[Mocha] TypeError: this.tracer._exporter.getItrConfiguration is not a function

[JohnDaly]

Expected behaviour dd-trace should allow a Mocha test suite to run when using the standard AgentExporter

Actual behaviour When trying to run a Mocha test suite, I get the following error:

TypeError: this.tracer._exporter.getItrConfiguration is not a function
    at /node_modules/dd-trace/packages/dd-trace/src/plugins/ci_plugin.js:19:29
    at Subscription._handler (/node_modules/dd-trace/packages/dd-trace/src/plugins/plugin.js:14:9)
    at Channel.publish (node:diagnostics_channel:56:9)
    at /node_modules/dd-trace/packages/datadog-instrumentations/src/mocha.js:351:26
    at exports.AsyncResource.runInAsyncScope (node:async_hooks:203:9)
    at Mocha.run (/node_modules/dd-trace/packages/datadog-instrumentations/src/mocha.js:350:27)

Steps to reproduce

As far as I can tell, here is what seems to be happening:

The Exporter for the tracer is being set to AgentExporter when config.experimental.exporter is not provided: https://github.com/DataDog/dd-trace-js/blob/a96389bc5de239da74769f6fb8cfdfbcefb8e386/packages/dd-trace/src/opentracing/tracer.js#L23

https://github.com/DataDog/dd-trace-js/blob/a96389bc5de239da74769f6fb8cfdfbcefb8e386/packages/dd-trace/src/exporter.js#L25

ITR Configuration Channel is set up here: https://github.com/DataDog/dd-trace-js/blob/a96389bc5de239da74769f6fb8cfdfbcefb8e386/packages/datadog-instrumentations/src/mocha.js#L20

Event is published to that channel here, when Mocha starts: https://github.com/DataDog/dd-trace-js/blob/a96389bc5de239da74769f6fb8cfdfbcefb8e386/packages/datadog-instrumentations/src/mocha.js#L358

Published event is handled is called here: https://github.com/DataDog/dd-trace-js/blob/a96389bc5de239da74769f6fb8cfdfbcefb8e386/packages/dd-trace/src/plugins/ci_plugin.js#L19

Handler fails because the _exporter (AgentExporter) on the tracer was never set up with a getItrConfiguration function.

Environment

• Operation system: Mac
• Node.js version: 16.17.0
• Tracer version: 3.11.0
• Agent version: N/A
• Relevant library versions: mocha@6.1.4

[JohnDaly]

After some more investigation, the problem seems to occur when Mocha is loaded after the tracer is initialized.

Here's a minimal repro:

// Initialize dd-trace
const { tracer } = require('dd-trace');
tracer.init();

// Simulate 'mocha' being loaded in another module
require('mocha');

// Tests
const assert = require('assert');

describe('Sample', function () {
  it('should pass', function () {
    assert.equal(1 + 1, 2);
  });
});

[juan-fernandez]

hi @JohnDaly ! Thanks for the detailed description and the reproducible case.

As a note, keep in mind that the way to initialise dd-trace to use CI Visibility (where the mocha plugin reports) is through dd-trace/ci/init: https://docs.datadoghq.com/continuous_integration/tests/javascript/?tab=onpremisesciproviderdatadogagent#instrument-your-tests. The ci prefix in the init makes sure that the correct exporter is used.

Whatever the case, this error should not happen with any exporter so I'll get to fixing this.

[juan-fernandez]

https://github.com/DataDog/dd-trace-js/pull/2711 should do the trick 😄