gateway: remove dependency on apollo-server-caching (#2029)

The point of apollo-server-caching is to provide an abstraction over
multiple cache backends. Gateway is not using that abstraction; it's
just using one particular implementation, which is a wrapper around an
old version of lru-cache.

As part of apollographql/apollo-server#6057
and apollographql/apollo-server#6719 we want
to remove dependencies on Apollo Server from Apollo Gateway. Technically
we don't really need to remove this dependency (since
apollo-server-caching doesn't depend on anything else in AS) but
apollo-server-caching won't be updated any more (in fact, even in AS3 it
has already been replaced by `@apollo/utils.keyvaluecache`), so let's do
it.

While we're at it, we make a few other improvements:
- Ever since #440, the queryPlanStore field is always set, so we can
  remove some conditionals around it.
- Instead of using the old lru-cache@6 wrapped by the
  apollo-server-caching package, we use the newer lru-cache@7 (which
  improves the algorithm internally and changes the names of methods a
  bit).
- The get and set methods on InMemoryLRUCache were only async because
  they implement the abstract KeyValueCache interface: the
  implementations didn't actually do anything async. So we no longer
  need to await them or include a giant comment about how we're not
  awaiting them.

gateway-js/package.json

@@ -35,12 +35,12 @@
  "@opentelemetry/api": "^1.0.1",
  "@types/node-fetch": "2.6.2",
  "apollo-reporting-protobuf": "^0.8.0 || ^3.0.0",
- "apollo-server-caching": "^0.7.0 || ^3.0.0",
  "apollo-server-core": "^2.23.0 || ^3.0.0",
  "apollo-server-errors": "^2.5.0 || ^3.0.0",
  "apollo-server-types": "^0.9.0 || ^3.0.0",
  "async-retry": "^1.3.3",
  "loglevel": "^1.6.1",
+ "lru-cache": "^7.13.1",
  "make-fetch-happen": "^10.1.2",
  "pretty-format": "^28.0.0"
  },

gateway-js/src/index.ts

@@ -5,7 +5,7 @@ import {
  GraphQLRequestContextExecutionDidStart,
 } from 'apollo-server-types';
 import type { Logger } from '@apollo/utils.logger';
-import { InMemoryLRUCache } from 'apollo-server-caching';
+import LRUCache from 'lru-cache';
 import {
  isObjectType,
  isIntrospectionType,
@@ -128,7 +128,7 @@ export class ApolloGateway implements GraphQLService {
  private serviceMap: DataSourceMap = Object.create(null);
  private config: GatewayConfig;
  private logger: Logger;
- private queryPlanStore: InMemoryLRUCache<QueryPlan>;
+ private queryPlanStore: LRUCache<string, QueryPlan>;
  private apolloConfig?: ApolloConfigFromAS3;
  private onSchemaChangeListeners = new Set<(schema: GraphQLSchema) => void>();
  private onSchemaLoadOrUpdateListeners = new Set<
@@ -210,14 +210,14 @@ export class ApolloGateway implements GraphQLService {
  }
 
  private initQueryPlanStore(approximateQueryPlanStoreMiB?: number) {
- return new InMemoryLRUCache<QueryPlan>({
+ return new LRUCache<string, QueryPlan>({
  // Create ~about~ a 30MiB InMemoryLRUCache. This is less than precise
  // since the technique to calculate the size of a DocumentNode is
  // only using JSON.stringify on the DocumentNode (and thus doesn't account
  // for unicode characters, etc.), but it should do a reasonable job at
  // providing a caching document store for most operations.
  maxSize: Math.pow(2, 20) * (approximateQueryPlanStoreMiB || 30),
- sizeCalculator: approximateObjectSize,
+ sizeCalculation: approximateObjectSize,
  });
  }
 
@@ -607,7 +607,7 @@ export class ApolloGateway implements GraphQLService {
  // Once we remove the deprecated onSchemaChange() method, we can remove this.
  legacyDontNotifyOnSchemaChangeListeners: boolean = false,
  ): void {
- if (this.queryPlanStore) this.queryPlanStore.flush();
+ this.queryPlanStore.clear();
  this.schema = toAPISchema(coreSchema);
  this.queryPlanner = new QueryPlanner(coreSchema);
 
@@ -843,10 +843,7 @@ export class ApolloGateway implements GraphQLService {
  return { errors: validationErrors };
  }
 
- let queryPlan: QueryPlan | undefined;
- if (this.queryPlanStore) {
- queryPlan = await this.queryPlanStore.get(queryPlanStoreKey);
- }
+ let queryPlan = this.queryPlanStore.get(queryPlanStoreKey);
 
  if (!queryPlan) {
  queryPlan = tracer.startActiveSpan(
@@ -868,25 +865,11 @@ export class ApolloGateway implements GraphQLService {
  },
  );
 
- if (this.queryPlanStore) {
- // The underlying cache store behind the `documentStore` returns a
- // `Promise` which is resolved (or rejected), eventually, based on the
- // success or failure (respectively) of the cache save attempt. While
- // it's certainly possible to `await` this `Promise`, we don't care about
- // whether or not it's successful at this point. We'll instead proceed
- // to serve the rest of the request and just hope that this works out.
- // If it doesn't work, the next request will have another opportunity to
- // try again. Errors will surface as warnings, as appropriate.
- //
- // While it shouldn't normally be necessary to wrap this `Promise` in a
- // `Promise.resolve` invocation, it seems that the underlying cache store
- // is returning a non-native `Promise` (e.g. Bluebird, etc.).
- Promise.resolve(
- this.queryPlanStore.set(queryPlanStoreKey, queryPlan),
- ).catch((err) =>
- this.logger.warn(
- 'Could not store queryPlan' + ((err && err.message) || err),
- ),
+ try {
+ this.queryPlanStore.set(queryPlanStoreKey, queryPlan);
+ } catch (err) {
+ this.logger.warn(
+ 'Could not store queryPlan' + ((err && err.message) || err),
  );
  }
  }