Controller Docs CMD Update

Update Command

The update command allows developers to update previously deployed application containers. This allows for the Docker image to be changed, the set of exposed endpoints to be reconfigured, and the minimum and maximum number of instance replications to be changed. This could be achived using teardown and deploy; however, update allows the application container to be updated without any downtime.

Command

The update command is made available to developers through the express-controller executable.

express-controller update <name> [flags]

Flags:
      --endpoint-config string   The configuration file for accessing the deployed API.
      --image string             The new Docker image to roll out.
      --max int32                The minimum number of instances.
      --min int32                The minimum number of instances.

Parameters

The update command allows all parameters defined in the deploy command to be modified except for port. The only way to update the port of a deployed application container is to use teardown followed by deploy which will result in some downtime.

1. Name. The name of the application container to be updated must be specified. This must match the name passed to the deploy command and be present when using the list command. Nothin is changed if the name does not match an existing deployment.
2. Endpoints Configuration. The endpoints configuration .yaml file may be updated to expose, hide or change the required scopes of endpoints.
3. Image. The Docker Image of the application may be updated. This may be a new version of the same image or a different image but must listen on the original port. If the image is changed, the instances of the new application container are brought up before the old version is taken down to ensure zero downtime occurs.
4. Minimum Replicas. The minimum number of instances of the application container to deploy. This is enforced by the autoscaler to ensure that the number of available instances never drops below this number regardless of CPU utilization.
5. Maximum Replicas. The maximum number of instances of the application container to deploy. This is enforced by the autoscaler to ensure that the number of available instances never exceeds this number regardless of CPU utilization.

Access

Once an application container has been updated, the new version will not be available immediately. The changes will take the longest to take effect if the image is changed because it must be pulled from the remote Docker repository.

Although Express does not support checking when the status of the rollout, this can be monitored using the Kubernetes kubectl rollout status deployment <name> command.