[8.19] Sample logs scenario - send to wired streams and classic streams at the same time (elastic#220737) (elastic#221151)

# Backport

This will backport the following commits from `main` to `8.19`:
- [Sample logs scenario - send to wired streams and classic streams at
the same time (elastic#220737)](elastic#220737)

<!--- Backport version: 9.6.6 -->

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

<!--BACKPORT [{"author":{"name":"Joe
Reuter","email":"[email protected]"},"sourceCommit":{"committedDate":"2025-05-21T16:19:33Z","message":"Sample
logs scenario - send to wired streams and classic streams at the same
time (elastic#220737)\n\nTo be able to better test classic vs. wired streams,
this PR expands the\n`sample_logs` scenario to send to both of these
places.\n\n<img width=\"1130\" alt=\"Screenshot 2025-05-11 at 10 55
36\"\nsrc=\"https://github.com/user-attachments/assets/0e75c82e-e96c-4f81-abcc-32347cd82d6b\"\n/>\n\n```\nnode
scripts/synthtrace.js sample_logs --live
--kibana=http://elastic:changeme@localhost:5601
--target=http://elastic:changeme@localhost:9200
--liveBucketSize=1000\n```","sha":"ab7734797388d79077184818dc720c76d9d58f1e","branchLabelMapping":{"^v9.1.0$":"main","^v(\\d+).(\\d+).\\d+$":"$1.$2"}},"sourcePullRequest":{"labels":["release_note:skip","Team:obs-ux-logs","Team:obs-ux-infra_services","backport:version","Feature:Streams","v9.1.0","v8.19.0"],"title":"Sample
logs scenario - send to wired streams and classic streams at the same
time","number":220737,"url":"https://github.com/elastic/kibana/pull/220737","mergeCommit":{"message":"Sample
logs scenario - send to wired streams and classic streams at the same
time (elastic#220737)\n\nTo be able to better test classic vs. wired streams,
this PR expands the\n`sample_logs` scenario to send to both of these
places.\n\n<img width=\"1130\" alt=\"Screenshot 2025-05-11 at 10 55
36\"\nsrc=\"https://github.com/user-attachments/assets/0e75c82e-e96c-4f81-abcc-32347cd82d6b\"\n/>\n\n```\nnode
scripts/synthtrace.js sample_logs --live
--kibana=http://elastic:changeme@localhost:5601
--target=http://elastic:changeme@localhost:9200
--liveBucketSize=1000\n```","sha":"ab7734797388d79077184818dc720c76d9d58f1e"}},"sourceBranch":"main","suggestedTargetBranches":["8.19"],"targetPullRequestStates":[{"branch":"main","label":"v9.1.0","branchLabelMappingKey":"^v9.1.0$","isSourceBranch":true,"state":"MERGED","url":"https://github.com/elastic/kibana/pull/220737","number":220737,"mergeCommit":{"message":"Sample
logs scenario - send to wired streams and classic streams at the same
time (elastic#220737)\n\nTo be able to better test classic vs. wired streams,
this PR expands the\n`sample_logs` scenario to send to both of these
places.\n\n<img width=\"1130\" alt=\"Screenshot 2025-05-11 at 10 55
36\"\nsrc=\"https://github.com/user-attachments/assets/0e75c82e-e96c-4f81-abcc-32347cd82d6b\"\n/>\n\n```\nnode
scripts/synthtrace.js sample_logs --live
--kibana=http://elastic:changeme@localhost:5601
--target=http://elastic:changeme@localhost:9200
--liveBucketSize=1000\n```","sha":"ab7734797388d79077184818dc720c76d9d58f1e"}},{"branch":"8.19","label":"v8.19.0","branchLabelMappingKey":"^v(\\d+).(\\d+).\\d+$","isSourceBranch":false,"state":"NOT_CREATED"}]}]
BACKPORT-->

Co-authored-by: Joe Reuter <[email protected]>

Author: kibanamachine

src/platform/packages/shared/kbn-apm-synthtrace/src/lib/streams/streams_synthtrace_client.ts

@@ -24,7 +24,7 @@ export class StreamsSynthtraceClient extends SynthtraceEsClient<StreamsDocument>
       ...options,
       pipeline: streamsPipeline(),
     });
-    this.dataStreams = ['logs', 'logs.*'];
+    this.dataStreams = ['logs', 'logs.*', 'logs-generic-default'];
   }
 
   async forkStream(
@@ -86,7 +86,12 @@ function streamsRoutingTransform() {
   return new Transform({
     objectMode: true,
     transform(document: ESDocumentWithOperation<StreamsDocument>, encoding, callback) {
-      document._index = 'logs';
+      // 50-50 send to logs or to logs-generic-default
+      if (Math.random() > 0.5) {
+        document._index = 'logs-generic-default';
+      } else {
+        document._index = 'logs';
+      }
       callback(null, document);
     },
   });