[APM Agent] Replace support for apm.dev.js with support for kibana.dev.yml in apm-config-loader

[joshdover]

Currently, the @kbn/apm-config-loader package supports a special kibana.dev.js file for configuring the APM agent in development. This should be replaced with the more standard supported kibana.dev.yml file for a more standard development experience

[elasticmachine]

Pinging @elastic/kibana-platform (Team:Platform)

[pgayvallet]

This should be replaced with the more standard supported kibana.dev.yml file

Is this file still used though? I don't see anything adding it to the list of config files in dev mode in src/cli.

[TinaHeiligers]

Possibly a related issue: #84840

[trentm]

The current support is apm.dev.js, rather than kibana.dev.js, right?

packages/kbn-apm-config-loader/src/config.ts
129:      const apmDevConfigPath = join(this.rootDir, 'config', 'apm.dev.js');

packages/kbn-apm-config-loader/src/config.test.mocks.ts
34:jest.doMock(join(mockedRootDir, 'config', 'apm.dev.js'), () => devConfigMock.raw, {

x-pack/plugins/fleet/dev_docs/tracing.md
14:      - <details><summary>via env variable or <code>config/apm.dev.js</code></summary>
20:      - By default traces are sent to a remote server, but you can send to a local APM by setting the <code>serverUrl</code> value in  <code>config/apm.dev.js</code>

docs/developer/getting-started/debugging.asciidoc
31:creating an appropriate config file under `config/apm.dev.js`. For
36:Example `config/apm.dev.js` file:

[trentm]

At #84840 (comment) @tylersmalley mentioned that he and @watson had discussed keeping "apm.dev.js" support. I don't have a strong opinion either way (I'm not a Kibana dev, I'm new to the Node.js APM team), but I'm slightly biased against having .js executable config files.

[watson]

I can just give my 5 cents on why I opted to support JS config files to begin with:

Sometimes it's nice to be able to load config programatically, e.g. say you want to set the agent to active depending on for instance the content of an environment variable:

active: process.env.NODE_ENV === 'production'

Or maybe you want to set some global tags based on the content of a file, e.g:

globalLabels: {
  uuid: fs.readFileSync('./data/uuid', { encoding: 'utf8' })
}

However these are of course not 100% necessary and there are other workaround to achieve the same goal without having Kibana look for this file on boot.

[Mpdreamz]

I think this can now be closed as of #127892 👍 cc @lizozom

[sorenlouv]

@joshdover should the docs be updated? I tried adding config/apm.dev.js and it didn't work.

[sorenlouv]

FYI: for others looking for how to enable APM instrumentation in Kibana. It seems that the approach today is to use kibana.dev.yml like this:

elastic:
  apm:
    active: true
    serverUrl: http://localhost:8200
    secretToken: very_secret
    centralConfig: true
    breakdownMetrics: true
    transactionSampleRate: 0.1