Limit concurrency during plugin compilation

Summary:
My MBP just crashed again during startup. I would like to
understand why every plugin compilation appears to start
up a new electron process, but until that's understood
and hopefully fixed, it's probably best to limit the number
of processes we spawn by setting an upper bound here.

N.B. My Linux box doesn't mind this at all.

Reviewed By: jknoxville, danielbuechele

Differential Revision: D17419289

fbshipit-source-id: a11562a21a984059dc35e826eb20d869df218546

package.json

@@ -126,6 +126,7 @@
     "mkdirp": "^0.5.1",
     "node-fetch": "^2.3.0",
     "openssl-wrapper": "^0.3.4",
+    "p-map": "^3.0.0",
     "pkg": "^4.3.7",
     "promise-retry": "^1.1.1",
     "promisify-child-process": "^3.1.1",

static/compilePlugins.js

@@ -12,6 +12,7 @@ const Metro = require('metro');
 const util = require('util');
 const recursiveReaddir = require('recursive-readdir');
 const expandTilde = require('expand-tilde');
+const pMap = require('p-map');
 const HOME_DIR = require('os').homedir();
 
 /* eslint-disable prettier/prettier */
@@ -38,12 +39,12 @@ module.exports = async (
     fs.mkdirSync(pluginCache);
   }
   watchChanges(plugins, reloadCallback, pluginCache, options);
-  const compilations = Object.values(plugins).map(plugin => {
+  const compilations = pMap(Object.values(plugins), plugin => {
     const dynamicOptions = Object.assign(options, {force: false});
     return compilePlugin(plugin, pluginCache, dynamicOptions);
-  });
+  }, {concurrency: 4});
 
-  const dynamicPlugins = (await Promise.all(compilations)).filter(c => c != null);
+  const dynamicPlugins = (await compilations).filter(c => c != null);
   console.log('✅  Compiled all plugins.');
   return dynamicPlugins;
 };

yarn.lock

@@ -1484,6 +1484,14 @@ agentkeepalive@^2.2.0:
   resolved "https://registry.yarnpkg.com/agentkeepalive/-/agentkeepalive-2.2.0.tgz#c5d1bd4b129008f1163f236f86e5faea2026e2ef"
   integrity sha1-xdG9SxKQCPEWPyNvhuX66iAm4u8=
 
+aggregate-error@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/aggregate-error/-/aggregate-error-3.0.0.tgz#5b5a3c95e9095f311c9ab16c19fb4f3527cd3f79"
+  integrity sha512-yKD9kEoJIR+2IFqhMwayIBgheLYbB3PS2OBhWae1L/ODTd/JF/30cW0bc9TqzRL3k4U41Dieu3BF4I29p8xesA==
+  dependencies:
+    clean-stack "^2.0.0"
+    indent-string "^3.2.0"
+
 ajv-keywords@^3.4.0:
   version "3.4.1"
   resolved "https://registry.yarnpkg.com/ajv-keywords/-/ajv-keywords-3.4.1.tgz#ef916e271c64ac12171fd8384eaae6b2345854da"
@@ -2468,6 +2476,11 @@ class-utils@^0.3.5:
     isobject "^3.0.0"
     static-extend "^0.1.1"
 
+clean-stack@^2.0.0:
+  version "2.2.0"
+  resolved "https://registry.yarnpkg.com/clean-stack/-/clean-stack-2.2.0.tgz#ee8472dbb129e727b31e8a10a427dee9dfe4008b"
+  integrity sha512-4diC9HaTE+KRAMWhDhrGOECgWZxoevMc5TlkObMqNSsVU62PYzXZ/SMTjzyGAFF1YusgxGcSWTEXBhp0CPwQ1A==
+
 cli-boxes@^2.2.0:
   version "2.2.0"
   resolved "https://registry.yarnpkg.com/cli-boxes/-/cli-boxes-2.2.0.tgz#538ecae8f9c6ca508e3c3c95b453fe93cb4c168d"
@@ -4765,6 +4778,11 @@ indent-string@^2.1.0:
   dependencies:
     repeating "^2.0.0"
 
+indent-string@^3.2.0:
+  version "3.2.0"
+  resolved "https://registry.yarnpkg.com/indent-string/-/indent-string-3.2.0.tgz#4a5fd6d27cc332f37e5419a504dbb837105c9289"
+  integrity sha1-Sl/W0nzDMvN+VBmlBNu4NxBckok=
+
 indexof@0.0.1:
   version "0.0.1"
   resolved "https://registry.yarnpkg.com/indexof/-/indexof-0.0.1.tgz#82dc336d232b9062179d05ab3293a66059fd435d"
@@ -6863,6 +6881,13 @@ p-locate@^3.0.0:
   dependencies:
     p-limit "^2.0.0"
 
+p-map@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/p-map/-/p-map-3.0.0.tgz#d704d9af8a2ba684e2600d9a215983d4141a979d"
+  integrity sha512-d3qXVTF/s+W+CdJ5A29wywV2n8CQQYahlgz2bFiA+4eVNJbHJodPZ+/gXwPGh0bOqA+j8S+6+ckmvLGPk1QpxQ==
+  dependencies:
+    aggregate-error "^3.0.0"
+
 p-reduce@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/p-reduce/-/p-reduce-1.0.0.tgz#18c2b0dd936a4690a529f8231f58a0fdb6a47dfa"