[Console] Update autocomplete route configuration to include proxy headers (#149498)

### Summary

This PR updates the autocomplete route configuration to include missing
proxy headers such as `x-forwarded-for`,
`x-forwarded-host`, `x-forwarded-port`, and `x-forwarded-proto` to
ensure that remote headers are forwarded to the Elasticsearch server.
And also adds a check to ensure that the `host` header is set to the
hostname if it is not already set. Users reported that the autocomplete
indices were not showing up in the autocomplete dropdown in some cases
due to the misconfiguration in autocomplete route. This PR should fix
that issue.

### Testing

To test this PR, verify that the correct headers are being sent to the
Elasticsearch server when using the autocomplete route. You can use the
`console.log` statement in the
[`getEntity`](https://github.com/elastic/kibana/pull/149498/files#diff-dc97f758bd78991f73f2f928fc59d00923790286e12766dd7c91d148ec40cfeeR118)
function to verify that the headers are being sent correctly.

#### Release note

This PR fixes an issue where the autocomplete indices were not showing
up in the autocomplete dropdown in some cases due to the
misconfiguration in autocomplete route.


### Checklist

Delete any items that are not applicable to this PR.

- [ ] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/packages/kbn-i18n/README.md)
- [ ]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials
- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [ ] Any UI touched in this PR is usable by keyboard only (learn more
about [keyboard accessibility](https://webaim.org/techniques/keyboard/))
- [ ] Any UI touched in this PR does not create any new axe failures
(run axe in browser:
[FF](https://addons.mozilla.org/en-US/firefox/addon/axe-devtools/),
[Chrome](https://chrome.google.com/webstore/detail/axe-web-accessibility-tes/lhdoppojpmngadmnindnejefpokejbdd?hl=en-US))
- [ ] If a plugin configuration key changed, check if it needs to be
allowlisted in the cloud and added to the [docker
list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)
- [ ] This renders correctly on smaller devices using a responsive
layout. (You can test this [in your
browser](https://www.browserstack.com/guide/responsive-testing-on-local-server))
- [ ] This was checked for [cross-browser
compatibility](https://www.elastic.co/support/matrix#matrix_browsers)


### Risk Matrix

Delete this section if it is not applicable to this PR.

Before closing this PR, invite QA, stakeholders, and other developers to
identify risks that should be tested prior to the change/feature
release.

When forming the risk matrix, consider some of the following examples
and how they may potentially impact the change:

| Risk | Probability | Severity | Mitigation/Notes |

|---------------------------|-------------|----------|-------------------------|
| Multiple Spaces—unexpected behavior in non-default Kibana Space.
| Low | High | Integration tests will verify that all features are still
supported in non-default Kibana Space and when user switches between
spaces. |
| Multiple nodes—Elasticsearch polling might have race conditions
when multiple Kibana nodes are polling for the same tasks. | High | Low
| Tasks are idempotent, so executing them multiple times will not result
in logical error, but will degrade performance. To test for this case we
add plenty of unit tests around this logic and document manual testing
procedure. |
| Code should gracefully handle cases when feature X or plugin Y are
disabled. | Medium | High | Unit tests will verify that any feature flag
or plugin combination still results in our service operational. |
| [See more potential risk
examples](https://github.com/elastic/kibana/blob/main/RISK_MATRIX.mdx) |


### For maintainers

- [ ] This was checked for breaking API changes and was [labeled
appropriately](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)

Co-authored-by: Muhammad Ibragimov <muhammad.ibragimov@elastic.co>
Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

src/plugins/console/server/routes/api/console/autocomplete_entities/index.ts

@@ -16,7 +16,7 @@ import type { SemVer } from 'semver';
 import type { RouteDependencies } from '../../..';
 import { sanitizeHostname } from '../../../../lib/utils';
 import type { ESConfigForProxy } from '../../../../types';
-import { getRequestConfig } from '../proxy/create_handler';
+import { getRequestConfig, getProxyHeaders } from '../proxy/create_handler';
 
 interface SettingsToRetrieve {
   indices: boolean;
@@ -25,7 +25,7 @@ interface SettingsToRetrieve {
   dataStreams: boolean;
 }
 
-type Config = ESConfigForProxy & { headers: KibanaRequest['headers'] } & { kibanaVersion: SemVer };
+type Config = ESConfigForProxy & { request: KibanaRequest } & { kibanaVersion: SemVer };
 
 const MAX_RESPONSE_SIZE = 10 * 1024 * 1024; // 10MB
 // Limit the response size to 10MB, because the response can be very large and sending it to the client
@@ -103,15 +103,40 @@ const getEntity = (path: string, config: Config) => {
       const host = hosts[idx];
       const uri = new URL(host + path);
       const { protocol, hostname, port } = uri;
-      const { headers } = getRequestConfig(config.headers, config, uri.toString(), kibanaVersion);
+      const { headers, agent } = getRequestConfig(
+        config.request.headers,
+        config,
+        uri.toString(),
+        kibanaVersion
+      );
+      const proxyHeaders = getProxyHeaders(config.request);
       const client = protocol === 'https:' ? https : http;
+
+      const requestHeaders = {
+        ...headers,
+        ...proxyHeaders,
+      };
+
+      const hasHostHeader = Object.keys(requestHeaders).some((key) => key.toLowerCase() === 'host');
+      // if the host header is not set, then set it to the hostname. This is needed because the
+      // request will fail if the host header is not set and it is used to determine the node to
+      // send the request to in a multi-node cluster.
+      if (!hasHostHeader) {
+        requestHeaders.host = hostname;
+      }
+
       const options = {
         method: 'GET',
-        headers: { ...headers },
+        headers: {
+          ...requestHeaders,
+          'content-type': 'application/json',
+          'transfer-encoding': 'chunked',
+        },
         host: sanitizeHostname(hostname),
         port: port === '' ? undefined : parseInt(port, 10),
         protocol,
         path: `${path}?pretty=false`, // add pretty=false to compress the response by removing whitespace
+        agent,
       };
 
       try {
@@ -171,20 +196,20 @@ export const registerAutocompleteEntitiesRoute = (deps: RouteDependencies) => {
       }
 
       const legacyConfig = await deps.proxy.readLegacyESConfig();
-      const configWithHeaders = {
+      const config = {
         ...legacyConfig,
-        headers: request.headers,
+        request,
         kibanaVersion: deps.kibanaVersion,
       };
 
       // Wait for all requests to complete, in case one of them fails return the successfull ones
       const results = await Promise.allSettled([
-        getMappings(settings, configWithHeaders),
-        getAliases(settings, configWithHeaders),
-        getDataStreams(settings, configWithHeaders),
-        getLegacyTemplates(settings, configWithHeaders),
-        getIndexTemplates(settings, configWithHeaders),
-        getComponentTemplates(settings, configWithHeaders),
+        getMappings(settings, config),
+        getAliases(settings, config),
+        getDataStreams(settings, config),
+        getLegacyTemplates(settings, config),
+        getIndexTemplates(settings, config),
+        getComponentTemplates(settings, config),
       ]);
 
       const [mappings, aliases, dataStreams, legacyTemplates, indexTemplates, componentTemplates] =

src/plugins/console/server/routes/api/console/proxy/create_handler.ts

@@ -70,7 +70,7 @@ export function getRequestConfig(
   };
 }
 
-function getProxyHeaders(req: KibanaRequest) {
+export function getProxyHeaders(req: KibanaRequest) {
   const headers = Object.create(null);
 
   // Scope this proto-unsafe functionality to where it is being used.