Stricter Setup / Start API separation

[mshustov]

From the very beginning Kibana platform uses a notion of lifecycles to separate runtime process into different stages:

• setup - the preparatory stage. It should be used to declare cross-plugin dependencies and dependencies on the platform functionality. Kibana remains at this stage for a limited amount of time. In the future, this amount of time may be reduced to one tick.
• start - the runtime stage. Meant to be used to perform the Kibana functionality. It's a long-running stage. Kibana is in this state most of the time while it's running.
• stop - the teardown stage. It might be used to clean up resources and stop ongoing operations.

However, all the stages exist merely as a convention. This has led to the fact that plugins (and the platform itself) mix functionality up and provide runtime API from setup phase. As a result, when the platform decided to refactor public contracts we have realized it cannot be done due to the number of existing external dependencies.
Not the full list of the blocked tasks:

• Move elasticsearch client creation/access API from core setup to start contract #55397

To prevent problems in the future, we are going to reinforce the separation of the lifecycle stages. Otherwise, we have to add defensive checks in the code that API can be called, which is an error-prone approach. By default API exposed from start lifecycle stage unless it's crucial to move it to the setup stage

Suggestions:

• to move platform API meant to be used in runtime to the start phase.
• identify plugins that can be affected by this change and create issues for code owners to refactor the public API.
• add a tracking mechanism to monitor all the cases when API is called from a not-relevant stage.
• fix all the problem places.
• enforce a hard separation for API. Invoking API from another stage will throw an exception.

Child tasks:

• Remove UISettings accessors from core setup contract #55396

[elasticmachine]

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

[mshustov]

a preliminary list of changes on the server side to understand the magnitude of refactoring:

• all the http API except create router

  kibana/src/core/server/http/http_service.ts

  Line 103 in e67cc85

  createRouter: (path: string, pluginId: PluginOpaqueId = this.coreContext.coreId) => {

• context service API

  kibana/src/core/server/context/context_service.ts

  Line 34 in 0f85337

  createContextContainer: <THandler extends HandlerFunction<any>>() => {

• uuid service service API

  kibana/src/core/server/uuid/uuid_service.ts

  Line 58 in 9bdd23a

  getInstanceUuid: () => this.uuid,

• status service API

  kibana/src/core/server/status/status_service.ts

  Line 59 in f84773f

  core$,

• getImportExportObjectLimit from saved object service API

  kibana/src/core/server/saved_objects/saved_objects_service.ts

  Line 163 in 97d1685

  getImportExportObjectLimit: () => number;

• rendering service API

  kibana/src/core/server/rendering/rendering_service.tsx

  Line 49 in af09fed

  render: async (

• metrics service API

  kibana/src/core/server/metrics/metrics_service.ts

  Line 52 in 1f8da9d

  getOpsMetrics$: () => metricsObservable,

• docLinks service API
• fatalErrors service API
  

  kibana/src/core/public/fatal_errors/fatal_errors_service.tsx

  Line 115 in 4ff4b54

  return this.fatalErrors!;

• http service
  fetch, delete, get, head, options, patch, post, put, addLoadingCountSource, getLoadingCount$
• Notifications
  toasts API
• UiSettings
  

  kibana/src/core/public/notifications/notifications_service.ts

  Line 60 in 4ff4b54

  return notificationSetup;

[joshdover]

context service API

I believe this one should still be in setup since it is used to expose a context provider registry to other plugins.

[pgayvallet]

all the http API except create router

We even want to move to start the lifecycle hook registrations such as registerOnPreAuth ?

[mshustov]

We are going to start with logging a warning whenever lifecycle API is called outside of the current lifecycle timeframe #124039