# DigitalDownConverter — Troubleshooting

## Pipeline stuck in `configuring`

**Cause**: mkrecv cannot bind to the multicast group, or the input stream address is
unreachable.

**Resolution**: Check that the multicast group in `input_data_streams[0].ip` is reachable
from the host NIC. Verify that the packetizer is transmitting.

**Diagnostic commands**:
```bash
docker logs ddc_processor
# look for "mkrecv" bind errors or "no data received"
```

---

## `output_data_streams` count mismatch

**Cause**: `len(output_data_streams) != 2 × len(f_lo)`. The pipeline raises
`EDDPipelineError` during configure.

**Resolution**: Ensure the configuration contains exactly two output stream keys per entry
in `f_lo` (one `_lower`, one `_upper`).

---

## NUMA check failure

**Cause**: The pipeline detects that the GPU and input NIC are on different NUMA nodes,
which causes suboptimal PCIe transfers.

**Resolution**: This is a warning by default. Set `nonfatal_numacheck: true` to suppress it
if the system cannot be reconfigured. For production, ensure GPU and NIC share a NUMA node.

---

## High heap drop rate in mkrecv

**Cause**: Input buffer (`dada_nslots`) is too shallow for the incoming data rate, or the
GPU processing falls behind.

**Resolution**: Increase `dada_nslots`. Check GPU utilisation and ensure no other process
competes for GPU resources.

**Diagnostic commands**:
```bash
# inside container
dada_db -l   # list PSRDADA ring buffers and fill levels
```

---

## `output-rate` sensor reports 0

**Cause**: The pipeline has not yet reached `running` state, or `output_type` is set to
`[]`.

**Resolution**: Confirm the pipeline state via `?sensor-value pipeline-status`. Ensure
`output_type` contains at least one valid entry.

---

## Log locations

| Log | Location |
|---|---|
| Container stdout | `docker logs ddc_processor` |
| mkrecv output | included in container stdout |
| InfluxDB metrics | Grafana → dada\_monitor panel |