Summary

Closes #33783

Introduces RequestHandlerContext passed to a request handler as the very first argument.

// my-plugin.ts
deps.http.registerRouteHandlerContext(
  'myApp',
  (context, req) => {
    async function search (id: string) {
      return await context.elasticsearch.adminClient.callAsInternalUser('endpoint', id);
    }
    return { search };
  }
);

// my-route-handler.ts
router.get({ path: '/', validate: false }, async (context, req, res) => {
  const response = await context.myApp.search(...);
  return res.ok(response);
});

Currently extended only with elasticsearch service, which provides cluster clients scoped to the current request.

declare module '../../server' {
  interface RequestHandlerContext {
    elasticsearch: {
      dataClient: ScopedClusterClient;
      adminClient: ScopedClusterClient;
    };
  }
}

Use strikethroughs to remove checklist items you don't feel are applicable to this PR.

• [ ] This was checked for cross-browser compatibility, including a check against IE11
• [ ] Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• [ ] Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• [ ] This was checked for keyboard-only and screenreader accessibility

For maintainers

• This was checked for breaking API changes and was labeled appropriately
• This includes a feature addition or change that requires a release note and was labeled appropriately

Dev docs

Kibana facilitates new Handler context pattern to provide core services API to plugins. The central purpose of this pattern is to hide some implementation details and provide a set of API specific for the current context. For example, RequestHandlerContext contains tailored elasticsearch service API, letting a plugin to perform a request to elasticsearch on behalf of the user requesting Kibana. RequestHandlerContext is exposed to the route handlers as the very first argument.

class MyPlugin {
  setup(core) {
    const router = core.http.createRouter();
    router.get({ path: '/ping', validate: false }, async (context, req, res) => {
      const response = await context.core.elasticsearch.adminClient.callAsInternalUser('ping');
      return res.ok({ body: `Pong: ${response}` });
    });
  }
}