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import * as fs from 'fs';
import * as events from 'events';
import { APIError, Request, RequestPromise, Response } from '../model/api.ts';
import { getToken } from '../database/tokens.ts';
import { PriorityQueue } from './priority_queue.ts';
// queue processor module variables
const bus = new events.EventEmitter(); // a bus to notify the queue processor to start processing messages
let busy = false; // true if we are already sending api requests.
let backoffSeconds = 0;
let running = false;
// other module variables
let headers: {[key:string]:string}|null = null; // a file scoped variable so that we only evaluate these once.
let queue = new PriorityQueue(); // a priority queue to hold api calls we want to send, allows for throttling.
async function queue_processor() {
if (running) {
throw 'refusing to start a second queue processor';
}
running = true;
while(true) {
try {
if (backoffSeconds > 0) {
await sleep(backoffSeconds * 1000);
backoffSeconds = 0;
}
if (queue.isEmpty()) {
busy = false;
await new Promise(resolve => bus.once('send', resolve));
busy = true;
}
const before = new Date().getTime();
const data = queue.dequeue() as RequestPromise<unknown>;
await send_this(data);
const duration = new Date().getTime() - before;
if (duration < 400) { // 333 should work, but 400 should still allow some manual requests to go through during development
await sleep(400 - duration);
}
} catch (e) {
running = false;
throw e;
}
}
}
queue_processor();
export async function send<T>(request: Request): Promise<T|APIError> {
const response = await send_one<T>(request);
if (response.error) return response.error;
return response.data;
}
export async function sendPaginated<T>(request: Request): Promise<Array<T>|APIError> {
if (request.page === undefined) request.page = 1;
let ret: Array<T> = [];
while (true) {
const response = await send_one<T>(request);
if (response.meta === undefined) {
throw {"message": "paginated request did not return a meta block", "request": request, "response": response};
}
ret = ret.concat(response.data);
if (response.meta.limit * response.meta.page >= response.meta.total) {
return ret;
}
request.page++;
}
}
function send_one<T>(request: Request): Promise<Response<T>> {
return new Promise((resolve, reject) => {
const data: RequestPromise<T> = {
reject: reject,
request: request,
resolve: resolve,
};
queue.enqueue(data, request.priority ? request.priority : 10);
if (!busy) {
bus.emit('send'); // the queue was previously empty, let's wake up the queue_processor
}
});
}
// send_this take a data object as argument built in the send function above
async function send_this(data: RequestPromise<unknown>) {
if (headers === null) {
const token = getToken();
if (token === null) {
throw 'Could not get token from the database. Did you init or register yet?';
}
headers = {
'Content-Type': 'application/json',
'Authorization': `Bearer ${token}`
};
}
let options: {[key:string]:any} = {
headers: headers,
};
if (data.request.method !== undefined) {
options['method'] = data.request.method;
}
if (data.request.payload !== undefined) {
options['body'] = JSON.stringify(data.request.payload);
}
let pagination = "";
if (data.request.page !== undefined) {
pagination=`?limit=20&page=${data.request.page}`;
}
fs.writeFileSync('log', JSON.stringify({event: 'send', date: new Date(), data: data}) + '\n', {flag: 'a+'});
try {
const response = await fetch(`https://api.spacetraders.io/v2${data.request.endpoint}${pagination}`, options);
const json = await response.json() as Response<unknown>;
switch(json.error?.code) {
case 401: // TODO 401 means a server reset happened
throw json;
// TODO reject all promises in queue
// reset database
// logrotate
// spawnSync?
// break;
case 429: // 429 means rate limited, let's hold back as instructed
backoffSeconds = json.error.data.retryAfter;
queue.enqueue(data, 1);
break;
case 503: // 503 means maintenance mode, let's hold back for 1 minute
backoffSeconds = 60;
queue.enqueue(data, 1);
break;
default: // no error!
fs.writeFileSync('log', JSON.stringify({event: 'response', date: new Date(), data: json}) + '\n', {flag: 'a+'});
return data.resolve(json);
}
} catch (_err) {
const err = _err as {cause?: {code: string}};
fs.writeFileSync('log', JSON.stringify({event: 'error', date: new Date(), data: err}) + '\n', {flag: 'a+'});
switch(err.cause?.code) {
case 'EAI_AGAIN': // DNS lookup timed out error, let's hold back for 5 seconds
backoffSeconds = 5;
queue.enqueue(data, 1);
break;
case 'ECONNRESET':
queue.enqueue(data, 1);
break;
case 'UND_ERR_CONNECT_TIMEOUT':
queue.enqueue(data, 1);
break;
default:
data.reject(err);
}
}
}
export function debugLog(ctx: any) {
console.log(`--- ${Date()} -----------------------------------------------------------------------------`);
console.log(JSON.stringify(ctx, null, 2));
}
export function sleep(delay: number): Promise<unknown> {
return new Promise((resolve) => setTimeout(resolve, delay));
}
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