[performance] support triggering subset of journeys against KIbana PR in CI (#193175)

## Summary

It’s common request for Dev teams to run specific journeys on a PR to
compare performance metrics against the `main` branch. These requests
usually focus on a particular area, such as the Dashboard or Discover
app.

To streamline the process, this PR groups relevant journeys into
categories that can be triggered through an environment variable. For
example, setting `JOURNEYS_GROUP=dashboard` will execute only the three
dashboard-specific journeys, which are (usually) sufficient for
evaluating the performance impact of code changes within the Dashboard
app.

Current Process for Triggering Performance Builds:
- Create a new kibana-single-user-performance
[build](https://buildkite.com/elastic/kibana-single-user-performance#new)
- Provide the following arguments:

Branch: `refs/pull/<PR_number>/head`
Under Options, set the environment variable:
`JOURNEYS_GROUP=<group_name>`

Currently supported journey groups:
- kibanaStartAndLoad
- crud
- dashboard
- discover
- maps
- ml

[Build example

](https://buildkite.com/elastic/kibana-single-user-performance/builds/14427)
Each group focuses on a specific set of journeys tied to its respective
area in Kibana, allowing for more targeted performance testing. Since
running group takes ~5-10 min on bare metal worker, it should not delay
the regular (every 3h) runs against `main` branch


test locally with `node scripts/run_performance.js --group <group_name>`

.buildkite/scripts/steps/functional/performance_playwright.sh

@@ -39,8 +39,13 @@ if [ "$BUILDKITE_PIPELINE_SLUG" == "kibana-performance-data-set-extraction" ]; t
   node scripts/run_performance.js --kibana-install-dir "$KIBANA_BUILD_LOCATION" --skip-warmup
 else
   # pipeline should use bare metal static worker
-  echo "--- Running performance tests"
-  node scripts/run_performance.js --kibana-install-dir "$KIBANA_BUILD_LOCATION"
+  if [[ -z "${JOURNEYS_GROUP+x}" ]]; then
+    echo "--- Running performance tests"
+    node scripts/run_performance.js --kibana-install-dir "$KIBANA_BUILD_LOCATION"
+  else
+    echo "--- Running performance tests: '$JOURNEYS_GROUP' group"
+    node scripts/run_performance.js --kibana-install-dir "$KIBANA_BUILD_LOCATION" --group "$JOURNEYS_GROUP"
+  fi
 fi
 
 echo "--- Upload journey step screenshots"

dev_docs/tutorials/performance/adding_performance_journey.mdx

@@ -89,6 +89,27 @@ simulate real life internet connection. This means that all requests have a fixe
 In order to keep track on performance metrics stability, journeys are run on main branch with a scheduled interval.
 Bare metal machine is used to produce results as stable and reproducible as possible.
 
+#### Running subset of journeys for the PR
+
+Some code changes might affect the Kibana performance and it might be benefitial to run relevant journeys against the PR
+and compare performance metrics vs. the ones on main branch.
+
+In oder to trigger the build for Kibana PR, you can follow these steps:
+
+- Create a new kibana-single-user-performance [build](https://buildkite.com/elastic/kibana-single-user-performance#new)
+- Provide the following arguments:
+  - Branch: `refs/pull/<PR_number>/head`
+  - Under Options, set the environment variable: `JOURNEYS_GROUP=<group_name>`
+
+Currently supported journey groups:
+
+- kibanaStartAndLoad
+- crud
+- dashboard
+- discover
+- maps
+- ml
+
 #### Machine specifications
 
 All benchmarks are run on bare-metal machines with the [following specifications](https://www.hetzner.com/dedicated-rootserver/ex100):

src/dev/performance/run_performance_cli.ts

@@ -35,6 +35,19 @@ interface TestRunProps extends EsRunProps {
   kibanaInstallDir: string | undefined;
 }
 
+interface JourneyTargetGroups {
+  [key: string]: string[];
+}
+
+const journeyTargetGroups: JourneyTargetGroups = {
+  kibanaStartAndLoad: ['login'],
+  crud: ['tags_listing_page', 'dashboard_listing_page'],
+  dashboard: ['ecommerce_dashboard', 'data_stress_test_lens', 'flight_dashboard'],
+  discover: ['many_fields_discover', 'many_fields_discover_esql'],
+  maps: ['ecommerce_dashboard_map_only'],
+  ml: ['aiops_log_rate_analysis', 'many_fields_transform', 'tsdb_logs_data_visualizer'],
+};
+
 const readFilesRecursively = (dir: string, callback: Function) => {
   const files = fs.readdirSync(dir);
   files.forEach((file) => {
@@ -48,6 +61,44 @@ const readFilesRecursively = (dir: string, callback: Function) => {
   });
 };
 
+const getAllJourneys = (dir: string) => {
+  const journeys: Journey[] = [];
+
+  readFilesRecursively(dir, (filePath: string) =>
+    journeys.push({
+      name: path.parse(filePath).name,
+      path: path.resolve(dir, filePath),
+    })
+  );
+
+  return journeys;
+};
+
+const getJourneysToRun = ({ journeyPath, group }: { journeyPath?: string; group?: string }) => {
+  if (group && typeof group === 'string') {
+    if (!(group in journeyTargetGroups)) {
+      throw createFlagError(`Group '${group}' is not defined, try again`);
+    }
+
+    const fileNames = journeyTargetGroups[group];
+    const dir = path.resolve(REPO_ROOT, JOURNEY_BASE_PATH);
+
+    return getAllJourneys(dir).filter((journey) => fileNames.includes(journey.name));
+  }
+
+  if (journeyPath && !fs.existsSync(journeyPath)) {
+    throw createFlagError('--journey-path must be an existing path');
+  }
+
+  if (journeyPath && fs.statSync(journeyPath).isFile()) {
+    return [{ name: path.parse(journeyPath).name, path: journeyPath }];
+  } else {
+    // default dir is x-pack/performance/journeys_e2e
+    const dir = journeyPath ?? path.resolve(REPO_ROOT, JOURNEY_BASE_PATH);
+    return getAllJourneys(dir);
+  }
+};
+
 async function startEs(props: EsRunProps) {
   const { procRunner, log, logsDir } = props;
   await procRunner.run('es', {
@@ -115,29 +166,17 @@ run(
     const skipWarmup = flagsReader.boolean('skip-warmup');
     const kibanaInstallDir = flagsReader.path('kibana-install-dir');
     const journeyPath = flagsReader.path('journey-path');
+    const group = flagsReader.string('group');
+
+    if (group && journeyPath) {
+      throw createFlagError('--group and --journeyPath cannot be used simultaneously');
+    }
 
     if (kibanaInstallDir && !fs.existsSync(kibanaInstallDir)) {
       throw createFlagError('--kibana-install-dir must be an existing directory');
     }
 
-    if (journeyPath && !fs.existsSync(journeyPath)) {
-      throw createFlagError('--journey-path must be an existing path');
-    }
-
-    const journeys: Journey[] = [];
-
-    if (journeyPath && fs.statSync(journeyPath).isFile()) {
-      journeys.push({ name: path.parse(journeyPath).name, path: journeyPath });
-    } else {
-      // default dir is x-pack/performance/journeys_e2e
-      const dir = journeyPath ?? path.resolve(REPO_ROOT, JOURNEY_BASE_PATH);
-      readFilesRecursively(dir, (filePath: string) =>
-        journeys.push({
-          name: path.parse(filePath).name,
-          path: path.resolve(dir, filePath),
-        })
-      );
-    }
+    const journeys = getJourneysToRun({ journeyPath, group });
 
     if (journeys.length === 0) {
       throw new Error('No journeys found');
@@ -191,13 +230,14 @@ run(
   },
   {
     flags: {
-      string: ['kibana-install-dir', 'journey-path'],
+      string: ['kibana-install-dir', 'journey-path', 'group'],
       boolean: ['skip-warmup'],
       help: `
       --kibana-install-dir=dir      Run Kibana from existing install directory instead of from source
       --journey-path=path           Define path to performance journey or directory with multiple journeys
                                     that should be executed. '${JOURNEY_BASE_PATH}' is run by default
       --skip-warmup                 Journey will be executed without warmup (TEST phase only)
+      --group                       Run subset of journeys, defined in the specified group
     `,
     },
   }