undici mocks are not picked up by elasticsearch-client

[djmadeira]

🐛 Bug Report

When using undici's MockAgent to mock requests, the elastic client does not pick up any of the mocks specified. I understand I could also use elasticsearch-mock, and for the most part I do, but in my tests that validate initializing the client is working, I want to test against actual HTTP requests. So this is a desirable feature to suppport

To Reproduce

Jest test which demonstrates the issue:

const { setGlobalDispatcher, MockAgent } = require('undici');
const { Client } = require('@elastic/elasticsearch');
const { request } = require('undici');

const mockAgent = new MockAgent();

beforeAll(() => {
  mockAgent.disableNetConnect();
  setGlobalDispatcher(mockAgent);
});

const response = {
  '_index': 'test-index',
  '_type': '_doc',
  '_id': 'TEST_ID',
  '_version': 1,
  '_seq_no': 0,
  '_primary_term': 1,
  'found': true,
  '_source': {}
};

test('undici', async () => {
  mockAgent.get('http://test-cluster:9200')
    .intercept({ path: '/test-index/_doc/TEST_ID', method: 'GET' })
    .reply(200, response);

  const { body } = await request('http://test-cluster:9200/test-index/_doc/TEST_ID');

  expect(await body.json()).toEqual(response);
});

test('elasticsearch-client', async () => {
  mockAgent.get('http://test-cluster:9200')
    .intercept({ path: '/test-index/_doc/TEST_ID', method: 'GET' })
    .reply(200, response);

  const client = new Client({
    node: 'http://test-cluster:9200'
  });

  // Throws ConnectionError: getaddrinfo ENOTFOUND test-cluster
  const result = await client.get({
    index: 'test-index',
    id: 'TEST_ID'
  });

  expect(result).toEqual(response);
});

Expected behavior

elasticsearch-client should respect the Agent set by setGlobalDispatcher, but it does not.

Your Environment

• node version: 16
• @elastic/elasticsearch version: >=8.0.0
• os: Mac

[delvedor]

Confirmed, currently working on a fix.

[delvedor]

I've opened elastic/elastic-transport-js#48 which will solve your issue.
The tl;dr is that the client is using the low-level API of undici, and the global dispatcher won't be picked up. The only solution for now is to allow the user to pass the custom mock agent. I'm chatting with the undici core team to understand if we can improve this before releasing our fix.

Meanwhile, I recommend you checkout @elastic/elasticsearch-mock, a mocking utility designed for this library.

[delvedor]

Hello! With nodejs/undici#1405 your issue should be solved! :)

[djmadeira]

@delvedor the test case above still doesn't work on 8.2.1