async-await-queue
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async/await simple priority queues
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<h1 class="page-title">Source: index.mjs</h1>
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<pre class="prettyprint source linenums"><code>var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
return new (P || (P = Promise))(function (resolve, reject) {
function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
step((generator = generator.apply(thisArg, _arguments || [])).next());
});
};
var __generator = (this && this.__generator) || function (thisArg, body) {
var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g;
return g = { next: verb(0), "throw": verb(1), "return": verb(2) }, typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
function verb(n) { return function (v) { return step([n, v]); }; }
function step(op) {
if (f) throw new TypeError("Generator is already executing.");
while (g && (g = 0, op[0] && (_ = 0)), _) try {
if (f = 1, y && (t = op[0] & 2 ? y["return"] : op[0] ? y["throw"] || ((t = y["return"]) && t.call(y), 0) : y.next) && !(t = t.call(y, op[1])).done) return t;
if (y = 0, t) op = [op[0] & 2, t.value];
switch (op[0]) {
case 0: case 1: t = op; break;
case 4: _.label++; return { value: op[1], done: false };
case 5: _.label++; y = op[1]; op = [0]; continue;
case 7: op = _.ops.pop(); _.trys.pop(); continue;
default:
if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
if (t[2]) _.ops.pop();
_.trys.pop(); continue;
}
op = body.call(thisArg, _);
} catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
}
};
var _a;
import { PriorityQueue } from 'typescript-collections';
// This will be optimized away by V8 as I have proven in
// https://bugs.chromium.org/p/v8/issues/detail?id=12756
var debug = ((_a = process === null || process === void 0 ? void 0 : process.env) === null || _a === void 0 ? void 0 : _a.QUEUE_DEBUG) ? console.debug.bind(console) : function () { return undefined; };
function prioCompare(a, b) {
return b.prio - a.prio || b.counter - a.counter;
}
var Queue = /** @class */ (function () {
/**
* @class Queue
*
* Priority queue with rate limiting<br>
* See the medium article:<br>
* https://mmomtchev.medium.com/parallelizing-download-loops-in-js-with-async-await-queue-670420880cd6
* (the code has changed a lot since that article but the basic idea of using Promises as locks remains the same)
*
* @param {number} [maxConcurrent=1] Number of tasks allowed to run simultaneously
* @param {number} [minCycle=0] Minimum number of milliseconds between two consecutive tasks
*/
function Queue(maxConcurrent, minCycle) {
this.maxConcurrent = maxConcurrent || 1;
this.minCycle = minCycle || 0;
this.queueRunning = new Map;
this.queueWaiting = new PriorityQueue(prioCompare);
this.lastRun = 0;
this.nextTimer = null;
this.counter = 0;
}
/**
* @private
*/
Queue.prototype.tryRun = function () {
var _this = this;
debug('tryRun');
this.nextTimer = null;
if (!this.queueWaiting.peek() || this.queueRunning.size >= this.maxConcurrent)
return;
/* Wait if it is too soon */
if (Date.now() - this.lastRun < this.minCycle) {
debug('will throttle', Date.now() % 1000, (this.minCycle + this.lastRun) % 1000, Date.now() - this.lastRun);
if (this.nextTimer === null) {
this.nextTimer = new Promise(function (resolve) { return setTimeout(function () {
_this.tryRun();
resolve();
}, _this.minCycle - Date.now() + _this.lastRun); });
}
}
else {
/* Choose the next task to run and unblock its promise */
var next = this.queueWaiting.dequeue();
debug('wont throttle', this.lastRun % 1000, Date.now() % 1000, 'next is ', next === null || next === void 0 ? void 0 : next.hash);
if (next !== undefined) {
var finishSignal_1;
var finishWait = new Promise(function (resolve) {
finishSignal_1 = resolve;
});
var finish = { wait: finishWait, signal: finishSignal_1 };
var nextRunning = { hash: next.hash, prio: next.prio, finish: finish };
this.queueRunning.set(next.hash, nextRunning);
this.lastRun = Date.now();
next.start.signal();
}
}
};
/**
* Signal that the task `hash` has finished.<br>
* Frees its slot in the queue
*
* @method end
* @param {any} hash Unique hash identifying the task, Symbol() works very well
*/
Queue.prototype.end = function (hash) {
debug(hash, 'end');
var me = this.queueRunning.get(hash);
if (me === undefined)
throw new Error('queue desync');
this.queueRunning["delete"](hash);
me.finish.signal();
this.tryRun();
};
/**
* Wait for a slot in the queue
*
* @method wait
* @param {any} hash Unique hash identifying the task
* @param {number} [priority=0] Optional priority, -1 is higher priority than 1
* @return {Promise<void>} Resolved when the task is ready to run
*/
Queue.prototype.wait = function (hash, priority) {
return __awaiter(this, void 0, void 0, function () {
var prio, signal, wait, meWaiting;
return __generator(this, function (_a) {
switch (_a.label) {
case 0:
prio = priority !== null && priority !== void 0 ? priority : 0;
debug(hash, 'waiting');
wait = new Promise(function (resolve) {
signal = resolve;
});
meWaiting = { hash: hash, prio: prio, start: { signal: signal, wait: wait }, counter: this.counter++ };
/* Get in the line */
this.queueWaiting.enqueue(meWaiting);
this.tryRun();
return [4 /*yield*/, wait];
case 1:
_a.sent();
this.lastRun = Date.now();
debug(hash, 'will run', this.lastRun % 1000, Date.now() % 1000);
return [2 /*return*/];
}
});
});
};
/**
* Run a job (equivalent to calling Queue.wait(), fn() and then Queue.end())<br>
* fn can be both synchronous or asynchronous function
*
* @method run
* @param {Function} job The job
* @param {number} [priority=0] Optional priority, -1 is higher priority than 1
* @return {Promise<any>} Resolved when the task has finished with the return value of fn
*/
Queue.prototype.run = function (job, priority) {
var _this = this;
var prio = priority !== null && priority !== void 0 ? priority : 0;
var id = Symbol();
return this.wait(id, prio)
.then(job)["finally"](function () {
_this.end(id);
});
};
/**
* Return the number of running and waiting jobs
*
* @method stat
* @return {QueueStats} running, waiting, last
*/
Queue.prototype.stat = function () {
return {
running: this.queueRunning.size,
waiting: this.queueWaiting.size(),
last: this.lastRun
};
};
/**
* Returns a promise that resolves when the queue is empty
*
* @method flush
* @return {Promise<void>}
*/
Queue.prototype.flush = function () {
return __awaiter(this, void 0, void 0, function () {
var waiting, running;
return __generator(this, function (_a) {
switch (_a.label) {
case 0:
debug('flush', this.stat());
_a.label = 1;
case 1:
if (!(this.queueRunning.size > 0 || this.queueWaiting.size() > 0)) return [3 /*break*/, 6];
waiting = this.queueWaiting.peek();
if (!waiting) return [3 /*break*/, 3];
return [4 /*yield*/, waiting.start.wait];
case 2:
_a.sent();
_a.label = 3;
case 3:
if (!(this.queueRunning.size > 0)) return [3 /*break*/, 5];
running = this.queueRunning.values().next().value;
return [4 /*yield*/, running.finish.wait];
case 4:
_a.sent();
_a.label = 5;
case 5:
debug('retry flush', this.stat());
return [3 /*break*/, 1];
case 6: return [2 /*return*/];
}
});
});
};
return Queue;
}());
export { Queue };
export default Queue;
//# sourceMappingURL=index.js.map</code></pre>
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<h2><a href="index.html">Home</a></h2><h3>Global</h3><ul><li><a href="global.html#end">end</a></li><li><a href="global.html#flush">flush</a></li><li><a href="global.html#run">run</a></li><li><a href="global.html#stat">stat</a></li><li><a href="global.html#wait">wait</a></li></ul>
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