Deploying and Scaling Applications

Introduction

You can use multiple methods to deploy applications in an OpenShift cluster. This guide provides some examples. For more information, see Creating applications using the Developer perspective in the OpenShift Container Platform documentation.

Deploying application images

OpenShift supports application deployment using an image that is stored in an external image registry. Images have the necessary packages and program tools to run the applications by default.

To deploy an application that is already part of an image, complete the following steps. Unless specified otherwise, run all the commands as user core in CSAH.

1. Log in to the OpenShift cluster:

[core@csah ~]$ oc login -u <user name>

2. Create a project: 

[core@csah ~]$ oc new-project <project name>

3. Create an application:

[core@csah ~]$ oc new-app <image-name>

This guide uses openshift/hello-openshift for the image name that is being tested.

4. After the image is deployed, identify all the objects that are created as part of the deployment by running the oc get all command, as shown in the following figure:

Figure 13.     Sample application deployment status

Deploying S2I

OpenShift supports application deployment by using a source from GitHub and specifying an image. One good application example is Source-to-Image (S2I), a toolkit and workflow for building reproducible container images from source code. A build configuration is generated for the S2I deployment in a new pod called Build Pod. In the build configuration, you can configure the triggers that are required to automate the new build process every time a condition meets the specifications that you defined. After the deployment is complete, a new image with injected source code is created automatically.

Follow these steps to deploy an application using a source from GitHub. The source in the sample deployment is httpd-ex.

1. Log in to the OpenShift cluster:

[core@csah ~]$ oc login -u <user name>

2. Create a project:

[core@csah ~]$ oc new-project <project name>

3. Create an application by using the GitHub source and specifying the image of which the application will be a part:

[core@csah ~]$ oc new-app centos/httpd-24-centos7~https://github.com/sclorg/httpd-ex.git

Note: The image is centos/httpd-24-centos7. The GitHub source is https://github.com/sclorg/httpd-ex.git. You can obtain build logs by running oc logs -f bc/httpd-ex for this example.

4. After the image is deployed, identify all the objects that were created as part of the deployment by running the command oc get all:

Figure 14.     Sample S2I deployment status

5. Obtain triggers for this deployment by checking the YAML template of the build configuration:

[core@csah ~]$ oc get buildconfig httpd-ex -o yaml

Accessing applications from an external network

You can access applications that are deployed within the OpenShift cluster using images or source code from GitHub by using the service IP address that is associated with the deployments. External access to the applications is not available by default.

To enable access to the applications from an external network:

1. Log in to the OpenShift cluster:

[core@csah ~]$ oc login -u <user name>

2. Switch to the project under which the application is running:

[core@csah ~]$ oc project sample

Now using project "sample" on server "https://api.ocp.example.com:6443".

3. Identify the service that is associated with the application.

Note: Typically, the name of the service is the same as the name of the deployment.

 [core@csah ~]$ oc get svc

NAME              TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)             AGE

hello-openshift   ClusterIP   172.30.93.229   <none>        8080/TCP,8888/TCP   23m

4. Expose the route for service of your application:

[core@csah yaml]$ oc expose svc/hello-openshift

route.route.openshift.io/hello-openshift exposed

5. Obtain the routes that were created:

[core@csah ~]$ oc get routes

NAME              HOST/PORT                                     PATH   SERVICES          PORT       TERMINATION   WILDCARD

hello-openshift   hello-openshift-sample.apps.ocp.example.com          hello-openshift   8080-tcp                 None

6. Open a web browser, enter hello-openshift-sample.apps.ocp.example.com, and press Enter.
7. Repeat the preceding steps to expose the service for S2I deployment.