feat: Add startup warning for OTEL_EXPORTER_OTLP_ENDPOINT environment…

[apollo-mateuswgoettems]

---

Description

This PR adds a startup warning to alert users when the OTEL_EXPORTER_OTLP_ENDPOINT environment variable is set.

The warning message informs users that this environment variable takes precedence over default router configurations and may override trace export to Apollo Studio, which could cause unexpected behavior in telemetry collection.

Motivation

Users may accidentally set OTEL_EXPORTER_OTLP_ENDPOINT globally or in their deployment configuration without realizing it takes precedence over the router's configured telemetry settings. This can silently redirect traces away from Apollo Studio, making it difficult to diagnose why traces are not appearing.

Changes

• Added environment variable check in apollo-router/src/executable.rs during router startup
• Displays a warning log message when OTEL_EXPORTER_OTLP_ENDPOINT is detected
• Warning is only shown when the variable is actually set (no unnecessary warnings)

Checklist

Complete the checklist (and note appropriate exceptions) before the PR is marked ready-for-review.

• PR description explains the motivation for the change and relevant context for reviewing
• PR description links appropriate GitHub/Jira tickets (creating when necessary)
• Changeset is included for user-facing changes
• Changes are compatible[^1]
• Documentation[^2] completed
• Performance impact assessed and acceptable
• Metrics and logs are added[^3] and documented
• Tests added and passing[^4]
  • Unit tests
  • Integration tests
  • Manual tests, as necessary

Exceptions

• Documentation: This is a simple startup warning message. No additional documentation is required as the warning itself is self-explanatory.
• Performance impact: Negligible - only a single env::var() check during startup (one-time operation).
• Tests: Manual testing required to verify warning appears when variable is set.

Testing

Manual Testing

To verify this change:

1. Start the router with the environment variable set:

   OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4317 cargo run -- -s supergraph.graphql
   

[apollo-librarian]

✅ Docs preview ready

The preview is ready to be viewed. View the preview

File Changes

0 new, 10 changed, 0 removed

* graphos/routing/(latest)/configuration/yaml.mdx
* graphos/routing/(latest)/customization/native-plugins.mdx
* graphos/routing/(latest)/performance/caching/response-caching/customization.mdx
* graphos/routing/(latest)/performance/caching/response-caching/faq.mdx
* graphos/routing/(latest)/performance/caching/response-caching/invalidation.mdx
* graphos/routing/(latest)/performance/caching/response-caching/observability.mdx
* graphos/routing/(latest)/performance/caching/response-caching/overview.mdx
* graphos/routing/(latest)/performance/caching/response-caching/quickstart.mdx
* graphos/routing/(latest)/upgrade/from-router-v1.mdx
* graphos/routing/(latest)/federation-version-support.mdx

Build ID: bce0d0a11966d1959e89eea3
Build Logs: View logs

URL: https://www.apollographql.com/docs/deploy-preview/bce0d0a11966d1959e89eea3

[bonnici]

Looks good to me but what's the reason for adding the new schema.json file? We may need to get someone from the router team to take a look at that one.

[apollo-mateuswgoettems]

Apologies, I was testing something earlier with schema.json and accidentally left it in. It has now been removed.