Buildpacks are used by Kf to turn an application's source code into an executable image. Cloud Native Buildpacks use the latest Buildpack API v3 and companies including VMware and Heroku are actively adding v3 support to existing buildpacks.
Kf supports Buildpacks conforming to both V2 and V3 of the Buildpack API specification.
Comparison between V2 and V3 buildpacks
| V2 Buildpacks | V3 Buildpacks | |
|---|---|---|
| Alternate names | Cloud Foundry Buildpacks | Cloud Native Buildpacks (CNB), Builder Images |
| Status | Being Replaced | Current |
| Ownership | Cloud Foundry | Buildpacks.io |
| Stack | Shared by builder and runtime | Optionally different for builder and runtime |
| Local development | Not possible | Yes, with the pack CLI |
| Custom buildpacks | Available at runtime | Must be built into the builder |
Buildpack lifecycle
| Step | Cloud Foundry | Kf with Buildpacks V2 | Kf with Buildpacks V3 |
|---|---|---|---|
| Source location | BITS service | Container registry | Container registry |
| Buildpack location | BOSH/HTTP | HTTP | Container registry |
| Stack location | BOSH | Container registry | Container registry |
| Result | Droplet (App binary without stack) | Image (Droplet on a stack) | Image |
| Runtime | Droplet glued on top of stack and run | Run produced image | Run produced image |
Kf always produces a full, executable image as a result of its build process. Cloud Foundry, on the other hand, produces parts of an executable image at build time and the rest is added at runtime.
Kf chose to follow the model of always producing a full image for the following reasons:
- Images can be exported, run locally, and inspected statically
- Better security and auditing with tools like binary authorization
- App deployments are reproducible
Kf and Buildpacks
Kf stores its global list of buildpacks and stacks in the config-defaults ConfigMap in the kf Namespace.
Each Space reflects these buildpacks in its status field.
For a Space named buildpack-docs you could run the following to see the full Space configuration:
$ kf space buildpack-docs
Getting Space buildpack-docs
API Version: kf.dev/v1alpha1
Kind: Space
Metadata:
Creation Timestamp: 2020-02-14T15:09:52Z
Name: buildpack-docs
Self Link: /apis/kf.dev/v1alpha1/spaces/buildpack-docs
UID: 0cf1e196-4f3c-11ea-91a4-42010a80008d
Status:
Build Config:
Buildpacks V2:
- Name: staticfile_buildpack
URL: https://github.com/cloudfoundry/staticfile-buildpack
Disabled: false
- Name: java_buildpack
URL: https://github.com/cloudfoundry/java-buildpack
Disabled: false
Stacks V2:
- Image: cloudfoundry/cflinuxfs3
Name: cflinuxfs3
Stacks V3:
- Build Image: cloudfoundry/cnb:cflinuxfs3
Description: A large Cloud Foundry stack based on Ubuntu 18.04
Name: org.cloudfoundry.stacks.cflinuxfs3
Run Image: cloudfoundry/run:full-cnb
Under the Build Config section there are three fields to look at:
- Buildpacks V2 contains a list of V2 compatible buildpacks in the order they'll be run
- Stacks V2 indicates the stacks that can be chosen to trigger a V2 buildpack build
- Stacks V3 indicates the stacks that can be chosen to trigger a V3 buildpack build
You can also list the stacks with kf stacks:
$ kf stacks
Getting stacks in Space: buildpack-docs
Version Name Build Image Run Image Description
V2 cflinuxfs3 cloudfoundry/cflinuxfs3 cloudfoundry/cflinuxfs3
V3 org.cloudfoundry.stacks.cflinuxfs3 cloudfoundry/cnb:cflinuxfs3 cloudfoundry/run:full-cnb A large Cloud Foundry stack based on Ubuntu 18.04
Because V3 build images already have their buildpacks built-in, you must use kf buildpacks to get the list:
$ kf buildpacks
Getting buildpacks in Space: buildpack-docs
Buildpacks for V2 stacks:
Name Position URL
staticfile_buildpack 0 https://github.com/cloudfoundry/staticfile-buildpack
java_buildpack 1 https://github.com/cloudfoundry/java-buildpack
V3 Stack: org.cloudfoundry.stacks.cflinuxfs3:
Name Position Version Latest
org.cloudfoundry.jdbc 0 v1.0.179 true
org.cloudfoundry.jmx 1 v1.0.180 true
org.cloudfoundry.go 2 v0.0.2 true
org.cloudfoundry.tomcat 3 v1.1.102 true
org.cloudfoundry.distzip 4 v1.0.171 true
org.cloudfoundry.springboot 5 v1.1.2 true
...
Customizing V3 Buildpacks
You can customize the buildpacks that are available to your developers by creating your own builder image with exactly the buildpacks they should have access to. You can also use builder images published by other authors.
Use a third-party builder image
A list of published CNB stacks is available from the Buildpack CLI pack. As of this writing, pack suggest-stacks outputs:
$ pack suggest-stacks
Stacks maintained by the community:
Stack ID: heroku-18
Description: The official Heroku stack based on Ubuntu 18.04
Maintainer: Heroku
Build Image: heroku/pack:18-build
Run Image: heroku/pack:18
Stack ID: io.buildpacks.stacks.bionic
Description: A minimal Cloud Foundry stack based on Ubuntu 18.04
Maintainer: Cloud Foundry
Build Image: cloudfoundry/build:base-cnb
Run Image: cloudfoundry/run:base-cnb
Stack ID: org.cloudfoundry.stacks.cflinuxfs3
Description: A large Cloud Foundry stack based on Ubuntu 18.04
Maintainer: Cloud Foundry
Build Image: cloudfoundry/build:full-cnb
Run Image: cloudfoundry/run:full-cnb
Stack ID: org.cloudfoundry.stacks.tiny
Description: A tiny Cloud Foundry stack based on Ubuntu 18.04, similar to distroless
Maintainer: Cloud Foundry
Build Image: cloudfoundry/build:tiny-cnb
Run Image: cloudfoundry/run:tiny-cnb
To modify Kf to use the stack published by Heroku, edit the config-defaults ConfigMap in the kf Namespace.
Add an entry to the spaceStacksV3 key like the following:
$ kubectl edit configmap config-defaults -n kf
spaceStacksV3: |
- name: org.cloudfoundry.stacks.cflinuxfs3
description: A large Cloud Foundry stack based on Ubuntu 18.04
buildImage: cloudfoundry/cnb:cflinuxfs3
runImage: cloudfoundry/run:full-cnb
- name: heroku-18
description: The official Heroku stack based on Ubuntu 18.04
buildImage: heroku/pack:18-build
runImage: heroku/pack:18
Then, run stacks again:
$ kf stacks
Getting stacks in Space: buildpack-docs
Version Name Build Image Run Image Description
V2 cflinuxfs3 cloudfoundry/cflinuxfs3 cloudfoundry/cflinuxfs3
V3 org.cloudfoundry.stacks.cflinuxfs3 cloudfoundry/cnb:cflinuxfs3 cloudfoundry/run:full-cnb A large Cloud Foundry stack based on Ubuntu 18.04
V3 heroku-18 heroku/pack:18-build heroku/pack:18 The official Heroku stack based on Ubuntu 18.04
Create your own builder image
The Buildpack CLI pack is used to create your own builder image. You can follow pack's Working with builders using create-builder documentation to create your own builder image. Once created, push it to a container registry and use add it to the config-defaults ConfigMap.
Setting a default stack
Apps will be assigned a default stack if one isn't supplied in their manifest. The default stack is the first in the V2 or V3 stacks list. Unless overridden, a V2 stack is chosen for compatibility with Cloud Foundry.
You can force Kf to use a V3 stack instead of a V2 by setting the
spaceDefaultToV3Stack field in the config-defaults ConfigMap in the kf
Namespace to be "true":
$ kubectl edit configmap config-defaults -n kf
spaceDefaultToV3Stack: "true"
This option can also be modified on a per-Space basis by changing setting the
spec.buildConfig.defaultToV3Stack field to be true or false. If unset,
the value from the config-defaults ConfigMap is used.
config-defaults value for spaceDefaultToV3Stack |
Space's spec.buildConfig.defaultToV3Stack |
Default stack |
|---|---|---|
| unset | unset | V2 |
"false" |
unset | V2 |
"true" |
unset | V3 |
| any | false |
V2 |
| any | true |
V3 |