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http: added scheduling option to http agent · nodejs/node@cce4645 · GitHub

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http: added scheduling option to http agent
In some cases, it is preferable to use a lifo scheduling strategy for the free sockets instead of default one, which is fifo. This commit introduces a scheduling option to add the ability to choose which strategy best fits your needs. Backport-PR-URL: #35649 PR-URL: #33278 Reviewed-By: Robert Nagy <ronagy@icloud.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
1 parent d477e2e commit cce4645

3 files changed

Lines changed: 174 additions & 1 deletion

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‎doc/api/http.md‎

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@@ -116,6 +116,10 @@ changes:
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- version: v12.19.0
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pr-url: https://github.com/nodejs/node/pull/33617
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description: Add `maxTotalSockets` option to agent constructor.
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- version: REPLACEME
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pr-url: https://github.com/nodejs/node/pull/33278
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description: Add `scheduling` option to specify the free socket
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scheduling strategy.
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-->
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* `options` {Object} Set of configurable options to set on the agent.
@@ -142,6 +146,18 @@ changes:
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* `maxFreeSockets` {number} Maximum number of sockets to leave open
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in a free state. Only relevant if `keepAlive` is set to `true`.
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**Default:** `256`.
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* `scheduling` {string} Scheduling strategy to apply when picking
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the next free socket to use. It can be `'fifo'` or `'lifo'`.
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The main difference between the two scheduling strategies is that `'lifo'`
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selects the most recently used socket, while `'fifo'` selects
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the least recently used socket.
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In case of a low rate of request per second, the `'lifo'` scheduling
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will lower the risk of picking a socket that might have been closed
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by the server due to inactivity.
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In case of a high rate of request per second,
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the `'fifo'` scheduling will maximize the number of open sockets,
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while the `'lifo'` scheduling will keep it as low as possible.
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**Default:** `'fifo'`.
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* `timeout` {number} Socket timeout in milliseconds.
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This will set the timeout when the socket is created.
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‎lib/_http_agent.js‎

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@@ -38,6 +38,7 @@ const { async_id_symbol } = require('internal/async_hooks').symbols;
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const {
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codes: {
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ERR_OUT_OF_RANGE,
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ERR_INVALID_OPT_VALUE,
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},
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} = require('internal/errors');
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const { validateNumber } = require('internal/validators');
@@ -102,6 +103,12 @@ function Agent(options) {
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this.maxTotalSockets = Infinity;
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}
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this.scheduling = this.options.scheduling || 'fifo';
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if (this.scheduling !== 'fifo' && this.scheduling !== 'lifo') {
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throw new ERR_INVALID_OPT_VALUE('scheduling', this.scheduling);
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}
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this.on('free', (socket, options) => {
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const name = this.getName(options);
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debug('agent.on(free)', name);
@@ -238,7 +245,9 @@ Agent.prototype.addRequest = function addRequest(req, options, port/* legacy */,
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while (freeSockets.length && freeSockets[0].destroyed) {
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freeSockets.shift();
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}
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socket = freeSockets.shift();
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socket = this.scheduling === 'fifo' ?
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freeSockets.shift() :
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freeSockets.pop();
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if (!freeSockets.length)
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delete this.freeSockets[name];
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}

‎test/parallel/test-http-agent-scheduling.js‎

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@@ -0,0 +1,148 @@
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'use strict';
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const common = require('../common');
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const assert = require('assert');
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const http = require('http');
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function createServer(count) {
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return http.createServer(common.mustCallAtLeast((req, res) => {
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// Return the remote port number used for this connection.
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res.end(req.socket.remotePort.toString(10));
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}), count);
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}
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function makeRequest(url, agent, callback) {
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http
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.request(url, { agent }, (res) => {
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let data = '';
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res.setEncoding('ascii');
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res.on('data', (c) => {
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data += c;
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});
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res.on('end', () => {
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process.nextTick(callback, data);
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});
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})
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.end();
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}
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function bulkRequest(url, agent, done) {
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const ports = [];
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let count = agent.maxSockets;
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for (let i = 0; i < agent.maxSockets; i++) {
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makeRequest(url, agent, callback);
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}
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function callback(port) {
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count -= 1;
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ports.push(port);
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if (count === 0) {
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done(ports);
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}
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}
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}
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function defaultTest() {
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const server = createServer(8);
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server.listen(0, onListen);
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function onListen() {
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const url = `http://localhost:${server.address().port}`;
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const agent = new http.Agent({
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keepAlive: true,
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maxSockets: 5
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});
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bulkRequest(url, agent, (ports) => {
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makeRequest(url, agent, (port) => {
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assert.strictEqual(ports[0], port);
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makeRequest(url, agent, (port) => {
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assert.strictEqual(ports[1], port);
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makeRequest(url, agent, (port) => {
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assert.strictEqual(ports[2], port);
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server.close();
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agent.destroy();
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});
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});
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});
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});
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}
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}
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function fifoTest() {
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const server = createServer(8);
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server.listen(0, onListen);
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function onListen() {
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const url = `http://localhost:${server.address().port}`;
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const agent = new http.Agent({
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keepAlive: true,
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maxSockets: 5,
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scheduling: 'fifo'
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});
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bulkRequest(url, agent, (ports) => {
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makeRequest(url, agent, (port) => {
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assert.strictEqual(ports[0], port);
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makeRequest(url, agent, (port) => {
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assert.strictEqual(ports[1], port);
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makeRequest(url, agent, (port) => {
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assert.strictEqual(ports[2], port);
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server.close();
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agent.destroy();
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});
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});
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});
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});
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}
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}
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function lifoTest() {
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const server = createServer(8);
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server.listen(0, onListen);
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function onListen() {
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const url = `http://localhost:${server.address().port}`;
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const agent = new http.Agent({
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keepAlive: true,
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maxSockets: 5,
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scheduling: 'lifo'
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});
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bulkRequest(url, agent, (ports) => {
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makeRequest(url, agent, (port) => {
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assert.strictEqual(ports[ports.length - 1], port);
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makeRequest(url, agent, (port) => {
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assert.strictEqual(ports[ports.length - 1], port);
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makeRequest(url, agent, (port) => {
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assert.strictEqual(ports[ports.length - 1], port);
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server.close();
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agent.destroy();
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});
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});
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});
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});
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}
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}
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function badSchedulingOptionTest() {
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try {
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new http.Agent({
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keepAlive: true,
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maxSockets: 5,
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scheduling: 'filo'
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});
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} catch (err) {
137+
assert.strictEqual(err.code, 'ERR_INVALID_OPT_VALUE');
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assert.strictEqual(
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err.message,
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'The value "filo" is invalid for option "scheduling"'
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);
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}
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}
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defaultTest();
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fifoTest();
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lifoTest();
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badSchedulingOptionTest();

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