Add support to max network concurrent requests (yarnpkg#2129)

src/cli/index.js

@@ -80,6 +80,7 @@ commander.option(
   '--no-progress',
   'disable progress bar',
 );
+commander.option('--network-concurrency <number>', 'maximum number of concurrent network requests');
 
 // get command name
 let commandName: ?string = args.shift() || '';
@@ -360,6 +361,7 @@ config.init({
   production: commander.production,
   httpProxy: commander.proxy,
   httpsProxy: commander.httpsProxy,
+  networkConcurrency: commander.networkConcurrency,
   commandName,
 }).then(() => {
   const exit = () => {

src/config.js

@@ -34,6 +34,7 @@ export type ConfigOptions = {
   cafile?: ?string,
   production?: boolean,
   binLinks?: boolean,
+  networkConcurrency?: number,
 
   // Loosely compare semver for invalid cases like "0.01.0"
   looseSemver?: ?boolean,
@@ -199,6 +200,8 @@ export default class Config {
       cafile: String(opts.cafile || this.getOption('cafile') || ''),
       cert: String(opts.cert || this.getOption('cert') || ''),
       key: String(opts.key || this.getOption('key') || ''),
+      networkConcurrency: Number(opts.networkConcurrency || this.getOption('network-concurrency') ||
+        constants.NETWORK_CONCURRENCY),
     });
 
     //init & create cacheFolder, tempFolder

src/util/request-manager.js

@@ -42,6 +42,7 @@ type RequestParams<T> = {
   encoding?: ?string,
   ca?: Array<string>,
   cert?: string,
+  networkConcurrency?: number,
   key?: string,
   forever?: boolean,
   strictSSL?: boolean,
@@ -114,6 +115,7 @@ export default class RequestManager {
     ca?: Array<string>,
     cafile?: string,
     cert?: string,
+    networkConcurrency?: number,
     key?: string,
   }) {
     if (opts.userAgent != null) {
@@ -144,6 +146,10 @@ export default class RequestManager {
       this.ca = opts.ca;
     }
 
+    if (opts.networkConcurrency != null) {
+      this.max = opts.networkConcurrency;
+    }
+
     if (opts.cafile != null && opts.cafile != '') {
       // The CA bundle file can contain one or more certificates with comments/text between each PEM block.
       // tls.connect wants an array of certificates without any comments/text, so we need to split the string