[apollo-datasource-rest] - "TypeError cannot read property of 'fetch' of undefined"

[markcdev]

Node - 10.15.0
Typescript - 3.1.2
apollo-datasource-rest - 0.1.5

I have a very simple data source class that extends the RESTDataSource class and makes a GET call to the star wars api. However at run time I'm getting the following error - "TypeError cannot read property fetch of undefined" which is located from line 148 in the RESTDataSource.js file on the following line -

const response = yield this.httpCache.fetch(...

[markcdev]

AH! I for some reason node-fetch wasn't included as a dependency! please close, sorry.

[jplock]

I just ran into this and had to call initialize(config) in the constructor to initialize the HTTPCache:

class MyAPI extends RESTDataSource {
  constructor(config) {
    super();
    this.initialize(config);
  }
}

[abernix]

@jplock What version of Apollo Server were you using that Data Source with? Did you have that data source declared in the dataSources property of the ApolloServer constructor? The initialize function is called automatically, so you shouldn't need to call it explicitly:

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

Lines 450 to 464 in 8850e0f

	function initializeDataSources() {
	if (config.dataSources) {
	const context = requestContext.context;
	const dataSources = config.dataSources();
	for (const dataSource of Object.values(dataSources)) {
	if (dataSource.initialize) {
	dataSource.initialize({
	context,
	cache: requestContext.cache,
	});
	}
	}

[jplock]

@abernix we're using apollo-server-lambda v2.4.3 and we did have the data sources declared. I was trying to test the data source independently of Apollo (unit tests), and I had to execute initialize() for my unit tests.

[abernix]

Aha, that makes sense. Since DataSources intentionally don't call initialize and, as I demonstrated above, are only initialized by the server itself, you would need to call initialize manually in your case. I would advise calling .initialize directly, not adding it to the constructor as you've done above, but I would strongly recommend testing the datasources using createTestClient as seen in that guide on testing from the server docs, which actually has an example for testing RESTDataSources.

I'll close this, but happy to assist further if I can be of help.

[mrdulin]

Hit this issue.

After reading @abernix 's explain. Here is my case:

I don't inject my application datasources to ApolloServer directly. Because I think dataSource like DAO. Instead of injecting to ApolloServer dataSources, I inject my datasources to service layer, the business logic layer. The code like this:

  const context = {} as ApplicationContext;
  const cache = new InMemoryLRUCache();
  const httpDataSourceConfig: DataSourceConfig<ApplicationContext> = { context, cache };

  const customerDataSource = new CustomerDataSourceImpl(googleAdwordsDataSourceOptions);
  customerDataSource.initialize(httpDataSourceConfig);
  const managedCustomerDataSource = new ManagedCustomerDataSourceImpl({
    baseURL: `https://us-central1-${process.env.GOOGLE_CLOUD_PROJECT}.cloudfunctions.net/`,
  });
  managedCustomerDataSource.initialize(httpDataSourceConfig);


const managedCustomerService = new ManagedCustomerService({
          managedCustomerDataSource,
          googleAccountDataSource,
          userDataSource,
          googleAdwordsDataSource,
        }),

And, I inject these serivces to Apollo context.

If you don't call initialize method when you use dataSource outside which means you don't inject datasource to dataSources configuration of ApolloServer, it will throw TypeError cannot read property of 'fetch' of undefined.

P.S. You can use some IoC implements the DIP, instead of using new keyword, but this is another topic.

[mImranAziz]

In my case error was in ~\node_modules\apollo-datasource-rest\src\RESTDataSource.ts,

line await this.httpCache.fetch(request

I resolved this by initializing httpCache as:

constructor() {
super();
this.baseURL = v6url;
this.httpCache = new HTTPCache()
}

So it's not null.

[abernix]

@mImranAziz DataSources have their initialize method called automatically by Apollo Server if they are declared in the dataSources Array of the ApolloServer constructor options:

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

Lines 580 to 587 in 1948d24

	for (const dataSource of Object.values(dataSources)) {
	if (dataSource.initialize) {
	dataSource.initialize({
	context,
	cache: requestContext.cache,
	});
	}
	}

The default cache should be set to an InMemoryLRUCache if you haven't specified a top-level cache yourself:

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

Lines 212 to 214 in 489cbb4

	if (!requestOptions.cache) {
	requestOptions.cache = new InMemoryLRUCache();
	}

Do any of these things sound possible? Your workaround shouldn't be necessary.

[esemeniuc]

@abernix I also needed to use @mImranAziz fix. Running apollo server 2.8.1 as well.

My solution was to not override initialize(config) since that prevents the abstract method from running this.httpCache = new HTTPCache(config.cache, this.httpFetch);

[linteck]

@abernix Why does "DataSources have their initialize method called automatically by Apollo Server"? Is it necessary? Why not put the initializer() into the constructor? Or at least write this trick into document.

[wzup]

@abernix
Somehow this is not true.
If you do not call initialize directly, it is never set auto-magically.

[wzup]

@markcdev

AH! I for some reason node-fetch wasn't included as a dependency! please close, sorry.

And what does it mean? What actions are you expecting from us after your AH!-answer?

[robe007]

I had the same problem with apollo-datasource-rest combined with graphql-yoga, but I was able to get it work.

You can see my comments about it here