Merge pull request #1139 from damienr74/implement-replica-transform

Implement replica transformer as patch alternative

docs/fields.md

@@ -36,6 +36,7 @@ What transformations (customizations) should be applied?
 | [nameSuffix](#namesuffix) | string | The value is appended to the names of all resources. |
 | [commonLabels](#commonlabels) | string | Adds annotions (non-identifying metadata) to add all resources. Like labels, these are key value pairs. |
 | [images](#images) | list | Images modify the name, tags and/or digest for images without creating patches. |
+| [replicas](#replicas) | list | Replicas modify the number of replicas for a resource without creating patches. |
 |[patchesStrategicMerge](#patchesstrategicmerge)| list |Each entry in this list should resolve to a partial or complete resource definition file.|
 |[patchesJson6902](#patchesjson6902)| list  |Each entry in this list should resolve to a kubernetes object and a JSON patch that will be applied to the object.|
 |[transformers](#transformers)|list|[plugin](plugins.md) configuration files|
@@ -236,6 +237,24 @@ images:
   digest: sha256:24a0c4b4a4c0eb97a1aabb8e29f18e917d05abfe1b7a7c07857230879ce7d3d3
 ```
 
+### replicas
+
+Replicas modify the number of replicas for a resource without creating patches.
+E.g. Given this kubernetes Deployment fragment:
+```
+metadata:
+  name: deployment-name
+spec:
+  replicas: 3
+```
+
+one can change the number of replicas to 5 with the following *kustomization*:
+```
+replicas:
+- name: deployment-name
+  count: 5
+```
+note that replicas is a list, so many replicas can be modified at the same time.
 
 ### kind
 

pkg/target/kusttarget_configplugin.go

@@ -69,6 +69,7 @@ func (kt *KustTarget) configureBuiltinTransformers(
 		kt.configureBuiltinLabelTransformer,
 		kt.configureBuiltinAnnotationsTransformer,
 		kt.configureBuiltinPatchJson6902Transformer,
+		kt.configureBuiltinReplicaCountTransformer,
 	}
 	var result []transformers.Transformer
 	for _, f := range configurators {
@@ -78,6 +79,7 @@ func (kt *KustTarget) configureBuiltinTransformers(
 		}
 		result = append(result, r...)
 	}
+
 	return result, nil
 }
 
@@ -233,6 +235,24 @@ func (kt *KustTarget) configureBuiltinImageTagTransformer(
 	return
 }
 
+func (kt *KustTarget) configureBuiltinReplicaCountTransformer(
+	tConfig *config.TransformerConfig) (
+	result []transformers.Transformer, err error) {
+	var c struct {
+		Replica types.Replica
+	}
+	for _, args := range kt.kustomization.Replicas {
+		c.Replica = args
+		p := builtin.NewReplicaCountTransformerPlugin()
+		err = kt.configureBuiltinPlugin(p, c, "replica")
+		if err != nil {
+			return nil, err
+		}
+		result = append(result, p)
+	}
+	return
+}
+
 func (kt *KustTarget) configureBuiltinPlugin(
 	p plugins.Configurable, c interface{}, id string) (err error) {
 	var y []byte

pkg/types/kustomization.go

@@ -79,6 +79,10 @@ type Kustomization struct {
 	// patch, but this operator is simpler to specify.
 	Images []image.Image `json:"images,omitempty" yaml:"images,omitempty"`
 
+	// Replicas is a list of {resourcename, count} that allows for simpler replica
+	// specification. This can also be done with a patch.
+	Replicas []Replica `json:"replicas,omitempty" yaml:"replicas,omitempty"`
+
 	// Vars allow things modified by kustomize to be injected into a
 	// container specification. A var is a name (e.g. FOO) associated
 	// with a field in a specific resource instance.  The field must
@@ -355,3 +359,15 @@ type PatchTarget struct {
 // stategic merge patch with the format
 // https://github.com/kubernetes/community/blob/master/contributors/devel/strategic-merge-patch.md
 type PatchStrategicMerge string
+
+// Replica specifies a modification to a replica config.
+// The number of replicas of a resource whose name matches will be set to count.
+// This struct is used by the ReplicaCountTransform, and is meant to supplement
+// the existing patch functionality with a simpler syntax for replica configuration.
+type Replica struct {
+	// The name of the resource to change the replica count
+	Name string `json:"name,omitempty" yaml:"name,omitempty"`
+
+	// The number of replicas required.
+	Count uint `json:"count,omitempty" yaml:"count,omitempty"`
+}

plugin/builtin/ReplicaCountTransformer.go

@@ -0,0 +1,59 @@
+// Code generated by pluginator on ReplicaCountTransformer; DO NOT EDIT.
+package builtin
+
+import (
+	"fmt"
+
+	"sigs.k8s.io/kustomize/pkg/ifc"
+	"sigs.k8s.io/kustomize/pkg/resid"
+	"sigs.k8s.io/kustomize/pkg/resmap"
+	"sigs.k8s.io/kustomize/pkg/types"
+	"sigs.k8s.io/yaml"
+)
+
+const (
+	fldReplica = "replicas"
+	fldSpec    = "spec"
+)
+
+// Find matching replicas declarations and replace the count.
+// Eases the kustomization configuration of replica changes.
+type ReplicaCountTransformerPlugin struct {
+	Replica types.Replica `json:"replica,omitempty" yaml:"replica,omitempty"`
+}
+
+func NewReplicaCountTransformerPlugin() *ReplicaCountTransformerPlugin {
+	return &ReplicaCountTransformerPlugin{}
+}
+
+func (p *ReplicaCountTransformerPlugin) Config(
+	ldr ifc.Loader, rf *resmap.Factory, c []byte) (err error) {
+
+	p.Replica = types.Replica{}
+	return yaml.Unmarshal(c, p)
+}
+
+func (p *ReplicaCountTransformerPlugin) Transform(m resmap.ResMap) error {
+	matcher := func(r resid.ResId) bool {
+		return r.ItemId.Name == p.Replica.Name
+	}
+
+	for _, r := range m.GetMatchingIds(matcher) {
+		kMap := m[r].Map()
+
+		specInterface, ok := kMap[fldSpec]
+		if !ok {
+			return fmt.Errorf("object %s missing field %s, cannot update %s",
+				p.Replica.Name, fldSpec, fldReplica)
+		}
+
+		if spec, ok := specInterface.(map[string]interface{}); ok {
+			spec[fldReplica] = p.Replica.Count
+			kMap[fldSpec] = spec
+		} else {
+			return fmt.Errorf("object %s has a malformed %s", p.Replica.Name, fldSpec)
+		}
+	}
+
+	return nil
+}

plugin/builtin/replicacounttransformer/ReplicaCountTransformer.go

@@ -0,0 +1,60 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+//go:generate go run sigs.k8s.io/kustomize/plugin/pluginator
+package main
+
+import (
+	"fmt"
+
+	"sigs.k8s.io/kustomize/pkg/ifc"
+	"sigs.k8s.io/kustomize/pkg/resid"
+	"sigs.k8s.io/kustomize/pkg/resmap"
+	"sigs.k8s.io/kustomize/pkg/types"
+	"sigs.k8s.io/yaml"
+)
+
+const (
+	fldReplica = "replicas"
+	fldSpec    = "spec"
+)
+
+// Find matching replicas declarations and replace the count.
+// Eases the kustomization configuration of replica changes.
+type plugin struct {
+	Replica types.Replica `json:"replica,omitempty" yaml:"replica,omitempty"`
+}
+
+var KustomizePlugin plugin
+
+func (p *plugin) Config(
+	ldr ifc.Loader, rf *resmap.Factory, c []byte) (err error) {
+
+	p.Replica = types.Replica{}
+	return yaml.Unmarshal(c, p)
+}
+
+func (p *plugin) Transform(m resmap.ResMap) error {
+	matcher := func(r resid.ResId) bool {
+		return r.ItemId.Name == p.Replica.Name
+	}
+
+	for _, r := range m.GetMatchingIds(matcher) {
+		kMap := m[r].Map()
+
+		specInterface, ok := kMap[fldSpec]
+		if !ok {
+			return fmt.Errorf("object %s missing field %s, cannot update %s",
+				p.Replica.Name, fldSpec, fldReplica)
+		}
+
+		if spec, ok := specInterface.(map[string]interface{}); ok {
+			spec[fldReplica] = p.Replica.Count
+			kMap[fldSpec] = spec
+		} else {
+			return fmt.Errorf("object %s has a malformed %s", p.Replica.Name, fldSpec)
+		}
+	}
+
+	return nil
+}

plugin/builtin/replicacounttransformer/ReplicaCountTransformer_test.go

@@ -0,0 +1,49 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package main_test
+
+import (
+	"testing"
+
+	"sigs.k8s.io/kustomize/pkg/kusttest"
+	"sigs.k8s.io/kustomize/plugin"
+)
+
+func TestReplicaCountTransformer(t *testing.T) {
+	tc := plugin.NewEnvForTest(t).Set()
+	defer tc.Reset()
+
+	tc.BuildGoPlugin(
+		"builtin", "", "ReplicaCountTransformer")
+
+	th := kusttest_test.NewKustTestPluginHarness(t, "/app")
+
+	rm := th.LoadAndRunTransformer(`
+apiVersion: builtin
+kind: ReplicaCountTransformer
+metadata:
+  name: notImportantHere
+replica:
+  name: deploy1
+  count: 23
+`, `
+group: apps
+apiVersion: v1
+kind: Deployment
+metadata:
+  name: deploy1
+spec:
+  replicas: 1
+`)
+
+	th.AssertActualEqualsExpected(rm, `
+apiVersion: v1
+group: apps
+kind: Deployment
+metadata:
+  name: deploy1
+spec:
+  replicas: 23
+`)
+}