Applications

To create applications, you must have created a project or have access to a project with the appropriate roles and permissions. You can create an application by using either the Developer perspective in the web console, installed Operators, or the OpenShift Container Platform CLI. You can source the applications to be added to the project from Git, JAR files, devfiles, or the developer catalog.

You can also use components that include source or binary code, images, and templates to create an application by using the OpenShift Container Platform CLI. With the OpenShift Container Platform web console, you can create an application from an Operator installed by a cluster administrator.

After you create the application you can use the web console to monitor your project or application metrics. You can also edit or delete the application using the web console. When the application is running, not all applications resources are used. As a cluster administrator, you can choose to idle these scalable resources to reduce resource consumption.

You can deploy your application using Deployment or DeploymentConfig objects and manage them from the web console. You can create deployment strategies that help reduce downtime during a change or an upgrade to the application.

You can also use Helm, a software package manager that simplifies deployment of applications and services to OpenShift Container Platform clusters.

If allowed by your cluster administrator, you can create a new project.

You can use the Developer perspective in the OpenShift Container Platform web console to create a project in your cluster.

If allowed by your cluster administrator, you can create a new project.

When viewing projects, you are restricted to seeing only the projects you have access to view based on the authorization policy.

You can use the Project view in the Developer perspective to grant or revoke access permissions to your project.

You can also use:

You can delete a project by using the OpenShift Container Platform web console.

When you delete a project, the server updates the project status to Terminating from Active. Then, the server clears all content from a project that is in the Terminating state before finally removing the project. While a project is in Terminating status, you cannot add new content to the project. Projects can be deleted from the CLI or the web console.

You can configure a request to the OpenShift Container Platform API to act as though it originated from another user. For more information, see User impersonation in the Kubernetes documentation.

You can impersonate a different user when you create a project request. Because system:authenticated:oauth is the only bootstrap group that can create project requests, you must impersonate that group.

The OpenShift Container Platform API server automatically provisions new projects based on the project template that is identified by the projectRequestTemplate parameter in the cluster’s project configuration resource. If the parameter is not defined, the API server creates a default template that creates a project with the requested name, and assigns the requesting user to the admin role for that project.

When a project request is submitted, the API substitutes the following parameters into the template:

Access to the API is granted to developers with the self-provisioner role and the self-provisioners cluster role binding. This role is available to all authenticated developers by default.

As a cluster administrator, you can modify the default project template so that new projects are created using your custom requirements.

To create your own custom project template:

You can prevent an authenticated user group from self-provisioning new projects.

When a developer or a service account that is unable to self-provision projects makes a project creation request using the web console or CLI, the following error message is returned by default:

You may not request a new project via this API.

Cluster administrators can customize this message. Consider updating it to provide further instructions on how to request a new project specific to your organization. For example:

To customize the project request message:

To create applications using the Developer perspective ensure that:

To create serverless applications, in addition to the preceding prerequisites, ensure that:

You can use the basic sample applications in the +Add flow of the Developer perspective to create, build, and deploy applications quickly.

The following procedure explains the Samples option in the Developer perspective to create a sample application.

You can use the Developer perspective to create, build, and deploy an application on OpenShift Container Platform using an existing codebase in GitHub.

The following procedure walks you through the From Git option in the Developer perspective to create an application.

You use the Developer Catalog to deploy applications and services based on Operator backed services such as Databases, Builder Images, and Helm Charts. The Developer Catalog contains a collection of application components, services, event sources, or source-to-image builders that you can add to your project. Cluster administrators can customize the content made available in the catalog.

This procedure walks through creating a new etcd cluster using the etcd Operator, managed by Operator Lifecycle Manager (OLM).

You now have an etcd cluster that will react to failures and rebalance data as pods become unhealthy or are migrated between nodes in the cluster. Most importantly, cluster administrators or developers with proper access can now easily use the database with their applications.

With the new-app command you can create applications from source code in a local or remote Git repository.

The new-app command creates a build configuration, which itself creates a new application image from your source code. The new-app command typically also creates a Deployment object to deploy the new image, and a service to provide load-balanced access to the deployment running your image.

OpenShift Container Platform automatically detects whether the pipeline or source build strategy should be used, and in the case of source builds, detects an appropriate language builder image.

$ oc new-app /<path to source code>

$ oc new-app https://github.com/sclorg/cakephp-ex

$ oc new-app https://github.com/youruser/yourprivaterepo --source-secret=yoursecret

$ oc new-app https://github.com/sclorg/s2i-ruby-container.git \
    --context-dir=2.0/test/puma-test-app

$ oc new-app https://github.com/openshift/ruby-hello-world.git#beta4

$ oc new-app /home/user/code/myapp --strategy=docker

$ oc new-app myproject/my-ruby~https://github.com/openshift/ruby-hello-world.git

$ oc new-app openshift/ruby-20-centos7:latest~/home/user/code/my-ruby-app

You can deploy an application from an existing image. Images can come from image streams in the OpenShift Container Platform server, images in a specific registry, or images in the local Docker server.

The new-app command attempts to determine the type of image specified in the arguments passed to it. However, you can explicitly tell new-app whether the image is a container image using the --docker-image argument or an image stream using the -i|--image-stream argument.

$ oc new-app mysql

$ oc new-app myregistry:5000/example/myimage

$ oc new-app my-stream:v1

You can create an application from a previously stored template or from a template file, by specifying the name of the template as an argument. For example, you can store a sample application template and use it to create an application.

Upload an application template to your current project’s template library. The following example uploads an application template from a file called examples/sample-app/application-template-stibuild.json:

$ oc create -f examples/sample-app/application-template-stibuild.json

Then create a new application by referencing the application template. In this example, the template name is ruby-helloworld-sample:

$ oc new-app ruby-helloworld-sample

To create a new application by referencing a template file in your local file system, without first storing it in OpenShift Container Platform, use the -f|--file argument. For example:

$ oc new-app -f examples/sample-app/application-template-stibuild.json

$ oc new-app ruby-helloworld-sample \
    -p ADMIN_USERNAME=admin -p ADMIN_PASSWORD=mypassword

ADMIN_USERNAME=admin
ADMIN_PASSWORD=mypassword

$ oc new-app ruby-helloworld-sample --param-file=helloworld.params

The new-app command generates OpenShift Container Platform objects that build, deploy, and run the application that is created. Normally, these objects are created in the current project and assigned names that are derived from the input source repositories or the input images. However, with new-app you can modify this behavior.

$ oc new-app openshift/postgresql-92-centos7 \
    -e POSTGRESQL_USER=user \
    -e POSTGRESQL_DATABASE=db \
    -e POSTGRESQL_PASSWORD=password

POSTGRESQL_USER=user
POSTGRESQL_DATABASE=db
POSTGRESQL_PASSWORD=password

$ oc new-app openshift/postgresql-92-centos7 --env-file=postgresql.env

$ cat postgresql.env | oc new-app openshift/postgresql-92-centos7 --env-file=-

$ oc new-app openshift/ruby-23-centos7 \
    --build-env HTTP_PROXY=http://myproxy.net:1337/ \
    --build-env GEM_HOME=~/.gem

HTTP_PROXY=http://myproxy.net:1337/
GEM_HOME=~/.gem

$ oc new-app openshift/ruby-23-centos7 --build-env-file=ruby.env

$ cat ruby.env | oc new-app openshift/ruby-23-centos7 --build-env-file=-

$ oc new-app https://github.com/openshift/ruby-hello-world -l name=hello-world

$ oc new-app https://github.com/openshift/ruby-hello-world \
    -o yaml > myapp.yaml

$ vi myapp.yaml

$ oc create -f myapp.yaml

$ oc new-app https://github.com/openshift/ruby-hello-world --name=myapp

$ oc new-app https://github.com/openshift/ruby-hello-world -n myproject

$ oc new-app https://github.com/openshift/ruby-hello-world mysql

$ oc new-app ruby+mysql

$ oc new-app \
    ruby~https://github.com/openshift/ruby-hello-world \
    mysql \
    --group=ruby+mysql

$ oc new-app --search php

To view your applications in the Topology view and interact with them, ensure that:

You can navigate to the Topology view using the left navigation panel in the Developer perspective. After you deploy an application, you are directed automatically to the Graph view where you can see the status of the application pods, quickly access the application on a public URL, access the source code to modify it, and see the status of your last build. You can zoom in and out to see more details for a particular application.

The Topology view also provides you the option to monitor your applications using the List view. Use the List view icon ( ) to see a list of all your applications and use the Graph view icon ( ) to switch back to the graph view.

You can customize the views as required using the following:

The Topology view in the Developer perspective of the web console provides the following options to interact with applications and components:

The Topology view provides the details of the deployed components in the Overview panel. You can use the Overview and Resources tabs to scale the application pods, check build status, services, and routes as follows:

Figure 3.4. Adding component via quick search

Alternatively, you can also use the Import from Git, Container Image, Database, From Catalog, Operator Backed, Helm Charts, Samples, or Upload JAR file options in the context menu by right-clicking in the topology Graph view to add a component to your project.

Figure 3.5. Context menu to add services

You can use the +Add view to add multiple components or services to your project and use the topology Graph view to group applications and resources within an application group.

Alternatively, you can also add the component to an application as follows:

In addition to grouping multiple components within an application, you can also use the Topology view to connect components with each other. You can either use a binding connector or a visual one to connect components.

A binding connection between the components can be established only if the target node is an Operator-backed service. This is indicated by the Create a binding connector tool-tip which appears when you drag an arrow to such a target node. When an application is connected to a service using a binding connector a service binding request is created. Then, the Service Binding Operator controller uses an intermediate secret to inject the necessary binding data into the application deployment as environment variables. After the request is successful, the application is redeployed establishing an interaction between the connected components.

A visual connector establishes only a visual connection between the components, depicting an intent to connect. No interaction between the components is established. If the target node is not an Operator-backed service the Create a visual connector tool-tip is displayed when you drag an arrow to a target node.

3.4.7.1. Creating a visual connection between components

You can depict an intent to connect application components using the visual connector.

This procedure walks through an example of creating a visual connection between a MongoDB service and a Node.js application.

Prerequisites

• Ensure that you have created and deployed a Node.js application using the Developer perspective.
• Ensure that you have created and deployed a MongoDB service using the Developer perspective.

Procedure

1. Hover over the MongoDB service to see a dangling arrow on the node.

   Figure 3.7. Connector

   
2. Click and drag the arrow towards the Node.js component to connect the MongoDB service with it.
3. Click on the MongoDB service to see the Overview Panel. In the Annotations section, click the edit icon to see the Key = app.openshift.io/connects-to and Value = [{"apiVersion":"apps.openshift.io/v1","kind":"DeploymentConfig","name":"nodejs-ex"}] annotation added to the service.

Similarly you can create other applications and components and establish connections between them.

Figure 3.8. Connecting multiple applications

3.4.7.2. Creating a binding connection between components

Important

Service Binding is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview/.

Note

Currently, a few specific Operators like the etcd and the PostgresSQL Database Operator’s service instances are bindable.

You can establish a binding connection with Operator-backed components.

This procedure walks through an example of creating a binding connection between a PostgreSQL Database service and a Node.js application. To create a binding connection with a service that is backed by the PostgreSQL Database Operator, you must first add the Red Hat-provided PostgreSQL Database Operator to the OperatorHub using a CatalogSource resource, and then install the Operator. The PostreSQL Database Operator then creates and manages the Database resource, which exposes the binding information in secrets, config maps, status, and spec attributes.

Prerequisites

• Ensure that you have created and deployed a Node.js application using the Developer perspective.
• Ensure that you have installed the Service Binding Operator from OperatorHub.

Procedure

1. Create a CatalogSource resource that adds the PostgresSQL Database Operator provided by Red Hat to the OperatorHub.

   1. In the +Add view, click the YAML option to see the Import YAML screen.

   2. Add the following YAML file to apply the CatalogSource resource:

      apiVersion: operators.coreos.com/v1alpha1
      kind: CatalogSource
      metadata:
          name: sample-db-operators
          namespace: openshift-marketplace
      spec:
          sourceType: grpc
          image: quay.io/redhat-developer/sample-db-operators-olm:v1
          displayName: Sample DB OLM registry
          updateStrategy:
              registryPoll:
                  interval: 30m

   3. Click Create to create the CatalogSource resource in your cluster.

2. Install the Red Hat-provided PostgreSQL Database Operator:

   1. In the Administrator perspective of the console, navigate to Operators → OperatorHub.
   2. In the Database category, select the PostgreSQL Database Operator and install it.

3. Create a database (DB) instance for the application:

   1. Switch to the Developer perspective and ensure that you are in the appropriate project, for example, test-project.
   2. In the +Add view, click the YAML option to see the Import YAML screen.

   3. Add the service instance YAML in the editor and click Create to deploy the service. Following is an example of what the service YAML will look like:

      apiVersion: postgresql.baiju.dev/v1alpha1
      kind: Database
      metadata:
       name: db-demo
      spec:
       image: docker.io/postgres
       imageName: postgres
       dbName: db-demo

      A DB instance is now deployed in the Topology view.

4. In the Topology view, hover over the Node.js component to see a dangling arrow on the node.

5. Click and drag the arrow towards the db-demo-postgresql service to make a binding connection with the Node.js application. A service binding request is created and the Service Binding Operator controller injects the DB connection information into the application deployment as environment variables. After the request is successful, the application is redeployed and the connection is established.

   Figure 3.9. Binding connector

   

Note

You can also use the context menu by dragging the dangling arrow to add and create a binding connection to an operator-backed service.

Figure 3.10. Context menu to create binding connection

The Topology view uses the following labels and annotations:

For detailed information on the labels and annotations OpenShift Container Platform applications must use, see Guidelines for labels and annotations for OpenShift applications.

You can use the Topology view in the Developer perspective to edit the source code of your application.

You can use the Topology view in the Developer perspective to edit the configuration of your application.

Helm is a software package manager that simplifies deployment of applications and services to OpenShift Container Platform clusters.

Helm uses a packaging format called charts. A Helm chart is a collection of files that describes the OpenShift Container Platform resources.

A running instance of the chart in a cluster is called a release. A new release is created every time a chart is installed on the cluster.

Each time a chart is installed, or a release is upgraded or rolled back, an incremental revision is created.

You can use either the Developer perspective or the CLI to create Helm releases and see them in the Developer perspective of the web console.

You can upgrade, rollback, or uninstall a Helm release by using the Actions button on the side panel or by right-clicking a Helm release.

You can upgrade a Helm release to upgrade to a new chart version or update your release configuration.

If a release fails, you can rollback the Helm release to a previous version.

You can delete an application and all of its associated components using the Topology view in the Developer perspective:

You can also right-click the application you want to delete and click Delete Application to delete it.

Deployments and deployment configs are enabled by the use of native Kubernetes API objects ReplicaSet and ReplicationController, respectively, as their building blocks.

Users do not have to manipulate replication controllers, replica sets, or pods owned by DeploymentConfig objects or deployments. The deployment systems ensure changes are propagated appropriately.

The following sections provide further details on these objects.

apiVersion: v1
kind: ReplicationController
metadata:
  name: frontend-1
spec:
  replicas: 1  1
  selector:    2
    name: frontend
  template:    3
    metadata:
      labels:  4
        name: frontend 5
    spec:
      containers:
      - image: openshift/hello-openshift
        name: helloworld
        ports:
        - containerPort: 8080
          protocol: TCP
      restartPolicy: Always

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: frontend-1
  labels:
    tier: frontend
spec:
  replicas: 3
  selector: 1
    matchLabels: 2
      tier: frontend
    matchExpressions: 3
      - {key: tier, operator: In, values: [frontend]}
  template:
    metadata:
      labels:
        tier: frontend
    spec:
      containers:
      - image: openshift/hello-openshift
        name: helloworld
        ports:
        - containerPort: 8080
          protocol: TCP
      restartPolicy: Always

Building on replication controllers, OpenShift Container Platform adds expanded support for the software development and deployment lifecycle with the concept of DeploymentConfig objects. In the simplest case, a DeploymentConfig object creates a new replication controller and lets it start up pods.

However, OpenShift Container Platform deployments from DeploymentConfig objects also provide the ability to transition from an existing deployment of an image to a new one and also define hooks to be run before or after creating the replication controller.

The DeploymentConfig deployment system provides the following capabilities:

When you create a DeploymentConfig object, a replication controller is created representing the DeploymentConfig object’s pod template. If the deployment changes, a new replication controller is created with the latest pod template, and a deployment process runs to scale down the old replication controller and scale up the new one.

Instances of your application are automatically added and removed from both service load balancers and routers as they are created. As long as your application supports graceful shutdown when it receives the TERM signal, you can ensure that running user connections are given a chance to complete normally.

The OpenShift Container Platform DeploymentConfig object defines the following details:

Each time a deployment is triggered, whether manually or automatically, a deployer pod manages the deployment (including scaling down the old replication controller, scaling up the new one, and running hooks). The deployment pod remains for an indefinite amount of time after it completes the deployment to retain its logs of the deployment. When a deployment is superseded by another, the previous replication controller is retained to enable easy rollback if needed.

apiVersion: apps.openshift.io/v1
kind: DeploymentConfig
metadata:
  name: frontend
spec:
  replicas: 5
  selector:
    name: frontend
  template: { ... }
  triggers:
  - type: ConfigChange 1
  - imageChangeParams:
      automatic: true
      containerNames:
      - helloworld
      from:
        kind: ImageStreamTag
        name: hello-openshift:latest
    type: ImageChange  2
  strategy:
    type: Rolling      3

Kubernetes provides a first-class, native API object type in OpenShift Container Platform called Deployment. Deployment objects serve as a descendant of the OpenShift Container Platform-specific DeploymentConfig object.

Like DeploymentConfig objects, Deployment objects describe the desired state of a particular component of an application as a pod template. Deployments create replica sets, which orchestrate pod lifecycles.

For example, the following deployment definition creates a replica set to bring up one hello-openshift pod:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-openshift
spec:
  replicas: 1
  selector:
    matchLabels:
      app: hello-openshift
  template:
    metadata:
      labels:
        app: hello-openshift
    spec:
      containers:
      - name: hello-openshift
        image: openshift/hello-openshift:latest
        ports:
        - containerPort: 80

Both Kubernetes Deployment objects and OpenShift Container Platform-provided DeploymentConfig objects are supported in OpenShift Container Platform; however, it is recommended to use Deployment objects unless you need a specific feature or behavior provided by DeploymentConfig objects.

The following sections go into more detail on the differences between the two object types to further help you decide which type to use.

$ oc rollout pause deployments/<name>

DeploymentConfig objects can be managed from the OpenShift Container Platform web console’s Workloads page or using the oc CLI. The following procedures show CLI usage unless otherwise stated.

triggers:
  - type: "ConfigChange"

triggers:
  - type: "ImageChange"
    imageChangeParams:
      automatic: true 1
      from:
        kind: "ImageStreamTag"
        name: "origin-ruby-sample:latest"
        namespace: "myproject"
      containerNames:
        - "helloworld"

A rolling deployment slowly replaces instances of the previous version of an application with instances of the new version of the application. The rolling strategy is the default deployment strategy used if no strategy is specified on a DeploymentConfig object.

A rolling deployment typically waits for new pods to become ready via a readiness check before scaling down the old components. If a significant issue occurs, the rolling deployment can be aborted.

When to use a rolling deployment:

A rolling deployment means you have both old and new versions of your code running at the same time. This typically requires that your application handle N-1 compatibility.

strategy:
  type: Rolling
  rollingParams:
    updatePeriodSeconds: 1 1
    intervalSeconds: 1 2
    timeoutSeconds: 120 3
    maxSurge: "20%" 4
    maxUnavailable: "10%" 5
    pre: {} 6
    post: {}

The rolling strategy:

The maxUnavailable parameter is the maximum number of pods that can be unavailable during the update. The maxSurge parameter is the maximum number of pods that can be scheduled above the original number of pods. Both parameters can be set to either a percentage (e.g., 10%) or an absolute value (e.g., 2). The default value for both is 25%.

These parameters allow the deployment to be tuned for availability and speed. For example:

Generally, if you want fast rollouts, use maxSurge. If you have to take into account resource quota and can accept partial unavailability, use maxUnavailable.

The recreate strategy has basic rollout behavior and supports lifecycle hooks for injecting code into the deployment process.

strategy:
  type: Recreate
  recreateParams: 1
    pre: {} 2
    mid: {}
    post: {}

The recreate strategy:

When to use a recreate deployment:

A recreate deployment incurs downtime because, for a brief period, no instances of your application are running. However, your old code and new code do not run at the same time.

You can switch the deployment strategy from the default rolling update to a recreate update using the Developer perspective in the web console.

The custom strategy allows you to provide your own deployment behavior.

strategy:
  type: Custom
  customParams:
    image: organization/strategy
    command: [ "command", "arg1" ]
    environment:
      - name: ENV_1
        value: VALUE_1

In the above example, the organization/strategy container image provides the deployment behavior. The optional command array overrides any CMD directive specified in the image’s Dockerfile. The optional environment variables provided are added to the execution environment of the strategy process.

Additionally, OpenShift Container Platform provides the following environment variables to the deployment process:

The replica count of the new deployment will initially be zero. The responsibility of the strategy is to make the new deployment active using the logic that best serves the needs of the user.

Alternatively, use the customParams object to inject the custom deployment logic into the existing deployment strategies. Provide a custom shell script logic and call the openshift-deploy binary. Users do not have to supply their custom deployer container image; in this case, the default OpenShift Container Platform deployer image is used instead:

strategy:
  type: Rolling
  customParams:
    command:
    - /bin/sh
    - -c
    - |
      set -e
      openshift-deploy --until=50%
      echo Halfway there
      openshift-deploy
      echo Complete

This results in following deployment:

Started deployment #2
--> Scaling up custom-deployment-2 from 0 to 2, scaling down custom-deployment-1 from 2 to 0 (keep 2 pods available, don't exceed 3 pods)
    Scaling custom-deployment-2 up to 1
--> Reached 50% (currently 50%)
Halfway there
--> Scaling up custom-deployment-2 from 1 to 2, scaling down custom-deployment-1 from 2 to 0 (keep 2 pods available, don't exceed 3 pods)
    Scaling custom-deployment-1 down to 1
    Scaling custom-deployment-2 up to 2
    Scaling custom-deployment-1 down to 0
--> Success
Complete

If the custom deployment strategy process requires access to the OpenShift Container Platform API or the Kubernetes API the container that executes the strategy can use the service account token available inside the container for authentication.

The rolling and recreate strategies support lifecycle hooks, or deployment hooks, which allow behavior to be injected into the deployment process at predefined points within the strategy:

pre:
  failurePolicy: Abort
  execNewPod: {} 1

Every hook has a failure policy, which defines the action the strategy should take when a hook failure is encountered:

Hooks have a type-specific field that describes how to execute the hook. Currently, pod-based hooks are the only supported hook type, specified by the execNewPod field.

Pod-based lifecycle hook

Pod-based lifecycle hooks execute hook code in a new pod derived from the template in a DeploymentConfig object.

The following simplified example deployment uses the rolling strategy. Triggers and some other minor details are omitted for brevity:

kind: DeploymentConfig
apiVersion: apps.openshift.io/v1
metadata:
  name: frontend
spec:
  template:
    metadata:
      labels:
        name: frontend
    spec:
      containers:
        - name: helloworld
          image: openshift/origin-ruby-sample
  replicas: 5
  selector:
    name: frontend
  strategy:
    type: Rolling
    rollingParams:
      pre:
        failurePolicy: Abort
        execNewPod:
          containerName: helloworld 1
          command: [ "/usr/bin/command", "arg1", "arg2" ] 2
          env: 3
            - name: CUSTOM_VAR1
              value: custom_value1
          volumes:
            - data 4

In this example, the pre hook will be executed in a new pod using the openshift/origin-ruby-sample image from the helloworld container. The hook pod has the following properties:

In production environments, you can precisely control the distribution of traffic that lands on a particular shard. When dealing with large numbers of instances, you can use the relative scale of individual shards to implement percentage based traffic. That combines well with a proxy shard, which forwards or splits the traffic it receives to a separate service or application running elsewhere.

In the simplest configuration, the proxy forwards requests unchanged. In more complex setups, you can duplicate the incoming requests and send to both a separate cluster as well as to a local instance of the application, and compare the result. Other patterns include keeping the caches of a DR installation warm, or sampling incoming traffic for analysis purposes.

Any TCP (or UDP) proxy could be run under the desired shard. Use the oc scale command to alter the relative number of instances serving requests under the proxy shard. For more complex traffic management, consider customizing the OpenShift Container Platform router with proportional balancing capabilities.

Applications that have new code and old code running at the same time must be careful to ensure that data written by the new code can be read and handled (or gracefully ignored) by the old version of the code. This is sometimes called schema evolution and is a complex problem.

This can take many forms: data stored on disk, in a database, in a temporary cache, or that is part of a user’s browser session. While most web applications can support rolling deployments, it is important to test and design your application to handle it.

For some applications, the period of time that old code and new code is running side by side is short, so bugs or some failed user transactions are acceptable. For others, the failure pattern may result in the entire application becoming non-functional.

One way to validate N-1 compatibility is to use an A/B deployment: run the old code and new code at the same time in a controlled way in a test environment, and verify that traffic that flows to the new deployment does not cause failures in the old deployment.

OpenShift Container Platform and Kubernetes give application instances time to shut down before removing them from load balancing rotations. However, applications must ensure they cleanly terminate user connections as well before they exit.

On shutdown, OpenShift Container Platform sends a TERM signal to the processes in the container. Application code, on receiving SIGTERM, stop accepting new connections. This ensures that load balancers route traffic to other active instances. The application code then waits until all open connections are closed, or gracefully terminate individual connections at the next opportunity, before exiting.

After the graceful termination period expires, a process that has not exited is sent the KILL signal, which immediately ends the process. The terminationGracePeriodSeconds attribute of a pod or pod template controls the graceful termination period (default 30 seconds) and can be customized per application as necessary.

Blue-green deployments involve running two versions of an application at the same time and moving traffic from the in-production version (the blue version) to the newer version (the green version). You can use a rolling strategy or switch services in a route.

Because many applications depend on persistent data, you must have an application that supports N-1 compatibility, which means it shares data and implements live migration between the database, store, or disk by creating two copies of the data layer.

Consider the data used in testing the new version. If it is the production data, a bug in the new version can break the production version.

The A/B deployment strategy lets you try a new version of the application in a limited way in the production environment. You can specify that the production version gets most of the user requests while a limited fraction of requests go to the new version.

Because you control the portion of requests to each version, as testing progresses you can increase the fraction of requests to the new version and ultimately stop using the previous version. As you adjust the request load on each version, the number of pods in each service might have to be scaled as well to provide the expected performance.

In addition to upgrading software, you can use this feature to experiment with versions of the user interface. Since some users get the old version and some the new, you can evaluate the user’s reaction to the different versions to inform design decisions.

For this to be effective, both the old and new versions must be similar enough that both can run at the same time. This is common with bug fix releases and when new features do not interfere with the old. The versions require N-1 compatibility to properly work together.

OpenShift Container Platform supports N-1 compatibility through the web console as well as the CLI.

The following describes the set of compute resources and object types that can be managed by a quota.

Each quota can have an associated set of scopes. A quota only measures usage for a resource if it matches the intersection of enumerated scopes.

Adding a scope to a quota restricts the set of resources to which that quota can apply. Specifying a resource outside of the allowed set results in a validation error.

A BestEffort scope restricts a quota to limiting the following resources:

A Terminating, NotTerminating, and NotBestEffort scope restricts a quota to tracking the following resources:

After a resource quota for a project is first created, the project restricts the ability to create any new resources that may violate a quota constraint until it has calculated updated usage statistics.

After a quota is created and usage statistics are updated, the project accepts the creation of new content. When you create or modify resources, your quota usage is incremented immediately upon the request to create or modify the resource.

When you delete a resource, your quota use is decremented during the next full recalculation of quota statistics for the project. A configurable amount of time determines how long it takes to reduce quota usage statistics to their current observed system value.

If project modifications exceed a quota usage limit, the server denies the action, and an appropriate error message is returned to the user explaining the quota constraint violated, and what their currently observed usage statistics are in the system.

When allocating compute resources, each container might specify a request and a limit value each for CPU, memory, and ephemeral storage. Quotas can restrict any of these values.

If the quota has a value specified for requests.cpu or requests.memory, then it requires that every incoming container make an explicit request for those resources. If the quota has a value specified for limits.cpu or limits.memory, then it requires that every incoming container specify an explicit limit for those resources.

You can create a quota to constrain resource usage in a given project.

You can view usage statistics related to any hard limits defined in a project’s quota by navigating in the web console to the project’s Quota page.

You can also use the CLI to view quota details.

Configure explicit resource quotas in a project request template to apply specific resource quotas in new projects.

When creating quotas, you can select multiple projects based on annotation selection, label selection, or both.

A project administrator is not allowed to create or modify the multi-project quota that limits his or her project, but the administrator is allowed to view the multi-project quota documents that are applied to his or her project. The project administrator can do this via the AppliedClusterResourceQuota resource.

Because of the locking consideration when claiming quota allocations, the number of active projects selected by a multi-project quota is an important consideration. Selecting more than 100 projects under a single multi-project quota can have detrimental effects on API server responsiveness in those projects.

Config maps can be used to populate individual environment variables in containers or to populate environment variables in containers from all keys that form valid environment variable names.

As an example, consider the following config map:

apiVersion: v1
kind: ConfigMap
metadata:
  name: special-config 1
  namespace: default 2
data:
  special.how: very 3
  special.type: charm 4

apiVersion: v1
kind: ConfigMap
metadata:
  name: env-config 1
  namespace: default
data:
  log_level: INFO 2

A config map can also be used to set the value of the commands or arguments in a container. This is accomplished by using the Kubernetes substitution syntax $(VAR_NAME). Consider the following config map:

apiVersion: v1
kind: ConfigMap
metadata:
  name: special-config
  namespace: default
data:
  special.how: very
  special.type: charm

You can inject content into a volume by using config maps.

apiVersion: v1
kind: ConfigMap
metadata:
  name: special-config
  namespace: default
data:
  special.how: very
  special.type: charm

Idling multiple services is helpful if an application spans across a set of services within a project, or when idling multiple services in conjunction with a script to idle multiple applications in bulk within the same project.

You can apply conditions to your manually pruned images.

Separating the removal of OpenShift Container Platform image API objects and image data from the registry by using --prune-registry=false, followed by hard pruning the registry, can narrow timing windows and is safer when compared to trying to prune both through one command. However, timing windows are not completely removed.

For example, you can still create a pod referencing an image as pruning identifies that image for pruning. You should still keep track of an API object created during the pruning operations that might reference images so that you can mitigate any references to deleted content.

Re-doing the pruning without the --prune-registry option or with --prune-registry=true does not lead to pruning the associated storage in the image registry for images previously pruned by --prune-registry=false. Any images that were pruned with --prune-registry=false can only be deleted from registry storage by hard pruning the registry.

The secure connection is the preferred and recommended approach. It is done over HTTPS protocol with a mandatory certificate verification. The prune command always attempts to use it if possible. If it is not possible, in some cases it can fall-back to insecure connection, which is dangerous. In this case, either certificate verification is skipped or plain HTTP protocol is used.

The fall-back to insecure connection is allowed in the following cases unless --certificate-authority is specified:

Images not being pruned

If your images keep accumulating and the prune command removes just a small portion of what you expect, ensure that you understand the image prune conditions that must apply for an image to be considered a candidate for pruning.

Ensure that images you want removed occur at higher positions in each tag history than your chosen tag revisions threshold. For example, consider an old and obsolete image named sha:abz. By running the following command in namespace N, where the image is tagged, the image is tagged three times in a single image stream named myapp:

$ oc get is -n N -o go-template='{{range $isi, $is := .items}}{{range $ti, $tag := $is.status.tags}}'\
  '{{range $ii, $item := $tag.items}}{{if eq $item.image "'"sha:abz"\
  $'"}}{{$is.metadata.name}}:{{$tag.tag}} at position {{$ii}} out of {{len $tag.items}}\n'\
  '{{end}}{{end}}{{end}}{{end}}'

myapp:v2 at position 4 out of 5
myapp:v2.1 at position 2 out of 2
myapp:v2.1-may-2016 at position 0 out of 1

When default options are used, the image is never pruned because it occurs at position 0 in a history of myapp:v2.1-may-2016 tag. For an image to be considered for pruning, the administrator must either:

Tags having a date or time of a particular image’s build in their names should be avoided, unless the image must be preserved for an undefined amount of time. Such tags tend to have just one image in their history, which prevents them from ever being pruned.

Using a secure connection against insecure registry

If you see a message similar to the following in the output of the oc adm prune images command, then your registry is not secured and the oc adm prune images client attempts to use a secure connection:

error: error communicating with registry: Get https://172.30.30.30:5000/healthz: http: server gave HTTP response to HTTPS client

Using an insecure connection against a secured registry

If you see one of the following errors in the output of the oc adm prune images command, it means that your registry is secured using a certificate signed by a certificate authority other than the one used by oc adm prune images client for connection verification:

error: error communicating with registry: Get http://172.30.30.30:5000/healthz: malformed HTTP response "\x15\x03\x01\x00\x02\x02"
error: error communicating with registry: [Get https://172.30.30.30:5000/healthz: x509: certificate signed by unknown authority, Get http://172.30.30.30:5000/healthz: malformed HTTP response "\x15\x03\x01\x00\x02\x02"]

By default, the certificate authority data stored in the user’s configuration files is used; the same is true for communication with the master API.

Use the --certificate-authority option to provide the right certificate authority for the container image registry server.

Using the wrong certificate authority

The following error means that the certificate authority used to sign the certificate of the secured container image registry is different from the authority used by the client:

error: error communicating with registry: Get https://172.30.30.30:5000/: x509: certificate signed by unknown authority

Make sure to provide the right one with the flag --certificate-authority.

As a workaround, the --force-insecure flag can be added instead. However, this is not recommended.

Cluster administrators can install a common set of applications on OpenShift Container Platform clusters that connect to the Marketplace. They can also use the Marketplace to track cluster usage against subscriptions or quotas. Users that they add by using the Marketplace have their product usage tracked and billed to their organization.

During the cluster connection process, a Marketplace Operator is installed that updates the image registry secret, manages the catalog, and reports application usage.

Cluster administrators can install Marketplace applications from within OperatorHub in OpenShift Container Platform, or from the Marketplace web application.

You can access installed applications from the web console by clicking Operators > Installed Operators.

You can deploy Marketplace applications from the web console’s Administrator and Developer perspectives.

The Developer perspective

Developers can access newly installed capabilities by using the Developer perspective.

For example, after a database Operator is installed, a developer can create an instance from the catalog within their project. Database usage is aggregated and reported to the cluster administrator.

This perspective does not include Operator installation and application usage tracking.

The Administrator perspective

Cluster administrators can access Operator installation and application usage information from the Administrator perspective.

They can also launch application instances by browsing custom resource definitions (CRDs) in the Installed Operators list.