Kubernetes Mutating Webhook for Sidecar Injection of Prometheus Exporter Containers

This project allows you to dynamically add sidecar container for Metrics export by adding a single label inside your Pod Manifest. :mage_man: :mage_man: :mage_man:

🤫 (In reality you can add any container, just adding the right configuration you can add Exporter for Prometheus, standardize the container definition, backdoor and so on. Please use this with 🧠)

Prerequisites

• git
• go version v1.16+
• docker version 19.00+
• kubectl version v1.19.1+

Please run this command before start using this WebHook

kubectl api-versions | grep admissionregistration.k8s.io

The result should be:

admissionregistration.k8s.io/v1
admissionregistration.k8s.io/v1beta1

Working locally

1. Install all the go dependecies with go mod tidy
2. Start in local the webserver with
   go run ./src -sidecarCfgFilePath conf/exporters_configuration/config.json

## Stopping the container is based with SIGTERM or SIGKILL signal.

👾 Release it on the cluster

1. Move in the target K8s context and namespace
2. Modified the values inside Makefile for

IMAGE_REPO = YOUR_REPO_HERE
IMAGE_NAME = YOUR_IMAGE_NAME_HERE
IMAGE_TAG  = YOUR_TAG_HERE
APP		   = exporters-webhook
NAMESPACE  = YOUR_NAMESPACE
CSR_NAME   = exporters-webhook.YOUR_NAMESPACE.svc

3. Launch the command make release-chart

🚀 Or just release the chart!!

In any case you can directly use my DockerImage and use just release the chart inside the cluster. For doing so, please run the ./helm/release_chart.sh script from the root folder of the project.

🤔 How does it works?

1. Add the label exporter-injection: enabled in the PodSpec template definiton (it works also for Deployment or Pod object, check the examples.)
2. Add the label inject-exporters: value1,value2... for the exporter you want to add inside the pod definition
3. Keep in mind the fact that the exporter Split the label inject-exporters for the number of requested exporter and add it dynamically, so you can add 1 or more sidecar at the same time
4. Some exporters are defined inside the .Values.configurationMap field, if you want to add or override the exporters use this field.
5. The dataPath inside the CM must contain the config_ prefix (example: config_nginx.yaml and you will add inject-exporters: nginx for correctly retrieve the sidecarConfiguration)
6. The sidecar definition are based on the Container Struct from K8s.io. For example:

name: nginx-exporter
image: nginx/nginx-prometheus-exporter:0.4.2
ports:
  - containerPort: 9113
resources:
  requests:
    memory: 10Mi
    cpu: 10m
  limits:
    memory: 50Mi
    cpu: 200m
args: ["-nginx.scrape-uri", "http://localhost:81/nginx-status"]

😕 Throubleshooting

Sometimes you may find that pod is injected with sidecar container as expected, check the following items:

1. The sidecar-injector webhook is in running state and no error logs.
2. The namespace in which application pod is deployed has the correct labels as configured in mutatingwebhookconfiguration.
3. Check the caBundle is patched to mutatingwebhookconfiguration object by checking if caBundle fields is empty.
4. Check if the application pod has annotation exporter-injection: enabled.

Please refeer at the example inside the helm folder, files:

• test-deployment.yaml
• test-pod.yaml