lazy load unused lambda packages in core

CHANGELOG.md

@@ -9,6 +9,8 @@
 - core: Expose SHA-256 hex hash digest of the Engine API key to plugins, when available, as `engine.apiKeyHash`. [PR# 2685](https://github.com/apollographql/apollo-server/pull/2685)
 - `apollo-datasource-rest`: If another `Content-type` is already set on the response, don't overwrite it with `application/json`, allowing the user's initial `Content-type` to prevail. [PR #2520](https://github.com/apollographql/apollo-server/issues/2035)
 - `apollo-cache-control`: Do not respond with `Cache-control` headers if the HTTP response contains `errors`. [PR #2715](https://github.com/apollographql/apollo-server/pull/2715)
+- `apollo-server-core`: Skip loading `util.promifisy` polyfill in Node.js engines >= 8.0 [PR #2278](https://github.com/apollographql/apollo-server/pull/2278)
+- `apollo-server-core`: Lazy load `subscriptions-transport-ws` in core [PR #2278](https://github.com/apollographql/apollo-server/pull/2278)
 - `apollo-server-cache-redis`: **BREAKING FOR USERS OF `apollo-server-cache-redis`** (This is a package that must be updated separately but shares the same `CHANGELOG.md` with Apollo Server itself.)  A new **major** version of this package has been published and updated to support Redis Standalone, Cluster and Sentinel modes.  This is a breaking change since it is now based on [`ioredis`](https://github.com/luin/ioredis) instead of [`node_redis`](https://github.com/NodeRedis/node_redis).  Although this update is compatible with the most common uses of `apollo-server-cache-redis`, please check the [options supported by `ioredis`](https://github.com/luin/ioredis/blob/master/API.md#new-redisport-host-options) while updating to this version.  The constructor options are passed directly from `RedisCache` to the new Redis adapter.  The pre-1.0 versions should continue to work with Apollo Server without modification. [PR #1770](https://github.com/apollographql/apollo-server/pull/1770)
 
 ### v2.5.0

packages/apollo-server-core/src/ApolloServer.ts

@@ -439,7 +439,7 @@ export class ApolloServerBase {
         );
       }
     }
-
+    const { SubscriptionServer } = require('subscriptions-transport-ws');
     const {
       onDisconnect,
       onConnect,

packages/apollo-server-env/src/index.ts

@@ -1,7 +1,11 @@
 import './polyfills/Object.values';
 import './polyfills/Object.entries';
 
-require('util.promisify').shim();
+import runtimeSupportsPromisify from './utils/runtimeSupportsPromisify';
+
+if (!runtimeSupportsPromisify) {
+  require('util.promisify').shim();
+}
 
 export * from './polyfills/fetch';
 export * from './polyfills/url';

packages/apollo-server-env/src/utils/runtimeSupportsPromisify.ts

@@ -0,0 +1,24 @@
+const runtimeSupportsPromisify = (() => {
+  if (
+    process &&
+    process.release &&
+    process.release.name === 'node' &&
+    process.versions &&
+    typeof process.versions.node === 'string'
+  ) {
+    const [nodeMajor] = process.versions.node
+      .split('.', 1)
+      .map(segment => parseInt(segment, 10));
+
+    if (nodeMajor >= 8) {
+      return true;
+    }
+    return false;
+  }
+
+  // If we haven't matched any of the above criteria, we'll remain unsupported
+  // for this mysterious environment until a pull-request proves us otherwise.
+  return false;
+})();
+
+export default runtimeSupportsPromisify;