Generate schemaHash from schema

This commit adds a new field to the GraphQLServiceContext which is
a hashed representation of the schema. This is useful as a key value
to represent the schema and is sent as part of reporting to engine
when enabled

packages/apollo-server-core/package.json

@@ -38,11 +38,15 @@
     "graphql-subscriptions": "^1.0.0",
     "graphql-tag": "^2.9.2",
     "graphql-tools": "^4.0.0",
+    "json-stable-stringify": "^1.0.1",
     "lodash": "^4.17.10",
     "subscriptions-transport-ws": "^0.9.11",
     "ws": "^6.0.0"
   },
   "peerDependencies": {
     "graphql": "^0.12.0 || ^0.13.0 || ^14.0.0"
+  },
+  "devDependencies": {
+    "@types/json-stable-stringify": "^1.0.32"
   }
 }

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

@@ -44,6 +44,8 @@ import {
   PlaygroundRenderPageOptions,
 } from './playground';
 
+import { generateSchemaHash } from './utils/schemaHash';
+
 const NoIntrospection = (context: ValidationContext) => ({
   Field(node: FieldDefinitionNode) {
     if (node.name.value === '__schema' || node.name.value === '__type') {
@@ -87,6 +89,7 @@ export class ApolloServerBase {
   private engineReportingAgent?: EngineReportingAgent;
   private engineServiceId?: string;
   private extensions: Array<() => GraphQLExtension>;
+  private schemaHash: string;
   protected plugins: ApolloServerPlugin[] = [];
 
   protected schema: GraphQLSchema;
@@ -266,6 +269,10 @@ export class ApolloServerBase {
       });
     }
 
+    // The schema hash is a string representation of the shape of the schema
+    // it is used for reporting and can be used for a cache key if needed
+    this.schemaHash = generateSchemaHash(this.schema);
+
     // Note: doRunQuery will add its own extensions if you set tracing,
     // or cacheControl.
     this.extensions = [];
@@ -341,6 +348,7 @@ export class ApolloServerBase {
           plugin.serverWillStart &&
           plugin.serverWillStart({
             schema: this.schema,
+            schemaHash: this.schemaHash,
             engine: {
               serviceID: this.engineServiceId,
             },

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

@@ -15,6 +15,7 @@ import { KeyValueCache } from 'apollo-server-caching';
 
 export interface GraphQLServiceContext {
   schema: GraphQLSchema;
+  schemaHash: string;
   engine: {
     serviceID?: string;
   };

packages/apollo-server-core/src/utils/schemaHash.ts

@@ -0,0 +1,27 @@
+import { parse } from 'graphql/language';
+import { execute, ExecutionResult } from 'graphql/execution';
+import { getIntrospectionQuery, IntrospectionSchema } from 'graphql/utilities';
+import stableStringify from 'json-stable-stringify';
+import { GraphQLSchema } from 'graphql/type';
+import { createHash } from 'crypto';
+
+export function generateSchemaHash(schema: GraphQLSchema): string {
+  const introspectionQuery = getIntrospectionQuery();
+  const documentAST = parse(introspectionQuery);
+  const result = execute(schema, documentAST) as ExecutionResult;
+
+  if (!result || !result.data || !result.data.__schema) {
+    throw new Error('Unable to generate server introspection document.');
+  }
+
+  const introspectionSchema: IntrospectionSchema = result.data.__schema;
+
+  // It's important that we perform a deterministic stringification here
+  // since, depending on changes in the underlying `graphql-js` execution
+  // layer, varying orders of the properties in the introspection
+  const stringifiedSchema = stableStringify(introspectionSchema);
+
+  return createHash('sha512')
+    .update(stringifiedSchema)
+    .digest('hex');
+}