = this.nextRid_++;
const request =
ChannelRequest.createChannelRequest(this, this.channelDebug_, '', rid);
// mix the init headers
let extraHeaders = this.extraHeaders_;
if (this.initHeaders_) {
if (extraHeaders) {
extraHeaders = goog.object.clone(extraHeaders);
goog.object.extend(extraHeaders, this.initHeaders_);
} else {
extraHeaders = this.initHeaders_;
}
}
if (this.httpHeadersOverwriteParam_ === null) {
request.setExtraHeaders(extraHeaders);
}
const requestText = this.dequeueOutgoingMaps_(
request,
this.fastHandshake_ ? this.getMaxNumMessagesForFastHandshake_() :
WebChannelBase.MAX_MAPS_PER_REQUEST_);
const uri = this.forwardChannelUri_.clone();
uri.setParameterValue('RID', rid);
if (this.clientVersion_ > 0) {
uri.setParameterValue('CVER', this.clientVersion_);
}
// http-session-id to be generated as the response
if (this.getHttpSessionIdParam()) {
uri.setParameterValue(
WebChannel.X_HTTP_SESSION_ID, this.getHttpSessionIdParam());
}
// Add the reconnect parameters.
this.addAdditionalParams_(uri);
if (this.httpHeadersOverwriteParam_ && extraHeaders) {
httpCors.setHttpHeadersWithOverwriteParam(
uri, this.httpHeadersOverwriteParam_, extraHeaders);
}
this.forwardChannelRequestPool_.addRequest(request);
if (this.blockingHandshake_) {
uri.setParameterValue('TYPE', 'init'); // default to blocking in future
}
// Check the option and use GET to enable QUIC 0-RTT
if (this.fastHandshake_) {
uri.setParameterValue('$req', requestText);
// enable handshake upgrade
uri.setParameterValue('SID', 'null');
request.setDecodeInitialResponse();
request.xmlHttpPost(uri, null, true); // Send as a GET
} else {
request.xmlHttpPost(uri, requestText, true);
}
};
/**
* @return {number} The number of raw JSON messages to be encoded
* with the fast-handshake (GET) request, including zero. If messages are not
* encoded as raw JSON data, return WebChannelBase.MAX_MAPS_PER_REQUEST_
* @private
*/
WebChannelBase.prototype.getMaxNumMessagesForFastHandshake_ = function() {
'use strict';
let total = 0;
for (let i = 0; i < this.outgoingMaps_.length; i++) {
const map = this.outgoingMaps_[i];
const size = map.getRawDataSize();
if (size === undefined) {
break;
}
total += size;
if (total > WebChannelBase.MAX_CHARS_PER_GET_) {
return i;
}
if (total === WebChannelBase.MAX_CHARS_PER_GET_ ||
i === this.outgoingMaps_.length - 1) {
return i + 1;
}
}
return WebChannelBase.MAX_MAPS_PER_REQUEST_;
};
/**
* Makes a forward channel request using XMLHTTP.
* @param {!ChannelRequest=} opt_retryRequest A failed request to retry.
* @private
*/
WebChannelBase.prototype.makeForwardChannelRequest_ = function(
opt_retryRequest) {
'use strict';
let rid;
if (opt_retryRequest) {
rid = opt_retryRequest.getRequestId(); // Reuse the same RID for a retry
} else {
rid = this.nextRid_++;
}
const uri = this.forwardChannelUri_.clone();
uri.setParameterValue('SID', this.sid_);
uri.setParameterValue('RID', rid);
uri.setParameterValue('AID', this.lastArrayId_);
// Add the additional reconnect parameters.
this.addAdditionalParams_(uri);
if (this.httpHeadersOverwriteParam_ && this.extraHeaders_) {
httpCors.setHttpHeadersWithOverwriteParam(
uri, this.httpHeadersOverwriteParam_, this.extraHeaders_);
}
const request = ChannelRequest.createChannelRequest(
this, this.channelDebug_, this.sid_, rid,
this.forwardChannelRetryCount_ + 1);
if (this.httpHeadersOverwriteParam_ === null) {
request.setExtraHeaders(this.extraHeaders_);
}
let requestText;
if (opt_retryRequest) {
this.requeuePendingMaps_(opt_retryRequest);
}
requestText =
this.dequeueOutgoingMaps_(request, WebChannelBase.MAX_MAPS_PER_REQUEST_);
// Randomize from 50%-100% of the forward channel timeout to avoid
// a big hit if servers happen to die at once.
request.setTimeout(
Math.round(this.forwardChannelRequestTimeoutMs_ * 0.50) +
Math.round(this.forwardChannelRequestTimeoutMs_ * 0.50 * Math.random()));
this.forwardChannelRequestPool_.addRequest(request);
request.xmlHttpPost(uri, requestText, true);
};
/**
* Adds the additional parameters from the handler to the given URI.
* @param {!goog.Uri} uri The URI to add the parameters to.
* @private
*/
WebChannelBase.prototype.addAdditionalParams_ = function(uri) {
'use strict';
// Add the additional reconnect parameters as needed.
if (this.handler_) {
const params = this.handler_.getAdditionalParams(this);
if (params) {
goog.structs.forEach(params, function(value, key, coll) {
'use strict';
uri.setParameterValue(key, value);
});
}
}
};
/**
* Returns the request text from the outgoing maps and resets it.
* @param {!ChannelRequest} request The new request for sending the messages.
* @param {number} maxNum The maximum number of messages to be encoded
* @return {string} The encoded request text created from all the currently
* queued outgoing maps.
* @private
*/
WebChannelBase.prototype.dequeueOutgoingMaps_ = function(request, maxNum) {
'use strict';
const count = Math.min(this.outgoingMaps_.length, maxNum);
const badMapHandler = this.handler_ ?
goog.bind(this.handler_.badMapError, this.handler_, this) :
null;
const result = this.wireCodec_.encodeMessageQueue(
this.outgoingMaps_, count, badMapHandler);
request.setPendingMessages(this.outgoingMaps_.splice(0, count));
return result;
};
/**
* Requeues unacknowledged sent arrays for retransmission in the next forward
* channel request.
* @param {!ChannelRequest} retryRequest A failed request to retry.
* @private
*/
WebChannelBase.prototype.requeuePendingMaps_ = function(retryRequest) {
'use strict';
this.outgoingMaps_ =
retryRequest.getPendingMessages().concat(this.outgoingMaps_);
};
/**
* Ensures there is a backchannel request for receiving data from the server.
* @private
*/
WebChannelBase.prototype.ensureBackChannel_ = function() {
'use strict';
if (this.backChannelRequest_) {
// already have one
return;
}
if (this.backChannelTimerId_) {
// no need to start a new request - one is already scheduled
return;
}
this.backChannelAttemptId_ = 1;
// Use async.run instead of setTimeout(0) to avoid the 1s message delay
// from chrome/firefox background tabs
// backChannelTimerId_ stays unset, as with setTimeout(0)
goog.async.run(this.onStartBackChannelTimer_, this);
this.backChannelRetryCount_ = 0;
};
/**
* Schedules a back-channel retry, unless the max retries has been reached.
* @return {boolean} true iff a retry was scheduled.
* @private
*/
WebChannelBase.prototype.maybeRetryBackChannel_ = function() {
'use strict';
if (this.backChannelRequest_ || this.backChannelTimerId_) {
// Should be impossible to be called in this state.
this.channelDebug_.severe('Request already in progress');
return false;
}
if (this.backChannelRetryCount_ >= this.getBackChannelMaxRetries()) {
return false;
}
this.channelDebug_.debug('Going to retry GET');
this.backChannelAttemptId_++;
this.backChannelTimerId_ = requestStats.setTimeout(
goog.bind(this.onStartBackChannelTimer_, this),
this.getRetryTime_(this.backChannelRetryCount_));
this.backChannelRetryCount_++;
return true;
};
/**
* Timer callback for ensureBackChannel_.
* @private
*/
WebChannelBase.prototype.onStartBackChannelTimer_ = function() {
'use strict';
this.backChannelTimerId_ = null;
this.startBackChannel_();
if (!this.detectBufferingProxy_) {
return;
}
if (this.bpDetectionDone_) {
return;
}
if (this.backChannelRequest_ == null || this.handshakeRttMs_ <= 0) {
this.channelDebug_.warning(
'Skip bpDetectionTimerId_ ' + this.backChannelRequest_ + ' ' +
this.handshakeRttMs_);
return;
}
// This goes with each new request until bpDetectionDone_
const bpDetectionTimeout = 2 * this.handshakeRttMs_;
this.channelDebug_.info('BP detection timer enabled: ' + bpDetectionTimeout);
this.bpDetectionTimerId_ = requestStats.setTimeout(
goog.bind(this.onBpDetectionTimer_, this), bpDetectionTimeout);
};
/**
* Timer callback for bpDetection.
* @private
*/
WebChannelBase.prototype.onBpDetectionTimer_ = function() {
'use strict';
if (!this.bpDetectionTimerId_) {
this.channelDebug_.warning('Invalid operation.');
return;
}
this.bpDetectionTimerId_ = null;
this.channelDebug_.info('BP detection timeout reached.');
goog.asserts.assert(
this.backChannelRequest_ != null,
'Invalid state: no backchannel request');
// We wait for extra response payload in addition to just headers to
// cancel the timer.
if (this.backChannelRequest_.getXhr() != null) {
const responseData = this.backChannelRequest_.getXhr().getResponseText();
if (responseData) {
this.channelDebug_.warning(
'Timer should have been cancelled : ' + responseData);
}
}
// Enable long-polling
this.channelDebug_.info(
'Buffering proxy detected and switch to long-polling!');
this.enableStreaming_ = false;
this.bpDetectionDone_ = true;
requestStats.notifyStatEvent(requestStats.Stat.PROXY);
// Cancel the request and start a new one immediately
this.cancelBackChannelRequest_();
this.startBackChannel_();
};
/**
* Clears the timer for BP detection.
* @private
*/
WebChannelBase.prototype.clearBpDetectionTimer_ = function() {
'use strict';
if (this.bpDetectionTimerId_ != null) {
this.channelDebug_.debug('Cancel the BP detection timer.');
goog.global.clearTimeout(this.bpDetectionTimerId_);
this.bpDetectionTimerId_ = null;
}
};
/**
* Begins a new back channel operation to the server.
* @private
*/
WebChannelBase.prototype.startBackChannel_ = function() {
'use strict';
if (!this.okToMakeRequest_()) {
// channel is cancelled
return;
}
this.channelDebug_.debug('Creating new HttpRequest');
this.backChannelRequest_ = ChannelRequest.createChannelRequest(
this, this.channelDebug_, this.sid_, 'rpc', this.backChannelAttemptId_);
if (this.httpHeadersOverwriteParam_ === null) {
this.backChannelRequest_.setExtraHeaders(this.extraHeaders_);
}
this.backChannelRequest_.setReadyStateChangeThrottle(
this.readyStateChangeThrottleMs_);
const uri = this.backChannelUri_.clone();
uri.setParameterValue('RID', 'rpc');
uri.setParameterValue('SID', this.sid_);
uri.setParameterValue('CI', this.enableStreaming_ ? '0' : '1');
uri.setParameterValue('AID', this.lastArrayId_);
// Add the reconnect parameters.
this.addAdditionalParams_(uri);
uri.setParameterValue('TYPE', 'xmlhttp');
if (this.httpHeadersOverwriteParam_ && this.extraHeaders_) {
httpCors.setHttpHeadersWithOverwriteParam(
uri, this.httpHeadersOverwriteParam_, this.extraHeaders_);
}
if (this.backChannelRequestTimeoutMs_) {
this.backChannelRequest_.setTimeout(this.backChannelRequestTimeoutMs_);
}
this.backChannelRequest_.xmlHttpGet(
uri, true /* decodeChunks */, this.hostPrefix_);
this.channelDebug_.debug('New Request created');
};
/**
* Gives the handler a chance to return an error code and stop channel
* execution. A handler might want to do this to check that the user is still
* logged in, for example.
* @private
* @return {boolean} If it's OK to make a request.
*/
WebChannelBase.prototype.okToMakeRequest_ = function() {
'use strict';
if (this.handler_) {
const result = this.handler_.okToMakeRequest(this);
if (result != WebChannelBase.Error.OK) {
this.channelDebug_.debug(
'Handler returned error code from okToMakeRequest');
this.signalError_(result);
return false;
}
}
return true;
};
/**
* @override
*/
WebChannelBase.prototype.onFirstByteReceived = function(request, responseText) {
'use strict';
if (this.backChannelRequest_ == request && this.detectBufferingProxy_) {
if (!this.bpDetectionDone_) {
this.channelDebug_.info(
'Great, no buffering proxy detected. Bytes received: ' +
responseText.length);
goog.asserts.assert(
this.bpDetectionTimerId_, 'Timer should not have been cancelled.');
this.clearBpDetectionTimer_();
this.bpDetectionDone_ = true;
requestStats.notifyStatEvent(requestStats.Stat.NOPROXY);
}
}
};
/**
* @override
*/
WebChannelBase.prototype.onRequestData = function(request, responseText) {
'use strict';
if (this.state_ == WebChannelBase.State.CLOSED ||
(this.backChannelRequest_ != request &&
!this.forwardChannelRequestPool_.hasRequest(request))) {
// either CLOSED or a request we don't know about (perhaps an old request)
return;
}
this.lastStatusCode_ = request.getLastStatusCode();
// first to check if request has been upgraded to backchannel
if (!request.isInitialResponseDecoded() &&
this.forwardChannelRequestPool_.hasRequest(request) &&
this.state_ == WebChannelBase.State.OPENED) {
let response;
try {
response = this.wireCodec_.decodeMessage(responseText);
} catch (ex) {
response = null;
}
if (Array.isArray(response) && response.length == 3) {
this.handlePostResponse_(/** @type {!Array<?>} */ (response), request);
this.onForwardChannelFlushed_();
} else {
this.channelDebug_.debug('Bad POST response data returned');
this.signalError_(WebChannelBase.Error.BAD_RESPONSE);
}
} else {
if (request.isInitialResponseDecoded() ||
this.backChannelRequest_ == request) {
this.clearDeadBackchannelTimer_();
}
if (!goog.string.isEmptyOrWhitespace(responseText)) {
let response = this.wireCodec_.decodeMessage(responseText);
this.onInput_(/** @type {!Array<?>} */ (response), request);
}
}
};
/**
* Checks if we need call the flush callback.
*
* @private
*/
WebChannelBase.prototype.onForwardChannelFlushed_ = function() {
'use strict';
if (this.forwardChannelRequestPool_.getRequestCount() <= 1) {
if (this.forwardChannelFlushedCallback_) {
try {
this.forwardChannelFlushedCallback_();
} catch (ex) {
this.channelDebug_.dumpException(
ex, 'Exception from forwardChannelFlushedCallback_ ');
}
// reset
this.forwardChannelFlushedCallback_ = undefined;
}
}
};
/**
* Handles a POST response from the server.
* @param {Array<number>} responseValues The key value pairs in
* the POST response.
* @param {!ChannelRequest} forwardReq The forward channel request that
* triggers this function call.
* @private
*/
WebChannelBase.prototype.handlePostResponse_ = function(
responseValues, forwardReq) {
'use strict';
// The first response value is set to 0 if server is missing backchannel.
if (responseValues[0] == 0) {
this.handleBackchannelMissing_(forwardReq);
return;
}
this.lastPostResponseArrayId_ = responseValues[1];
const outstandingArrays = this.lastPostResponseArrayId_ - this.lastArrayId_;
if (0 < outstandingArrays) {
const numOutstandingBackchannelBytes = responseValues[2];
this.channelDebug_.debug(
numOutstandingBackchannelBytes + ' bytes (in ' + outstandingArrays +
' arrays) are outstanding on the BackChannel');
if (!this.shouldRetryBackChannel_(numOutstandingBackchannelBytes)) {
return;
}
if (!this.deadBackChannelTimerId_) {
// We expect to receive data within 2 RTTs or we retry the backchannel.
this.deadBackChannelTimerId_ = requestStats.setTimeout(
goog.bind(this.onBackChannelDead_, this),
2 * WebChannelBase.RTT_ESTIMATE);
}
}
};
/**
* Handles a POST response from the server telling us that it has detected that
* we have no hanging GET connection.
* @param {!ChannelRequest} forwardReq The forward channel request that
* triggers this function call.
* @private
*/
WebChannelBase.prototype.handleBackchannelMissing_ = function(forwardReq) {
'use strict';
// As long as the back channel was started before the POST was sent,
// we should retry the backchannel. We give a slight buffer of RTT_ESTIMATE
// so as not to excessively retry the backchannel
this.channelDebug_.debug('Server claims our backchannel is missing.');
if (this.backChannelTimerId_) {
this.channelDebug_.debug('But we are currently starting the request.');
return;
} else if (!this.backChannelRequest_) {
this.channelDebug_.warning('We do not have a BackChannel established');
} else if (
this.backChannelRequest_.getRequestStartTime() +
WebChannelBase.RTT_ESTIMATE <
forwardReq.getRequestStartTime()) {
this.clearDeadBackchannelTimer_();
this.cancelBackChannelRequest_();
} else {
return;
}
this.maybeRetryBackChannel_();
requestStats.notifyStatEvent(requestStats.Stat.BACKCHANNEL_MISSING);
};
/**
* Determines whether we should start the process of retrying a possibly
* dead backchannel.
* @param {number} outstandingBytes The number of bytes for which the server has
* not yet received acknowledgement.
* @return {boolean} Whether to start the backchannel retry timer.
* @private
*/
WebChannelBase.prototype.shouldRetryBackChannel_ = function(outstandingBytes) {
'use strict';
// Not too many outstanding bytes, not buffered and not after a retry.
return outstandingBytes <
WebChannelBase.OUTSTANDING_DATA_BACKCHANNEL_RETRY_CUTOFF &&
!this.isBuffered() && this.backChannelRetryCount_ == 0;
};
/**
* Decides which host prefix should be used, if any. If there is a handler,
* allows the handler to validate a host prefix provided by the server, and
* optionally override it.
* @param {?string} serverHostPrefix The host prefix provided by the server.
* @return {?string} The host prefix to actually use, if any. Will return null
* if the use of host prefixes was disabled via setAllowHostPrefix().
* @override
*/
WebChannelBase.prototype.correctHostPrefix = function(serverHostPrefix) {
'use strict';
if (this.allowHostPrefix_) {
if (this.handler_) {
return this.handler_.correctHostPrefix(serverHostPrefix);
}
return serverHostPrefix;
}
return null;
};
/**
* Handles the timer that indicates that our backchannel is no longer able to
* successfully receive data from the server.
* @private
*/
WebChannelBase.prototype.onBackChannelDead_ = function() {
'use strict';
if (this.deadBackChannelTimerId_ != null) {
this.deadBackChannelTimerId_ = null;
this.cancelBackChannelRequest_();
this.maybeRetryBackChannel_();
requestStats.notifyStatEvent(requestStats.Stat.BACKCHANNEL_DEAD);
}
};
/**
* Clears the timer that indicates that our backchannel is no longer able to
* successfully receive data from the server.
* @private
*/
WebChannelBase.prototype.clearDeadBackchannelTimer_ = function() {
'use strict';
if (this.deadBackChannelTimerId_ != null) {
goog.global.clearTimeout(this.deadBackChannelTimerId_);
this.deadBackChannelTimerId_ = null;
}
};
/**
* Returns whether or not the given error/status combination is fatal or not.
* On fatal errors we immediately close the session rather than retrying the
* failed request.
* @param {?ChannelRequest.Error} error The error code for the
* failed request.
* @param {number} statusCode The last HTTP status code.
* @return {boolean} Whether or not the error is fatal.
* @private
*/
WebChannelBase.isFatalError_ = function(error, statusCode) {
'use strict';
return error == ChannelRequest.Error.UNKNOWN_SESSION_ID ||
(error == ChannelRequest.Error.STATUS && statusCode > 0);
};
/**
* @override
*/
WebChannelBase.prototype.onRequestComplete = function(request) {
'use strict';
this.channelDebug_.debug('Request complete');
let type;
let pendingMessages = null;
if (this.backChannelRequest_ == request) {
this.clearDeadBackchannelTimer_();
this.clearBpDetectionTimer_();
this.backChannelRequest_ = null;
type = WebChannelBase.ChannelType_.BACK_CHANNEL;
} else if (this.forwardChannelRequestPool_.hasRequest(request)) {
pendingMessages = request.getPendingMessages();
this.forwardChannelRequestPool_.removeRequest(request);
type = WebChannelBase.ChannelType_.FORWARD_CHANNEL;
} else {
// return if it was an old request from a previous session
return;
}
this.lastStatusCode_ = request.getLastStatusCode();
if (this.state_ == WebChannelBase.State.CLOSED) {
return;
}
if (request.getSuccess()) {
if (type == WebChannelBase.ChannelType_.FORWARD_CHANNEL) {
const size = request.getPostData() ? request.getPostData().length : 0;
requestStats.notifyTimingEvent(
size, Date.now() - request.getRequestStartTime(),
this.forwardChannelRetryCount_);
this.ensureForwardChannel_();
this.onSuccess_(request);
} else { // i.e., back-channel
this.ensureBackChannel_();
}
return;
}
// Else unsuccessful. Fall through.
const lastError = request.getLastError();
if (!WebChannelBase.isFatalError_(lastError, this.lastStatusCode_)) {
// Maybe retry.
const self = this;
this.channelDebug_.debug(function() {
'use strict';
return 'Maybe retrying, last error: ' +
ChannelRequest.errorStringFromCode(lastError, self.lastStatusCode_);
});
if (type == WebChannelBase.ChannelType_.FORWARD_CHANNEL) {
if (this.maybeRetryForwardChannel_(request)) {
return;
}
}
if (type == WebChannelBase.ChannelType_.BACK_CHANNEL) {
if (this.maybeRetryBackChannel_()) {
return;
}
}
// Else exceeded max retries. Fall through.
this.channelDebug_.debug('Exceeded max number of retries');
} else {
// Else fatal error. Fall through and mark the pending maps as failed.
this.channelDebug_.debug('Not retrying due to error type');
}
// Abort the channel now
// Record pending messages from the failed request
if (pendingMessages && pendingMessages.length > 0) {
this.forwardChannelRequestPool_.addPendingMessages(pendingMessages);
}
this.channelDebug_.debug('Error: HTTP request failed');
switch (lastError) {
case ChannelRequest.Error.NO_DATA:
this.signalError_(WebChannelBase.Error.NO_DATA);
break;
case ChannelRequest.Error.BAD_DATA:
this.signalError_(WebChannelBase.Error.BAD_DATA);
break;
case ChannelRequest.Error.UNKNOWN_SESSION_ID:
this.signalError_(WebChannelBase.Error.UNKNOWN_SESSION_ID);
break;
default:
this.signalError_(WebChannelBase.Error.REQUEST_FAILED);
break;
}
};
/**
* @param {number} retryCount Number of retries so far.
* @return {number} Time in ms before firing next retry request.
* @private
*/
WebChannelBase.prototype.getRetryTime_ = function(retryCount) {
'use strict';
let retryTime = this.baseRetryDelayMs_ +
Math.floor(Math.random() * this.retryDelaySeedMs_);
if (!this.isActive()) {
this.channelDebug_.debug('Inactive channel');
retryTime = retryTime * WebChannelBase.INACTIVE_CHANNEL_RETRY_FACTOR;
}
// Backoff for subsequent retries
retryTime *= retryCount;
return retryTime;
};
/**
* @param {number} baseDelayMs The base part of the retry delay, in ms.
* @param {number} delaySeedMs A random delay between 0 and this is added to
* the base part.
*/
WebChannelBase.prototype.setRetryDelay = function(baseDelayMs, delaySeedMs) {
'use strict';
this.baseRetryDelayMs_ = baseDelayMs;
this.retryDelaySeedMs_ = delaySeedMs;
};
/**
* Apply any handshake control headers.
* @param {!ChannelRequest} request The underlying request object
* @private
*/
WebChannelBase.prototype.applyControlHeaders_ = function(request) {
'use strict';
const xhr = request.getXhr();
if (xhr) {
const clientProtocol =
xhr.getStreamingResponseHeader(WebChannel.X_CLIENT_WIRE_PROTOCOL);
if (clientProtocol) {
this.forwardChannelRequestPool_.applyClientProtocol(clientProtocol);
}
if (this.getHttpSessionIdParam()) {
const httpSessionIdHeader =
xhr.getStreamingResponseHeader(WebChannel.X_HTTP_SESSION_ID);
if (httpSessionIdHeader) {
this.setHttpSessionId(httpSessionIdHeader);
// update the cached uri
const httpSessionIdParam = this.getHttpSessionIdParam();
this.forwardChannelUri_.setParameterValue(
/** @type {string} */ (httpSessionIdParam), // never null
httpSessionIdHeader);
} else {
this.channelDebug_.warning(
'Missing X_HTTP_SESSION_ID in the handshake response');
}
}
}
};
/**
* Processes the data returned by the server.
* @param {!Array<!Array<?>>} respArray The response array returned
* by the server.
* @param {!ChannelRequest} request The underlying request object
* @private
*/
WebChannelBase.prototype.onInput_ = function(respArray, request) {
'use strict';
const batch =
this.handler_ && this.handler_.channelHandleMultipleArrays ? [] : null;
for (let i = 0; i < respArray.length; i++) {
let nextArray = respArray[i];
this.lastArrayId_ = nextArray[0];
nextArray = nextArray[1];
if (this.state_ == WebChannelBase.State.OPENING) {
if (nextArray[0] == 'c') {
this.sid_ = nextArray[1];
this.hostPrefix_ = this.correctHostPrefix(nextArray[2]);
const negotiatedVersion = nextArray[3];
if (negotiatedVersion != null) {
this.channelVersion_ = negotiatedVersion;
this.channelDebug_.info('VER=' + this.channelVersion_);
}
const negotiatedServerVersion = nextArray[4];
if (negotiatedServerVersion != null) {
this.serverVersion_ = negotiatedServerVersion;
this.channelDebug_.info('SVER=' + this.serverVersion_);
}
// CVER=22
const serverKeepaliveMs = nextArray[5];
if (serverKeepaliveMs != null &&
typeof serverKeepaliveMs === 'number' && serverKeepaliveMs > 0) {
const timeout = 1.5 * serverKeepaliveMs;
this.backChannelRequestTimeoutMs_ = timeout;
this.channelDebug_.info('backChannelRequestTimeoutMs_=' + timeout);
}
this.applyControlHeaders_(request);
this.state_ = WebChannelBase.State.OPENED;
if (this.handler_) {
this.handler_.channelOpened(this);
}
if (this.detectBufferingProxy_) {
this.handshakeRttMs_ = Date.now() - request.getRequestStartTime();
this.channelDebug_.info(
'Handshake RTT: ' + this.handshakeRttMs_ + 'ms');
}
this.startBackchannelAfterHandshake_(request);
if (this.outgoingMaps_.length > 0) {
this.ensureForwardChannel_();
}
} else if (nextArray[0] == 'stop' || nextArray[0] == 'close') {
// treat close also as an abort
this.signalError_(WebChannelBase.Error.STOP);
}
} else if (this.state_ == WebChannelBase.State.OPENED) {
if (nextArray[0] == 'stop' || nextArray[0] == 'close') {
if (batch && !(batch.length === 0)) {
this.handler_.channelHandleMultipleArrays(this, batch);
batch.length = 0;
}
if (nextArray[0] == 'stop') {
this.signalError_(WebChannelBase.Error.STOP);
} else {
this.disconnect();
}
} else if (nextArray[0] == 'noop') {
// ignore - noop to keep connection happy
} else {
if (batch) {
batch.push(nextArray);
} else if (this.handler_) {
this.handler_.channelHandleArray(this, nextArray);
}
}
// We have received useful data on the back-channel, so clear its retry
// count. We do this because back-channels by design do not complete
// quickly, so on a flaky connection we could have many fail to complete
// fully but still deliver a lot of data before they fail. We don't want
// to count such failures towards the retry limit, because we don't want
// to give up on a session if we can still receive data.
this.backChannelRetryCount_ = 0;
}
}
if (batch && !(batch.length === 0)) {
this.handler_.channelHandleMultipleArrays(this, batch);
}
};
/**
* Starts the backchannel after the handshake.
*
* @param {!ChannelRequest} request The underlying request object
* @private
*/
WebChannelBase.prototype.startBackchannelAfterHandshake_ = function(request) {
'use strict';
this.backChannelUri_ = this.getBackChannelUri(
this.hostPrefix_, /** @type {string} */ (this.path_));
if (request.isInitialResponseDecoded()) {
this.channelDebug_.debug('Upgrade the handshake request to a backchannel.');
this.forwardChannelRequestPool_.removeRequest(request);
request.resetTimeout(this.backChannelRequestTimeoutMs_);
this.backChannelRequest_ = request;
} else {
this.ensureBackChannel_();
}
};
/**
* Helper to ensure the channel is in the expected state.
* @param {...number} var_args The channel must be in one of the indicated
* states.
* @private
*/
WebChannelBase.prototype.ensureInState_ = function(var_args) {
'use strict';
goog.asserts.assert(
goog.array.contains(arguments, this.state_),
'Unexpected channel state: %s', this.state_);
};
/**
* Signals an error has occurred.
* @param {WebChannelBase.Error} error The error code for the failure.
* @private
*/
WebChannelBase.prototype.signalError_ = function(error) {
'use strict';
this.channelDebug_.info('Error code ' + error);
if (error == WebChannelBase.Error.REQUEST_FAILED) {
// Create a separate Internet connection to check
// if it's a server error or user's network error.
let imageUri = null;
if (this.handler_) {
imageUri = this.handler_.getNetworkTestImageUri(this);
}
netUtils.testNetwork(goog.bind(this.testNetworkCallback_, this), imageUri);
} else {
requestStats.notifyStatEvent(requestStats.Stat.ERROR_OTHER);
}
this.onError_(error);
};
/**
* Callback for netUtils.testNetwork during error handling.
* @param {boolean} networkUp Whether the network is up.
* @private
*/
WebChannelBase.prototype.testNetworkCallback_ = function(networkUp) {
'use strict';
if (networkUp) {
this.channelDebug_.info('Successfully pinged google.com');
requestStats.notifyStatEvent(requestStats.Stat.ERROR_OTHER);
} else {
this.channelDebug_.info('Failed to ping google.com');
requestStats.notifyStatEvent(requestStats.Stat.ERROR_NETWORK);
// Do not call onError_ again to eliminate duplicated Error events.
}
};
/**
* Called when messages have been successfully sent from the queue.
* @param {!ChannelRequest} request The request object
* @private
*/
WebChannelBase.prototype.onSuccess_ = function(request) {
'use strict';
if (this.handler_) {
this.handler_.channelSuccess(this, request);
}
};
/**
* Called when we've determined the final error for a channel. It closes the
* notifiers the handler of the error and closes the channel.
* @param {WebChannelBase.Error} error The error code for the failure.
* @private
*/
WebChannelBase.prototype.onError_ = function(error) {
'use strict';
this.channelDebug_.debug('HttpChannel: error - ' + error);
this.state_ = WebChannelBase.State.CLOSED;
if (this.handler_) {
this.handler_.channelError(this, error);
}
this.onClose_();
this.cancelRequests_();
};
/**
* Called when the channel has been closed. It notifiers the handler of the
* event, and reports any pending or undelivered maps.
* @private
*/
WebChannelBase.prototype.onClose_ = function() {
'use strict';
this.state_ = WebChannelBase.State.CLOSED;
this.lastStatusCode_ = -1;
if (this.handler_) {
const pendingMessages =
this.forwardChannelRequestPool_.getPendingMessages();
if (pendingMessages.length == 0 && this.outgoingMaps_.length == 0) {
this.handler_.channelClosed(this);
} else {
const self = this;
this.channelDebug_.debug(function() {
'use strict';
return 'Number of undelivered maps' +
', pending: ' + pendingMessages.length +
', outgoing: ' + self.outgoingMaps_.length;
});
this.forwardChannelRequestPool_.clearPendingMessages();
const copyOfUndeliveredMaps = goog.array.clone(this.outgoingMaps_);
this.outgoingMaps_.length = 0;
this.handler_.channelClosed(this, pendingMessages, copyOfUndeliveredMaps);
}
}
};
/**
* @override
*/
WebChannelBase.prototype.getForwardChannelUri = function(path) {
'use strict';
const uri = this.createDataUri(null, path);
this.channelDebug_.debug('GetForwardChannelUri: ' + uri);
return uri;
};
/**
* @override
*/
WebChannelBase.prototype.getConnectionState = function() {
'use strict';
return this.connState_;
};
/**
* @override
*/
WebChannelBase.prototype.getBackChannelUri = function(hostPrefix, path) {
'use strict';
const uri = this.createDataUri(
this.shouldUseSecondaryDomains() ? hostPrefix : null, path);
this.channelDebug_.debug('GetBackChannelUri: ' + uri);
return uri;
};
/**
* @override
*/
WebChannelBase.prototype.createDataUri = function(
hostPrefix, path, opt_overridePort) {
'use strict';
let uri = goog.Uri.parse(path);
const uriAbsolute = (uri.getDomain() != '');
if (uriAbsolute) {
if (hostPrefix) {
uri.setDomain(hostPrefix + '.' + uri.getDomain());
}
uri.setPort(opt_overridePort || uri.getPort());
} else {
const locationPage = goog.global.location;
let hostName;
if (hostPrefix) {
hostName = hostPrefix + '.' + locationPage.hostname;
} else {
hostName = locationPage.hostname;
}
const port = opt_overridePort || +locationPage.port;
uri = goog.Uri.create(locationPage.protocol, null, hostName, port, path);
}
if (this.extraParams_) {
goog.object.forEach(this.extraParams_, function(value, key) {
'use strict';
uri.setParameterValue(key, value);
});
}
const param = this.getHttpSessionIdParam();
const value = this.getHttpSessionId();
if (param && value) {
uri.setParameterValue(param, value);
}
// Add the protocol version to the URI.
uri.setParameterValue('VER', this.channelVersion_);
// Add the reconnect parameters.
this.addAdditionalParams_(uri);
return uri;
};
/**
* @override
* @param {?string} hostPrefix The host prefix, if we need an XhrIo object
* capable of calling a secondary domain.
* @param {boolean=} isStreaming Whether or not fetch/streams are enabled for
* the underlying HTTP request.
* @return {!goog.net.XhrIo} A new XhrIo object.
*/
WebChannelBase.prototype.createXhrIo = function(hostPrefix, isStreaming) {
'use strict';
if (hostPrefix && !this.supportsCrossDomainXhrs_) {
throw new Error('Can\'t create secondary domain capable XhrIo object.');
}
let xhr;
if (isStreaming && this.usesFetchStreams_ && !this.xmlHttpFactory_) {
xhr = new goog.net.XhrIo(
new goog.net.FetchXmlHttpFactory({streamBinaryChunks: true}));
} else {
xhr = new goog.net.XhrIo(this.xmlHttpFactory_);
}
xhr.setWithCredentials(this.supportsCrossDomainXhrs_);
return xhr;
};
/**
* @override
*/
WebChannelBase.prototype.isActive = function() {
'use strict';
return !!this.handler_ && this.handler_.isActive(this);
};
/**
* @override
*/
WebChannelBase.prototype.shouldUseSecondaryDomains = function() {
'use strict';
return this.supportsCrossDomainXhrs_;
};
/**
* Sets (overwrites) the forward channel flush callback.
*
* @param {function()} callback The callback to be invoked.
*/
WebChannelBase.prototype.setForwardChannelFlushCallback = function(callback) {
'use strict';
this.forwardChannelFlushedCallback_ = callback;
};
/**
* Abstract base class for the channel handler
* @constructor
* @struct
*/
WebChannelBase.Handler = function() {};
/**
* Callback handler for when a batch of response arrays is received from the
* server. When null, batched dispatching is disabled.
* @type {?function(!WebChannelBase, !Array<!Array<?>>)}
*/
WebChannelBase.Handler.prototype.channelHandleMultipleArrays = null;
/**
* Whether it's okay to make a request to the server. A handler can return
* false if the channel should fail. For example, if the user has logged out,
* the handler may want all requests to fail immediately.
* @param {WebChannelBase} channel The channel.
* @return {WebChannelBase.Error} An error code. The code should
* return WebChannelBase.Error.OK to indicate it's okay. Any other
* error code will cause a failure.
*/
WebChannelBase.Handler.prototype.okToMakeRequest = function(channel) {
'use strict';
return WebChannelBase.Error.OK;
};
/**
* Indicates the WebChannel has successfully negotiated with the server
* and can now send and receive data.
* @param {WebChannelBase} channel The channel.
*/
WebChannelBase.Handler.prototype.channelOpened = function(channel) {};
/**
* New input is available for the application to process.
*
* @param {WebChannelBase} channel The channel.
* @param {Array<?>} array The data array.
*/
WebChannelBase.Handler.prototype.channelHandleArray = function(
channel, array) {};
/**
* Indicates messages that have been successfully sent on the channel.
*
* @param {WebChannelBase} channel The channel.
* @param {!ChannelRequest} request The request object that contains
* the pending messages that have been successfully delivered to the server.
*/
WebChannelBase.Handler.prototype.channelSuccess = function(channel, request) {};
/**
* Indicates an error occurred on the WebChannel.
*
* @param {WebChannelBase} channel The channel.
* @param {WebChannelBase.Error} error The error code.
*/
WebChannelBase.Handler.prototype.channelError = function(channel, error) {};
/**
* Indicates the WebChannel is closed. Also notifies about which maps,
* if any, that may not have been delivered to the server.
* @param {WebChannelBase} channel The channel.
* @param {Array<Wire.QueuedMap>=} opt_pendingMaps The
* array of pending maps, which may or may not have been delivered to the
* server.
* @param {Array<Wire.QueuedMap>=} opt_undeliveredMaps
* The array of undelivered maps, which have definitely not been delivered
* to the server.
*/
WebChannelBase.Handler.prototype.channelClosed = function(
channel, opt_pendingMaps, opt_undeliveredMaps) {};
/**
* Gets any parameters that should be added at the time another connection is
* made to the server.
* @param {WebChannelBase} channel The channel.
* @return {!Object} Extra parameter keys and values to add to the requests.
*/
WebChannelBase.Handler.prototype.getAdditionalParams = function(channel) {
'use strict';
return {};
};
/**
* Gets the URI of an image that can be used to test network connectivity.
* @param {WebChannelBase} channel The channel.
* @return {goog.Uri?} A custom URI to load for the network test.
*/
WebChannelBase.Handler.prototype.getNetworkTestImageUri = function(channel) {
'use strict';
return null;
};
/**
* Gets whether this channel is currently active. This is used to determine the
* length of time to wait before retrying.
* @param {WebChannelBase} channel The channel.
* @return {boolean} Whether the channel is currently active.
*/
WebChannelBase.Handler.prototype.isActive = function(channel) {
'use strict';
return true;
};
/**
* Whether or not this channel uses WHATWG Fetch/streams.
* @override
* @return {boolean}
*/
WebChannelBase.prototype.usesFetchStreams = function() {
'use strict';
return this.usesFetchStreams_;
};
/**
* Called by the channel if enumeration of the map throws an exception.
* @param {WebChannelBase} channel The channel.
* @param {Object} map The map that can't be enumerated.
*/
WebChannelBase.Handler.prototype.badMapError = function(channel, map) {};
/**
* Allows the handler to override a host prefix provided by the server. Will
* be called whenever the channel has received such a prefix and is considering
* its use.
* @param {?string} serverHostPrefix The host prefix provided by the server.
* @return {?string} The host prefix the client should use.
*/
WebChannelBase.Handler.prototype.correctHostPrefix = function(
serverHostPrefix) {
'use strict';
return serverHostPrefix;
};
}); // goog.scope
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