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Diffstat (limited to 'testing/xpcshell/node-http2/lib/protocol/flow.js')
| -rw-r--r-- | testing/xpcshell/node-http2/lib/protocol/flow.js | 353 |
1 files changed, 353 insertions, 0 deletions
diff --git a/testing/xpcshell/node-http2/lib/protocol/flow.js b/testing/xpcshell/node-http2/lib/protocol/flow.js new file mode 100644 index 000000000..4ec5649be --- /dev/null +++ b/testing/xpcshell/node-http2/lib/protocol/flow.js @@ -0,0 +1,353 @@ +var assert = require('assert'); + +// The Flow class +// ============== + +// Flow is a [Duplex stream][1] subclass which implements HTTP/2 flow control. It is designed to be +// subclassed by [Connection](connection.html) and the `upstream` component of [Stream](stream.html). +// [1]: https://nodejs.org/api/stream.html#stream_class_stream_duplex + +var Duplex = require('stream').Duplex; + +exports.Flow = Flow; + +// Public API +// ---------- + +// * **Event: 'error' (type)**: signals an error +// +// * **setInitialWindow(size)**: the initial flow control window size can be changed *any time* +// ([as described in the standard][1]) using this method +// +// [1]: https://tools.ietf.org/html/rfc7540#section-6.9.2 + +// API for child classes +// --------------------- + +// * **new Flow([flowControlId])**: creating a new flow that will listen for WINDOW_UPDATES frames +// with the given `flowControlId` (or every update frame if not given) +// +// * **_send()**: called when more frames should be pushed. The child class is expected to override +// this (instead of the `_read` method of the Duplex class). +// +// * **_receive(frame, readyCallback)**: called when there's an incoming frame. The child class is +// expected to override this (instead of the `_write` method of the Duplex class). +// +// * **push(frame): bool**: schedules `frame` for sending. +// +// Returns `true` if it needs more frames in the output queue, `false` if the output queue is +// full, and `null` if did not push the frame into the output queue (instead, it pushed it into +// the flow control queue). +// +// * **read(limit): frame**: like the regular `read`, but the 'flow control size' (0 for non-DATA +// frames, length of the payload for DATA frames) of the returned frame will be under `limit`. +// Small exception: pass -1 as `limit` if the max. flow control size is 0. `read(0)` means the +// same thing as [in the original API](https://nodejs.org/api/stream.html#stream_stream_read_0). +// +// * **getLastQueuedFrame(): frame**: returns the last frame in output buffers +// +// * **_log**: the Flow class uses the `_log` object of the parent + +// Constructor +// ----------- + +// When a HTTP/2.0 connection is first established, new streams are created with an initial flow +// control window size of 65535 bytes. +var INITIAL_WINDOW_SIZE = 65535; + +// `flowControlId` is needed if only specific WINDOW_UPDATEs should be watched. +function Flow(flowControlId) { + Duplex.call(this, { objectMode: true }); + + this._window = this._initialWindow = INITIAL_WINDOW_SIZE; + this._flowControlId = flowControlId; + this._queue = []; + this._ended = false; + this._received = 0; + this._blocked = false; +} +Flow.prototype = Object.create(Duplex.prototype, { constructor: { value: Flow } }); + +// Incoming frames +// --------------- + +// `_receive` is called when there's an incoming frame. +Flow.prototype._receive = function _receive(frame, callback) { + throw new Error('The _receive(frame, callback) method has to be overridden by the child class!'); +}; + +// `_receive` is called by `_write` which in turn is [called by Duplex][1] when someone `write()`s +// to the flow. It emits the 'receiving' event and notifies the window size tracking code if the +// incoming frame is a WINDOW_UPDATE. +// [1]: https://nodejs.org/api/stream.html#stream_writable_write_chunk_encoding_callback_1 +Flow.prototype._write = function _write(frame, encoding, callback) { + var sentToUs = (this._flowControlId === undefined) || (frame.stream === this._flowControlId); + + if (sentToUs && (frame.flags.END_STREAM || (frame.type === 'RST_STREAM'))) { + this._ended = true; + } + + if ((frame.type === 'DATA') && (frame.data.length > 0)) { + this._receive(frame, function() { + this._received += frame.data.length; + if (!this._restoreWindowTimer) { + this._restoreWindowTimer = setImmediate(this._restoreWindow.bind(this)); + } + callback(); + }.bind(this)); + } + + else { + this._receive(frame, callback); + } + + if (sentToUs && (frame.type === 'WINDOW_UPDATE')) { + this._updateWindow(frame); + } +}; + +// `_restoreWindow` basically acknowledges the DATA frames received since it's last call. It sends +// a WINDOW_UPDATE that restores the flow control window of the remote end. +// TODO: push this directly into the output queue. No need to wait for DATA frames in the queue. +Flow.prototype._restoreWindow = function _restoreWindow() { + delete this._restoreWindowTimer; + if (!this._ended && (this._received > 0)) { + this.push({ + type: 'WINDOW_UPDATE', + flags: {}, + stream: this._flowControlId, + window_size: this._received + }); + this._received = 0; + } +}; + +// Outgoing frames - sending procedure +// ----------------------------------- + +// flow +// +-------------------------------------------------+ +// | | +// +--------+ +---------+ | +// read() | output | _read() | flow | _send() | +// <----------| |<----------| control |<------------- | +// | buffer | | buffer | | +// +--------+ +---------+ | +// | input | | +// ---------->| |-----------------------------------> | +// write() | buffer | _write() _receive() | +// +--------+ | +// | | +// +-------------------------------------------------+ + +// `_send` is called when more frames should be pushed to the output buffer. +Flow.prototype._send = function _send() { + throw new Error('The _send() method has to be overridden by the child class!'); +}; + +// `_send` is called by `_read` which is in turn [called by Duplex][1] when it wants to have more +// items in the output queue. +// [1]: https://nodejs.org/api/stream.html#stream_writable_write_chunk_encoding_callback_1 +Flow.prototype._read = function _read() { + // * if the flow control queue is empty, then let the user push more frames + if (this._queue.length === 0) { + this._send(); + } + + // * if there are items in the flow control queue, then let's put them into the output queue (to + // the extent it is possible with respect to the window size and output queue feedback) + else if (this._window > 0) { + this._blocked = false; + this._readableState.sync = true; // to avoid reentrant calls + do { + var moreNeeded = this._push(this._queue[0]); + if (moreNeeded !== null) { + this._queue.shift(); + } + } while (moreNeeded && (this._queue.length > 0)); + this._readableState.sync = false; + + assert((!moreNeeded) || // * output queue is full + (this._queue.length === 0) || // * flow control queue is empty + (!this._window && (this._queue[0].type === 'DATA'))); // * waiting for window update + } + + // * otherwise, come back when the flow control window is positive + else if (!this._blocked) { + this._parentPush({ + type: 'BLOCKED', + flags: {}, + stream: this._flowControlId + }); + this.once('window_update', this._read); + this._blocked = true; + } +}; + +var MAX_PAYLOAD_SIZE = 4096; // Must not be greater than MAX_HTTP_PAYLOAD_SIZE which is 16383 + +// `read(limit)` is like the `read` of the Readable class, but it guarantess that the 'flow control +// size' (0 for non-DATA frames, length of the payload for DATA frames) of the returned frame will +// be under `limit`. +Flow.prototype.read = function read(limit) { + if (limit === 0) { + return Duplex.prototype.read.call(this, 0); + } else if (limit === -1) { + limit = 0; + } else if ((limit === undefined) || (limit > MAX_PAYLOAD_SIZE)) { + limit = MAX_PAYLOAD_SIZE; + } + + // * Looking at the first frame in the queue without pulling it out if possible. + var frame = this._readableState.buffer[0]; + if (!frame && !this._readableState.ended) { + this._read(); + frame = this._readableState.buffer[0]; + } + + if (frame && (frame.type === 'DATA')) { + // * If the frame is DATA, then there's two special cases: + // * if the limit is 0, we shouldn't return anything + // * if the size of the frame is larger than limit, then the frame should be split + if (limit === 0) { + return Duplex.prototype.read.call(this, 0); + } + + else if (frame.data.length > limit) { + this._log.trace({ frame: frame, size: frame.data.length, forwardable: limit }, + 'Splitting out forwardable part of a DATA frame.'); + this.unshift({ + type: 'DATA', + flags: {}, + stream: frame.stream, + data: frame.data.slice(0, limit) + }); + frame.data = frame.data.slice(limit); + } + } + + return Duplex.prototype.read.call(this); +}; + +// `_parentPush` pushes the given `frame` into the output queue +Flow.prototype._parentPush = function _parentPush(frame) { + this._log.trace({ frame: frame }, 'Pushing frame into the output queue'); + + if (frame && (frame.type === 'DATA') && (this._window !== Infinity)) { + this._log.trace({ window: this._window, by: frame.data.length }, + 'Decreasing flow control window size.'); + this._window -= frame.data.length; + assert(this._window >= 0); + } + + return Duplex.prototype.push.call(this, frame); +}; + +// `_push(frame)` pushes `frame` into the output queue and decreases the flow control window size. +// It is capable of splitting DATA frames into smaller parts, if the window size is not enough to +// push the whole frame. The return value is similar to `push` except that it returns `null` if it +// did not push the whole frame to the output queue (but maybe it did push part of the frame). +Flow.prototype._push = function _push(frame) { + var data = frame && (frame.type === 'DATA') && frame.data; + var maxFrameLength = (this._window < 16384) ? this._window : 16384; + + if (!data || (data.length <= maxFrameLength)) { + return this._parentPush(frame); + } + + else if (this._window <= 0) { + return null; + } + + else { + this._log.trace({ frame: frame, size: frame.data.length, forwardable: this._window }, + 'Splitting out forwardable part of a DATA frame.'); + frame.data = data.slice(maxFrameLength); + this._parentPush({ + type: 'DATA', + flags: {}, + stream: frame.stream, + data: data.slice(0, maxFrameLength) + }); + return null; + } +}; + +// Push `frame` into the flow control queue, or if it's empty, then directly into the output queue +Flow.prototype.push = function push(frame) { + if (frame === null) { + this._log.debug('Enqueueing outgoing End Of Stream'); + } else { + this._log.debug({ frame: frame }, 'Enqueueing outgoing frame'); + } + + var moreNeeded = null; + if (this._queue.length === 0) { + moreNeeded = this._push(frame); + } + + if (moreNeeded === null) { + this._queue.push(frame); + } + + return moreNeeded; +}; + +// `getLastQueuedFrame` returns the last frame in output buffers. This is primarily used by the +// [Stream](stream.html) class to mark the last frame with END_STREAM flag. +Flow.prototype.getLastQueuedFrame = function getLastQueuedFrame() { + var readableQueue = this._readableState.buffer; + return this._queue[this._queue.length - 1] || readableQueue[readableQueue.length - 1]; +}; + +// Outgoing frames - managing the window size +// ------------------------------------------ + +// Flow control window size is manipulated using the `_increaseWindow` method. +// +// * Invoking it with `Infinite` means turning off flow control. Flow control cannot be enabled +// again once disabled. Any attempt to re-enable flow control MUST be rejected with a +// FLOW_CONTROL_ERROR error code. +// * A sender MUST NOT allow a flow control window to exceed 2^31 - 1 bytes. The action taken +// depends on it being a stream or the connection itself. + +var WINDOW_SIZE_LIMIT = Math.pow(2, 31) - 1; + +Flow.prototype._increaseWindow = function _increaseWindow(size) { + if ((this._window === Infinity) && (size !== Infinity)) { + this._log.error('Trying to increase flow control window after flow control was turned off.'); + this.emit('error', 'FLOW_CONTROL_ERROR'); + } else { + this._log.trace({ window: this._window, by: size }, 'Increasing flow control window size.'); + this._window += size; + if ((this._window !== Infinity) && (this._window > WINDOW_SIZE_LIMIT)) { + this._log.error('Flow control window grew too large.'); + this.emit('error', 'FLOW_CONTROL_ERROR'); + } else { + if (size != 0) { + this.emit('window_update'); + } + } + } +}; + +// The `_updateWindow` method gets called every time there's an incoming WINDOW_UPDATE frame. It +// modifies the flow control window: +// +// * Flow control can be disabled for an individual stream by sending a WINDOW_UPDATE with the +// END_FLOW_CONTROL flag set. The payload of a WINDOW_UPDATE frame that has the END_FLOW_CONTROL +// flag set is ignored. +// * A sender that receives a WINDOW_UPDATE frame updates the corresponding window by the amount +// specified in the frame. +Flow.prototype._updateWindow = function _updateWindow(frame) { + this._increaseWindow(frame.flags.END_FLOW_CONTROL ? Infinity : frame.window_size); +}; + +// A SETTINGS frame can alter the initial flow control window size for all current streams. When the +// value of SETTINGS_INITIAL_WINDOW_SIZE changes, a receiver MUST adjust the size of all stream by +// calling the `setInitialWindow` method. The window size has to be modified by the difference +// between the new value and the old value. +Flow.prototype.setInitialWindow = function setInitialWindow(initialWindow) { + this._increaseWindow(initialWindow - this._initialWindow); + this._initialWindow = initialWindow; +}; |