App runtime

The app runtime is the environment apps are executed in.

Buildpack Apps Container Image Apps
System libraries Provided by the Stack Provided in the container
Network access Full access through Envoy sidecar Full access through Envoy sidecar
File system Ephemeral storage Ephemeral storage
Language runtime Supplied by the Stack or Buildpack Built into the container
User Specified by the Stack Specified on the container
Isolation mechanism Kubernetes Pod Kubernetes Pod
DNS Provided by Kubernetes Provided by Kubernetes

Environment variables

Environment variables are injected into the app at runtime by Kubernetes. Variables are added based on the following order, where later values override earlier ones with the same name:

  1. Space (set by administrators)
  2. App (set by developers)
  3. System (set by Kf)

Kf provides the following system environment variables:

Variable Purpose
CF_INSTANCE_ADDR The cluster-visible IP:PORT of the App instance.
CF_INSTANCE_GUID The UUID of the App instance.
CF_INSTANCE_INDEX The index number of the App instance, this will ALWAYS be 0.
CF_INSTANCE_IP The cluster-visible IP of the App instance.
CF_INSTANCE_PORT The cluster-visible port of the App instance. In Kf this is the same as PORT.
DATABASE_URL The first URI found in a VCAP_SERVICES credential.
LANG Required by Buildpacks to ensure consistent script load order.
MEMORY_LIMIT The maximum amount of memory in MB the App can consume.
PORT The port the App should listen on for requests.
VCAP_APPLICATION A JSON structure containing App metadata.
VCAP_SERVICES A JSON structure specifying bound services.

Service credentials from bound services get injected into Apps via the VCAP_SERVICES environment variable. The variable is a valid JSON object with the following structure.


A JSON object where the keys are Service labels and the values are an array of VCAPService. The array represents every bound service with that label. User provided services are placed under the label user-provided.


  "mysql": [...],
  "postgresql": [...],
  "user-provided": [...]


This type represents a single bound service instance.


  "binding_name": string,
  "instance_name": string,
  "name": string,
  "label": string,
  "tags": string[],
  "plan": string,
  "credentials": object


Field Type Description
binding_name string The name assigned to the service binding by the user.
instance_name string The name assigned to the service instance by the user.
name string The binding_name if it exists; otherwise the instance_name.
label string The name of the service offering.
tags string[] An array of strings an app can use to identify a service instance.
plan string[] The service plan selected when the service instance was created.
credentials object The service-specific credentials needed to access the service instance.


TheVCAP_APPLICATION environment variable is a JSON object containing metadata about the App.


  "application_id": "12345",
  "application_name": "my-app",
  "application_uris": [""],
  "limits": {
    "disk": 1024,
    "mem": 256
  "name": "my-app",
  "process_id": "12345",
  "process_type": "web",
  "space_name": "my-ns",
  "uris": [""]


Field Type Description
application_id string The GUID identifying the App.
application_name string The name assigned to the App when it was pushed.
application_uris string[] The URIs assigned to the App.
limits object The limits to disk space, and memory permitted to the App. Memory and disk space limits are supplied when the App is deployed, either on the command line or in the App manifest. Disk and memory limits are represented as integers, with an assumed unit of MB.
name string Identical to application_name.
process_id string The UID identifying the process. Only present in running App containers.
process_type string The type of process. Only present in running App containers.
space_name string The human-readable name of the Space where the App is deployed.
uris string[] Identical to application_uris.

Missing Fields

Some fields in VCAP_APPLICATION that are in Cloud Foundry are currently not supported in Kf.

Besides CF-specific and deprecated fields (cf_api, host, users) the fields that are not supported in Kf are:

  • application_version (identical to version)
  • organization_id
  • organization_name
  • space_id
  • start (identical to started_at)
  • started_at_timestamp (identical to state_timestamp)