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Chapter 4. Creating and building an application using the CLI
4.1. Before you begin
- Review About the OpenShift CLI.
- You must be able to access a running instance of OpenShift Container Platform. If you do not have access, contact your cluster administrator.
-
You must have the OpenShift CLI (
oc
) downloaded and installed.
4.2. Logging in to the CLI
You can log in to the OpenShift CLI (oc
) to access and manage your cluster.
Prerequisites
- You must have access to an OpenShift Container Platform cluster.
-
You must have installed the OpenShift CLI (
oc
).
Procedure
Log into OpenShift Container Platform from the CLI using your username and password, with an OAuth token, or with a web browser:
With username and password:
$ oc login -u=<username> -p=<password> --server=<your-openshift-server> --insecure-skip-tls-verify
With an OAuth token:
$ oc login <https://api.your-openshift-server.com> --token=<tokenID>
With a web browser:
$ oc login <cluster_url> --web
You can now create a project or issue other commands for managing your cluster.
4.3. Creating a new project
A project enables a community of users to organize and manage their content in isolation. Projects are OpenShift Container Platform extensions to Kubernetes namespaces. Projects have additional features that enable user self-provisioning.
Users must receive access to projects from administrators. Cluster administrators can allow developers to create their own projects. In most cases, users automatically have access to their own projects.
Each project has its own set of objects, policies, constraints, and service accounts.
Prerequisites
- You must have access to an OpenShift Container Platform cluster.
-
You must have installed the OpenShift CLI (
oc
).
Procedure
To create a new project, enter the following command:
$ oc new-project user-getting-started --display-name="Getting Started with OpenShift"
Example output
Now using project "user-getting-started" on server "https://openshift.example.com:6443".
Additional resources
4.4. Granting view permissions
OpenShift Container Platform automatically creates a few special service accounts in every project. The default service account takes responsibility for running the pods. OpenShift Container Platform uses and injects this service account into every pod that launches.
The following procedure creates a RoleBinding
object for the default ServiceAccount
object. The service account communicates with the OpenShift Container Platform API to learn about pods, services, and resources within the project.
Prerequisites
- You must have access to an OpenShift Container Platform cluster.
-
You must have installed the OpenShift CLI (
oc
). - You have a deployed image.
-
You must have
cluster-admin
orproject-admin
privileges.
Procedure
To add the view role to the default service account in the
user-getting-started project
, enter the following command:$ oc adm policy add-role-to-user view -z default -n user-getting-started
Additional resources
4.5. Deploying your first image
The simplest way to deploy an application in OpenShift Container Platform is to run an existing container image. The following procedure deploys a front-end component of an application called national-parks-app
. The web application displays an interactive map. The map displays the location of major national parks across the world.
Prerequisites
- You must have access to an OpenShift Container Platform cluster.
-
Install the OpenShift CLI (
oc
).
Procedure
To deploy an application, enter the following command:
$ oc new-app quay.io/openshiftroadshow/parksmap:latest --name=parksmap -l 'app=national-parks-app,component=parksmap,role=frontend,app.kubernetes.io/part-of=national-parks-app'
Example output
--> Found container image 0c2f55f (12 months old) from quay.io for "quay.io/openshiftroadshow/parksmap:latest" * An image stream tag will be created as "parksmap:latest" that will track this image --> Creating resources with label app=national-parks-app,app.kubernetes.io/part-of=national-parks-app,component=parksmap,role=frontend ... imagestream.image.openshift.io "parksmap" created deployment.apps "parksmap" created service "parksmap" created --> Success
Additional resources
4.5.1. Creating a route
External clients can access applications running on OpenShift Container Platform through the routing layer and the data object behind that is a route. The default OpenShift Container Platform router (HAProxy) uses the HTTP header of the incoming request to determine where to proxy the connection.
Optionally, you can define security, such as TLS, for the route.
Prerequisites
- You must have access to an OpenShift Container Platform cluster.
-
You must have installed the OpenShift CLI (
oc
). - You have a deployed image.
-
You must have
cluster-admin
orproject-admin
privileges.
Procedure
To retrieve the created application service, enter the following command:
$ oc get service
Example output
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE parksmap ClusterIP <your-cluster-IP> <123.456.789> 8080/TCP 8m29s
To create a route, enter the following command:
$ oc create route edge parksmap --service=parksmap
Example output
route.route.openshift.io/parksmap created
To retrieve the created application route, enter the following command:
$ oc get route
Example output
NAME HOST/PORT PATH SERVICES PORT TERMINATION WILDCARD parksmap parksmap-user-getting-started.apps.cluster.example.com parksmap 8080-tcp edge None
Additional resources
4.5.2. Examining the pod
OpenShift Container Platform leverages the Kubernetes concept of a pod, which is one or more containers deployed together on one host, and the smallest compute unit that can be defined, deployed, and managed. Pods are the rough equivalent of a machine instance, physical or virtual, to a container.
You can view the pods in your cluster and to determine the health of those pods and the cluster as a whole.
Prerequisites
- You must have access to an OpenShift Container Platform cluster.
-
You must have installed the OpenShift CLI (
oc
). - You have a deployed image.
Procedure
To list all pods with node names, enter the following command:
$ oc get pods
Example output
NAME READY STATUS RESTARTS AGE parksmap-5f9579955-6sng8 1/1 Running 0 77s
To list all pod details, enter the following command:
$ oc describe pods
Example output
Name: parksmap-848bd4954b-5pvcc Namespace: user-getting-started Priority: 0 Node: ci-ln-fr1rt92-72292-4fzf9-worker-a-g9g7c/10.0.128.4 Start Time: Sun, 13 Feb 2022 14:14:14 -0500 Labels: app=national-parks-app app.kubernetes.io/part-of=national-parks-app component=parksmap deployment=parksmap pod-template-hash=848bd4954b role=frontend Annotations: k8s.v1.cni.cncf.io/network-status: [{ "name": "openshift-sdn", "interface": "eth0", "ips": [ "10.131.0.14" ], "default": true, "dns": {} }] k8s.v1.cni.cncf.io/network-status: [{ "name": "openshift-sdn", "interface": "eth0", "ips": [ "10.131.0.14" ], "default": true, "dns": {} }] openshift.io/generated-by: OpenShiftNewApp openshift.io/scc: restricted Status: Running IP: 10.131.0.14 IPs: IP: 10.131.0.14 Controlled By: ReplicaSet/parksmap-848bd4954b Containers: parksmap: Container ID: cri-o://4b2625d4f61861e33cc95ad6d455915ea8ff6b75e17650538cc33c1e3e26aeb8 Image: quay.io/openshiftroadshow/parksmap@sha256:89d1e324846cb431df9039e1a7fd0ed2ba0c51aafbae73f2abd70a83d5fa173b Image ID: quay.io/openshiftroadshow/parksmap@sha256:89d1e324846cb431df9039e1a7fd0ed2ba0c51aafbae73f2abd70a83d5fa173b Port: 8080/TCP Host Port: 0/TCP State: Running Started: Sun, 13 Feb 2022 14:14:25 -0500 Ready: True Restart Count: 0 Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-6f844 (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: kube-api-access-6f844: Type: Projected (a volume that contains injected data from multiple sources) TokenExpirationSeconds: 3607 ConfigMapName: kube-root-ca.crt ConfigMapOptional: <nil> DownwardAPI: true ConfigMapName: openshift-service-ca.crt ConfigMapOptional: <nil> QoS Class: BestEffort Node-Selectors: <none> Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s node.kubernetes.io/unreachable:NoExecute op=Exists for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 46s default-scheduler Successfully assigned user-getting-started/parksmap-848bd4954b-5pvcc to ci-ln-fr1rt92-72292-4fzf9-worker-a-g9g7c Normal AddedInterface 44s multus Add eth0 [10.131.0.14/23] from openshift-sdn Normal Pulling 44s kubelet Pulling image "quay.io/openshiftroadshow/parksmap@sha256:89d1e324846cb431df9039e1a7fd0ed2ba0c51aafbae73f2abd70a83d5fa173b" Normal Pulled 35s kubelet Successfully pulled image "quay.io/openshiftroadshow/parksmap@sha256:89d1e324846cb431df9039e1a7fd0ed2ba0c51aafbae73f2abd70a83d5fa173b" in 9.49243308s Normal Created 35s kubelet Created container parksmap Normal Started 35s kubelet Started container parksmap
Additional resources
4.5.3. Scaling the application
In Kubernetes, a Deployment
object defines how an application deploys. In most cases, users use Pod
, Service
, ReplicaSets
, and Deployment
resources together. In most cases, OpenShift Container Platform creates the resources for you.
When you deploy the national-parks-app
image, a deployment resource is created. In this example, only one Pod
is deployed.
The following procedure scales the national-parks-image
to use two instances.
Prerequisites
- You must have access to an OpenShift Container Platform cluster.
-
You must have installed the OpenShift CLI (
oc
). - You have a deployed image.
Procedure
To scale your application from one pod instance to two pod instances, enter the following command:
$ oc scale --current-replicas=1 --replicas=2 deployment/parksmap
Example output
deployment.apps/parksmap scaled
Verification
To ensure that your application scaled properly, enter the following command:
$ oc get pods
Example output
NAME READY STATUS RESTARTS AGE parksmap-5f9579955-6sng8 1/1 Running 0 7m39s parksmap-5f9579955-8tgft 1/1 Running 0 24s
To scale your application back down to one pod instance, enter the following command:
$ oc scale --current-replicas=2 --replicas=1 deployment/parksmap
Additional resources
4.6. Deploying a Python application
The following procedure deploys a back-end service for the parksmap
application. The Python application performs 2D geo-spatial queries against a MongoDB database to locate and return map coordinates of all national parks in the world.
The deployed back-end service is nationalparks
.
Prerequisites
- You must have access to an OpenShift Container Platform cluster.
-
You must have installed the OpenShift CLI (
oc
). - You have a deployed image.
Procedure
To create a new Python application, enter the following command:
$ oc new-app python~https://github.com/openshift-roadshow/nationalparks-py.git --name nationalparks -l 'app=national-parks-app,component=nationalparks,role=backend,app.kubernetes.io/part-of=national-parks-app,app.kubernetes.io/name=python' --allow-missing-images=true
Example output
--> Found image 0406f6c (13 days old) in image stream "openshift/python" under tag "3.9-ubi9" for "python" Python 3.9 ---------- Python 3.9 available as container is a base platform for building and running various Python 3.9 applications and frameworks. Python is an easy to learn, powerful programming language. It has efficient high-level data structures and a simple but effective approach to object-oriented programming. Python's elegant syntax and dynamic typing, together with its interpreted nature, make it an ideal language for scripting and rapid application development in many areas on most platforms. Tags: builder, python, python39, python-39, rh-python39 * A source build using source code from https://github.com/openshift-roadshow/nationalparks-py.git will be created * The resulting image will be pushed to image stream tag "nationalparks:latest" * Use 'oc start-build' to trigger a new build --> Creating resources with label app=national-parks-app,app.kubernetes.io/name=python,app.kubernetes.io/part-of=national-parks-app,component=nationalparks,role=backend ... imagestream.image.openshift.io "nationalparks" created buildconfig.build.openshift.io "nationalparks" created deployment.apps "nationalparks" created service "nationalparks" created --> Success
To create a route to expose your application,
nationalparks
, enter the following command:$ oc create route edge nationalparks --service=nationalparks
Example output
route.route.openshift.io/parksmap created
To retrieve the created application route, enter the following command:
$ oc get route
Example output
NAME HOST/PORT PATH SERVICES PORT TERMINATION WILDCARD nationalparks nationalparks-user-getting-started.apps.cluster.example.com nationalparks 8080-tcp edge None parksmap parksmap-user-getting-started.apps.cluster.example.com parksmap 8080-tcp edge None
Additional resources
4.7. Connecting to a database
Deploy and connect a MongoDB database where the national-parks-app
application stores location information. Once you mark the national-parks-app
application as a backend for the map visualization tool, parksmap
deployment uses the OpenShift Container Platform discover mechanism to display the map automatically.
Prerequisites
- You must have access to an OpenShift Container Platform cluster.
-
You must have installed the OpenShift CLI (
oc
). - You have a deployed image.
Procedure
To connect to a database, enter the following command:
$ oc new-app quay.io/centos7/mongodb-36-centos7 --name mongodb-nationalparks -e MONGODB_USER=mongodb -e MONGODB_PASSWORD=mongodb -e MONGODB_DATABASE=mongodb -e MONGODB_ADMIN_PASSWORD=mongodb -l 'app.kubernetes.io/part-of=national-parks-app,app.kubernetes.io/name=mongodb'
Example output
--> Found container image dc18f52 (8 months old) from quay.io for "quay.io/centos7/mongodb-36-centos7" MongoDB 3.6 ----------- MongoDB (from humongous) is a free and open-source cross-platform document-oriented database program. Classified as a NoSQL database program, MongoDB uses JSON-like documents with schemas. This container image contains programs to run mongod server. Tags: database, mongodb, rh-mongodb36 * An image stream tag will be created as "mongodb-nationalparks:latest" that will track this image --> Creating resources with label app.kubernetes.io/name=mongodb,app.kubernetes.io/part-of=national-parks-app ... imagestream.image.openshift.io "mongodb-nationalparks" created deployment.apps "mongodb-nationalparks" created service "mongodb-nationalparks" created --> Success
Additional resources
4.7.1. Creating a secret
The Secret
object provides a mechanism to hold sensitive information such as passwords, OpenShift Container Platform client configuration files, private source repository credentials, and so on. Secrets decouple sensitive content from the pods. You can mount secrets into containers using a volume plugin or the system can use secrets to perform actions on behalf of a pod. The following procedure adds the secret nationalparks-mongodb-parameters
and mounts it to the nationalparks
workload.
Prerequisites
- You must have access to an OpenShift Container Platform cluster.
-
You must have installed the OpenShift CLI (
oc
). - You have a deployed image.
Procedure
To create a secret, enter the following command:
$ oc create secret generic nationalparks-mongodb-parameters --from-literal=DATABASE_SERVICE_NAME=mongodb-nationalparks --from-literal=MONGODB_USER=mongodb --from-literal=MONGODB_PASSWORD=mongodb --from-literal=MONGODB_DATABASE=mongodb --from-literal=MONGODB_ADMIN_PASSWORD=mongodb
Example output
secret/nationalparks-mongodb-parameters created
To update the environment variable to attach the mongodb secret to the
nationalpartks
workload, enter the following command:$ oc set env --from=secret/nationalparks-mongodb-parameters deploy/nationalparks
Example output
deployment.apps/nationalparks updated
To show the status of the
nationalparks
deployment, enter the following command:$ oc rollout status deployment nationalparks
Example output
deployment "nationalparks" successfully rolled out
To show the status of the
mongodb-nationalparks
deployment, enter the following command:$ oc rollout status deployment mongodb-nationalparks
Example output
deployment "nationalparks" successfully rolled out deployment "mongodb-nationalparks" successfully rolled out
Additional resources
4.7.2. Loading data and displaying the national parks map
You deployed the parksmap
and nationalparks
applications and then deployed the mongodb-nationalparks
database. However, no data has been loaded into the database.
Prerequisites
- You must have access to an OpenShift Container Platform cluster.
-
You must have installed the OpenShift CLI (
oc
). - You have a deployed image.
Procedure
To load national parks data, enter the following command:
$ oc exec $(oc get pods -l component=nationalparks | tail -n 1 | awk '{print $1;}') -- curl -s http://localhost:8080/ws/data/load
Example output
"Items inserted in database: 2893"
To verify that your data is loaded properly, enter the following command:
$ oc exec $(oc get pods -l component=nationalparks | tail -n 1 | awk '{print $1;}') -- curl -s http://localhost:8080/ws/data/all
Example output (trimmed)
, {"id": "Great Zimbabwe", "latitude": "-20.2674635", "longitude": "30.9337986", "name": "Great Zimbabwe"}]
To add labels to the route, enter the following command:
$ oc label route nationalparks type=parksmap-backend
Example output
route.route.openshift.io/nationalparks labeled
To retrieve your routes to view your map, enter the following command:
$ oc get routes
Example output
NAME HOST/PORT PATH SERVICES PORT TERMINATION WILDCARD nationalparks nationalparks-user-getting-started.apps.cluster.example.com nationalparks 8080-tcp edge None parksmap parksmap-user-getting-started.apps.cluster.example.com parksmap 8080-tcp edge None
Copy and paste the
HOST/PORT
path you retrieved above into your web browser. Your browser should display a map of the national parks across the world.Figure 4.1. National parks across the world