From 65251b8df656fd08be2db59c59e7e1a9b897ca3e Mon Sep 17 00:00:00 2001
From: Andrew Clark <git@andrewclark.io>
Date: Tue, 28 May 2019 18:37:49 -0700
Subject: [PATCH] Parallelize the build script

Uses CircleCI's `parallelism` config option to spin up multiple build
processes.
---
 .circleci/config.yml    |  7 ++++--
 scripts/rollup/build.js | 48 ++++++++++++++++++++++++++---------------
 2 files changed, 36 insertions(+), 19 deletions(-)

diff --git a/.circleci/config.yml b/.circleci/config.yml
index 0056e61642623..6a272c11ab4a2 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -118,6 +118,7 @@ jobs:
   build:
     docker: *docker
     environment: *environment
+    parallelism: 10
     steps:
       - checkout
       - *restore_yarn_cache
@@ -125,8 +126,6 @@ jobs:
       - run: ./scripts/circleci/add_build_info_json.sh
       - run: ./scripts/circleci/update_package_versions.sh
       - run: yarn build
-      - store_artifacts:
-          path: ./scripts/error-codes/codes.json
       - persist_to_workspace:
           root: build
           paths:
@@ -153,6 +152,10 @@ jobs:
           path: ./build.tgz
       - store_artifacts:
           path: ./build/bundle-sizes.json
+      - store_artifacts:
+          # TODO: Update release script to use local file instead of pulling
+          # from artifacts.
+          path: ./scripts/error-codes/codes.json
 
   lint_build:
     docker: *docker
diff --git a/scripts/rollup/build.js b/scripts/rollup/build.js
index 57d3033778895..9feec644bb2e7 100644
--- a/scripts/rollup/build.js
+++ b/scripts/rollup/build.js
@@ -634,27 +634,41 @@ function handleRollupError(error) {
 }
 
 async function buildEverything() {
-  await asyncRimRaf('build');
-
   // Run them serially for better console output
   // and to avoid any potential race conditions.
+
+  let bundles = [];
   // eslint-disable-next-line no-for-of-loops/no-for-of-loops
   for (const bundle of Bundles.bundles) {
-    await createBundle(bundle, UMD_DEV);
-    await createBundle(bundle, UMD_PROD);
-    await createBundle(bundle, UMD_PROFILING);
-    await createBundle(bundle, NODE_DEV);
-    await createBundle(bundle, NODE_PROD);
-    await createBundle(bundle, NODE_PROFILING);
-    await createBundle(bundle, FB_WWW_DEV);
-    await createBundle(bundle, FB_WWW_PROD);
-    await createBundle(bundle, FB_WWW_PROFILING);
-    await createBundle(bundle, RN_OSS_DEV);
-    await createBundle(bundle, RN_OSS_PROD);
-    await createBundle(bundle, RN_OSS_PROFILING);
-    await createBundle(bundle, RN_FB_DEV);
-    await createBundle(bundle, RN_FB_PROD);
-    await createBundle(bundle, RN_FB_PROFILING);
+    bundles.push(
+      [bundle, UMD_DEV],
+      [bundle, UMD_PROD],
+      [bundle, UMD_PROFILING],
+      [bundle, NODE_DEV],
+      [bundle, NODE_PROD],
+      [bundle, NODE_PROFILING],
+      [bundle, FB_WWW_DEV],
+      [bundle, FB_WWW_PROD],
+      [bundle, FB_WWW_PROFILING],
+      [bundle, RN_OSS_DEV],
+      [bundle, RN_OSS_PROD],
+      [bundle, RN_OSS_PROFILING],
+      [bundle, RN_FB_DEV],
+      [bundle, RN_FB_PROD],
+      [bundle, RN_FB_PROFILING]
+    );
+  }
+
+  if (!shouldExtractErrors && process.env.CIRCLE_NODE_TOTAL) {
+    // In CI, parallelize bundles across multiple tasks.
+    const nodeTotal = parseInt(process.env.CIRCLE_NODE_TOTAL, 10);
+    const nodeIndex = parseInt(process.env.CIRCLE_NODE_INDEX, 10);
+    bundles = bundles.filter((_, i) => i % nodeTotal === nodeIndex);
+  }
+
+  // eslint-disable-next-line no-for-of-loops/no-for-of-loops
+  for (const [bundle, bundleType] of bundles) {
+    await createBundle(bundle, bundleType);
   }
 
   await Packaging.copyAllShims();