Code change:
var outTimestamp time.Time var err error if tc.metric.singleObject != nil { <del> outReplicas, outUtilization, outTimestamp, err = replicaCalc.GetObjectMetricReplicas(tc.currentReplicas, tc.metric.targetUtilization, tc.metric.name, testNamespace, tc.metric.singleObject) </del> <ins> outReplicas, outUtilization, outTimestamp, err = replicaCalc.GetObjectMetricReplicas(tc.currentReplicas, tc.metric.targetUtilization, tc.metric.name, testNamespace, tc.metric.singleObject, selector) </ins> } else if tc.metric.selector != nil { if tc.metric.targetUtilization > 0 { <del> outReplicas, outUtilization, outTimestamp, err = replicaCalc.GetExternalMetricReplicas(tc.currentReplicas, tc.metric.targetUtilization, tc.metric.name, testNamespace, tc.metric.selector) </del> <ins> outReplicas, outUtilization, outTimestamp, err = replicaCalc.GetExternalMetricReplicas(tc.currentReplicas, tc.metric.targetUtilization, tc.metric.name, testNamespace, tc.metric.selector, selector) </ins> } else if tc.metric.perPodTargetUtilization > 0 { outReplicas, outUtilization, outTimestamp, err = replicaCalc.GetExternalPerPodMetricReplicas(tc.currentReplicas, tc.metric.perPodTargetUtilization, tc.metric.name, testNamespace, tc.metric.selector) }

Related discussion:
text: metric definition { "type": "Object", "object": { "target": { "kind": "Service", "name": "prometheus-exporter" }, "metricName": "PercentUtilization", "targetValue": "20" } } which should handle as and doesn't check Pod state.
I think proper handling of unready pods is a difficult problem that will require significant work. I suspect we may find out we need to start distinguishing pods that are booting up from pods that are 'broken' and it took us quite a while to solve analogous problem with nodes in Cluster Autoscaler (to be clear: I don't know if we will have to do that, that's just my intuition for now). That being said I agree the formula in GetObjectMetricReplicas will generally lead to scaling-up too much if the pod takes longer to initialize then backoff period in HPA (3 minutes). Assume it takes pod 4 minutes to boot up and we're currently running 2 pods. Metric value is 20 and target is 10. In this case: scales-up to 4 pods (20/10 utilization 2 pods). are starting up, they're not doing anything yet. 3 minutes later HPA scales-up to 8 pods (20/10 utilization 4 pods). If we only counted ready pods the scale-up in 3 would not occur, because the desired replicas would still be 4 (20/10 * 2). My intuition would be that this is the expected behavior of HPA. Also if there is no space in the cluster we will just keep scaling-up until we hit max replicas. The only case where current behavior would be more correct than filtering out unready pods in this formula is if someone uses a metric that is calculated based on total number of replicas. Do we advertise that as the right way to use HPA? If we add to Object metrics in 1.11 this usage pattern will stop making sense. To sum up - I think we will need to change the formula to only count ready pods at some point. I can see how current behavior could be a problem in any use-case except the one described in paragraph above. I'm inclined to agree with and provide some way to change the behavior in 1.10 (a flag or an annotation?), treating it as a bug fix.