From 65cb03c22f63d7cf4bf0055f64c1199a361c3b35 Mon Sep 17 00:00:00 2001
From: Jean Lauliac <jeanlauliac@fb.com>
Date: Wed, 19 Apr 2017 10:51:34 -0700
Subject: [PATCH] packager: GlobalTransformCache: throat() the file fetching
 function

Reviewed By: cpojer

Differential Revision: D4914187

fbshipit-source-id: ae3b8aa4ed4dbd1896ca35cf498b7c02fd109f58
---
 .../metro-bundler/src/lib/GlobalTransformCache.js    | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/packages/metro-bundler/src/lib/GlobalTransformCache.js b/packages/metro-bundler/src/lib/GlobalTransformCache.js
index 2304f0ab..0a64db55 100644
--- a/packages/metro-bundler/src/lib/GlobalTransformCache.js
+++ b/packages/metro-bundler/src/lib/GlobalTransformCache.js
@@ -18,6 +18,7 @@ const crypto = require('crypto');
 const fetch = require('node-fetch');
 const jsonStableStringify = require('json-stable-stringify');
 const path = require('path');
+const throat = require('throat');
 
 import type {
   Options as TransformWorkerOptions,
@@ -260,7 +261,7 @@ class URIBasedGlobalTransformCache {
    * a second time if we expect them to be transient. We might even consider
    * waiting a little time before retring if experience shows it's useful.
    */
-  static fetchResultFromURI(uri: string): Promise<CachedResult> {
+  static _fetchResultFromURIWithRetry(uri: string): Promise<CachedResult> {
     return URIBasedGlobalTransformCache._fetchResultFromURI(uri).catch(error => {
       if (!URIBasedGlobalTransformCache.shouldRetryAfterThatError(error)) {
         throw error;
@@ -269,6 +270,12 @@ class URIBasedGlobalTransformCache {
     });
   }
 
+  /**
+   * The exposed version uses throat() to limit concurrency, as making too many parallel requests
+   * is more likely to trigger server-side throttling and cause timeouts.
+   */
+  static fetchResultFromURI: (uri: string) => Promise<CachedResult>;
+
   /**
    * We want to retry timeouts as they're likely temporary. We retry 503
    * (Service Unavailable) and 502 (Bad Gateway) because they may be caused by a
@@ -311,6 +318,9 @@ class URIBasedGlobalTransformCache {
 
 }
 
+URIBasedGlobalTransformCache.fetchResultFromURI =
+  throat(500, URIBasedGlobalTransformCache._fetchResultFromURIWithRetry);
+
 class OptionsHasher {
   _rootPath: string;
   _cache: WeakMap<TransformWorkerOptions, string>;