The Elasticsearch adapter for the K8S metrics APIs is an implementation of the Kubernetes resource metrics and custom metrics APIs.
It can be used to automatically scale applications, using the Horizontal Pod Autoscaler querying metrics collected by Metricbeat or Agent, and stored in Elasticsearch.
This adapter is currently considered as experimental, and is thus not yet fully supported in production by Elastic. We'd love to get your feedback for any issues or contributions, in the form of issues in this repository.
Refer to helm/README.md to configure and deploy the metrics adapter to your Kubernetes cluster.
The metricSets section contains the information required to discover the metrics exposed by the adapter:
metricSets:
- indices: [ 'metricbeat-*' ] # set of regular expressions to list the indices to be searched
fields:
- patterns: [ '^prometheus\.metrics\.' ] # set of regular expressions to list the fields exposed as metrics by the server
- patterns: [ '^kibana\.stats\.' ] # because we need Kibana metrics for the example belowComplex metrics can be calculated using a custom query, for example:
- name: "my-computed-metric" # name of the metric as it will be exposed to Kubernetes
search: # This is an example of an advanced custom search, calculated using an aggregation.
metricPath: ".aggregations.custom_name.buckets.[0].pod_load.value" # Path to the metric value.
timestampPath: ".aggregations.custom_name.buckets.[0].timestamp.value_as_string" # Path to the timestamp.
body: >
{
"query": {
... your query ...
},
"size": 0,
"aggs": {
"custom_name": {
"terms": {
"field": "kibana.stats.name"
},
"aggs": {
"pods_count": {
"cardinality": {
"field": "kubernetes.pod.name"
}
},
"maxLoad": {
"max": {
"field": "kibana.stats.load"
}
},
"timestamp": {
"max": {
"field": "@timestamp"
}
},
"pod_load": {
"bucket_script": {
"buckets_path": {
"load": "maxLoad"
},
"script": "params.load / {{ len .Objects }}"
}
}
}
}
}
}The body field must contain a valid Elasticsearch query. metricPath and timestampPath must contain valid JQ queries used to get the metric value and the timestamp from the Elasticsearch response.
You may want to also serve some metrics from an existing third party metric server like Prometheus or Stackdriver. This can be done by adding the third party adapter API endpoint to the metricServers list:
## Metric server of type "custom" can be used to reference an existing or third party metric adapter service.
metricServers:
- name: my-existing-metrics-adapter
serverType: custom # To be used to forward metric requests to a server which complies with https://github.com/kubernetes/metrics
clientConfig:
host: https://custom-metrics-apiserver.custom-metrics.svc
tls:
insecureSkipTLSVerify: trueThe example below assumes that:
- Your Kubernetes cluster is running Elastic Cloud on Kubernetes 1.7.0 (or later) which implements the
/scaleendpoint on Kibana. - A
Kibanaresource namedkibana-exampleis deployed. - Kibana metrics are collected using the Metricbeat Kibana module and stored in an Elasticsearch cluster.
⚠️ Metrics collected by Metricbeat must be sent tometricbeat-*indices,xpack.enabledmust be set to its default value:false
The example below shows how an HorizontalPodAutoscaler resource can be created to scale the aforementioned Kibana automatically according to the average number of concurrent connections:
apiVersion: autoscaling/v2beta2
kind: HorizontalPodAutoscaler
metadata:
name: kibana-hpa-example
namespace: my-namespace
spec:
minReplicas: 1
maxReplicas: 3
metrics:
- type: Pods
pods:
metric:
name: kibana.stats.concurrent_connections
target:
type: AverageValue
averageValue: 42
scaleTargetRef:
apiVersion: kibana.k8s.elastic.co/v1
kind: Kibana
name: kibana-example
behavior:
scaleDown:
stabilizationWindowSeconds: 5The Kubernetes Horizontal Pod Autoscaler is now able to scale Kibana to ensure that each Pod has at most 42 (as an average) concurrent connections:
% kubectl get hpa -w
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
kibana-hpa-example Kibana/kibana-example 12/42 1 3 1 17s
kibana-hpa-example Kibana/kibana-example 49/42 1 3 1 63s
kibana-hpa-example Kibana/kibana-example 49/42 1 3 2 80s
kibana-hpa-example Kibana/kibana-example 26/42 1 3 2 112s
kibana-hpa-example Kibana/kibana-example 104500m/42 1 3 3 2m23s
kibana-hpa-example Kibana/kibana-example 13/42 1 3 1 3m26sYou can call the Custom Metrics API from your local workstation to check what metrics are exposed and their current values.
In a first terminal start the kubectl proxy command:
% kubectl proxy
Starting to serve on 127.0.0.1:8001
From another terminal (or from your favorite API client) you can now run the following commands.
% curl http://127.0.0.1:8001/apis/custom.metrics.k8s.io/v1beta2/{
"kind": "APIResourceList",
"apiVersion": "v1",
"groupVersion": "custom.metrics.k8s.io/v1beta2",
"resources": [
{
"name": "pods/system.memory.hugepages.total",
"singularName": "",
"namespaced": true,
"kind": "MetricValueList",
"verbs": [
"get"
]
},
{
"name": "pods/aws.rds.storage_used.backup_retention_period.bytes",
"singularName": "",
"namespaced": true,
"kind": "MetricValueList",
"verbs": [
"get"
]
},
{
"name": "pods/postgresql.bgwriter.buffers.clean",
"singularName": "",
"namespaced": true,
"kind": "MetricValueList",
"verbs": [
"get"
]
},
[...]Metrics are requested by the Kubernetes control plane using 3 parameters:
- The name of the metric.
- The namespace in which the
Podsare running. - A label selector to retrieve the list of Pods.
You can run the following command to get the value of the metric kibana.stats.concurrent_connections for all the Pods that match the label selector common.k8s.elastic.co/type=kibana,kibana.k8s.elastic.co/name=kb in namespace my-ns:
% curl 'http://127.0.0.1:8001/apis/custom.metrics.k8s.io/v1beta2/namespaces/my-ns/pods/*/kibana.stats.concurrent_connections?labelSelector=common.k8s.elastic.co%2Ftype%3Dkibana%2Ckibana.k8s.elastic.co%2Fname%3Dkb'{
"kind": "MetricValueList",
"apiVersion": "custom.metrics.k8s.io/v1beta2",
"metadata": {},
"items": [
{
"describedObject": {
"kind": "Pod",
"namespace": "my-ns",
"name": "kb-background-tasks-kb-dcfff65c9-qxbw2",
"apiVersion": "/v1"
},
"metric": {
"name": "kibana.stats.concurrent_connections",
"selector": null
},
"timestamp": "2023-04-03T09:20:48Z",
"value": "10"
},
{
"describedObject": {
"kind": "Pod",
"namespace": "my-ns",
"name": "kb-ui-kb-77764d6f59-75hqz",
"apiVersion": "/v1"
},
"metric": {
"name": "kibana.stats.concurrent_connections",
"selector": null
},
"timestamp": "2023-04-03T09:20:46Z",
"value": "10"
}
]
}The describe API on the HorizontalPodAutoscaler is a good starting point to understand the behaviour or the root cause of an issue with the adapter.
% kubectl describe hpa kibana-hpa-example
Name: kibana-hpa-example
Namespace: stack-monitoring
Reference: Kibana/kibana-example
Metrics: ( current / target )
"kibana.stats.concurrent_connections" on pods: 13 / 42
Min replicas: 1
Max replicas: 3
Behavior:
Scale Up:
Stabilization Window: 0 seconds
Select Policy: Max
Policies:
- Type: Pods Value: 4 Period: 15 seconds
- Type: Percent Value: 100 Period: 15 seconds
Scale Down:
Stabilization Window: 5 seconds
Select Policy: Max
Policies:
- Type: Percent Value: 100 Period: 15 seconds
Kibana pods: 1 current / 1 desired
Conditions:
Type Status Reason Message
---- ------ ------ -------
AbleToScale True ReadyForNewScale recommended size matches current size
ScalingActive True ValidMetricFound the HPA was able to successfully calculate a replica count from pods metric kibana.stats.concurrent_connections
ScalingLimited False DesiredWithinRange the desired count is within the acceptable range
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal SuccessfulRescale 3m20s horizontal-pod-autoscaler New size: 2; reason: pods metric kibana.stats.concurrent_connections above target
Warning FailedGetPodsMetric 3m3s horizontal-pod-autoscaler unable to get metric kibana.stats.concurrent_connections: unable to fetch metrics from custom metrics API: no documents in map[_shards:map[failed:0 skipped:0 successful:1 total:1] hits:map[hits:[] max_score:<nil> total:map[relation:eq value:0]] timed_out:false took:45]
Warning FailedComputeMetricsReplicas 3m3s horizontal-pod-autoscaler failed to compute desired number of replicas based on listed metrics for Kibana/stack-monitoring/kibana: invalid metrics (1 invalid out of 1), first error is: failed to get pods metric value: unable to get metric kibana.stats.concurrent_connections: unable to fetch metrics from custom metrics API: no documents in map[_shards:map[failed:0 skipped:0 successful:1 total:1] hits:map[hits:[] max_score:<nil> total:map[relation:eq value:0]] timed_out:false took:45]
Normal SuccessfulRescale 2m17s horizontal-pod-autoscaler New size: 3; reason: pods metric kibana.stats.concurrent_connections above target
Warning FailedGetPodsMetric 105s (x2 over 2m) horizontal-pod-autoscaler unable to get metric kibana.stats.concurrent_connections: unable to fetch metrics from custom metrics API: no documents in map[_shards:map[failed:0 skipped:0 successful:1 total:1] hits:map[hits:[] max_score:<nil> total:map[relation:eq value:0]] timed_out:false took:0]
Warning FailedComputeMetricsReplicas 105s (x2 over 2m) horizontal-pod-autoscaler failed to compute desired number of replicas based on listed metrics for Kibana/stack-monitoring/kibana: invalid metrics (1 invalid out of 1), first error is: failed to get pods metric value: unable to get metric kibana.stats.concurrent_connections: unable to fetch metrics from custom metrics API: no documents in map[_shards:map[failed:0 skipped:0 successful:1 total:1] hits:map[hits:[] max_score:<nil> total:map[relation:eq value:0]] timed_out:false took:0]
Normal SuccessfulRescale 74s horizontal-pod-autoscaler New size: 1; reason: All metrics below targetNote that FailedGetPodsMetric or FailedComputeMetricsReplicas events may happen when the resource is being scaled up or scaled down.
Logs can be retrieved with the following command:
% kubectl logs -n elasticsearch-custom-metrics -l app=custom-metrics-apiserver
I0328 10:49:47.017359 1 provider.go:172] ListAllMetrics()
I0328 10:49:47.017699 1 httplog.go:89] "HTTP" verb="GET" URI="/apis/custom.metrics.k8s.io/v1beta2?timeout=32s" latency="3.901543ms" userAgent="kube-controller-manager/v1.18.14 (linux/amd64) kubernetes/44dfef4/system:serviceaccount:kube-system:resourcequota-controller" srcIP="10.28.112.1:51876" resp=200
I0328 10:49:47.065831 1 provider.go:172] ListAllMetrics()
I0328 10:49:47.066100 1 httplog.go:89] "HTTP" verb="GET" URI="/apis/custom.metrics.k8s.io/v1beta1?timeout=32s" latency="3.088834ms" userAgent="kube-controller-manager/v1.18.14 (linux/amd64) kubernetes/44dfef4/system:serviceaccount:kube-system:resourcequota-controller" srcIP="10.28.80.5:33018" resp=200
I0328 10:49:51.540363 1 provider.go:172] ListAllMetrics()
I0328 10:49:51.540363 1 provider.go:172] ListAllMetrics()
I0328 10:49:51.540782 1 httplog.go:89] "HTTP" verb="GET" URI="/apis/custom.metrics.k8s.io/v1beta2?timeout=32s" latency="4.749705ms" userAgent="kubectl/openshift (darwin/amd64) kubernetes/ffd6836" srcIP="10.28.112.1:51876" resp=200
I0328 10:49:51.540878 1 httplog.go:89] "HTTP" verb="GET" URI="/apis/custom.metrics.k8s.io/v1beta1?timeout=32s" latency="4.628104ms" userAgent="kubectl/openshift (darwin/amd64) kubernetes/ffd6836" srcIP="10.28.80.5:33018" resp=200
time="2021-03-28T10:49:55Z" level=info msg="GetMetricBySelector(namespace=stack-monitoring,selector=common.k8s.elastic.co/type=kibana,kibana.k8s.elastic.co/name=kibana-example,info=pods/kibana.stats.concurrent_connections(namespaced),metricSelector=)"
I0328 10:49:55.302521 1 httplog.go:89] "HTTP" verb="GET" URI="/apis/custom.metrics.k8s.io/v1beta2/namespaces/stack-monitoring/pods/%2A/kibana.stats.concurrent_connections?labelSelector=common.k8s.elastic.co%2Ftype%3Dkibana%2Ckibana.k8s.elastic.co%2Fname%3Dkibana-example" latency="34.605841ms" userAgent="vpa-recommender/v0.0.0 (linux/amd64) kubernetes/$Format/kuba-horizontal-pod-autoscaler" srcIP="10.28.80.4:50544" resp=200Verbosity can be increased with the --v flag:
...
containers:
- name: custom-metrics-apiserver
args:
- /adapter
- --secure-port=6443
- --logtostderr=true
- --v=9
...