## Summary Add a Rails application setting for the OTEL Collector endpoint URL used by CI Job Telemetry. Rails includes this URL in `features.tracing.otel_endpoints` when responding to runner job requests, so runners can push telemetry spans without static `config.toml` configuration. ## Background The [architecture design document](https://handbook.gitlab.com/handbook/engineering/architecture/design-documents/ci_job_telemetry/#job-payload-changes) specifies that the OTEL Collector endpoint is sent from Rails in the job payload as `features.tracing.otel_endpoints` (array of objects, max 2). Each endpoint object carries a `url` and optional typed `auth` configuration ([endpoint auth schema](https://handbook.gitlab.com/handbook/engineering/architecture/design-documents/ci_job_telemetry/#endpoint-auth-schema)). This was decided to ensure the feature works automatically for any runner based on version and namespace plan, without requiring administrators to configure each runner manager individually ([discussion](https://gitlab.com/gitlab-com/content-sites/handbook/-/merge_requests/17980#note_3112980648)). ## Requirements 1. Add an application setting (instance-level) for the primary OTEL Collector OTLP/HTTP endpoint URL - Setting name suggestion: `ci_telemetry_otel_endpoint` (string, nullable) - When blank/nil, `features.tracing` is not included in job payloads (telemetry disabled) 2. Include the configured URL as the first endpoint object in `features.tracing.otel_endpoints` in the `/api/v4/jobs/request` response. The endpoint object includes the `url` and optional `auth` configuration (for GitLab.com hosted runners, this is `http_bearer` auth using GCE metadata identity tokens) 3. The setting must be available for both GitLab.com (instance-level) and self-managed instances 4. For GitLab.com, this will be configured by infrastructure to point to the Observability team's OTEL Collector ### Future (not in scope for this issue) - Optional per-project/group BYO OTLP endpoint (second entry in `otel_endpoints` array, max 2 total) — tracked separately ## Architecture Reference - [Job payload changes](https://handbook.gitlab.com/handbook/engineering/architecture/design-documents/ci_job_telemetry/#job-payload-changes) - [Endpoint auth schema](https://handbook.gitlab.com/handbook/engineering/architecture/design-documents/ci_job_telemetry/#endpoint-auth-schema) - [Design decision: OTEL Collector endpoint configuration](https://handbook.gitlab.com/handbook/engineering/architecture/design-documents/ci_job_telemetry/#design-decisions) ## Dependencies - Feature negotiation (gitlab-org/gitlab#590588) — `features.tracing` is only included when the feature flag is enabled **and** the endpoint is configured - Trace context initialization (gitlab-org/gitlab#590587) — needs to include `otel_endpoints` alongside `trace_id` - Sampling rate application setting (gitlab-org/gitlab#593834) — `features.tracing` is only included when the pipeline is also sampled ## Parent Epic gitlab-org&20945