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docker-apps.md

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Docker applications support

Overview

Users can use the cf cli to push apps with docker images. Korifi then uses the docker image to schedule workloads that are bcked up by the docker image.

In contrast to CF for VMs, Korifi supports pushing docker images by default and the feature cannot be disabled.

To deploy a docker image from a container registry repository (such as Dockerhub), run:

cf push APP-NAME --docker-image REPO/IMAGE:TAG

For more information and examples, please refer to the CF documentation

Limitations

Korifi would reject docker images that are built to run their processes as the privileged (root) user. Such workloads on Kubernetes would run as the Kubernetes node root user and that is insecure.

Kubernetes user namespace support addresses that. However, this feature is only available in very recent Kubernetes versions that are currently not provided by major Kubernetes providers.

Running docker images with non-standard ports

Cloud Foundry expects that all apps listen on port 8080 to handle HTTP requests. Docker images may configure alternative ports via the EXPOSE directive in the Dockerfile. Korifi respects this metadata and would configure the default route acoordingly.

If the EXPOSE directive is not specified in the Dockerfile, Korifi would default to port 8080 when creating the default route. When the EXPOSE directive is missing and the app is listening on port other than 8080, the following procedure can be used to properly configure the app route:

APP_NAME=<your app name>
DOMAIN=<the domain name>
IMAGE=<repo/image:tag>
DESIRED_PORT=<app port>

cf push $APP_NAME --no-route --docker-image $IMAGE
cf create-route $DOMAIN --hostname $APP_NAME
route_guid=$(cf curl /v3/routes | jq -r ".resources[] | select(.host==\"$APP_NAME\").guid")
read -r -d '' destination <<EOF
{
   "destinations": [
   {
     "app": {
       "guid": "$(cf app $APP_NAME --guid)",
       "process": {
         "type": "web"
       }
     },
     "port": $DESIRED_PORT,
     "protocol": "http1"
   }
 ]
}
EOF
cf curl -XPOST "/v3/routes/$route_guid/destinations" -d "$destination"