Writing your first Ansible operator for OpenShift

by Keith Resar

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@KeithResar WRITING YOUR FIRST _ANSIBLE OPERATOR_ FOR OPENSHIFT

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@KeithResar Operators are _application aware Kubernetes objects._ Active throughout the application’s lifecycle, they manage instantiation, ongoing state, and destruction.

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@KeithResar FROM VISION TO _PROBLEM_

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@KeithResar _problem:_ _turnkey management of stateless application_ _solution:_ _kubernetes (we just saw this)_ _S2I, Helm_

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@KeithResar

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@KeithResar _build image from_ _source_

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@KeithResar _intra-cluster trafﬁc_ _management_

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@KeithResar _application runtime_ _conﬁguration_

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@KeithResar _external trafﬁc_

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@KeithResar

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@KeithResar _problem:_ _I’m a vendor or I create stateful apps, _kubernetes doesn’t know anything about me_

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@KeithResar etcd is a _distributed key value store_ that provides a reliable way to store data across a cluster of machines. Stand-in for your app

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@KeithResar Create and Destroy • Resize • Failover Rolling upgrade • Backup and Restore Stand-in for your app

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@KeithResar _problem:_ _I’m a vendor or I create stateful apps, _kubernetes doesn’t know anything about me_ _solution:_ _create custom resource deﬁnitions (CRD)_

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@KeithResar --- apiVersion: v1 kind: Service metadata: name: simpleapp spec: ports: - name: 8080-tcp port: 8080 protocol: TCP targetPort: 8080 selector: deploymentconfig: simpleapp sessionAffinity: None type: ClusterIP deﬁning a _service_ resource service resources are a built in object type.

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@KeithResar --- apiVersion: etcd.database.coreos.com/v1beta2 kind: EtcdCluster metadata: name: example-etcd-cluster spec: size: 3 version: "3.2.13" deﬁning an _EtcdCluster_ resource Our custom resource looks pretty similar.

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@KeithResar _problem:_ _golang isn’t going to ﬂy_ _solution:_ _skip go, succeed with helm charts or ansible_

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@KeithResar EVERY PROBLEM BRINGS A _SOLUTION_

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@KeithResar DS AS API Server Cluster Workload Compare desired state with actual state Reconcile process converges to desired state

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@KeithResar DS AS API Server 01010001 01010010 10101011 01011001 0101001 01010001 01010010 10101011 01011001 0101001 Cluster Workload 01010001 01010010 10101011 01011001 0101001 1x simpleapp 2x simpleapp 01010001 01010010 10101011 01011001 0101001

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@KeithResar DS AS API Server Cluster Workload Native K8s objects like... Pods Services Routes etc.

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@KeithResar AS DS _* operator_ watch reconcile action _________ _______________________ ______ _____________________________

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@KeithResar AS DS _Ansible operator_ watch reconcile ansible-runner _________ _______________________ ______ _____________________________ Ansible playbook or role This is the only component you need to worry about!

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@KeithResar kubernetes layer application layer

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@KeithResar kubernetes layer ETCD pod ETCD pod Phase I Manage native K8s objects application layer

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@KeithResar

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@KeithResar

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@KeithResar

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@KeithResar application layer kubernetes layer ETCD pod ETCD pod Phase II Manage application objects 01001 etcd data 01001 etcd data

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@KeithResar A GIFT OF THE _DEMO_ TO YOU

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@KeithResar Demo Operator for data service _SimpleDB,_ that manages instantiation and version upgrades. RBAC CRD CR DC

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@KeithResar Create service account, role, and role binding. Our operator uses these to monitor events and reconcile desired and actual states. RBAC CRD CR DC

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@KeithResar AS DS _Ansible operator_ watch reconcile ansible-runner _________ _______________________ ______ _____________________________

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@KeithResar RBAC CRD CR DC --- apiVersion: v1 kind: ServiceAccount metadata: name: simpledb --- apiVersion: rbac.authorization.k8s.io/v1 kind: Role metadata: name: simpledb rules: ... --- kind: RoleBinding apiVersion: rbac.authorization.k8s.io/v1 metadata: name: simpledb subjects: - kind: ServiceAccount name: simpledb roleRef: kind: Role name: simpledb apiGroup: rbac.authorization.k8s.io

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@KeithResar Deﬁne the custom resource SimpleDB. This extends what Kubernetes accepts, but doesn’t actually change any behavior. RBAC CRD CR DC

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@KeithResar RBAC CRD CR DC --- apiVersion: apiextensions.k8s.io/v1beta1 kind: CustomResourceDefinition metadata: name: simpledbs.example.com spec: group: example.com names: kind: SimpleDB listKind: SimpleDBList plural: simpledbs singular: simpledb scope: Namespaced version: v1alpha1

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@KeithResar Deﬁne and deploy the Ansible Operator container which executes an ansible-runner process. RBAC CRD CR DC

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@KeithResar AS DS _Ansible operator_ watch reconcile ansible-runner _________ _______________________ ______ _____________________________

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@KeithResar RBAC CRD CR DC --- apiVersion: apps/v1 kind: Deployment metadata: name: simpledb spec: template: spec: serviceAccountName: simpledb containers: - name: simpledb image: hk1232/operator-simpledb-runner:0.1 env: - name: WATCH_NAMESPACE valueFrom: fieldRef: fieldPath: metadata.namespace - name: OPERATOR_NAME value: "simpledb"

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@KeithResar RBAC CRD CR DC # Dockerfile FROM quay.io/water-hole/ansible-operator USER root RUN yum -y install MySQL-python && \ pip --no-cache-dir install dnspython COPY roles/ ${HOME}/roles/ COPY playbook.yaml ${HOME}/playbook.yaml COPY watches.yaml ${HOME}/watches.yaml

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@KeithResar AS DS _Ansible operator_ watch reconcile ansible-runner _________ _______________________ ______ _____________________________

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@KeithResar AS DS _Ansible operator_ watch reconcile ansible-runner _________ _______________________ ______ _____________________________

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@KeithResar RBAC CRD CR DC # watches.yml --- - version: v1alpha1 group: example.com kind: SimpleDB playbook: /opt/ansible/playbook.yaml

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@KeithResar RBAC CRD CR DC # playbook.yml --- - hosts: localhost gather_facts: no tasks: - import_role: name: "SimpleDB"

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@KeithResar RBAC CRD CR DC # roles/SimpleDB/tasks/main.yml ---

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@KeithResar RBAC CRD CR DC # roles/SimpleDB/tasks/main.yml --- # … (skip setting some variables)

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@KeithResar RBAC CRD CR DC # roles/SimpleDB/tasks/main.yml --- # … (skip setting some variables) # If no service defined then run our install playbook # This is idempotent so we could run it regardless - include_tasks: mariadb_install.yml when: mysql_ip == "NXDOMAIN" # Run our upgrade path if we need to change versions - include_tasks: mariadb_upgrade.yml when: version != version_query.json.version

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@KeithResar Deﬁne and deploy the Ansible Operator container which executes an ansible-runner process. RBAC CRD CR DC

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@KeithResar AS DS _Ansible operator_ watch reconcile ansible-runner _________ _______________________ ______ _____________________________

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@KeithResar Instantiate our custom resource object. The operator is listening for any SimpleDB events in our namespace. RBAC CRD CR DC

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@KeithResar RBAC CRD CR DC --- apiVersion: example.com/v1alpha1 kind: SimpleDB metadata: name: simpledb spec: # Add fields here version: 1

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@KeithResar GO FARTHER WITH THESE _RESOURCES_ ● Introducing the operator framework ● water-hole’s ansible-operator repo ● ansible-operator-demo repo ● Awesome operators in the wild

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@KeithResar THANKS