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Chapter 6. Using .NET Core 3.1 on OpenShift Container Platform

6.1. Installing .NET Core image streams
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To install .NET Core image streams, use image stream definitions from s2i-dotnetcore with the OpenShift Client (oc) binary. Image streams can be installed from Linux, Mac, and Windows. A script enables you to install, update or remove the image streams.

You can define .NET Core image streams in the global openshift namespace or locally in a project namespace. Sufficient permissions are required to update the openshift namespace definitions.

You can use OpenShift Client (oc) to install .NET Core image streams.

Prerequisites

Procedure

  1. List the available .NET Core image streams: 

    $ oc describe is dotnet

    The output shows installed images. If no images are installed, the Error from server (NotFound) message is displayed.

  2. Install the .NET Core image streams: 

    $ oc create -f https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/dotnet_imagestreams.json

  3. Include newer versions of existing .NET Core image streams: 

    $ oc replace -f https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/dotnet_imagestreams.json

6.1.2. Installing image streams on Linux and macOS
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You can use this script to install, upgrade, or remove the image streams on Linux and macOS.

Procedure

  1. Download the script.

    1. On Linux use: 

      $ wget https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/install-imagestreams.sh

    2. On Mac use: 

      $ curl https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/install-imagestreams.sh -o install-imagestreams.sh

  2. Make the script executable: 

    $ chmod +x install-imagestreams.sh

  3. Log in to the OpenShift cluster: 

    $ oc login

  4. Install image streams and add a pull secret for authentication against the registry.redhat.io: 

    ./install-imagestreams.sh --os rhel [--user subscription_username --password subscription_password]

    Replace subscription_username with the name of the user, and replace subscription_password with the user’s password. The credentials may be omitted if you do not plan to use the RHEL7-based images.

    If the pull secret is already present, the --user and --password arguments are ignored.

Additional information

  • ./install-imagestreams.sh --help

6.1.3. Installing image streams on Windows
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You can use this script to install, upgrade, or remove the image streams on Windows.

Procedure

  1. Download the script. 

    Invoke-WebRequest https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/install-imagestreams.ps1 -UseBasicParsing -OutFile install-imagestreams.ps1

  2. Log in to the OpenShift cluster: 

    $ oc login

  3. Install image streams and add a pull secret for authentication against the registry.redhat.io: 

    ./install-imagestreams.sh --OS rhel [-User subscription_username -Password subscription_password]

    Replace subscription_username with the name of the user, and replace subscription_password with the user’s password. The credentials may be omitted if you do not plan to use the RHEL7-based images.

    If the pull secret is already present, the -User and -Password arguments are ignored.

Note

The PowerShell ExecutionPolicy may prohibit executing this script. To relax the policy, run Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass -Force.

Additional information

  • Get-Help .\install-imagestreams.ps1

6.2. Deploying applications from source using oc
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The following example demonstrates how to deploy the example-app application using oc, which is in the app folder on the dotnetcore-3.1 branch of the redhat-developer/s2i-dotnetcore-ex GitHub repository:

Procedure

  1. Create a new OpenShift project: 

    $ oc new-project sample-project

  2. Add the ASP.NET Core application: 

    $ oc new-app --name=example-app 'dotnet:3.1~https://github.com/redhat-developer/s2i-dotnetcore-ex#dotnetcore-3.1' --build-env DOTNET_STARTUP_PROJECT=app

  3. Track the progress of the build: 

    $ oc logs -f bc/example-app

  4. View the deployed application once the build is finished: 

    $ oc logs -f dc/example-app

    The application is now accessible within the project.

  5. Optional: Make the project accessible externally: 

    $ oc expose svc/example-app

  6. Obtain the shareable URL: 

    $ oc get routes

You can use .NET Core Source-to-Image (S2I) builder image to build applications using binary artifacts that you provide.

Prerequisites

  1. Published application.

    For more information, see

Procedure

  1. Create a new binary build: 

    $ oc new-build --name=my-web-app dotnet:3.1 --binary=true

  2. Start the build and specify the path to the binary artifacts on your local machine: 

    $ oc start-build my-web-app --from-dir=bin/Release/netcoreapp3.1/publish

  3. Create a new application: 

    $ oc new-app my-web-app

6.4. Environmental variables for .NET Core 3.1
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The .NET Core images support several environment variables to control the build behavior of your .NET Core application. You can set these variables as part of the build configuration, or add them to the .s2i/environment file in the application source code repository.

Expand
Variable NameDescriptionDefault

DOTNET_STARTUP_PROJECT

Selects the project to run. This must be a project file (for example, csproj or fsproj) or a folder containing a single project file.

.

DOTNET_ASSEMBLY_NAME

Selects the assembly to run. This must not include the .dll extension. Set this to the output assembly name specified in csproj (PropertyGroup/AssemblyName).

The name of the csproj file

DOTNET_PUBLISH_READRYTORUN

When set to true, the application will be compiled ahead of time. This reduces startup time by reducing the amount of work the JIT needs to perform when the application is loading.

false

DOTNET_RESTORE_SOURCES

Specifies the space-separated list of NuGet package sources used during the restore operation. This overrides all of the sources specified in the NuGet.config file. This variable cannot be combined with DOTNET_RESTORE_CONFIGFILE.

 

DOTNET_RESTORE_CONFIGFILE

Specifies a NuGet.Config file to be used for restore operations. This variable cannot be combined with DOTNET_RESTORE_SOURCES.

 

DOTNET_TOOLS

Specifies a list of .NET tools to install before building the app. It is possible to install a specific version by post pending the package name with @<version>.

 

DOTNET_NPM_TOOLS

Specifies a list of NPM packages to install before building the application.

 

DOTNET_TEST_PROJECTS

Specifies the list of test projects to test. This must be project files or folders containing a single project file. dotnet test is invoked for each item.

 

DOTNET_CONFIGURATION

Runs the application in Debug or Release mode. This value should be either Release or Debug.

Release

DOTNET_VERBOSITY

Specifies the verbosity of the dotnet build commands. When set, the environment variables are printed at the start of the build. This variable can be set to one of the msbuild verbosity values (q[uiet], m[inimal], n[ormal], d[etailed], and diag[nostic]).

 

HTTP_PROXY, HTTPS_PROXY

Configures the HTTP or HTTPS proxy used when building and running the application, respectively.

 

DOTNET_RM_SRC

When set to true, the source code will not be included in the image.

 

DOTNET_SSL_DIRS

Specifies a list of folders or files with additional SSL certificates to trust. The certificates are trusted by each process that runs during the build and all processes that run in the image after the build (including the application that was built). The items can be absolute paths (starting with /) or paths in the source repository (for example, certificates).

 

NPM_MIRROR

Uses a custom NPM registry mirror to download packages during the build process.

 

ASPNETCORE_URLS

This variable is set to http://*:8080 to configure ASP.NET Core to use the port exposed by the image. Changing this is not recommended.

http://*:8080

DOTNET_RESTORE_DISABLE_PARALLEL

When set to true, disables restoring multiple projects in parallel. This reduces restore timeout errors when the build container is running with low CPU limits.

false

DOTNET_INCREMENTAL

When set to true, the NuGet packages will be kept so they can be re-used for an incremental build.

false

DOTNET_PACK

When set to true, creates a tar.gz file at /opt/app-root/app.tar.gz that contains the published application.

 

6.5. Creating the MVC sample application
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s2i-dotnetcore-ex is the default Model, View, Controller (MVC) template application for .NET Core.

This application is used as the example application by the .NET Core S2I image and can be created directly from the OpenShift UI using the Try Example link.

The application can also be created with the OpenShift client binary (oc).

Procedure

To create the sample application using oc:

  1. Add the .NET Core application: 

    $ oc new-app dotnet:3.1~https://github.com/redhat-developer/s2i-dotnetcore-ex#dotnetcore-3.1 --context-dir=app

  2. Make the application accessible externally: 

    $ oc expose service s2i-dotnetcore-ex

  3. Obtain the sharable URL: 

    $ oc get route s2i-dotnetcore-ex

Additional resources

6.6. Creating the CRUD sample application
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s2i-dotnetcore-persistent-ex is a simple Create, Read, Update, Delete (CRUD) .NET Core web application that stores data in a PostgreSQL database.

Procedure

To create the sample application using oc:

  1. Add the database: 

    $ oc new-app postgresql-ephemeral

  2. Add the .NET Core application: 

    $ oc new-app dotnet:3.1~https://github.com/redhat-developer/s2i-dotnetcore-persistent-ex#dotnetcore-3.1 --context-dir app

  3. Add environment variables from the postgresql secret and database service name environment variable: 

    $ oc set env dc/s2i-dotnetcore-persistent-ex --from=secret/postgresql -e database-service=postgresql

  4. Make the application accessible externally: 

    $ oc expose service s2i-dotnetcore-persistent-ex

  5. Obtain the sharable URL: 

    $ oc get route s2i-dotnetcore-persistent-ex

Additional resources

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