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subscriber.ts
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subscriber.ts
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/*!
* Copyright 2018 Google Inc. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import {replaceProjectIdToken} from '@google-cloud/projectify';
import {promisify} from '@google-cloud/promisify';
import {EventEmitter} from 'events';
import {ClientStub} from 'google-gax';
import {common as protobuf} from 'protobufjs';
import {Histogram} from './histogram';
import {FlowControlOptions, LeaseManager} from './lease-manager';
import {AckQueue, BatchOptions, ModAckQueue} from './message-queues';
import {MessageStream, MessageStreamOptions} from './message-stream';
import {Subscription} from './subscription';
/**
* @see https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.subscriptions/pull#ReceivedMessage
*/
interface ReceivedMessage {
ackId: string;
message: {
attributes: {},
data: Buffer,
messageId: string,
publishTime: protobuf.ITimestamp
};
}
/**
* @see https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.subscriptions/pull#body.PullResponse
*/
export interface PullResponse {
receivedMessages: ReceivedMessage[];
}
/**
* Message objects provide a simple interface for users to get message data and
* acknowledge the message.
*
* @private
* @class
*
* @param {Subscriber} sub The parent subscriber.
* @param {object} message The raw message response.
*/
export class Message {
ackId: string;
attributes: {};
data: Buffer;
id: string;
publishTime: Date;
received: number;
private _handled: boolean;
private _length: number;
private _subscriber: Subscriber;
constructor(sub: Subscriber, {ackId, message}: ReceivedMessage) {
this.ackId = ackId;
this.attributes = message.attributes || {};
this.data = message.data;
this.id = message.messageId;
this.publishTime = Message.formatTimestamp(message.publishTime);
this.received = Date.now();
this._handled = false;
this._length = this.data.length;
this._subscriber = sub;
}
/**
* The length of the message data.
*
* @type {number}
* @private
*/
get length() {
return this._length;
}
/**
* Acknowledges the message.
* @private
*/
ack(): void {
if (!this._handled) {
this._handled = true;
this._subscriber.ack(this);
}
}
/**
* Modifies the ack deadline.
*
* @param {number} deadline The number of seconds to extend the deadline.
* @private
*/
modAck(deadline: number): void {
if (!this._handled) {
this._subscriber.modAck(this, deadline);
}
}
/**
* Removes the message from our inventory and schedules it to be redelivered.
* If the delay parameter is unset, it will be redelivered immediately.
*
* @param {number} [delay=0] The desired time to wait before the
* redelivery occurs.
* @private
*/
nack(delay?: number): void {
if (!this._handled) {
this._handled = true;
this._subscriber.nack(this, delay);
}
}
/**
* Formats the protobuf timestamp into a JavaScript date.
*
* @private
*
* @param {object} timestamp The protobuf timestamp.
* @return {date}
*/
static formatTimestamp({nanos = 0, seconds = 0}: protobuf.ITimestamp): Date {
const ms: number = Number(nanos) / 1e6;
const s: number = Number(seconds) * 1000;
return new Date(ms + s);
}
}
/**
* @typedef {object} SubscriberOptions
* @property {number} [ackDeadline=10] Acknowledge deadline in seconds. If left
* unset the initial value will be 10 seconds, but it will evolve into the
* 99th percentile time it takes to acknowledge a message.
* @property {BatchingOptions} [batching] Request batching options.
* @property {FlowControlOptions} [flowControl] Flow control options.
* @property {MessageStreamOptions} [streamingOptions] Streaming options.
*/
export interface SubscriberOptions {
ackDeadline?: number;
batching?: BatchOptions;
flowControl?: FlowControlOptions;
streamingOptions?: MessageStreamOptions;
}
/**
* Subscriber class is used to manage all message related functionality.
*
* @private
* @class
*
* @param {Subscription} subscription The corresponding subscription.
* @param {SubscriberOptions} options The subscriber options.
*/
export class Subscriber extends EventEmitter {
ackDeadline: number;
isOpen: boolean;
private _acks!: AckQueue;
private _histogram: Histogram;
private _inventory!: LeaseManager;
private _isUserSetDeadline: boolean;
private _latencies: Histogram;
private _modAcks!: ModAckQueue;
private _name!: string;
private _options!: SubscriberOptions;
private _stream!: MessageStream;
private _subscription: Subscription;
constructor(subscription: Subscription, options = {}) {
super();
this.ackDeadline = 10;
this.isOpen = false;
this._isUserSetDeadline = false;
this._histogram = new Histogram({min: 10, max: 600});
this._latencies = new Histogram();
this._subscription = subscription;
this.setOptions(options);
}
/**
* The 99th percentile of request latencies.
*
* @type {number}
* @private
*/
get modAckLatency() {
const latency = this._latencies.percentile(99);
let bufferTime = 0;
if (this._modAcks) {
bufferTime = this._modAcks.maxMilliseconds;
}
return latency * 1000 + bufferTime;
}
/**
* The full name of the Subscription.
*
* @type {string}
* @private
*/
get name(): string {
if (!this._name) {
const {name, projectId} = this._subscription;
this._name = replaceProjectIdToken(name, projectId);
}
return this._name;
}
/**
* Acknowledges the supplied message.
*
* @param {Message} message The message to acknowledge.
* @returns {Promise}
* @private
*/
async ack(message: Message): Promise<void> {
if (!this._isUserSetDeadline) {
const ackTimeSeconds = (Date.now() - message.received) / 1000;
this._histogram.add(ackTimeSeconds);
this.ackDeadline = this._histogram.percentile(99);
}
this._acks.add(message);
await this._acks.onFlush();
this._inventory.remove(message);
}
/**
* Closes the subscriber. The returned promise will resolve once any pending
* acks/modAcks are finished.
*
* @returns {Promise}
* @private
*/
async close(): Promise<void> {
if (!this.isOpen) {
return;
}
this.isOpen = false;
this._stream.destroy();
this._inventory.clear();
await this._waitForFlush();
}
/**
* Gets the subscriber client instance.
*
* @returns {Promise<object>}
* @private
*/
async getClient(): Promise<ClientStub> {
const pubsub = this._subscription.pubsub;
const [client] = await promisify(pubsub.getClient_).call(pubsub, {
client: 'SubscriberClient'
});
return client;
}
/**
* Modifies the acknowledge deadline for the provided message.
*
* @param {Message} message The message to modify.
* @param {number} deadline The deadline.
* @returns {Promise}
* @private
*/
async modAck(message: Message, deadline: number): Promise<void> {
const startTime = Date.now();
this._modAcks.add(message, deadline);
await this._modAcks.onFlush();
const latency = (Date.now() - startTime) / 1000;
this._latencies.add(latency);
}
/**
* Modfies the acknowledge deadline for the provided message and then removes
* it from our inventory.
*
* @param {Message} message The message.
* @param {number} [delay=0] Delay to wait before redelivery.
* @return {Promise}
* @private
*/
async nack(message: Message, delay = 0): Promise<void> {
await this.modAck(message, delay);
this._inventory.remove(message);
}
/**
* Starts pulling messages.
* @private
*/
open(): void {
const {batching, flowControl, streamingOptions} = this._options;
this._acks = new AckQueue(this, batching);
this._modAcks = new ModAckQueue(this, batching);
this._inventory = new LeaseManager(this, flowControl);
this._stream = new MessageStream(this, streamingOptions);
this._stream.on('error', err => this.emit('error', err))
.on('data', (data: PullResponse) => this._onData(data));
this._inventory.on('full', () => this._stream.pause())
.on('free', () => this._stream.resume());
this.isOpen = true;
}
/**
* Sets subscriber options.
*
* @param {SubscriberOptions} options The options.
* @private
*/
setOptions(options: SubscriberOptions): void {
this._options = options;
if (options.ackDeadline) {
this.ackDeadline = options.ackDeadline;
this._isUserSetDeadline = true;
}
// in the event that the user has specified the maxMessages option, we want
// to make sure that the maxStreams option isn't higher
// it doesn't really make sense to open 5 streams if the user only wants
// 1 message at a time.
if (options.flowControl) {
const {maxMessages = 100} = options.flowControl;
if (!options.streamingOptions) {
options.streamingOptions = {} as MessageStreamOptions;
}
const {maxStreams = 5} = options.streamingOptions;
options.streamingOptions.maxStreams = Math.min(maxStreams, maxMessages);
}
}
/**
* Callback to be invoked when a new message is available.
*
* New messages will be added to the subscribers inventory, which in turn will
* automatically extend the messages ack deadline until either:
* a. the user acks/nacks it
* b. the maxExtension option is hit
*
* If the message puts us at/over capacity, then we'll pause our message
* stream until we've freed up some inventory space.
*
* New messages must immediately issue a ModifyAckDeadline request
* (aka receipt) to confirm with the backend that we did infact receive the
* message and its ok to start ticking down on the deadline.
*
* @private
*/
private _onData(response: PullResponse): void {
response.receivedMessages.forEach((data: ReceivedMessage) => {
const message = new Message(this, data);
message.modAck(this.ackDeadline);
this._inventory.add(message);
});
}
/**
* Returns a promise that will resolve once all pending requests have settled.
*
* @private
*
* @returns {Promise}
*/
private async _waitForFlush(): Promise<void> {
const promises: Array<Promise<void>> = [];
if (this._acks.numPendingRequests) {
promises.push(this._acks.onFlush());
this._acks.flush();
}
if (this._modAcks.numPendingRequests) {
promises.push(this._modAcks.onFlush());
this._modAcks.flush();
}
await Promise.all(promises);
}
}