Unable to write config file for Prometheus on Kubernetes - kubernetes

Question

I am running prometheus on a kubernetes cluster and trying to scrape pods, nodes, services. I am getting the following error when i reload the config by sending POST request-
failed to reload config: couldn't load configuration (-config.file=/etc/prometheus/conf/prometheus.yml): unknown fields in kubernetes_sd_config: api_server
While trying to follow official docs for writing config file, I am not able to understand the relabel_configs, source_labels, target_labels, action, keep, regex part. Can somebody explain these parts and also the use of labels in prometheus. Thanks in advance.
Following is the prometheus.yml file-
scrape_configs:
- job_name: 'kubernetes-nodes'
# Default to scraping over https. If required, just disable this or change to
# `http`.
scheme: https
# This TLS & bearer token file config is used to connect to the actual scrape
# endpoints for cluster components. This is separate to discovery auth
# configuration because discovery & scraping are two separate concerns in
# Prometheus. The discovery auth config is automatic if Prometheus runs inside
# the cluster. Otherwise, more config options have to be provided within the
# <kubernetes_sd_config>.
tls_config:
ca_file: /var/run/secrets/kubernetes.io/serviceaccount/ca.crt
# If your node certificates are self-signed or use a different CA to the
# master CA, then disable certificate verification below. Note that
# certificate verification is an integral part of a secure infrastructure
# so this should only be disabled in a controlled environment. You can
# disable certificate verification by uncommenting the line below.
#
# insecure_skip_verify: true
bearer_token_file: /var/run/secrets/kubernetes.io/serviceaccount/token
kubernetes_sd_configs:
- api_server: "https://kubernetes.default.svc"
- role: node
relabel_configs:
- action: labelmap
regex: __meta_kubernetes_node_label_(.+)
- target_label: __address__
replacement: kubernetes.default.svc:443
- source_labels: [__meta_kubernetes_node_name]
regex: (.+)
target_label: __metrics_path__
replacement: /api/v1/nodes/${1}/proxy/metrics
# Scrape config for service endpoints.
#
# The relabeling allows the actual service scrape endpoint to be configured
# via the following annotations:
#
# * `prometheus.io/scrape`: Only scrape services that have a value of `true`
# * `prometheus.io/scheme`: If the metrics endpoint is secured then you will need
# to set this to `https` & most likely set the `tls_config` of the scrape config.
# * `prometheus.io/path`: If the metrics path is not `/metrics` override this.
# * `prometheus.io/port`: If the metrics are exposed on a different port to the
# service then set this appropriately.
# Example scrape config for probing services via the Blackbox Exporter.
#
# The relabeling allows the actual service scrape endpoint to be configured
# via the following annotations:
#
# * `prometheus.io/probe`: Only probe services that have a value of `true`
- job_name: 'kubernetes-services'
metrics_path: /probe
params:
module: [http_2xx]
kubernetes_sd_configs:
- api_server: "https://kubernetes.default.svc"
- role: service
relabel_configs:
- source_labels: [__meta_kubernetes_service_annotation_prometheus_io_probe]
action: keep
regex: true
- source_labels: [__address__]
target_label: __param_target
- target_label: __address__
replacement: blackbox
- source_labels: [__param_target]
target_label: instance
- action: labelmap
regex: __meta_kubernetes_service_label_(.+)
- source_labels: [__meta_kubernetes_namespace]
target_label: kubernetes_namespace
- source_labels: [__meta_kubernetes_service_name]
target_label: kubernetes_name
# Example scrape config for pods
#
# The relabeling allows the actual pod scrape endpoint to be configured via the
# following annotations:
#
# * `prometheus.io/scrape`: Only scrape pods that have a value of `true`
# * `prometheus.io/path`: If the metrics path is not `/metrics` override this.
# * `prometheus.io/port`: Scrape the pod on the indicated port instead of the
# pod's declared ports (default is a port-free target if none are declared).
- job_name: 'kubernetes-pods'
kubernetes_sd_configs:
- api_server: "https://kubernetes.default.svc"
- role: pod
relabel_configs:
- source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_scrape]
action: keep
regex: true
- source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_path]
action: replace
target_label: __metrics_path__
regex: (.+)
- source_labels: [__address__, __meta_kubernetes_pod_annotation_prometheus_io_port]
action: replace
regex: ([^:]+)(?::\d+)?;(\d+)
replacement: $1:$2
target_label: __address__
- action: labelmap
regex: __meta_kubernetes_pod_label_(.+)
- source_labels: [__meta_kubernetes_namespace]
action: replace
target_label: kubernetes_namespace
- source_labels: [__meta_kubernetes_pod_name]
action: replace
target_label: kubernetes_pod_name

Answer 1

Your yaml file is off, try this:
- job_name: 'kubernetes-services'
...
kubernetes_sd_configs:
- api_server: "https://kubernetes.default.svc"
role: service
...

Answer 2

This is the working Prometheus Configmap example file, fwiw.
https://github.com/kayrus/prometheus-kubernetes/blob/master/prometheus-configmap.yaml#L214-L241
I found that to reduce the noise of what kubectl thinks it is doing to use yamllint. If you get the config map with options yaml; when reading that file back in the kubectl command puts all the sections that are meant for data inside the data: section and it should know to ignore the other 3 sections (apiVersion, kind, and metadata)
So make sure to have only the data: section when/if you load it as a new config map.
apiVersion: v1
data:
kind: ConfigMap
metadata:
Command to get the config map
kubectl get configmap prometheus-config --namespace prometheus -o yaml > prometheus.yml
Take out all the excess comments and extra blank lines in both files (yours and the example) to save it as prometheus[#].yml then get yamllint and run it on the file(s)
yamllint -d relaxed prometheus[#].yml
Most of the time yamllint will complain lines are > 80 characters long.
If it is a JSON syntax issue then it will show up quickly.
HTH