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:
- Space (set by administrators)
- App (set by developers)
- 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. |
INSTANCE_GUID |
Alias of CF_INSTANCE_GUID . |
CF_INSTANCE_INDEX |
The index number of the App instance, this will ALWAYS be 0. |
INSTANCE_INDEX |
Alias of CF_INSTANCE_INDEX . |
CF_INSTANCE_IP |
The cluster-visible IP of the App instance. |
CF_INSTANCE_INTERNAL_IP |
Alias of CF_INSTANCE_IP |
VCAP_APP_HOST |
Alias of CF_INSTANCE_IP |
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_APP_PORT |
Alias of PORT . |
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.
VCAPServices
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
.
Example
{
"mysql": [...],
"postgresql": [...],
"user-provided": [...]
}
VCAPService
This type represents a single bound service instance.
Example
{
"binding_name": string,
"instance_name": string,
"name": string,
"label": string,
"tags": string[],
"plan": string,
"credentials": object
}
Fields
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. |
VCAP_APPLICATION
TheVCAP_APPLICATION
environment variable is a JSON object containing metadata about the App.
Example
{
"application_id": "12345",
"application_name": "my-app",
"application_uris": ["my-app.example.com"],
"limits": {
"disk": 1024,
"mem": 256
},
"name": "my-app",
"process_id": "12345",
"process_type": "web",
"space_name": "my-ns",
"uris": ["my-app.example.com"]
}
Fields
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 toversion
)organization_id
organization_name
space_id
start
(identical tostarted_at
)started_at_timestamp
(identical tostate_timestamp
)