如何使用Kustomize替换HTTPRoute的backendRefs.name字段

自Kustomize 5.0.0起，vars功能被弃用，迁移至replacements后，仅能成功替换HTTPRoute的metadata.labels.app字段，spec.rules.backendRefs.name字段无法完成替换。

原文件内容 #

main.yaml #

apiVersion: v1
kind: Service
metadata:
  labels:
    app: foooooooooooooooo
  name: service
---
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  labels:
    app: WANT_TO_REPLACE_THIS
  name: route
spec:
  hostnames:
    - "*"
  rules:
    - backendRefs:
        - name: WANT_TO_REPLACE_THIS
          port: 3000
      matches:
        - path:
            type: PathPrefix
            value: /path

kustomization.yaml #

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - main.yaml
replacements:
  - source:
      kind: Service
      name: service
      fieldPath: metadata.labels.app
    targets:
      - select:
          kind: HTTPRoute
          name: route
        fieldPaths:
          - metadata.labels.app
          - spec.rules.[backendRefs.name=WANT_TO_REPLACE_THIS].backendRefs.[name=WANT_TO_REPLACE_THIS].name

执行kustomize build后的结果 #

apiVersion: v1
kind: Service
metadata:
  labels:
    app: foooooooooooooooo
  name: service
---
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  labels:
    app: foooooooooooooooo
  name: route
spec:
  hostnames:
  - '*'
  rules:
  - backendRefs:
    - name: WANT_TO_REPLACE_THIS
      port: 3000
    matches:
    - path:
        type: PathPrefix
        value: /path

问题原因与解决办法 #

问题根源 #

原fieldPath写法不符合Kustomize Replacements的数组筛选语法：rules和backendRefs都是数组类型，错误的嵌套筛选写法无法匹配到目标字段。

修正方案 #

根据需求选择以下两种写法之一：

1. 替换所有backendRefs的name字段（通配符匹配）

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - main.yaml
replacements:
  - source:
      kind: Service
      name: service
      fieldPath: metadata.labels.app
    targets:
      - select:
          kind: HTTPRoute
          name: route
        fieldPaths:
          - metadata.labels.app
          - spec.rules[*].backendRefs[*].name

2. 精准匹配name为WANT_TO_REPLACE_THIS的backendRef条目

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - main.yaml
replacements:
  - source:
      kind: Service
      name: service
      fieldPath: metadata.labels.app
    targets:
      - select:
          kind: HTTPRoute
          name: route
        fieldPaths:
          - metadata.labels.app
          - spec.rules[*].backendRefs.[name=WANT_TO_REPLACE_THIS].name

修正后执行kustomize build的结果 #

apiVersion: v1
kind: Service
metadata:
  labels:
    app: foooooooooooooooo
  name: service
---
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  labels:
    app: foooooooooooooooo
  name: route
spec:
  hostnames:
  - '*'
  rules:
  - backendRefs:
    - name: foooooooooooooooo
      port: 3000
    matches:
    - path:
        type: PathPrefix
        value: /path

内容的提问来源于stack exchange，提问作者akrsum