[BUG] The data schema named Data Prepper in the observability->traces->services page does not display services properly

[linghengqian]

Describe the bug
A clear and concise description of what the bug is.

• The data schema named Data Prepper in the observability->traces->services page does not display services properly. I created a minimal reproducible example at https://github.com/linghengqian/data-prepper-logs-test .

To Reproduce
Steps to reproduce the behavior:

1. Execute the following command on the Ubuntu 22.04.5 instance with SDKMAN! and Docker Engine installed. Refer to https://github.com/linghengqian/data-prepper-logs-test . This uses OpenJDK 23.

sdk install java 23-open
sdk use java 23-open

git clone [email protected]:linghengqian/data-prepper-logs-test.git
cd ./data-prepper-logs-test/

docker compose --file ./opensearch/docker-compose.yml up -d

./mvnw clean dependency:get -Dartifact=io.opentelemetry.javaagent:opentelemetry-javaagent:2.9.0

./mvnw clean spring-boot:run \
  -Dspring-boot.run.agents="$HOME/.m2/repository/io/opentelemetry/javaagent/opentelemetry-javaagent/2.9.0/opentelemetry-javaagent-2.9.0.jar" \
  -Dspring-boot.run.jvmArguments="\
  -Dotel.service.name='1-linghengqian-smoke-tests' \
  -Dotel.exporter.otlp.endpoint='http://localhost:24321'\
  "

This occupies host ports 14321 and 24321.

2. Open http://localhost:14321/app/observability-traces#/services in Microsoft Edge browser and log in with the
   account admin and the password opensearchNode1Test.
   The data schema named Data Prepper will not have any services. Although traces do collect APM data.

• 
• 

3. However, the data schema named Custom source will display 1-linghengqian-smoke-tests normally. From beginning to end, the Spring Boot application did not throw any exceptions.

• 

Expected behavior
A clear and concise description of what you expected to happen.

• The data schema named Data Prepper in the observability->traces->services page can display services normally.

Screenshots
If applicable, add screenshots to help explain your problem.

• Already mentioned above.

Environment (please complete the following information):

• OS: [e.g. Ubuntu 20.04 LTS] Ubuntu WSL 22.04.5 LTS
• Version [e.g. 22] opensearchproject/data-prepper:2.10.1

Additional context
Add any other context about the problem here.

• An interesting point is that neither https://github.com/opensearch-project/data-prepper/tree/main/examples/jaeger-hotrod nor Fixes the issue of not being able to receive Jaeger HotROD 1.63.0 via OpenTelemetry SDK #4972 have this problem. Am I supposed to understand that for a data schema named Data Prepper, the service map is only available when there are multiple services?
• Also, the data schema named Data Prepper seems to be able to directly accept the grpc data sent by the otlp exporter, so why does the OpenSearch website require the additional deployment of data prepper? otel/opentelemetry-collector-contrib can actually directly convert the Opentelemetry SDK data into opensearch documents. Another additional topic is, wouldn’t it be better if the opensearch dashboard directly integrates the logs, metrics, and traces sent by the Opentelemetry SDK into a single web page? Why split logs, metrics, and traces into different web pages?
• 

[dlvenable]

We did once have a bug where an isolated service did not show in the service map, see #628. However, we have fixed that. Perhaps it doesn't work when there are no other services, but we'd need to check that.