last fixups

src/cockpit/channels/pcp.py

@@ -284,7 +284,7 @@ def convert_metric_description(self, context: 'pmapi.pmContext', metric: JsonObj
  pm_units = pm_desc.units
  if units:
  try:
- [pm_units, factor] = context.pmParseUnitsStr(units)
+ [parsed_units, factor] = context.pmParseUnitsStr(units)
  except pmapi.pmErr as exc:
  if exc.errno() == c_api.PM_ERR_NAME:
  raise ChannelError('not-found', message=f'no such metric: {name}') from None
@@ -293,8 +293,8 @@ def convert_metric_description(self, context: 'pmapi.pmContext', metric: JsonObj
 
  self.try_convert_unit(context, pm_desc, pm_units)
 
- if units != pm_units or factor != 1.0:
- units = pm_units
+ if units != parsed_units or factor != 1.0:
+ pm_units = parsed_units
 
  return MetricInfo(pmid=pm_ids[0],
  name=name,
@@ -373,8 +373,7 @@ def send_meta(self, results: 'pmapi.pmResult', context: 'pmapi.pmContext') -> No
  instance_desc = context.pmNameInDom(metric_desc.desc, value.inst)
  insts.append(instance_desc)
 
- if len(insts) > 0:
- desc['instances'] = insts
+ desc['instances'] = insts
 
  metrics.append(desc)
 
@@ -441,9 +440,10 @@ def sample(self, context: 'pmapi.pmContext', archive_batch: int, limit: int, tot
  self.send_meta(results, context)
  else:
  if self.needs_meta_update(results):
- # Flush all metrics and send new meta
- self.send_updates(fetched)
- fetched.clear()
+ # Flush all metrics and send new meta, but only if there is data
+ if fetched:
+ self.send_updates(fetched)
+ fetched.clear()
  self.send_meta(results, context)
 
  fetched.append(self.parse_fetched_results(context, results))

test/pytest/test_pcp.py

@@ -576,7 +576,6 @@ async def test_pcp_disk_metrics(transport, disk_metrics_archive):
  assert len(metrics) == 9
  network_metric = metrics[8]
  assert network_metric['name'] == 'network.interface.total.bytes'
- assert 'instances' not in network_metric
 
  _, data = await transport.next_frame()
  data = json.loads(data)
@@ -586,7 +585,7 @@ async def test_pcp_disk_metrics(transport, disk_metrics_archive):
  meta = json.loads(data)
  network_metric = metrics[8]
  assert network_metric['name'] == 'network.interface.total.bytes'
- assert 'instances' not in network_metric
+ assert network_metric['instances'] == []
 
  # Another meta
  assert_metrics_meta(meta, str(disk_metrics_archive), 1597663540413, 1000)