# FieldSystemInterface — Troubleshooting

## Service fails to start or exits immediately

**Cause**: The config file is missing or malformed, or the DBBC host is unreachable.

**Resolution**: Check that `config.json` was rendered correctly and is mounted at
`/etc/edd/field_system_interface/config.json` inside the container. Verify network
connectivity to the DBBC host.

**Diagnostic commands**:
```bash
docker logs field_system_interface
```

---

## KATCP sensors show stale values

**Cause**: The DBBC or Mark5b connection was lost; the sensor cache TTL has expired but
reconnection failed.

**Resolution**: Check DBBC and Mark5b connectivity. Restart the service if the connection
does not recover automatically.

```bash
docker restart field_system_interface
```

---

## VDIFPacker does not start recording when a scan begins

**Cause**: The `mq_control` name in the FieldSystemInterface configuration does not match
the name in the VDIFPacker configuration.

**Resolution**: Ensure `mq_control` in both configurations refers to the same POSIX message
queue name (default `/vdif_control_message_server`).

---

## `connection refused` to DBBC port 5000

**Cause**: The DBBC hardware is not reachable from the container's network namespace, or
the DBBC control daemon is not running.

**Resolution**: Verify that the EDD host can reach the DBBC IP on port 5000:
```bash
docker exec field_system_interface nc -zv <dbbc_host> 5000
```

---

## Log locations

| Log | Location |
|---|---|
| Container stdout | `docker logs field_system_interface` |
| Config file | `/etc/edd/field_system_interface/config.json` (inside container) |