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Basic Deployment Operations

Starting a Deployment

You can start a new deployment process manually using the web console, or from the CLI:

$ oc deploy --latest dc/<name>

If a deployment process is already in progress, the command will display a message and a new replication controller will not be deployed.

Viewing a Deployment

To get basic information about all the available revisions of your application:

$ oc rollout history dc/<name>

This will show details about all recently created replication controllers for the provided deployment configuration, including any currently running deployment process.

You can view details specific to a revision by using the --revision flag:

$ oc rollout history dc/<name> --revision=1

For more detailed information about a deployment configuration and its latest revision:

$ oc describe dc <name>

The web console shows deployments in the Browse tab.

Rolling Back a Deployment

Rollbacks revert an application back to a previous revision and can be performed using the REST API, the CLI, or the web console.

To rollback to the last successful deployed revision of your configuration:

$ oc rollout undo dc/<name>

The deployment configuration’s template will be reverted to match the deployment revision specified in the undo command, and a new replication controller will be started. If no revision is specified with --to-revision, then the last successfully deployed revision will be used.

Image change triggers on the deployment configuration are disabled as part of the rollback to prevent accidentally starting a new deployment process soon after the rollback is complete. To re-enable the image change triggers:

$ oc set triggers dc/<name> --auto

Deployment configurations also support automatically rolling back to the last successful revision of the configuration in case the latest deployment process fails. In that case, the latest template that failed to deploy stays intact by the system and it is up to users to fix their configurations.

Executing Commands Inside a Container

You can add a command to a container, which modifies the container’s startup behavior by overruling the image’s ENTRYPOINT. This is different from a lifecycle hook, which instead can be run once per deployment at a specified time.

Add the command parameters to the spec field of the deployment configuration. You can also add an args field, which modifies the command (or the ENTRYPOINT if command does not exist).

...
spec:
  containers:
    -
    name: <container_name>
    image: 'image'
    command:
      - '<command>'
    args:
      - '<argument_1>'
      - '<argument_2>'
      - '<argument_3>'
...

For example, to execute the java command with the -jar and /opt/app-root/springboots2idemo.jar arguments:

...
spec:
  containers:
    -
    name: example-spring-boot
    image: 'image'
    command:
      - java
    args:
      - '-jar'
      - /opt/app-root/springboots2idemo.jar
...

Viewing Deployment Logs

To stream the logs of the latest revision for a given deployment configuration:

$ oc logs -f dc/<name>

If the latest revision is running or failed, oc logs will return the logs of the process that is responsible for deploying your pods. If it is successful, oc logs will return the logs from a pod of your application.

You can also view logs from older failed deployment processes, if and only if these processes (old replication controllers and their deployer pods) exist and have not been pruned or deleted manually:

$ oc logs --version=1 dc/<name>

For more options on retrieving logs see:

$ oc logs --help

Setting Deployment Triggers

A deployment configuration can contain triggers, which drive the creation of new deployment processes in response to events inside the cluster.

If no triggers are defined on a deployment configuration, a ConfigChange trigger is added by default. If triggers are defined as an empty field, deployments must be started manually.

Configuration Change Trigger

The ConfigChange trigger results in a new replication controller whenever changes are detected in the pod template of the deployment configuration.

If a ConfigChange trigger is defined on a deployment configuration, the first replication controller will be automatically created soon after the deployment configuration itself is created and it is not paused.
Example 1. A ConfigChange Trigger
triggers:
  - type: "ConfigChange"

ImageChange Trigger

The ImageChange trigger results in a new replication controller whenever the content of an image stream tag changes (when a new version of the image is pushed).

Example 2. An ImageChange Trigger
triggers:
  - type: "ImageChange"
    imageChangeParams:
      automatic: true (1)
      from:
        kind: "ImageStreamTag"
        name: "origin-ruby-sample:latest"
        namespace: "myproject"
      containerNames:
        - "helloworld"
1 If the imageChangeParams.automatic field is set to false, the trigger is disabled.

With the above example, when the latest tag value of the origin-ruby-sample image stream changes and the new image value differs from the current image specified in the deployment configuration’s helloworld container, a new replication controller is created using the new image for the helloworld container.

If an ImageChange trigger is defined on a deployment configuration (with a ConfigChange trigger and automatic=false, or with automatic=true) and the ImageStreamTag pointed by the ImageChange trigger does not exist yet, then the initial deployment process will automatically start as soon as an image is imported or pushed by a build to the ImageStreamTag.

Using the Command Line

The oc set triggers command can be used to set a deployment trigger for a deployment configuration. For the example above, you can set the ImageChangeTrigger by using the following command:

$ oc set triggers dc/frontend --from-image=myproject/origin-ruby-sample:latest -c helloworld

For more information, see:

$ oc set triggers --help

Setting Deployment Resources

A deployment is completed by a pod that consumes resources (memory and CPU) on a node. By default, pods consume unbounded node resources. However, if a project specifies default container limits, then pods consume resources up to those limits.

You can also limit resource use by specifying resource limits as part of the deployment strategy. Deployment resources can be used with the Recreate, Rolling, or Custom deployment strategies.

In the following example, each of resources, cpu, and memory is optional:

type: "Recreate"
resources:
  limits:
    cpu: "100m" (1)
    memory: "256Mi" (2)
1 cpu is in CPU units: 100m represents 0.1 CPU units (100 * 1e-3).
2 memory is in bytes: 256Mi represents 268435456 bytes (256 * 2 ^ 20).

However, if a quota has been defined for your project, one of the following two items is required:

  • A resources section set with an explicit requests:

      type: "Recreate"
  resources:
    requests: (1)
      cpu: "100m"
      memory: "256Mi"
    1 The requests object contains the list of resources that correspond to the list of resources in the quota.

See Quotas and Limit Ranges to learn more about compute resources and the differences between requests and limits.

  • A limit range defined in your project, where the defaults from the LimitRange object apply to pods created during the deployment process.

Otherwise, deploy pod creation will fail, citing a failure to satisfy quota.

Manual Scaling

In addition to rollbacks, you can exercise fine-grained control over the number of replicas from the web console, or by using the oc scale command. For example, the following command sets the replicas in the deployment configuration frontend to 3.

$ oc scale dc frontend --replicas=3

The number of replicas eventually propagates to the desired and current state of the deployment configured by the deployment configuration frontend.

Pods can also be autoscaled using the oc autoscale command. See Pod Autoscaling for more details.

Assigning Pods to Specific Nodes

You can use node selectors in conjunction with labeled nodes to control pod placement.

OpenShift Container Platform administrators can assign labels during an advanced installation, or added to a node after installation.

Cluster administrators can set the default node selector for your project in order to restrict pod placement to specific nodes. As an OpenShift Container Platform developer, you can set a node selector on a pod configuration to restrict nodes even further.

To add a node selector when creating a pod, edit the pod configuration, and add the nodeSelector value. This can be added to a single pod configuration, or in a pod template:

apiVersion: v1
kind: Pod
spec:
  nodeSelector:
    disktype: ssd
...

Pods created when the node selector is in place are assigned to nodes with the specified labels.

The labels specified here are used in conjunction with the labels added by a cluster administrator.

For example, if a project has the type=user-node and region=east labels added to a project by the cluster administrator, and you add the above disktype: ssd label to a pod, the pod will only ever be scheduled on nodes that have all three labels.

Labels can only be set to one value, so setting a node selector of region=west in a pod configuration that has region=east as the administrator-set default, results in a pod that will never be scheduled.

Running a Pod with a Different Service Account

You can run a pod with a service account other than the default:

  1. Edit the deployment configuration:

    $ oc edit dc/<deployment_config>

  2. Add the serviceAccount and serviceAccountName parameters to the spec field, and specify the service account you want to use:

    spec:
  securityContext: {}
  serviceAccount: <service_account>
  serviceAccountName: <service_account>

Adding Secrets to Deployment Configurations from the Web Console

Add a secret to your deployment configuration so that it can access a private repository.

  1. Create a new OpenShift Container Platform project.

  2. Create a secret that contains credentials for accessing a private image repository.

  3. Create a deployment configuration.

  4. On the deployment configuration editor page or in the fromimage page of the web console, set the Pull Secret.

  5. Click the Save button.