http: set lifo as the default scheduling strategy in Agent.

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
     - v12.19.0
@@ -161,7 +164,7 @@ 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

@@ -95,7 +95,7 @@ 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();
           });