Shell Script to write configmap - bash

Question

Looking for some help / guidance on writing a shell script to generate a configmap to use in my cluster. I wanted to write a shell script to loop through a map or dictionary of values to fill out a configmap.
Example:
apiVersion: v1
kind: ConfigMap
metadata:
annotations:
meta.helm.sh/release-name: prometheus-adapter
meta.helm.sh/release-namespace: prometheus
labels:
app.kubernetes.io/component: metrics
app.kubernetes.io/instance: prometheus-adapter
app.kubernetes.io/managed-by: Helm
app.kubernetes.io/name: prometheus-adapter
app.kubernetes.io/part-of: prometheus-adapter
app.kubernetes.io/version: v0.10.0
helm.sh/chart: prometheus-adapter-3.4.1
name: prometheus-adapter
namespace: prometheus
data:
config.yaml: |
rules:
- seriesQuery: 'haproxy_backend_http_requests_total{namespace!="", pod!="", proxy="pod1"}'
metricsQuery: 'sum(rate(haproxy_backend_http_requests_total{namespace!="", pod!="", proxy="pod1"}[2m])) by (<<.GroupBy>>)'
resources:
overrides:
namespace: {resource: "namespace"}
name:
matches: "^(.*)_total$"
# The metric we want the individual pod to match
as: "dfs_requests_per_second"
I wanted to write a shell script that adds everything from -seriesQuery and below replacing values such as the proxy="value" and the [2m] metric interval wherever that assignment variable exists.
And for each key / value pair, it would add the same block with indents. Kind of like this
pod names: [pod1, pod2]
interval: [2m, 3m]
- seriesQuery: 'haproxy_backend_http_requests_total{namespace!="", pod!="", proxy="pod1"}'
metricsQuery: 'sum(rate(haproxy_backend_http_requests_total{namespace!="", pod!="", proxy="pod1"}[2m])) by (<<.GroupBy>>)'
resources:
overrides:
namespace: {resource: "namespace"}
name:
matches: "^(.*)_total$"
# The metric we want the individual pod to match
as: "dfs_requests_per_second"
- seriesQuery: 'haproxy_backend_http_requests_total{namespace!="", pod!="", proxy="pod2"}'
metricsQuery: 'sum(rate(haproxy_backend_http_requests_total{namespace!="", pod!="", proxy="pod2"}[3m])) by (<<.GroupBy>>)'
resources:
overrides:
namespace: {resource: "namespace"}
name:
matches: "^(.*)_total$"
# The metric we want the individual pod to match
as: "dfs_requests_per_second"
And would append that to everything below
apiVersion: v1
kind: ConfigMap
metadata:
annotations:
meta.helm.sh/release-name: prometheus-adapter
meta.helm.sh/release-namespace: prometheus
labels:
app.kubernetes.io/component: metrics
app.kubernetes.io/instance: prometheus-adapter
app.kubernetes.io/managed-by: Helm
app.kubernetes.io/name: prometheus-adapter
app.kubernetes.io/part-of: prometheus-adapter
app.kubernetes.io/version: v0.10.0
helm.sh/chart: prometheus-adapter-3.4.1
name: prometheus-adapter
namespace: prometheus
data:
config.yaml: |
rules:

Answer 1

It would be preferable to use a template engine that's YAML-aware but, provided that your pod names and intervals don't contain any problematic character, then you can generate your config file easily with bash:
#!/bin/bash
pods=( pod1 pod2 )
intervals=( 2m 3m )
cat <<'EOF'
apiVersion: v1
kind: ConfigMap
metadata:
annotations:
meta.helm.sh/release-name: prometheus-adapter
meta.helm.sh/release-namespace: prometheus
labels:
app.kubernetes.io/component: metrics
app.kubernetes.io/instance: prometheus-adapter
app.kubernetes.io/managed-by: Helm
app.kubernetes.io/name: prometheus-adapter
app.kubernetes.io/part-of: prometheus-adapter
app.kubernetes.io/version: v0.10.0
helm.sh/chart: prometheus-adapter-3.4.1
name: prometheus-adapter
namespace: prometheus
data:
config.yaml: |
rules:
EOF
for i in "${!pods[#]}"
do
cat <<EOF
- seriesQuery: 'haproxy_backend_http_requests_total{namespace!="", pod!="", proxy="${pods[i]}"}'
metricsQuery: 'sum(rate(haproxy_backend_http_requests_total{namespace!="", pod!="", proxy="${pods[i]}"}[${intervals[i]}])) by (<<.GroupBy>>)'
resources:
overrides:
namespace: {resource: "namespace"}
name:
matches: "^(.*)_total$"
# The metric we want the individual pod to match
as: "dfs_requests_per_second"
EOF
done