# Simulation troubleshooting
<a name="simulation-troubleshooting"></a>

## Problem: Simulation service not starting
<a name="problem-simulation-service-not-starting"></a>

### Resolution
<a name="resolution-14"></a>

1. Check if port 5001 is already in use:

   ```
   lsof -i :5001
   # Kill the process if needed
   kill -9 <PID>
   ```

1. Ensure Python dependencies are installed:

   ```
   cd services/simulation
   pip install flask flask-cors boto3 requests
   ```

1. Make the management script executable:

   ```
   chmod +x manage_simulation.sh
   ```

1. Start the service and check logs:

   ```
   ./manage_simulation.sh start
   ./manage_simulation.sh logs
   ```

## Problem: No vehicles available for simulation
<a name="problem-no-vehicles-for-simulation"></a>

The simulation UI shows no vehicles when "Real Vehicles" is selected.

### Resolution
<a name="resolution-15"></a>

1. Vehicles must have IoT certificates to be used in simulations. Create vehicles in the Fleet Manager UI with "Create IoT Core certificate" enabled.

1. Verify vehicles have certificates in DynamoDB:

   ```
   aws dynamodb scan --table-name cms-dev-storage-vehicles \
     --filter-expression "has_certificate = :t" \
     --expression-attribute-values '{":t": {"BOOL": true}}' \
     --select COUNT
   ```

1. If using FleetWise Edge mode, verify the vehicle VIN exists in the vehicles table and has a valid IoT thing registered.

## Problem: FWE agent Docker container not starting
<a name="problem-fwe-container-not-starting"></a>

The simulation service fails to start FWE agent containers in FleetWise Edge mode.

### Resolution
<a name="resolution-16"></a>

1. Verify Docker is running:

   ```
   docker info
   ```

1. Check if the FWE Docker image is built:

   ```
   docker images | grep fwe
   ```

1. If the image is missing, build it:

   ```
   cd services/simulation
   ./build_sim_image.sh
   ```

1. Check the FWE container logs for startup errors:

   ```
   docker logs fwe-YOUR_VIN --tail 50
   ```

1. Verify the FWE persistency files are generated correctly:

   ```
   ls -la services/simulation/fwe_config/persistency/
   ```

## Problem: Simulation running but telemetry not appearing in dashboard
<a name="problem-simulation-telemetry-not-appearing"></a>

### Resolution
<a name="resolution-17"></a>

1. Check the simulation logs for MQTT publish errors:

   ```
   tail -f services/simulation/simulation_service.log
   ```

1. Verify the IoT endpoint is reachable:

   ```
   aws iot describe-endpoint --endpoint-type iot:Data-ATS
   ```

1. Verify the vehicle’s IoT certificate is activated:

   ```
   # Get certificate ARN from DynamoDB, then check status
   aws iot describe-certificate --certificate-id YOUR_CERT_ID \
     --query "certificateDescription.status"
   ```

1. Check the full pipeline: IoT Core → MSK → SimulatorPreprocessor → EventDrivenTelemetryProcessor → DynamoDB/Redis. Any stopped Flink processor in this chain will break the pipeline (see [Problem: Telemetry reaching MSK but not appearing in DynamoDB](telemetry-pipeline-troubleshooting.md#problem-telemetry-not-reaching-dynamodb)).