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UTC_E_FORWARDER_ALREADY_ENABLED
Locate the rejected contract: trigger-forwarder state
The code UTC_E_FORWARDER_ALREADY_ENABLED (0x87C51007) belongs to trigger-forwarder lifecycle, inside the Universal Telemetry Client/DiagTrack workflow. The symbolic name points to a narrow UTC contract that can be tested directly. It identifies trigger-forwarder state and reports that an enable operation targeted a forwarder whose current state is already enabled; it does not by itself prove that all Windows diagnostic data collection is unavailable.
Trigger forwarders connect a producer to scenario trigger processing and have their own registration and enable state. Reusing a handle after configuration reload or crossing producer types can fail before any scenario filter is evaluated.
Capture checklist
| UTC diagnostic field | Value |
|---|---|
| Producing layer | trigger-forwarder lifecycle |
| Owning state or object | trigger-forwarder state |
| Evidence to collect | forwarder type, producer identity, registration handle, enable timestamp and duplicate caller |
| Narrow comparison | disable and re-enable the same instance once, then repeat the enable call to confirm idempotency behavior |
| Do not confuse with | UTC_E_FORWARDER_PRODUCER_MISMATCH indicates a type/producer mismatch rather than a duplicate state change |
Comparison with a passing case
- Export the relevant
Microsoft-Windows-UniversalTelemetryClient/Operationalevents and preserve their ActivityId or request correlation alongside this result. - Capture forwarder type, producer identity, registration handle, enable timestamp and duplicate caller. Do this before restarting the service or deleting any working directory.
- Perform this one-variable comparison: disable and re-enable the same instance once, then repeat the enable call to confirm idempotency behavior.
- After the comparison, record the next HRESULT and whether the requested session, action, trigger or output object was actually created.
Nearby result: UTC_E_FORWARDER_PRODUCER_MISMATCH — indicates a type/producer mismatch rather than a duplicate state change.
Platform-state note
Capture capability and identity state at the moment this result is returned. Session, container, service and destination state can change asynchronously, so a later successful query does not describe the state at failure.
Resolution and regression test
Make enable idempotent in the caller or skip it when the queried state is already enabled.
Technical references
- Microsoft Open Specifications: Windows error-code registry — reference for trigger-forwarder lifecycle while interpreting this result.
- Microsoft: Universal Telemetry Client configuration diagnosis — reference for trigger-forwarder lifecycle while interpreting it.
- Microsoft: Event Tracing for Windows
- Microsoft: UniversalTelemetryClient operational-log guidance
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