Function Patch and Transform

Function Patch and Transform allows you to write a Composition that specifies managed resource (MR) templates, and uses “patch and transform” operations to fill them out. Crossplane fills the templates out with values copied from a claim or composite resource (XR).

A patch copies a value from one resource and patches it onto another resource. A transform modifies the values before applying the patch.

Here’s an example Composition that uses Function Patch and Transform. When you create an AcmeBucket XR that uses this Composition, Crossplane uses the template to create the Amazon S3 Bucket MR.

Crossplane copies the value from the AcmeBucket XR’s spec.desiredRegion field and patch it onto the Bucket managed resource’s spec.forProvider.region field.

 1apiVersion: apiextensions.crossplane.io/v1
 2kind: Composition
 3metadata:
 4  name: example
 5spec:
 6  compositeTypeRef:
 7    apiVersion: custom-api.example.org/v1alpha1
 8    kind: AcmeBucket
 9  mode: Pipeline
10  pipeline:
11  - step: patch-and-transform
12    functionRef:
13      name: function-patch-and-transform
14    input:
15      apiVersion: pt.fn.crossplane.io/v1beta1
16      kind: Resources
17      resources:
18      - name: storage-bucket
19        base:
20          apiVersion: s3.aws.upbound.io/v1beta1
21          kind: Bucket
22          spec:
23            forProvider:
24              region: "us-east-2"
25        patches:
26        - type: FromCompositeFieldPath
27          fromFieldPath: spec.desiredRegion
28          toFieldPath: spec.forProvider.region

Install the function

You must install Function Patch and Transform before you can use it in a Composition. Apply this manifest to install Function Patch and Transform:

1apiVersion: pkg.crossplane.io/v1
2kind: Function
3metadata:
4  name: function-patch-and-transform
5spec:
6  package: xpkg.upbound.io/crossplane-contrib/function-patch-and-transform:v0.1.4

Resource templates

The resources field the function’s input defines the set of things that a composite resource creates when it uses this function.

For example, the input can define a template to create a virtual machine and an associated storage bucket at the same time.

The resources field lists the individual resources with a name. This name identifies the resource inside the Composition. It isn’t related to the external name used with the Provider.

The contents of the base are identical to creating a standalone managed resource.

This example uses Upbound’s Provider AWS to define a S3 storage Bucket and EC2 compute Instance.

After defining the apiVersion and kind, define the spec.forProvider fields defining the settings of the resource.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3resources:
 4- name: storage-bucket
 5  base:
 6    apiVersion: s3.aws.upbound.io/v1beta1
 7    kind: Bucket
 8    spec:
 9      forProvider:
10        region: "us-east-2"
11- name: vm
12  base:
13    apiVersion: ec2.aws.upbound.io/v1beta1
14    kind: Instance
15    spec:
16      forProvider:
17        ami: ami-0d9858aa3c6322f73
18        instanceType: t2.micro
19        region: "us-east-2"

When a composite resource uses this function, the composite resource creates two new managed resources with all the provided spec.forProvider settings.

The spec supports any settings used in a managed resource, including applying annotations and labels or using a specific providerConfigRef.

Create a patch

Each entry in the resources list can include a list of patches. The patches field takes a list of patches to apply to the individual resource.

Each patch has a type, which defines what kind of patch action Crossplane applies.

Patches reference fields inside different resources depending on the patch type, but all patches reference a fromFieldPath and toFieldPath.

The fromFieldPath is the path to the patch’s input values. The toFieldPath is the path the patch applies to.

Here’s an example of a patch that copies a value from the composite resource’s spec.field1 field to the composed Bucket’s labels.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3resources:
 4- name: storage-bucket
 5  base:
 6    apiVersion: s3.aws.upbound.io/v1beta1
 7    kind: Bucket
 8    spec:
 9      forProvider:
10        region: "us-east-2"
11  patches:
12    - type: FromCompositeFieldPath
13      fromFieldPath: spec.field1
14      toFieldPath: metadata.labels["patchLabel"]

Selecting fields

Crossplane selects fields in a composite resource or managed resource with a subset of JSONPath selectors, called “field paths.”

Field paths can select any field in a composite resource or managed resource object, including the metadata, spec or status fields.

Field paths can be a string matching a field name or an array index, in brackets. Field names may use a . character to select child elements.

Example field paths

Here are some example selectors from a composite resource object.

 1$ kubectl get composite -o yaml
 2apiVersion: example.org/v1alpha1
 3kind: XExample
 4metadata:
 5  # Removed for brevity
 6  labels:
 7    crossplane.io/claim-name: my-example-claim
 8    crossplane.io/claim-namespace: default
 9    crossplane.io/composite: my-example-claim-978mh
10spec:
11  desiredRegion: eu-north-1
12  field1: field1-text
13  resourceRefs:
14  - apiVersion: s3.aws.upbound.io/v1beta1
15    kind: Bucket
16    name: my-example-claim-978mh-r6z64
17  - apiVersion: s3.aws.upbound.io/v1beta1
18    kind: Bucket
19    name: my-example-claim-978mh-cnlhj
20  - apiVersion: s3.aws.upbound.io/v1beta1
21    kind: Bucket
22    name: my-example-claim-978mh-rv5nm

Reuse a patch

You can reuse a patch object on multiple resources by using a PatchSet.

To create a PatchSet, define a patchSets object in the function’s input.

Each patch inside a PatchSet has a name and a list of patches.

Apply the PatchSet to a resource with a patch type: PatchSet. Set the patchSetName to the name of the PatchSet.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3patchSets:
 4- name: my-patchset
 5  patches:
 6  - type: FromCompositeFieldPath
 7    fromFieldPath: spec.desiredRegion
 8    toFieldPath: spec.forProvider.region
 9resources:
10- name: bucket1
11  base:
12    # Removed for brevity
13  patches:
14    - type: PatchSet
15      patchSetName: my-patchset
16- name: bucket2
17  base:
18    # Removed for brevity
19  patches:
20    - type: PatchSet
21      patchSetName: my-patchset  

Patching between resources

Function Patch and Transform can’t directly patch between two composed resources. For example, generating a network resource and patching the resource name to a compute resource.

A resource can patch to a user-defined status field in the composite resource. Another resource can then read from that Status field to patch a field.

First, define a custom status in the composite resource Definition and a custom field, for example secondResource

 1kind: CompositeResourceDefinition
 2# Removed for brevity.
 3spec:
 4  # Removed for brevity.
 5  versions:
 6  - name: v1alpha1
 7    schema:
 8      openAPIV3Schema:
 9        type: object
10        properties:
11          spec:
12            # Removed for brevity.
13          status:
14              type: object
15              properties:
16                secondResource:
17                  type: string

Inside the function input the resource with the source data uses a ToCompositeFieldPath patch to write data to the status.secondResource field in the composite resource.

The destination resource uses a FromCompositeFieldPath patch to read data from the composite resource status.secondResource field in the composite resource and write it to a label named secondResource in the managed resource.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3resources:
 4- name: bucket1
 5  base:
 6    apiVersion: s3.aws.upbound.io/v1beta1
 7    kind: Bucket
 8    # Removed for brevity
 9  patches:
10    - type: ToCompositeFieldPath
11      fromFieldPath: metadata.name
12      toFieldPath: status.secondResource
13- name: bucket2
14  base:
15    apiVersion: s3.aws.upbound.io/v1beta1
16    kind: Bucket
17    # Removed for brevity
18  patches:
19    - type: FromCompositeFieldPath
20      fromFieldPath: status.secondResource
21      toFieldPath: metadata.labels['secondResource']

Describe the composite resource to view the resources and the status.secondResource value.

 1$ kubectl describe composite
 2Name:         my-example-claim-jp7rx
 3Spec:
 4  # Removed for brevity
 5  Resource Refs:
 6    Name:         my-example-claim-jp7rx-gfg4m
 7    # Removed for brevity
 8    Name:         my-example-claim-jp7rx-fttpj
 9Status:
10  # Removed for brevity
11  Second Resource:         my-example-claim-jp7rx-gfg4m

Describe the destination managed resource to see the label secondResource.

1$ kubectl describe bucket
2kubectl describe bucket my-example-claim-jp7rx-fttpj
3Name:         my-example-claim-jp7rx-fttpj
4Labels:       crossplane.io/composite=my-example-claim-jp7rx
5              secondResource=my-example-claim-jp7rx-gfg4m

Patch with EnvironmentConfigs

Crossplane uses EnvironmentConfigs to create in-memory data stores. Compositions can read and write from this data store as part of the patch process.

EnvironmentConfigs can predefine data that Compositions can use or a composite resource can write data to their in-memory environment for other resources to read.

To apply a patch using EnvironmentConfigs, first define which EnvironmentConfigs to use with environment.environmentConfigs.

Use either a reference or a selector to identify the EnvironmentConfigs to use.

1apiVersion: apiextensions.crossplane.io/v1
2kind: Composition
3# Removed for Brevity
4spec:
5  environment:
6    environmentConfigs:
7      - ref:
8          name: example-environment
9  # Removed for Brevity

Patch a composite resource

To patch between the composite resource and the in-memory environment use patches inside of the environment.

Use the ToCompositeFieldPath to copy data from the in-memory environment to the composite resource.

Use the FromCompositeFieldPath to copy data from the composite resource to the in-memory environment.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3environment:
 4  patches:
 5  - type: ToCompositeFieldPath
 6    fromFieldPath: tags
 7    toFieldPath: metadata.labels[envTag]
 8  - type: FromCompositeFieldPath
 9    fromFieldPath: metadata.name
10    toFieldPath: newEnvironmentKey

Individual resources can use any data written to their in-memory environment.

Patch an individual resource

To patch an individual resource, inside the patches of the resource, use ToEnvironmentFieldPath to copy data from the resource to the in-memory environment.

Use FromEnvironmentFieldPath to copy data to the resource from the in-memory environment.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3resources:
 4- name: vpc
 5  base:
 6    apiVersion: ec2.aws.upbound.io/v1beta1
 7    kind: VPC
 8    spec:
 9      forProvider:
10        cidrBlock: 172.16.0.0/16
11  patches:
12  - type: ToEnvironmentFieldPath
13    fromFieldPath: status.atProvider.id
14    toFieldPath: vpcId
15  - type: FromEnvironmentFieldPath
16    fromFieldPath: tags
17    toFieldPath: spec.forProvider.tags

The EnvironmentConfigs page has more information on EnvironmentConfigs options and usage.

Types of patches

Function Patch and Transform supports multiple patch types, each using a different source for data and applying the patch to a different location.

Summary of Crossplane patches

 1apiVersion: apiextensions.crossplane.io/v1
 2kind: Composition
 3metadata:
 4  name: example-composition
 5spec:
 6  compositeTypeRef:
 7    apiVersion: example.org/v1alpha1
 8    kind: xExample
 9  environment:
10    environmentConfigs:
11    - ref:
12        name: example-environment
13  mode: Pipeline
14  pipeline:
15  - step: patch-and-transform
16    functionRef:
17      name: function-patch-and-transform
18    input:
19      apiVersion: pt.fn.crossplane.io/v1beta1
20      kind: Resources
21      resources:
22      - name: bucket1
23        base:
24          apiVersion: s3.aws.upbound.io/v1beta1
25          kind: Bucket
26          spec:
27            forProvider:
28              region: us-east-2
29      - name: bucket2
30        base:
31          apiVersion: s3.aws.upbound.io/v1beta1
32          kind: Bucket
33          spec:
34            forProvider:
35              region: us-east-2

 1apiVersion: apiextensions.crossplane.io/v1
 2kind: CompositeResourceDefinition
 3metadata:
 4  name: xexamples.example.org
 5spec:
 6  group: example.org
 7  names:
 8    kind: xExample
 9    plural: xexamples
10  claimNames:
11    kind: ExampleClaim
12    plural: exampleclaims
13  versions:
14  - name: v1alpha1
15    served: true
16    referenceable: true
17    schema:
18      openAPIV3Schema:
19        type: object
20        properties:
21          spec:
22            type: object
23            properties:
24              field1:
25                type: string
26              field2:
27                type: string
28              field3: 
29                type: string
30              desiredRegion: 
31                type: string
32              boolField:
33                type: boolean
34              numberField:
35                type: integer
36          status:
37              type: object
38              properties:
39                url:
40                  type: string

 1apiVersion: example.org/v1alpha1
 2kind: ExampleClaim
 3metadata:
 4  name: my-example-claim
 5spec:
 6  field1: "field1-text"
 7  field2: "field2-text"
 8  desiredRegion: "eu-north-1"
 9  boolField: false
10  numberField: 10

 1apiVersion: apiextensions.crossplane.io/v1alpha1
 2kind: EnvironmentConfig
 3metadata:
 4  name: example-environment
 5data:
 6  locations:
 7    us: us-east-2
 8    eu: eu-north-1
 9  key1: value1
10  key2: value2

FromCompositeFieldPath

The FromCompositeFieldPath patch takes a value in a composite resource and applies it to a field in the composed resource.

For example, to use the value desiredRegion provided by a user in a composite resource to a managed resource’s region.

The fromFieldPath value is a field in the composite resource.

The toFieldPath value is the field in the composed resource to change.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3resources:
 4- name: bucket1
 5  base:
 6    apiVersion: s3.aws.upbound.io/v1beta1
 7    kind: Bucket
 8    spec:
 9      forProvider:
10        region: us-east-2
11  patches:
12    - type: FromCompositeFieldPath
13      fromFieldPath: spec.desiredRegion
14      toFieldPath: spec.forProvider.region

View the managed resource to see the updated region

1$ kubectl describe bucket
2Name:         my-example-claim-qlr68-29nqf
3# Removed for brevity
4Spec:
5  For Provider:
6    Region:  eu-north-1

ToCompositeFieldPath

The ToCompositeFieldPath writes data from an individual composed resource to the composite resource that created it.

For example, after Crossplane creates a new managed resource, take the value hostedZoneID and apply it as a label in the composite resource.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3resources:
 4- name: bucket1
 5  base:
 6    apiVersion: s3.aws.upbound.io/v1beta1
 7    kind: Bucket
 8    spec:
 9      forProvider:
10        region: us-east-2
11  patches:
12    - type: ToCompositeFieldPath
13      fromFieldPath: status.atProvider.hostedZoneId
14      toFieldPath: metadata.labels['ZoneID']

View the created managed resource to see the Hosted Zone Id field.

1$ kubectl describe bucket
2Name:         my-example-claim-p5pxf-5vnp8
3# Removed for brevity
4Status:
5  At Provider:
6    Hosted Zone Id:       Z2O1EMRO9K5GLX
7    # Removed for brevity

Next view the composite resource and confirm the patch applied the label

1$ kubectl describe composite
2Name:         my-example-claim-p5pxf
3Labels:       ZoneID=Z2O1EMRO9K5GLX

CombineFromComposite

The CombineFromComposite patch takes values from the composite resource, combines them and applies them to the composed resource.

For example, use the Claim value desiredRegion and field2 to generate the managed resource’s name

The CombineFromComposite patch only supports the combine option.

The variables are the list of fromFieldPath values from the composite resource to combine.

The only supported strategy is strategy: string.

Optionally you can apply a string.fmt, based on Go string formatting to specify how to combine the strings.

The toFieldPath is the field in the composed resource to apply the new string to.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3resources:
 4- name: bucket1
 5  base:
 6    apiVersion: s3.aws.upbound.io/v1beta1
 7    kind: Bucket
 8    spec:
 9      forProvider:
10        region: us-east-2
11  patches:
12    - type: CombineFromComposite
13      combine:
14        variables:
15          - fromFieldPath: spec.desiredRegion
16          - fromFieldPath: spec.field2
17        strategy: string
18        string:
19          fmt: "my-resource-%s-%s"
20      toFieldPath: metadata.name

Describe the managed resource to see the applied patch.

1$ kubectl describe bucket
2Name:         my-resource-eu-north-1-field2-text

CombineToComposite

The CombineToComposite patch takes values from the composed resource, combines them and applies them to the composite resource.

For example, use the managed resource name and region to generate a custom url field.

The CombineToComposite patch only supports the combine option.

The variables are the list of fromFieldPath the managed resource to combine.

The only supported strategy is strategy: string.

Optionally you can apply a string.fmt, based on Go string formatting to specify how to combine the strings.

The toFieldPath is the field in the composite resource to apply the new string to.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3resources:
 4- name: bucket1
 5  base:
 6    apiVersion: s3.aws.upbound.io/v1beta1
 7    kind: Bucket
 8    spec:
 9      forProvider:
10        region: us-east-2
11  patches:
12    - type: CombineToComposite
13      combine:
14        variables:
15          - fromFieldPath: metadata.name
16          - fromFieldPath: spec.forProvider.region
17        strategy: string
18        string:
19          fmt: "https://%s.%s.com"
20      toFieldPath: status.url

View the composite resource to verify the applied patch.

1$ kubectl describe composite
2Name:         my-example-claim-bjdjw
3API Version:  example.org/v1alpha1
4Kind:         xExample
5# Removed for brevity
6Status:
7  # Removed for brevity
8  URL:                     https://my-example-claim-bjdjw-r6ncd.us-east-2.com

FromEnvironmentFieldPath

The FromEnvironmentFieldPath patch takes values from the in-memory environment and applies them to the composed resource.

For example, use the environment’s locations.eu value and apply it as the region.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3resources:
 4- name: bucket1
 5  base:
 6    apiVersion: s3.aws.upbound.io/v1beta1
 7    kind: Bucket
 8    spec:
 9      forProvider:
10        region: us-east-2
11    patches:
12    - type: FromEnvironmentFieldPath
13      fromFieldPath: locations.eu
14      toFieldPath: spec.forProvider.region

Verify managed resource to confirm the applied patch.

1kubectl describe bucket
2Name:         my-example-claim-8vrvc-xx5sr
3Labels:       crossplane.io/claim-name=my-example-claim
4# Removed for brevity
5Spec:
6  For Provider:
7    Region:  eu-north-1
8  # Removed for brevity

ToEnvironmentFieldPath

The ToEnvironmentFieldPath patch takes a value from the composed resource and applies it to the in-memory environment.

For example, use the desired region value and apply it as the environment’s key1.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3resources:
 4- name: bucket1
 5  base:
 6    apiVersion: s3.aws.upbound.io/v1beta1
 7    kind: Bucket
 8    spec:
 9      forProvider:
10        region: us-east-2
11    patches:
12    - type: ToEnvironmentFieldPath
13      fromFieldPath: spec.forProvider.region
14      toFieldPath: key1

Because the environment is in-memory, there is no command to confirm the patch wrote the value to the environment.

CombineFromEnvironment

The CombineFromEnvironment patch combines multiple values from the in-memory environment and applies them to the composed resource.

For example, combine multiple fields in the environment to create a unique annotation .

The CombineFromEnvironment patch only supports the combine option.

The only supported strategy is strategy: string.

The variables are the list of fromFieldPath values from the in-memory environment to combine.

Optionally you can apply a string.fmt, based on Go string formatting to specify how to combine the strings.

The toFieldPath is the field in the composed resource to apply the new string to.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3resources:
 4- name: bucket1
 5  base:
 6    apiVersion: s3.aws.upbound.io/v1beta1
 7    kind: Bucket
 8    spec:
 9      forProvider:
10        region: us-east-2
11  patches:
12    - type: CombineFromEnvironment
13      combine:
14        strategy: string
15        variables:
16        - fromFieldPath: key1
17        - fromFieldPath: key2
18        string: 
19          fmt: "%s-%s"
20      toFieldPath: metadata.annotations[EnvironmentPatch]

Describe the managed resource to see new annotation.

1$ kubectl describe bucket
2Name:         my-example-claim-zmxdg-grl6p
3# Removed for brevity
4Annotations:  EnvironmentPatch: value1-value2
5# Removed for brevity

CombineToEnvironment

The CombineToEnvironment patch combines multiple values from the composed resource and applies them to the in-memory EnvironmentConfig environment.

For example, combine multiple fields in the managed resource to create a unique string and store it in the environment’s key2 value.

The string combines the managed resource Kind and region.

The CombineToEnvironment patch only supports the combine option.

The only supported strategy is strategy: string.

The variables are the list of fromFieldPath values in the managed resource to combine.

Optionally you can apply a string.fmt, based on Go string formatting to specify how to combine the strings.

The toFieldPath is the key in the environment to write the new string to.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3resources:
 4- name: bucket1
 5  base:
 6    apiVersion: s3.aws.upbound.io/v1beta1
 7    kind: Bucket
 8    spec:
 9      forProvider:
10        region: us-east-2
11  patches:
12    - type: CombineToEnvironment
13      combine:
14        strategy: string
15        variables:
16        - fromFieldPath: kind
17        - fromFieldPath: spec.forProvider.region
18        string:
19          fmt: "%s.%s"
20      toFieldPath: key2

Because the environment is in-memory, there is no command to confirm the patch wrote the value to the environment.

Transform a patch

When applying a patch, Crossplane supports modifying the data before applying it as a patch. Crossplane calls this a “transform” operation.

Summary of Crossplane transforms.

Apply a transform directly to an individual patch with the transforms field.

A transform requires a type, indicating the transform action to take.

The other transform field is the same as the type, in this example, map.

The other fields depend on the patch type used.

This example uses a type: map transform, taking the input spec.desiredRegion, matching it to either us or eu and returning the corresponding AWS region for the spec.forProvider.region value.

 1apiVersion: pt.fn.crossplane.io/v1beta1
 2kind: Resources
 3resources:
 4- name: bucket1
 5  base:
 6    apiVersion: s3.aws.upbound.io/v1beta1
 7    kind: Bucket
 8    spec:
 9      forProvider:
10        region: us-east-2
11  patches:
12    - type: FromCompositeFieldPath
13      fromFieldPath: spec.desiredRegion
14      toFieldPath: spec.forProvider.region
15      transforms:
16        - type: map
17          map:
18            us: us-east-2
19            eu: eu-north-1

Convert transforms

The convert transform type changes the input data type to a different data type.

A convert transform requires a toType, defining the output data type.

1patches:
2- type: FromCompositeFieldPath
3  fromFieldPath: spec.numberField
4  toFieldPath: metadata.label["numberToString"]
5  transforms:
6    - type: convert
7      convert:
8        toType: string

Supported toType values:

Converting strings to booleans

When converting from a string to a bool Crossplane considers the string values
1, t, T, TRUE, True and true equal to the boolean value True.

The strings 0, f, F, FALSE, False and false are equal to the boolean value False.

Converting numbers to booleans

Crossplane considers the integer 1 and float 1.0 equal to the boolean value True. Any other integer or float value is False.

Converting booleans to numbers

Crossplane converts the boolean value True to the integer 1 or float64 1.0.

The value False converts to the integer 0 or float64 0.0

Converting strings to float64

When converting from a string to a float64 Crossplane supports an optional
format: quantity field.

Using format: quantity translates size suffixes like M for megabyte or Mi for megabit into the correct float64 value.

Add format: quantity to the convert object to enable quantity suffix support.

1- type: convert
2  convert:
3   toType: float64
4   format: quantity

Converting strings to objects

Crossplane converts JSON strings to objects.

Add format: json to the convert object which is the only supported string format for this conversion.

1- type: convert
2  convert:
3   toType: object
4   format: json

The following example adds a tag to a resource with a customized key:

 1    - type: FromCompositeFieldPath
 2      fromFieldPath: spec.clusterName
 3      toFieldPath: spec.forProvider.tags
 4      transforms:
 5      - type: string
 6        string:
 7          type: Format
 8          fmt: '{"kubernetes.io/cluster/%s": "true"}'
 9      - type: convert
10        convert:
11          toType: object
12          format: json

Converting strings to arrays

Crossplane converts JSON strings to arrays.

Add format: json to the convert object which is the only supported string format for this conversion.

1- type: convert
2  convert:
3   toType: array
4   format: json

Map transforms

The map transform type maps an input value to an output value.

The map transform compares the value from the fromFieldPath to the options listed in the map.

If Crossplane finds the value, Crossplane puts the mapped value in the toFieldPath.

spec.field1 is the string "field1-text" then Crossplane uses the string firstField for the annotation.

If spec.field1 is the string "field2-text" then Crossplane uses the string secondField for the annotation.

1patches:
2  - type: FromCompositeFieldPath
3    fromFieldPath: spec.field1
4    toFieldPath: metadata.annotations["myAnnotation"]
5    transforms:
6      - type: map
7        map:
8          "field1-text": "firstField"
9          "field2-text": "secondField"

In this example, the value of spec.field1 is field1-text.

1$ kubectl describe composite
2Name:         my-example-claim-twx7n
3Spec:
4  # Removed for brevity
5  field1:         field1-text

The annotation applied to the managed resource is firstField.

1$ kubectl describe bucket
2Name:         my-example-claim-twx7n-ndb2f
3Annotations:  crossplane.io/composition-resource-name: bucket1
4              myAnnotation: firstField
5# Removed for brevity.

Match transform

The match transform is like the map transform.

The match transform adds support for regular expressions along with exact strings and can provide default values if there isn’t a match.

A match object requires a patterns object.

The patterns is a list of one or more patterns to attempt to match the input value against.

 1patches:
 2  - type: FromCompositeFieldPath
 3    fromFieldPath: spec.field1
 4    toFieldPath: metadata.annotations["myAnnotation"]
 5    transforms:
 6      - type: match
 7        match:
 8          patterns:
 9            - type: literal
10              # Removed for brevity
11            - type: regexp
12              # Removed for brevity

Match patterns can be either type: literal to match an exact string or type: regexp to match a regular expression.

Match an exact string

Use a pattern with type: literal to match an exact string.

On a successful match Crossplane provides the result: to the patch toFieldPath.

 1patches:
 2  - type: FromCompositeFieldPath
 3    fromFieldPath: spec.field1
 4    toFieldPath: metadata.annotations["myAnnotation"]
 5    transforms:
 6      - type: match
 7        match:
 8          patterns:
 9            - type: literal
10              literal: "field1-text"
11              result: "matchedLiteral"

Match a regular expression

Use a pattern with type: regexp to match a regular expression.
Define a regexp key with the value of the regular expression to match.

On a successful match Crossplane provides the result: to the patch toFieldPath.

 1patches:
 2  - type: FromCompositeFieldPath
 3    fromFieldPath: spec.field1
 4    toFieldPath: metadata.annotations["myAnnotation"]
 5    transforms:
 6      - type: match
 7        match:
 8          patterns:
 9            - type: regexp
10              regexp: '^field1.*'
11              result: "foundField1"

Using default values

Optionally you can provide a default value to use if there is no matching pattern.

The default value can either be the original input value or a defined default value.

Use fallbackTo: Value to provide a default value if a match isn’t found.

For example if the string unknownString isn’t matched, Crossplane provides the Value StringNotFound to the toFieldPath

 1patches:
 2  - type: FromCompositeFieldPath
 3    fromFieldPath: spec.field1
 4    toFieldPath: metadata.annotations["myAnnotation"]
 5    transforms:
 6      - type: match
 7        match:
 8          patterns:
 9            - type: literal
10              literal: "UnknownString"
11              result: "foundField1"
12          fallbackTo: Value
13          fallbackValue: "StringNotFound"

To use the original input as the fallback value use fallbackTo: Input.

Crossplane uses the original fromFieldPath input for the toFieldPath value.

 1patches:
 2  - type: FromCompositeFieldPath
 3    fromFieldPath: spec.field1
 4    toFieldPath: metadata.annotations["myAnnotation"]
 5    transforms:
 6      - type: match
 7        match:
 8          patterns:
 9            - type: literal
10              literal: "UnknownString"
11              result: "foundField1"
12          fallbackTo: Input

Math transforms

Use the math transform to multiply an input or apply a minimum or maximum value.

1patches:
2  - type: FromCompositeFieldPath
3    fromFieldPath: spec.numberField
4    toFieldPath: metadata.annotations["mathAnnotation"]
5    transforms:
6      - type: math
7        math:
8          ...

clampMin

The type: clampMin uses a defined minimum value if an input is larger than the type: clampMin value.

For example, this type: clampMin requires an input to be greater than 20.

If an input is lower than 20, Crossplane uses the clampMin value for the toFieldPath.

1patches:
2  - type: FromCompositeFieldPath
3    fromFieldPath: spec.numberField
4    toFieldPath: metadata.annotations["mathAnnotation"]
5    transforms:
6      - type: math
7        math:
8          type: clampMin
9          clampMin: 20

clampMax

The type: clampMax uses a defined minimum value if an input is larger than the type: clampMax value.

For example, this type: clampMax requires an input to be less than 5.

If an input is higher than 5, Crossplane uses the clampMax value for the toFieldPath.

1patches:
2  - type: FromCompositeFieldPath
3    fromFieldPath: spec.numberField
4    toFieldPath: metadata.annotations["mathAnnotation"]
5    transforms:
6      - type: math
7        math:
8          type: clampMax
9          clampMax: 5

Multiply

The type: multiply multiplies the input by the multiply value.

For example, this type: multiply multiplies the value from the fromFieldPath value by 2

1patches:
2  - type: FromCompositeFieldPath
3    fromFieldPath: spec.numberField
4    toFieldPath: metadata.annotations["mathAnnotation"]
5    transforms:
6      - type: math
7        math:
8          type: multiply
9          multiply: 2

String transforms

The string transform applies string formatting or manipulation to string inputs.

1patches:
2  - type: FromCompositeFieldPath
3    fromFieldPath: spec.field1
4    toFieldPath: metadata.annotations["stringAnnotation"]
5    transforms:
6      - type: string
7        string:
8          type: ...

String transforms support the following types

• Convert
• Format
• Join
• Regexp
• TrimPrefix
• TrimSuffix

String convert

The type: convert converts the input based on one of the following conversion types:

• ToUpper - Change the string to all upper case letters.
• ToLower - Change the string to all lower case letters.
• ToBase64 - Create a new base64 string from the input.
• FromBase64 - Create a new text string from a base64 input.
• ToJson - Convert the input string to valid JSON.
• ToSha1 - Create a SHA-1 hash of the input string.
• ToSha256 - Create a SHA-256 hash of the input string.
• ToSha512 - Create a SHA-512 hash of the input string.
• ToAdler32 - Create an Adler32 hash of the input string.

1patches:
2  - type: FromCompositeFieldPath
3    fromFieldPath: spec.field1
4    toFieldPath: metadata.annotations["FIELD1-TEXT"]
5    transforms:
6      - type: string
7        string:
8          type: Convert
9          convert: "ToUpper"

String format

The type: format applies Go string formatting to the input.

1patches:
2  - type: FromCompositeFieldPath
3    fromFieldPath: spec.field1
4    toFieldPath: metadata.annotations["stringAnnotation"]
5    transforms:
6      - type: string
7        string:
8          type: Format
9          fmt: "the-field-%s"

Join

The type: Join joins all values in the input array into a string using the given separator.

This transform only works with array inputs.

 1patches:
 2  - type: FromCompositeFieldPath
 3    fromFieldPath: spec.parameters.inputList
 4    toFieldPath: spec.targetJoined
 5    transforms:
 6      - type: string
 7        string:
 8          type: Join
 9          join:
10            separator: ","

Regular expression type

The type: Regexp extracts the part of the input matching a regular expression.

Optionally use a group to match a regular expression capture group.
By default Crossplane matches the entire regular expression.

 1patches:
 2  - type: FromCompositeFieldPath
 3    fromFieldPath: spec.desiredRegion
 4    toFieldPath: metadata.annotations["euRegion"]
 5    transforms:
 6      - type: string
 7        string:
 8          type: Regexp
 9          regexp:
10            match: '^eu-(.*)-'
11            group: 1

Trim prefix

The type: TrimPrefix uses Go’s TrimPrefix and removes characters from the beginning of a line.

1patches:
2  - type: FromCompositeFieldPath
3    fromFieldPath: spec.desiredRegion
4    toFieldPath: metadata.annotations["north-1"]
5    transforms:
6      - type: string
7        string:
8          type: TrimPrefix
9          trim: `eu-

Trim suffix

The type: TrimSuffix uses Go’s TrimSuffix and removes characters from the end of a line.

1patches:
2  - type: FromCompositeFieldPath
3    fromFieldPath: spec.desiredRegion
4    toFieldPath: metadata.annotations["eu"]
5    transforms:
6      - type: string
7        string:
8          type: TrimSuffix
9          trim: `-north-1'

Patch policies

Crossplane supports two types of patch policies:

• fromFieldPath
• toFieldPath

fromFieldPath policy

Using a fromFieldPath: Required policy on a patch requires the fromFieldPath to exist in the data source resource.

By default, Crossplane applies the policy fromFieldPath: Optional. With fromFieldPath: Optional Crossplane ignores a patch if the fromFieldPath doesn’t exist.

With fromFieldPath: Required the composite resource produces an error if the fromFieldPath doesn’t exist.

1patches:
2  - type: FromCompositeFieldPath
3    fromFieldPath: spec.desiredRegion
4    toFieldPath: metadata.annotations["eu"]
5    policy:
6      fromFieldPath: Required

toFieldPath policy

By default when applying a patch the function replaces the destination data. Use toFieldPath to allow patches to merge arrays and objects without overwriting them.

The toFieldPath policy supports these options:

1patches:
2  - type: FromCompositeFieldPath
3    fromFieldPath: spec.desiredRegion
4    toFieldPath: metadata.annotations["eu"]
5    policy:
6      toFieldPath: MergeObjectsAppendArrays

Composite resource connection details

Function patch and Transform must define the specific secret keys a resource creates with the connectionDetails object.

 1kind: Composition
 2spec:
 3  writeConnectionSecretsToNamespace: other-namespace
 4  mode: Pipeline
 5  pipeline:
 6  - step: patch-and-transform
 7    functionRef:
 8      name: function-patch-and-transform
 9    input:
10      apiVersion: pt.fn.crossplane.io/v1beta1
11      kind: Resources
12      resources:
13      - name: key
14        base:
15          # Removed for brevity
16          spec:
17            forProvider:
18            # Removed for brevity
19            writeConnectionSecretToRef:
20              namespace: docs
21              name: key1
22        connectionDetails:
23          - name: my-username
24            type: FromConnectionSecretKey
25            fromConnectionSecretKey: username
26          - name: my-field-secret
27            type: FromFieldPath
28            fromFieldPath: spec.forProvider.user
29          - name: my-status-secret
30            type: FromValue
31            value: "docs.crossplane.io"