[8.12] [Synthetics] Remove legacy screenshot image codepath (#172684) (#172980)

# Backport

This will backport the following commits from `main` to `8.12`:
- [[Synthetics] Remove legacy screenshot image codepath
(#172684)](https://github.com/elastic/kibana/pull/172684)

<!--- Backport version: 8.9.7 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT [{"author":{"name":"Justin
Kambic","email":"jk@elastic.co"},"sourceCommit":{"committedDate":"2023-12-08T17:13:45Z","message":"[Synthetics]
Remove legacy screenshot image codepath (#172684)\n\n##
Summary\r\n\r\nWe have not used full screenshot image data since early
alpha versions\r\nof Synthetics, and there is no reason to _not_ use
screenshot blocks\r\ninstead as they make far more efficient storage
performance.\r\n\r\nRemoves the route that returns full image data. I
may later include\r\nchanges to remove references to this on the client
as well, or do that\r\nin a
follow-up.","sha":"8d3e8cd838ad80f8955c986fe830a9e6590a60de","branchLabelMapping":{"^v8.13.0$":"main","^v(\\d+).(\\d+).\\d+$":"$1.$2"}},"sourcePullRequest":{"labels":["bug","release_note:fix","v8.12.0","Team:obs-ux-infra_services","Team:uptime","v8.13.0"],"number":172684,"url":"https://github.com/elastic/kibana/pull/172684","mergeCommit":{"message":"[Synthetics]
Remove legacy screenshot image codepath (#172684)\n\n##
Summary\r\n\r\nWe have not used full screenshot image data since early
alpha versions\r\nof Synthetics, and there is no reason to _not_ use
screenshot blocks\r\ninstead as they make far more efficient storage
performance.\r\n\r\nRemoves the route that returns full image data. I
may later include\r\nchanges to remove references to this on the client
as well, or do that\r\nin a
follow-up.","sha":"8d3e8cd838ad80f8955c986fe830a9e6590a60de"}},"sourceBranch":"main","suggestedTargetBranches":["8.12"],"targetPullRequestStates":[{"branch":"8.12","label":"v8.12.0","labelRegex":"^v(\\d+).(\\d+).\\d+$","isSourceBranch":false,"state":"NOT_CREATED"},{"branch":"main","label":"v8.13.0","labelRegex":"^v8.13.0$","isSourceBranch":true,"state":"MERGED","url":"https://github.com/elastic/kibana/pull/172684","number":172684,"mergeCommit":{"message":"[Synthetics]
Remove legacy screenshot image codepath (#172684)\n\n##
Summary\r\n\r\nWe have not used full screenshot image data since early
alpha versions\r\nof Synthetics, and there is no reason to _not_ use
screenshot blocks\r\ninstead as they make far more efficient storage
performance.\r\n\r\nRemoves the route that returns full image data. I
may later include\r\nchanges to remove references to this on the client
as well, or do that\r\nin a
follow-up.","sha":"8d3e8cd838ad80f8955c986fe830a9e6590a60de"}}]}]
BACKPORT-->

Co-authored-by: Justin Kambic <jk@elastic.co>

x-pack/plugins/synthetics/server/queries/journey_screenshots.ts

@@ -9,10 +9,12 @@ import {
   getJourneyScreenshot,
   ScreenshotReturnTypesUnion,
 } from '../legacy_uptime/lib/requests/get_journey_screenshot';
-import { isFullScreenshot, isRefResult, RefResult } from '../../common/runtime_types';
+import { isRefResult, RefResult } from '../../common/runtime_types';
 import { RouteContext, UptimeRouteContext } from '../routes/types';
 
-export type ClientContract = Buffer | { screenshotRef: RefResult };
+export interface ClientContract {
+  screenshotRef: RefResult;
+}
 
 function getSharedHeaders(stepName: string, totalSteps: number) {
   return {
@@ -35,15 +37,7 @@ export const journeyScreenshotHandler = async ({
     stepIndex,
   });
 
-  if (isFullScreenshot(result) && typeof result.synthetics?.blob !== 'undefined') {
-    return response.ok({
-      body: Buffer.from(result.synthetics.blob, 'base64'),
-      headers: {
-        'content-type': result.synthetics.blob_mime || 'image/png', // falls back to 'image/png' for earlier versions of synthetics
-        ...getSharedHeaders(result.synthetics.step.name, result.totalSteps),
-      },
-    });
-  } else if (isRefResult(result)) {
+  if (isRefResult(result)) {
     return response.ok({
       body: {
         screenshotRef: result,

x-pack/plugins/uptime/server/legacy_uptime/routes/pings/journey_screenshots.test.ts

@@ -105,94 +105,6 @@ describe('journey screenshot route', () => {
     expect(response.body.screenshotRef).toEqual(mock);
   });
 
-  it('returns full screenshot blob', async () => {
-    const mock = {
-      synthetics: {
-        blob: 'a blob',
-        blob_mime: 'image/jpeg',
-        step: {
-          name: 'a step name',
-        },
-        type: 'step/screenshot',
-      },
-    };
-
-    handlerContext.uptimeEsClient.search = jest.fn().mockResolvedValue({
-      body: {
-        hits: {
-          total: {
-            value: 3,
-          },
-          hits: [],
-        },
-        aggregations: { step: { image: { hits: { hits: [{ _source: mock }] } } } },
-      },
-    });
-
-    const route = createJourneyScreenshotRoute({
-      requests: {
-        getJourneyScreenshot: jest.fn().mockReturnValue(mock),
-      },
-    } as unknown as UMServerLibs);
-
-    expect(await route.handler(handlerContext as any)).toMatchInlineSnapshot(`
-      Object {
-        "body": Object {
-          "data": Array [
-            105,
-            185,
-            104,
-          ],
-          "type": "Buffer",
-        },
-        "headers": Object {
-          "cache-control": "max-age=600",
-          "caption-name": "a step name",
-          "content-type": "image/jpeg",
-          "max-steps": "3",
-        },
-        "message": "Ok",
-        "status": 200,
-      }
-    `);
-  });
-
-  it('defaults to png when mime is undefined', async () => {
-    const mock = {
-      synthetics: {
-        blob: 'a blob',
-        step: {
-          name: 'a step name',
-        },
-        type: 'step/screenshot',
-      },
-    };
-    handlerContext.uptimeEsClient.search = jest.fn().mockResolvedValue({
-      body: {
-        hits: {
-          total: {
-            value: 3,
-          },
-          hits: [],
-        },
-        aggregations: { step: { image: { hits: { hits: [{ _source: mock }] } } } },
-      },
-    });
-    const route = createJourneyScreenshotRoute({
-      requests: {
-        getJourneyScreenshot: jest.fn().mockReturnValue(mock),
-      },
-    } as unknown as UMServerLibs);
-
-    const response = (await route.handler(
-      handlerContext as any
-    )) as IKibanaResponse<ClientContract>;
-
-    expect(response.status).toBe(200);
-    // @ts-expect-error incomplete implementation for testing
-    expect(response.headers['content-type']).toBe('image/png');
-  });
-
   it('returns 404 for screenshot missing blob', async () => {
     const route = createJourneyScreenshotRoute({
       requests: {

x-pack/plugins/uptime/server/legacy_uptime/routes/pings/journey_screenshots.ts

@@ -6,11 +6,7 @@
  */
 import { IKibanaResponse } from '@kbn/core-http-server';
 import { schema } from '@kbn/config-schema';
-import {
-  isRefResult,
-  isFullScreenshot,
-  RefResult,
-} from '../../../../common/runtime_types/ping/synthetics';
+import { isRefResult, RefResult } from '../../../../common/runtime_types/ping/synthetics';
 import { UMServerLibs } from '../../lib/lib';
 import {
   getJourneyScreenshot,
@@ -19,7 +15,9 @@ import {
 import { RouteContext, UMRestApiRouteFactory, UptimeRouteContext } from '../types';
 import { API_URLS } from '../../../../common/constants';
 
-export type ClientContract = Buffer | { screenshotRef: RefResult };
+export interface ClientContract {
+  screenshotRef: RefResult;
+}
 
 function getSharedHeaders(stepName: string, totalSteps: number) {
   return {
@@ -30,7 +28,7 @@ function getSharedHeaders(stepName: string, totalSteps: number) {
 }
 
 export const createJourneyScreenshotRoute: UMRestApiRouteFactory<ClientContract> = (
-  libs: UMServerLibs
+  _libs: UMServerLibs
 ) => ({
   method: 'GET',
   path: API_URLS.JOURNEY_SCREENSHOT,
@@ -58,15 +56,7 @@ export const journeyScreenshotHandler = async ({
     stepIndex,
   });
 
-  if (isFullScreenshot(result) && typeof result.synthetics?.blob !== 'undefined') {
-    return response.ok({
-      body: Buffer.from(result.synthetics.blob, 'base64'),
-      headers: {
-        'content-type': result.synthetics.blob_mime || 'image/png', // falls back to 'image/png' for earlier versions of synthetics
-        ...getSharedHeaders(result.synthetics.step.name, result.totalSteps),
-      },
-    });
-  } else if (isRefResult(result)) {
+  if (isRefResult(result)) {
     return response.ok({
       body: {
         screenshotRef: result,