Profiles: Patches

Patches are a way to perform minor overrides to the configuration without having to create a separate config file. Patch functionality follows JSON Patch(RFC) semantics, as implemented by the yaml-patch library.

Example

Patches are ideal for reflecting changes between different environments, e.g. dev, staging and production.

images:
  backend:
    image: john/devbackend
  backend-debugger:
    image: john/debugger
deployments:
- name: backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/devbackend
      - image: john/debugger
profiles:
- name: production
  patches:
  - op: replace
    path: images.backend.image
    value: john/prodbackend
  - op: remove
    path: deployments.name=backend.helm.values.containers[1]
  - op: add
    path: deployments.name=backend.helm.values.containers
    value:
      image: john/cache

Explanation:

• The above example defines 1 profile: production
• When using the profile production, the config would be patched with 3 patches.
• The resulting config used in-memory when the profile production is used would look like this:

# In-Memory Config After Applying Patches For Profile `production`
images:
  backend:
    image: john/devbackend
  backend-debugger:
    image: john/debugger
deployments:
- name: backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/prodbackend
      - image: john/cache

Configuration

name

The name option is mandatory and expects a string defining the name of the profile.

patches

The patches option expects a patch object which consists of the following properties:

• op stating the patch operation (possible values: replace, add, remove)
• path stating a jsonpath or an xpath within the config (e.g. images.backend.image, deployments.name=backend.helm.values.containers[1])
• value stating an arbitrary value used by the operation (e.g. a string, an integer, a boolean, a yaml object)

op: add only for arrays

Using op: add only works as expected when path points to an array value. Using op: add to add properties to an object (e.g. deployments[*].helm.values) will not work and instead replace all existing properties.

Array Paths

When you want to define a path that contains an array (e.g. deployments), you have two options:

1. Use the index of the array item you want to patch, e.g. deployments[0]
2. Use a property selector matching the array item(s) you want to patch, e.g. deployments.name=backend

Using a property selector is often better because it is more resilient and will not cause any issues even if the order of an array's items is changed later on. A property selector is also able to select multiple array items if all of them have the same value for this property.

Value For Replace / Add

If you use the replace or add operation, value is a mandatory property.

info

If value is defined, the new value must provide the correct type to be used when adding or replacing the existing value found under path using the newly provided value, e.g. an array must be replaced with an array.

note

The patches of a profile can modify all parts of the configuration except the sections profiles and commands.

Example: Config Patches

images:
  backend:
    image: john/devbackend
  backend-debugger:
    image: john/debugger
deployments:
- name: backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/devbackend
      - image: john/debugger
profiles:
- name: staging
  patches:
  - op: replace
    path: images.backend.image
    value: john/stagingbackend
  - op: remove
    path: deployments.name=backend.helm.values.containers[1]
- name: production
  patches:
  - op: replace
    path: images.backend.image
    value: john/prodbackend
  - op: remove
    path: deployments.name=backend.helm.values.containers[1]
  - op: add
    path: deployments.name=backend.helm.values.containers
    value:
      image: john/cache

Explanation:

• The above example defines 2 profiles: staging, production
• Users can use the flag -p staging to use the staging profile for a single command execution
• Users can use the flag -p production to use the production profile for a single command execution
• Users can permanently switch to the staging profile using: devspace use profile staging
• Users can permanently switch to the production profile using: devspace use profile production

parent

The parent option is optional and expects the name of another profile which should be applied before this profile. The kind of profile inheritance that the parent option provides can help to reduce redundancy when multiple profiles need to change the config in a similar way.

Execution Order

A parent profile is applied before the profile that defines the parent. A parent profile can have a parent of its own.

Example: Defining a Parent Profile

images:
  backend:
    image: john/devbackend
  backend-debugger:
    image: john/debugger
deployments:
- name: backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/devbackend
      - image: john/debugger
profiles:
- name: production
  parent: staging
  patches:
  - op: add
    path: deployments.name=backend.helm.values.containers
    value:
      image: john/cache
- name: staging
  replace:
    images:
      backend:
        image: john/backendprod
  patches:
  - op: replace
    path: deployments.name=backend.helm.values.container[0].image
    value: john/backendprod
  - op: remove
    path: deployments.name=backend.helm.values.containers[1]

When the production profile is active, the replace and patches statements configured in staging would be applied first because of the parent: staging statement in line 16. After applying the staging profile, DevSpace would additionally apply the currently active production profile. In this example, the production profile is based on the staging profile and the only difference is that the production profile adds another container to the backend deployment which is using the image john/cache.

Useful Commands

devspace print -p [profile]

The following command is useful to verify that the profile modifies the config as intended:

devspace print -p my-profile

The above command would print the config after applying all profile patches and replace statements as well as after replacing all config variables.