express - 将获取响应 header 转发到 Apollo graphql 响应

Question

我在 Apollo/Graphql 上设置了 apollo-datasource-rest 数据源
Expressjs 服务器。我想将一些标题从 fetch 响应转发到/graphql 响应。

这是流程:

POST /graphql

Graphql makes fetch request using this.get('http://example.com/api')
Response from this fetch contains the header "cache-status"

Response from /graphql
I'd like to include the "cache-status" header from the example.com/api response here in the /graphql response

我在其余数据源类的 didReceiveResponse() 方法中看到了 header 。我不确定这是访问和存储它的正确位置。如何在 POST/graphql 响应中包含“cache-status” header ？

Answer 1

假设您是 RESTDataSource来自 apollo-datasource-rest ，您可以覆盖 didReceiveResponse拦截响应并返回自定义返回值。
这是 Typescript 中的代码片段，如果需要，可以通过删除参数/返回类型和访问修饰符轻松将其转换为 Javascript。

class MyRestDataSource extends RESTDataSource {
  public constructor(baseUrl: string) {
    super();
    this.baseURL = baseUrl;
  }

  public async getSomething(): Promise<any & { headers?: { [key: string]: string } }> {
    // make the get request
    return this.get('path/to/something');
  }

  // intercept response after receiving it
  protected async didReceiveResponse(response: Response, _request: Request) {

    // get the value that is returned by default, by calling didReceiveResponse from the base class
    const defaultReturnValue = await super.didReceiveResponse(response, _request);

    // check if it makes sense to replace return value for this type of request
    if (_request.url.endsWith('path/to/something')) {
      // if yes get the headers from response headers and add it to the returned value
      return {
        ...defaultReturnValue,
        headers: { headerValue: response.headers.get('header_name') },
      };
    }

    return defaultReturnValue;
  }
}