[core] avoid doing plugin discovery when bootstrapping the dev server

[spalger]

When running the dev server locally, before the platform code loads up the ClusterManager it runs plugin discovery which loads all the plugin source code. This seems like it might be necessary to get the configuration validated, but shouldn't be necessary just to get the ClusterManager running. Hoping someone on the platform team would be able to take a look at ways we could avoid running plugin discovery when env.isDevClusterMaster is true.

Skipping plugin discovery would likely allow us to disable the babel-register cache in the parent process of the dev cli or at least would make loading the parent process much faster.

[elasticmachine]

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

[mshustov]

There are already quite a few places disabling different platform functionality based on env.isDevClusterMaster (http server listening on a port, plugin initialization, etc.)
Probably we should change the way we create ClusterManager not to bootstrap the platform at all? More details on why we need ClusterManager: #78710

[pgayvallet]

Probably we should change the way we create ClusterManager not to bootstrap the platform at all?

Yea... atm starting the ClusterManager is the last thing we are starting, as the legacy service is one of the last to start.

Before we removed we legacy plugin system, the legacy plugin discovery was required to enhance the legacy config, and the legacy discovery had to run after the KP plugins discovery.

kibana/src/core/server/legacy/legacy_service.ts

Lines 186 to 190 in 0d09cea

	return new ClusterManager(
	this.coreContext.env.cliArgs,
	config,
	await basePathProxy$.toPromise()
	);

Now that this is gone, we could probably improve that. Ideally for that, ClusterManager would accept the KP configuration instead of using the legacy one. The clusterManager could even load the config itself now that the kbn/config package is (almost) a thing, avoiding to even load core.

[spalger]

By the way, I took a stab at disabling plugin discovery via env.isDevClusterMaster by preventing discover() from being called and it's working pretty well from what I can tell. The core is relatively tiny when it doesn't do any discovery so I think this might be a suitable solution if I can get platform sign off in the PR.

[spalger]

Closed by #79358

[mshustov]

reopen as we still need to decouple dev tools and ClusterManager from the platform code

[spalger]

I feel like that deserves its own issue personally.

[mshustov]

@spalger ok, closed in favour of #76935