Include a new Kubernetes event source

This commit includes a new events source
plugin for monitoring changes in a Kubernetes cluster. This plugin enables the usage of any API class
from the Kubernetes Python client.

Closes: #36
Closes: #37

demos/dynatrace-demo/instructions.md

@@ -1,7 +1,7 @@
 # Ansible Rulebook + Dynatrace DEMO
 
 ## Description
-In this demo we will register a host to Dynatrace and set up a webhook to send
+In this demo, we will register a host to Dynatrace and set up a webhook to send
 problem notifications to ansible-rulebook CLI. Dynatrace monitors the
 availability of a process. Upon receiving a problem notification the ansible-
 rulebook CLI runs a remedy playbook to restart the process.
@@ -30,7 +30,7 @@ crashing.
 3. Update `inventory.yml` with correct ip and user to access the client node
 4. Start the rulebook CLI:
 ```
-  ansible-rulebook -i demos/dynatrace-demo/inventory.yml --rules demos/dynatrace-demo/rulebook.yml
+  ansible-rulebook -i demos/dynatrace-demo/inventory.yml -r demos/dynatrace-demo/rulebook.yml
 ```
 This rulebook starts an alertmanager source that listens on port 5050
 

demos/kubernetes/example_playbook.yml

@@ -0,0 +1,12 @@
+---
+- name: Example triggered playbook
+  hosts: localhost
+  tasks:
+    - name: Print a message
+      ansible.builtin.debug:
+        msg: |
+          We received a resource with the attributes:
+          Type: {{ type }}
+          Kind: {{ kind }}
+          ApiVersion: {{ apiversion }}
+          Name: {{ name }}

demos/kubernetes/instructions.md

@@ -0,0 +1,137 @@
+# Ansible Rulebook + Kubernetes
+
+## Description
+
+In this demo, we will configure a single-node K8s development environment,
+and we will set up ansible-rulebook CLI to consume events from the
+cluster using the Kubernetes event source. Upon triggering this watcher
+method the ansible-rulebook CLI will run a playbook to execute any additional
+action in response to this event.
+
+## Instructions
+
+### Installing a development environment
+
+The method to install a small development environment is straightforward. The reasoning
+for choosing K3D is based on the fact that GitHub actions support Ubuntu with Docker so
+the next steps can be easily integrated into a functional end-to-end GitHub actions workflow.
+
+```
+# Installing kubectl
+curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
+chmod +x ./kubectl
+sudo mv ./kubectl /usr/local/bin/kubectl
+# Installing K3D
+curl -s https://raw.githubusercontent.com/k3d-io/k3d/main/install.sh | bash
+# Creating a cluster
+k3d cluster create testcluster --api-port 6443 --servers 1 --agents 1 --port "30500-31000:30500-31000@server:0"
+# Test the cluster
+kubectl get nodes
+```
+
+### Rulebook return parameters
+
+When an event is triggered and returned, there are two keys in the
+result dictionary, `type`, and `resource`.
+
+These output parameters come from the
+[stream method](https://github.com/kubernetes-client/python/blob/master/kubernetes/base/watch/watch.py#L116)
+in the watch class monitoring for changes in the state of the cluster.
+
+The possible values of type are the types of event such as "ADDED", "DELETED", etc.
+The resource value is a dictionary representing the watched object.
+
+For example, a condition that can be monitored is:
+
+```
+condition: event.type == "ADDED" and event.resource.kind == 'Pod'
+```
+
+The previous condition will be met after there was `ADDED` a new object of the kind `Pod`.
+
+For the further implementation of additional rules, the user must know the
+representation of the watched object.
+This logic will be handled in the rulebook rules and not in the event source plugin
+enabling users to use the Python Kubernetes client without restrictions.
+
+### Monitoring resources
+
+For a better reference review the main list of APIs and methods that are
+[supported](https://github.com/kubernetes-client/python/blob/master/kubernetes/README.md).
+
+#### Monitoring for new ADDED Pods
+
+1. Have ansible-rulebook CLI and its dependencies installed
+2. Have ansible.eda collection installed with the Kubernetes event source
+3. Start the rulebook CLI:
+```
+  # Go to the Kubernetes demos folder and run:
+  ansible-rulebook -i inventory.yml -r rulebook_monitor_pods.yml
+```
+4. Once the ansible-rulebook is running, add a pod to the cluster by running:
+```
+kubectl apply -f k8s_deployment_no_namespace.yml
+```
+
+An event for the new Pod creation should be triggered and
+the `demos/kubernetes/example_playbook.yml` playbook executed.
+
+#### Monitoring for a new ADDED deployment
+
+It is possible also to monitor deployments, for instance,
+run the rulebook to check the status of the deployments:
+
+```
+ansible-rulebook -i inventory.yml -r rulebook_monitor_deployment.yml
+```
+
+Or by namespaces:
+
+```
+ansible-rulebook -i inventory.yml -r rulebook_monitor_deploymentns.yml
+```
+
+And then create the deployments:
+
+```
+kubectl apply -f k8s_deployment_no_namespace.yml
+```
+
+Or create a deployment in a namespace:
+
+```
+kubectl apply -f k8s_deployment_namespace.yml
+kubectl apply -f k8s_deployment_with_namespace.yml
+
+```
+
+#### Monitoring for a new ADDED custom resource
+
+Custom resources can be monitored also, any resource as long it has
+a valid API and method to watch for changes should work without any
+major change.
+
+Let's watch for changes in the CR.
+
+```
+ansible-rulebook -i inventory.yml -r rulebook_monitor_cr.yml
+```
+
+Create a custom resource definition with its custom object:
+```
+kubectl apply -f k8s_crontab_crd.yml
+kubectl apply -f k8s_crontab_cr.yml
+```
+
+#### Monitoring for a new ADDED config maps
+
+It is possible also for looking for changes in con
+
+```
+ansible-rulebook -i inventory.yml -r rulebook_monitor_configmaps.yml
+```
+
+Create a custom resource definition with the configmap:
+```
+kubectl apply -f k8s_configmap.yml
+```

demos/kubernetes/inventory.yml

@@ -0,0 +1,5 @@
+---
+hosts:
+  vars:
+    ansible_connection: local
+    ansible_python_interpreter: "{{ansible_playbook_python}}"

demos/kubernetes/k8s_configmap.yml

@@ -0,0 +1,8 @@
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: configmap-demo
+data:
+  parameter_1: "value_1"
+  parameter_2: "value_2"

demos/kubernetes/k8s_crontab_cr.yml

@@ -0,0 +1,7 @@
+apiVersion: "stable.example.com/v1"
+kind: CronTab
+metadata:
+  name: my-new-cron-object
+spec:
+  cronSpec: "* * * * */5"
+  image: my-awesome-cron-image

demos/kubernetes/k8s_crontab_crd.yml

@@ -0,0 +1,41 @@
+---
+apiVersion: apiextensions.k8s.io/v1
+kind: CustomResourceDefinition
+metadata:
+  # name must match the spec fields below, and be in the form: <plural>.<group>
+  name: crontabs.stable.example.com
+spec:
+  # group name to use for REST API: /apis/<group>/<version>
+  group: stable.example.com
+  # list of versions supported by this CustomResourceDefinition
+  versions:
+    - name: v1
+      # Each version can be enabled/disabled by Served flag.
+      served: true
+      # One and only one version must be marked as the storage version.
+      storage: true
+      schema:
+        openAPIV3Schema:
+          type: object
+          properties:
+            spec:
+              type: object
+              properties:
+                cronSpec:
+                  type: string
+                image:
+                  type: string
+                replicas:
+                  type: integer
+  # either Namespaced or Cluster
+  scope: Namespaced
+  names:
+    # plural name to be used in the URL: /apis/<group>/<version>/<plural>
+    plural: crontabs
+    # singular name to be used as an alias on the CLI and for display
+    singular: crontab
+    # kind is normally the CamelCased singular type. Your resource manifests use this.
+    kind: CronTab
+    # shortNames allow shorter string to match your resource on the CLI
+    shortNames:
+    - ct

demos/kubernetes/k8s_deployment_namespace.yml

@@ -0,0 +1,7 @@
+---
+kind: Namespace
+apiVersion: v1
+metadata:
+  name: nginx-deployment-namespaced
+  labels:
+    name: nginx-deployment-namespaced

demos/kubernetes/k8s_deployment_no_namespace.yml

@@ -0,0 +1,20 @@
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nginx-deployment
+spec:
+  selector:
+    matchLabels:
+      app: nginx
+  replicas: 2
+  template:
+    metadata:
+      labels:
+        app: nginx
+    spec:
+      containers:
+      - name: nginx
+        image: nginx:1.14.2
+        ports:
+        - containerPort: 80

demos/kubernetes/k8s_deployment_with_namespace.yml

@@ -0,0 +1,21 @@
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nginx-deployment-namespaced
+  namespace: nginx-deployment-namespaced
+spec:
+  selector:
+    matchLabels:
+      app: nginx
+  replicas: 2
+  template:
+    metadata:
+      labels:
+        app: nginx
+    spec:
+      containers:
+      - name: nginx
+        image: nginx:1.14.2
+        ports:
+        - containerPort: 80

demos/kubernetes/rulebook_monitor_configmaps.yml

@@ -0,0 +1,23 @@
+---
+- name: Listen for changes in a custom resource
+  hosts: localhost
+  sources:
+    - name: Check for configmaps in the cluster
+      ansible.eda.kubernetes:
+        api: CoreV1Api
+        method: list_config_map_for_all_namespaces
+        params: {}
+  rules:
+    - name: A configmap was found
+      condition: >
+        event.type == "ADDED" and
+        event.resource.kind == 'ConfigMap' and
+        event.resource.metadata.name == 'configmap-demo'
+      action:
+        run_playbook:
+          name: example_playbook.yml
+          extra_vars:
+            type: "{{ event.type }}"
+            kind: "{{ event.resource.kind }}"
+            apiversion: "{{ event.resource.apiVersion }}"
+            name: "{{ event.resource.metadata.name }}"

demos/kubernetes/rulebook_monitor_cr.yml

@@ -0,0 +1,23 @@
+---
+- name: Listen for changes in a custom resource
+  hosts: localhost
+  sources:
+    - name: Check for pods in the cluster
+      ansible.eda.kubernetes:
+        api: CustomObjectsApi
+        method: list_cluster_custom_object
+        params:
+          group: stable.example.com
+          version: v1
+          plural: crontabs
+  rules:
+    - name: A CustomResource was found
+      condition: event.type == "ADDED"
+      action:
+        run_playbook:
+          name: example_playbook.yml
+          extra_vars:
+            type: "{{ event.type }}"
+            kind: "{{ event.resource.kind }}"
+            apiversion: "{{ event.resource.apiVersion }}"
+            name: "{{ event.resource.metadata.name }}"

demos/kubernetes/rulebook_monitor_deployment.yml

@@ -0,0 +1,20 @@
+---
+- name: Listen for changes in pods on a Kubernetes cluster
+  hosts: localhost
+  sources:
+    - name: Check for deployments in the cluster
+      ansible.eda.kubernetes:
+        api: AppsV1Api
+        method: list_deployment_for_all_namespaces
+        params: {}
+  rules:
+    - name: A deployment creation was found with a name nginx-deployment
+      condition: event.type == "ADDED" and event.resource.kind == 'Deployment' and event.resource.metadata.name == 'nginx-deployment'
+      action:
+        run_playbook:
+          name: example_playbook.yml
+          extra_vars:
+            type: "{{ event.type }}"
+            kind: "{{ event.resource.kind }}"
+            apiversion: "{{ event.resource.apiVersion }}"
+            name: "{{ event.resource.metadata.name }}"

demos/kubernetes/rulebook_monitor_deploymentns.yml

@@ -0,0 +1,21 @@
+---
+- name: Listen for changes in pods on a Kubernetes cluster
+  hosts: localhost
+  sources:
+    - name: Check for deployments in the cluster
+      ansible.eda.kubernetes:
+        api: AppsV1Api
+        method: list_namespaced_deployment
+        params:
+          namespace: nginx-deployment-namespaced
+  rules:
+    - name: A deployment condition matched
+      condition: event.type == "ADDED" and event.resource.metadata.namespace == 'nginx-deployment-namespaced'
+      action:
+        run_playbook:
+          name: example_playbook.yml
+          extra_vars:
+            type: "{{ event.type }}"
+            kind: "{{ event.resource.kind }}"
+            apiversion: "{{ event.resource.apiVersion }}"
+            name: "{{ event.resource.metadata.name }}"

demos/kubernetes/rulebook_monitor_pods.yml

@@ -0,0 +1,20 @@
+---
+- name: Listen for changes in pods on a Kubernetes cluster
+  hosts: localhost
+  sources:
+    - name: Check for pods in the cluster
+      ansible.eda.kubernetes:
+        api: CoreV1Api
+        method: list_pod_for_all_namespaces
+        params: {}
+  rules:
+    - name: A pod condition was found
+      condition: event.type == "ADDED" and event.resource.kind == 'Pod'
+      action:
+        run_playbook:
+          name: example_playbook.yml
+          extra_vars:
+            type: "{{ event.type }}"
+            kind: "{{ event.resource.kind }}"
+            apiversion: "{{ event.resource.apiVersion }}"
+            name: "{{ event.resource.metadata.name }}"