Added MetricLookback setting (influxdata#9045)

* Added MetricLookback setting

* Fixed go mod issue

plugins/inputs/vsphere/README.md

@@ -181,6 +181,12 @@ vm_metric_exclude = [ "*" ]
   ## preserve the full precision when averaging takes place.
   # use_int_samples = true
 
+  ## The number of vSphere 5 minute metric collection cycles to look back for non-realtime metrics. In 
+  ## some versions (6.7, 7.0 and possible more), certain metrics, such as cluster metrics, may be reported
+  ## with a significant delay (>30min). If this happens, try increasing this number. Please note that increasing
+  ## it too much may cause performance issues.
+  # metric_lookback = 3
+
   ## Custom attributes from vCenter can be very useful for queries in order to slice the
   ## metrics along different dimension and for forming ad-hoc relationships. They are disabled
   ## by default, since they can add a considerable amount of tags to the resulting metrics. To

plugins/inputs/vsphere/endpoint.go

@@ -29,8 +29,6 @@ var isIPv4 = regexp.MustCompile("^(?:[0-9]{1,3}\\.){3}[0-9]{1,3}$")
 
 var isIPv6 = regexp.MustCompile("^(?:[A-Fa-f0-9]{0,4}:){1,7}[A-Fa-f0-9]{1,4}$")
 
-const metricLookback = 3 // Number of time periods to look back at for non-realtime metrics
-
 const maxSampleConst = 10 // Absolute maximum number of samples regardless of period
 
 const maxMetadataSamples = 100 // Number of resources to sample for metric metadata
@@ -901,7 +899,7 @@ func (e *Endpoint) chunkify(ctx context.Context, res *resourceKind, now time.Tim
 			}
 			start, ok := e.hwMarks.Get(object.ref.Value, metricName)
 			if !ok {
-				start = latest.Add(time.Duration(-res.sampling) * time.Second * (metricLookback - 1))
+				start = latest.Add(time.Duration(-res.sampling) * time.Second * (time.Duration(e.Parent.MetricLookback) - 1))
 			}
 			start = start.Truncate(20 * time.Second) // Truncate to maximum resolution
 

plugins/inputs/vsphere/vsphere.go

@@ -48,6 +48,7 @@ type VSphere struct {
 	CustomAttributeExclude  []string
 	UseIntSamples           bool
 	IPAddresses             []string
+	MetricLookback          int
 
 	MaxQueryObjects         int
 	MaxQueryMetrics         int
@@ -237,6 +238,12 @@ var sampleConfig = `
   # custom_attribute_include = []
   # custom_attribute_exclude = ["*"]
 
+  ## The number of vSphere 5 minute metric collection cycles to look back for non-realtime metrics. In 
+  ## some versions (6.7, 7.0 and possible more), certain metrics, such as cluster metrics, may be reported
+  ## with a significant delay (>30min). If this happens, try increasing this number. Please note that increasing
+  ## it too much may cause performance issues.
+  # metric_lookback = 3
+
   ## Optional SSL Config
   # ssl_ca = "/path/to/cafile"
   # ssl_cert = "/path/to/certfile"
@@ -363,6 +370,7 @@ func init() {
 			MaxQueryMetrics:         256,
 			CollectConcurrency:      1,
 			DiscoverConcurrency:     1,
+			MetricLookback:          3,
 			ForceDiscoverOnInit:     true,
 			ObjectDiscoveryInterval: config.Duration(time.Second * 300),
 			Timeout:                 config.Duration(time.Second * 60),