pyvmomi 7.0 to call the vCenter 6.7U3,the return value collected from ESXi performance was "-1"

Describe the bug

Cu use pyvmomi 7.0 to call the vCenter 6.7U3 for ESXi host's performance data.

But sometimes,the return value was "-1". It's not a reasonable value.

--The question were:

1.What's mean with the return value "-1" ?

Was it a special flag ?

2.What's the possible reason for the the return value "-1" ?

--The code as follow:

from pyVim.connect import SmartConnectNoSSL

from pyVmomi import vim

si = SmartConnectNoSSL(host="xxx",user="xxx",pwd="xxx",port=443)

content = si.RetrieveContent()

#list of performance counter we want

perf_list = ["net.usage.average","datastore.read.average"]

#Here to collect performance data

#some code was ignored.At last the value in "perf_list" was put into "spec".

spec = vim.PerformanceManager.QuerySpec(maxSample=1,entity="xxx",metricId="xxxx",intervalId=20)

specs.append(spec)

results = content.perManager.QueryPerf(querySpec=specs)

for entity in results:

print(entity.value) #Sometimes,the output was "-1".

--

Reproduction steps

--The code as follow:

from pyVim.connect import SmartConnectNoSSL

from pyVmomi import vim



si = SmartConnectNoSSL(host="xxx",user="xxx",pwd="xxx",port=443)

content = si.RetrieveContent()



#list of performance counter

perf_list = ["net.usage.average","datastore.read.average"] 

#Here to collect performance data

#some code was ignored.At last the value in "perf_list" was put into "spec".

spec = vim.PerformanceManager.QuerySpec(maxSample=1,entity="xxx",metricId="xxxx",intervalId=20)

specs.append(spec)

results = content.perManager.QueryPerf(querySpec=specs)

for entity in results:

   print(entity.value)

Expected behavior

Cu use pyvmomi 7.0 to call the vCenter 6.7U3 for ESXi host's performance data.

Additional context

No response

Start with the pyVmomi.vim PerformanceManager.QuerySpec and QueryPerf calls shown in the issue, checking how metricId, entity, and intervalId=20 are populated. Compare the returned value with the VMware vSphere performance API documentation and a minimal reproducible query. Done means identifying whether -1 is a documented sentinel or reporting a confirmed API or binding defect with complete reproduction details.