117 lines
3.9 KiB
JavaScript
117 lines
3.9 KiB
JavaScript
'use strict';
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let express = require('express');
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let app = express();
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let mcache = require('memory-cache');
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const request = require('superagent');
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const prom = require('prom-client');
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let cors = require('cors');
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app.use(cors());
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const register = new prom.Registry();
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prom.collectDefaultMetrics({register: register});
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const responses = new prom.Counter({
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name: 'cache_http_responses_total',
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help: 'A counter for cache response codes for every API request.',
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labelNames: ['scheme', 'target', 'code'],
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registers: [register]
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});
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const entries = new prom.Gauge({
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name: 'cache_used_entries',
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help: 'A counter to count cache entries',
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registers: [register]
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});
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const histogram = new prom.Histogram({
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name: 'cache_http_request_duration_seconds',
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help: 'A Histogram for cache. Providing information about a cache request and load latency in seconds.',
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labelNames: ['scheme', 'target', 'cache'],
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registers: [register],
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buckets: [0.1, 0.2, 0.5, 1, 2]
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});
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let cache = (duration) => {
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return (req, res, next) => {
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if(req.query.url) {
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let key = '__express__' + req.query.url;
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let cachedBody = mcache.get(key);
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const url = new URL(req.query.url);
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const target = url.host + '/' + url.pathname.split('/')[1];
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const scheme = url.protocol.replace(':', '');
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if (cachedBody) {
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const end = histogram.startTimer({scheme: scheme, target: target, cache: 'hit'});
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res.send(JSON.parse(cachedBody));
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responses.inc({scheme: scheme, target: target, code: res.statusCode});
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end();
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} else {
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const end = histogram.startTimer({scheme: scheme, target: target, cache: 'miss'});
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res.sendResponse = res.send;
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res.send = (body) => {
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let alreadyCached = !!mcache.get(key);
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entries.set(mcache.size());
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if(!alreadyCached) {
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responses.inc({scheme: scheme, target: target, code: res.statusCode});
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end();
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}
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if (res.statusCode === 200) {
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mcache.put(key, body, duration * 1000, () => {
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entries.set(mcache.size());
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});
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}
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res.sendResponse(body);
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};
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next();
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}
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} else {
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next();
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}
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};
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};
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app.get('/metrics', (req, res) => {
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res.set('Content-Type', register.contentType);
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res.end(register.metrics());
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});
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app.get('/get', cache(30), cors(), (req, res) => {
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setTimeout(() => {
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const url = (req.query) ? req.query.url : null;
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if (!url) {
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res.status(404).send(getResponse(404, "Not Found ")) //not found
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} else {
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request.get(url, function (err, response) {
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// res.header("Access-Control-Allow-Origin", "http://localhost:3000");
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res.header("Access-Control-Allow-Headers", "Origin, Content-Type, Content-Length");
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res.header("Access-Control-Allow-Methods", "GET, OPTIONS");
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res.header("Access-Control-Allow-Methods", "GET, OPTIONS");
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res.header("Content-Type", "application/json");
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if (!response && err) {
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res.status(500).send(getResponse(500, "An error occurred for " + url))
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} else {
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res.status(response.status).send(response.body);
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}
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})
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}
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})
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});
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app.use((req, res) => {
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res.status(404).send(getResponse(404, "Not Found")); //not found
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});
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app.listen((process.env.PORT) ? process.env.PORT : 3000, function () {
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console.log(`Example app listening on port ${process.env.PORT}!`)
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});
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function getResponse(code, message) {
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var response = {};
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response["code"] = code;
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response["message"] = message;
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return response;
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}
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