http: set lifo as the default scheduling strategy in Agent

PR-URL: #36685
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>

doc/api/http.md

@@ -113,6 +113,9 @@ http.get({
 <!-- YAML
 added: v0.3.4
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/36685
+    description: Change the default scheduling from 'fifo' to 'lifo'.
   - version: v14.5.0
     pr-url: https://github.com/nodejs/node/pull/33617
     description: Add `maxTotalSockets` option to agent constructor.
@@ -157,7 +160,7 @@ changes:
     In case of a high rate of request per second,
     the `'fifo'` scheduling will maximize the number of open sockets,
     while the `'lifo'` scheduling will keep it as low as possible.
-    **Default:** `'fifo'`.
+    **Default:** `'lifo'`.
   * `timeout` {number} Socket timeout in milliseconds.
     This will set the timeout when the socket is created.
 

lib/_http_agent.js

@@ -94,7 +94,7 @@ function Agent(options) {
   this.keepAlive = this.options.keepAlive || false;
   this.maxSockets = this.options.maxSockets || Agent.defaultMaxSockets;
   this.maxFreeSockets = this.options.maxFreeSockets || 256;
-  this.scheduling = this.options.scheduling || 'fifo';
+  this.scheduling = this.options.scheduling || 'lifo';
   this.maxTotalSockets = this.options.maxTotalSockets;
   this.totalSocketCount = 0;
 

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

@@ -56,11 +56,11 @@ function defaultTest() {
 
     bulkRequest(url, agent, (ports) => {
       makeRequest(url, agent, (port) => {
-        assert.strictEqual(ports[0], port);
+        assert.strictEqual(ports[ports.length - 1], port);
         makeRequest(url, agent, (port) => {
-          assert.strictEqual(ports[1], port);
+          assert.strictEqual(ports[ports.length - 1], port);
           makeRequest(url, agent, (port) => {
-            assert.strictEqual(ports[2], port);
+            assert.strictEqual(ports[ports.length - 1], port);
             server.close();
             agent.destroy();
           });