In this lesson, you will learn how to use a web console and create a database instance in Developer Sandbox for Red Hat OpenShift. You will also learn how to create a Node.js instance from source code and bind it with the database running in OpenShift.
In order to get full benefit from this lesson, you need to:
- Understand how Kubernetes is the foundational technology for OpenShift.
- Know how to access the Developer Sandbox for Red Hat OpenShift via web browser.
- Know how to use the web console to add applications and components to OpenShift.
- Understand how environment variables provide information to an application are runtime.
In this lesson, you will:
- Install a MongoDB ephemeral database template at the command line, making it available to the web console.
- Create an instance of a database in Developer Sandbox for Red Hat OpenShift using the web console.
- Create an instance of a Node.js application from source code stored in GitHub using the web console.
- Bind the Node.js application to the database running in OpenShift.
Understand the demonstration scenario
The objective of this lesson is to demonstrate installing and running a Node.js application that is bound to a database that you will also install. Both the Node.js application and the database will run in the Developer Sandbox for Red Hat OpenShift.
The Node.js application publishes a web page that allows users to choose a name at random then store that random name in a database to which the application is bound. Also, the application web page displays a list of names stored in the database (Figure 1).
The demonstration scenario uses a MongoDB database which you’ll install using the web console. Also, you’ll install the Node.js application in OpenShift using the install from source code feature available in the web console.
The Node.js application has a server-side API that stores and retrieves data stored in the MongoDB database. Also, the Node.js application publishes a web page that is bound to the server-side API. Users interact with the web page and the web page, in turn, interacts with the server-side API (Figure 2).
The way that Node.js binds to the MongoDB database is by way of a connection URL that’s created by OpenShift during the database installation process. The URL will contain the username and password information. You’ll declare the username and password information when you install the MongoDB database.
The Node.js application references the MongoDB connection URL to create a connection to the database. The way that the Node.js application knows the connection URL is by way of an environment variable that’s created as part of the process of installing the Node.js application in the Developer Sandbox for Red Hat OpenShift.
The sections that follow demonstrate how to install the MongoDB database and install the Node.js application along with steps necessary to expose and consume the MongoDB connection URL.
Install the MongoDB ephemeral database template at the command line
Log in to your cluster at the command line. If you’re unsure how to do this, you can find instructions here: Access your Developer Sandbox for Red Hat OpenShift from the command line.
Run the following two commands to create the MongoDB ephemeral database template:
oc create -f https://raw.githubusercontent.com/openshift-labs/starter-guides/ocp-4.8/mongodb-template.yaml
oc import-image mongodb:3.6 --from=registry.access.redhat.com/rhscl/mongodb-36-rhel7 --confirm
Access the OpenShift web console using the Developer Sandbox for Red Hat OpenShift
Take the following steps to access the OpenShift web console in the Developer Sandbox for Red Hat OpenShift. You’ll do the work of installing and configuring the MongoDB and Node.js instances using the web console.
- Using your web browser, navigate here and select Start your sandbox for free (Figure 3).
- Provide the username and password for your Red Hat account (Figure 4).
Install a database using the OpenShift web console
This demonstration scenario requires that you install a MongoDB database in the Developer Sandbox for Red Hat OpenShift. You will install the database by using a template listed in the web console’s Developer Catalog:
- Click +Add on the left side of the web console (Figure 5, Callout 1).
- The Developer Catalog page will appear. Click Database (Figure 5, Callout 2).
- The web page with database text blocks will appear. Click MongoDB (Figure 5, Callout 3).
- The MongoDB template page will appear. Click Instantiate Template to expose the web page where you will enter configuration information for the MongoDB database (Figure 6, Callout 1).
genuserin the MongoDB Connection Username text box (Figure 6, Callout 2).
passwordin the MongoDB Connection Password text box (Figure 6, Callout 3).
namegenin the MongoDB Database Name text box (Figure 6, Callout 4).
passwordin the MongoDB Admin Password text box (Figure 6, Callout 5).
- Select Create (Figure 6, Callout 6).
- Executing the steps shown above will create an instance of MongoDB in the Developer Sandbox for Red Hat OpenShift. OpenShift will automatically implement the following connection URL:
- The connection URL is constructed according to the following naming pattern:
About the parameters:
usernameis the username you defined earlier when you configured the MongoDB template.
connection passwordis the password you defined earlier when you configured the MongoDB template.
service nameis the underlying Kubernetes service that is created as part of the database installation process. In this case, the service name is mongodb, which was provided by default in the MongoDB Template configuration page (Figure 7).
After you create the MongoDB instance, it will appear in the Topology view (Figure 8).
Once the MongoDB database is installed and the connection URL is known, you’re ready to install the Node.js application.
Install a Node.js application from GitHub using the web console
The following describes the steps required to install the Node.js application into the Developer Console. You will install the application using the OpenShift Install from Git feature.
- Select +Add on the left side of the web console (Figure 9, Callout 1).
- The Developer Catalog page will appear. Select the Import from Git text block (Figure 9, Callout 2).
- An Import from Git web page will appear when you click the text block (Figure 10, Callout 1). Enter the following URLinto the Git Repository URL text box:
- Scroll down the page until you come to the Application name text box (Figure 10, Callout 2) and enter the following text:
- Enter the following text (Figure 10, Callout 3) in the Name text box:
- Scroll further down the Import from Git web page to the section above the Create button. You will see an option, Build configuration. Select this option (Figure 11, Callout 1).
- The web page will expand to display a section titled Build configuration (Figure 11, Callout 2). Enter the following text in the Name text box of the section labeled Environmental variable (build and runtime):
- Enter the following text (Figure 11, Callout 3) in the Value field:
- Notice that the value of the environment variable is the connection URL to the MongoDB instance you installed previously. The environment variable is the mechanism that provides the Node.js application with the information it needs to connect to the MongoDB database.
- Select Create. This will start the process of installing the Node.js application from source code (Figure 11, Callout 4).
- Behind the scenes, OpenShift will automatically do the work of converting the source code into a Linux container that gets added to a Kubernetes pod that OpenShift also created. That pod represents the application in the Developer Sandbox for Red Hat OpenShift. Also, OpenShift will create the Kubernetes service and route that will make the application accessible on the Internet.
- The Node.js application will appear in the Topology view as a graphic with a light-blue circle. The light-blue circle means that the application is building (Figure 12).
- When the application’s build process is complete, the circle in the Node.js application graphic in Topology view will turn dark blue (Figure 13).
View the web application in a browser
Once the circle in the Topology view Node.js graphic turns dark blue, click the icon on the upper right corner of Node.js graphic. Clicking the icon will open up a window in your browser that displays the Node.js application’s web page (Figure 14).
The application is now up and running. You can exercise the application by selecting Get Random Name. An automatically generated random name will appear.
Also, the button labeled Save Name will be enabled. Click the Save Name button to add the newly created random name to List of Names.
In this lesson, you learned how to install an instance of MongoDB template in the OpenShift Catalog using the web console. You learned how to declare a database user, password, and default database during the installation process.
In addition, you learned how to use the Developer Sandbox for Red Hat OpenShift web console to install an instance of a custom application from source code in GitHub. Also, you learned how to configure the application to bind to the MongoDB database by assigning a connection URL for the MongoDB instance to an environment variable that you declared during the installation process of the custom application.
Finally, after installing the MongoDB instance and custom application in the Developer Sandbox for Red Hat OpenShift, you exercised the custom application from a browser window via its web interface.
In the next lesson, you’ll learn how to install a database and custom application that uses a database using the