split context creation to avoid unecessary computations

packages/vulcan-lib/lib/server/apollo-server/apollo_server2.js

@@ -22,7 +22,7 @@ export let executableSchema;
 import './settings';
 import { engineConfig } from './engine';
 import { defaultConfig, defaultOptions } from './defaults';
-import computeContext from './computeContext';
+import { initContext, computeContextFromReq } from './context.js';
 import getPlaygroundConfig from './playground';
 
 /**
@@ -37,6 +37,7 @@ const createApolloServer = ({ options: givenOptions = {}, config: givenConfig =
 
   // get the options and merge in defaults
   const options = { ...defaultOptions, ...givenOptions };
+  const context = initContext(options.context);
   // given options contains the schema
   const apolloServer = new ApolloServer({
     engine: engineConfig,
@@ -46,7 +47,7 @@ const createApolloServer = ({ options: givenOptions = {}, config: givenConfig =
     // this replace the previous syntax graphqlExpress(async req => { ... })
     // this function takes the context, which contains the current request,
     // and setup the options accordingly ({req}) => { ...; return options }
-    context: computeContext(options.context, contextFromReq)
+    context: computeContextFromReq(context, contextFromReq)
   });
 
   // default function does nothing

packages/vulcan-lib/lib/server/apollo-server/context.js

@@ -13,7 +13,7 @@
 //import deepmerge from 'deepmerge';
 import DataLoader from 'dataloader';
 import { getSetting } from '../../modules/settings.js';
-import { _hashLoginToken, _tokenExpiration } from '../accounts_helpers';
+import { _hashLoginToken, _tokenExpiration } from '../accounts_helpers.js';
 import { Collections } from '../../modules/collections.js';
 import { runCallbacks } from '../../modules/callbacks.js';
 import findByIds from '../../modules/findbyids.js';
@@ -21,7 +21,31 @@ import { GraphQLSchema } from '../../modules/graphql.js';
 import { Utils } from '../../modules/utils.js';
 import _merge from 'lodash/merge';
 
-const computeContext = (currentContext, contextFromReq) => {
+/**
+ * Called once on server creation
+ * @param {*} currentContext
+ */
+export const initContext = currentContext => {
+  let context;
+  if (currentContext) {
+    context = { ...currentContext };
+  } else {
+    context = {};
+  }
+  // merge with custom context
+  // TODO: deepmerge created an infinite loop here
+  context = _merge({}, context, GraphQLSchema.context);
+  // go over context and add Dataloader to each collection
+  Collections.forEach(collection => {
+    context[collection.options.collectionName].loader = new DataLoader(ids => findByIds(collection, ids, context), {
+      cache: true
+    });
+  });
+  return context;
+};
+
+// Call on every request
+export const computeContextFromReq = (currentContext, contextFromReq) => {
   // givenOptions can be either a function of the request or an object
   const getBaseContext = req => (contextFromReq ? { ...currentContext, ...contextFromReq(req) } : currentContext);
   const setupAuthToken = async (context, req) => {
@@ -50,14 +74,6 @@ const computeContext = (currentContext, contextFromReq) => {
       }
     }
   };
-  // go over context and add Dataloader to each collection
-  const setupDataLoader = context => {
-    Collections.forEach(collection => {
-      context[collection.options.collectionName].loader = new DataLoader(ids => findByIds(collection, ids, context), {
-        cache: true
-      });
-    });
-  };
 
   // create options given the current request
   const handleReq = async ({ req }) => {
@@ -66,13 +82,6 @@ const computeContext = (currentContext, contextFromReq) => {
 
     context = getBaseContext(req);
 
-    if (context) {
-      // don't mutate the context provided in options
-      context = { ...context };
-    } else {
-      context = {};
-    }
-
     // note: custom default resolver doesn't currently work
     // see https://github.com/apollographql/apollo-server/issues/716
     // options.fieldResolver = (source, args, context, info) => {
@@ -84,12 +93,6 @@ const computeContext = (currentContext, contextFromReq) => {
     //add the headers to the context
     context.headers = req.headers;
 
-    // merge with custom context
-    // TODO: deemerge created an infinite loop here
-    context = _merge({}, context, GraphQLSchema.context);
-
-    setupDataLoader(context);
-
     // console.log('// apollo_server.js user-agent:', req.headers['user-agent']);
     // console.log('// apollo_server.js locale:', req.headers.locale);
 
@@ -100,5 +103,3 @@ const computeContext = (currentContext, contextFromReq) => {
 
   return handleReq;
 };
-
-export default computeContext;