如何使用ytt向现有的Kubernetes部署中添加sidecar容器？

Question

我想将一个fluent位代理添加到现有的通过外部工具( Istio入口 Deployment，istioctl)生成的sidecar容器中。我认为使用ytt及其覆盖层可以很好地实现这一点，因为它应该允许我在Deployment中附加一个额外的container和一些额外的volumes，同时保留生成的YAML的其余部分。

下面是一个占位符Deployment，它近似于一个istio-ingressgateay以帮助可视化结构：

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: istio-ingressgateway
  namespace: istio-system
spec:
  selector:
    matchLabels:
      app: istio-ingressgateway
  template:
    metadata:
      labels:
        app: istio-ingressgateway
    spec:
      containers:
      - args:
        - example-args
        command: ["example-command"]
        image: gcr.io/istio/proxyv2
        imagePullPolicy: Always
        name: istio-proxy
      volumes:
        - name: example-volume-secret
          secret:
            secretName: example-secret
        - name: example-volume-configmap
          configMap:
            name: example-configmap

我想在这个文件中添加一个容器，如下所示：

- name: fluent-bit
  image: fluent/fluent-bit
  resources:
    limits:
      memory: 100Mi
    requests:
      cpu: 10m
      memory: 10Mi
  volumeMounts:
  - name: fluent-bit-config
    mountPath: /fluent-bit/etc
  - name: varlog
    mountPath: /var/log
  - name: dockercontainers
    mountPath: /var/lib/docker/containers
    readOnly: true

并且volumes看起来像：

- name: fluent-bit-config
  configMap:
    name: ingressgateway-fluent-bit-forwarder-config
- name: varlog
  hostPath:
    path: /var/log
- name: dockercontainers
  hostPath:
    path: /var/lib/docker/containers

通过修改ytt操场上的覆盖文件示例，我成功地破解了一些东西，如下所示：

#@ load("@ytt:overlay", "overlay")
 #@overlay/match by=overlay.subset({"kind": "Deployment", "metadata":{"name":"istio-ingressgateway"}}),expects=1
 ---
 spec:
   template:
     spec:
       containers:
       #@overlay/append
       - name: fluent-bit
         image: fluent/fluent-bit
         resources:
           limits:
             memory: 100Mi
           requests:
             cpu: 10m
             memory: 10Mi
         volumeMounts:
         - name: fluent-bit-config
           mountPath: /fluent-bit/etc
         - name: varlog
           mountPath: /var/log
         - name: dockercontainers
           mountPath: /var/lib/docker/containers
           readOnly: true
 #@overlay/match by=overlay.subset({"kind": "Deployment", "metadata":{"name":"istio-ingressgateway"}}),expects=1
 ---
 spec:
   template:
     spec:
       volumes:
       #@overlay/append
       - name: fluent-bit-config
         configMap:
           name: ingressgateway-fluent-bit-forwarder-config
       #@overlay/append
       - name: varlog
         hostPath:
           path: /var/log
       #@overlay/append
       - name: dockercontainers
         hostPath:
           path: /var/lib/docker/containers

然而，我想知道的是，使用ytt来做这件事的最好、最惯用的方法是什么？

谢谢!

Answer 1

你现在拥有的是好的！我要提出的一个建议是，如果体积和容器总是需要加在一起，它们就会被合并到相同的覆盖层中，如下所示：

#@ load("@ytt:overlay", "overlay")

#@overlay/match by=overlay.subset({"kind": "Deployment", "metadata":{"name":"istio-ingressgateway"}}),expects=1
---
spec:
  template:
    spec:
      containers:
      #@overlay/append
      - name: fluent-bit
        image: fluent/fluent-bit
        resources:
          limits:
            memory: 100Mi
          requests:
            cpu: 10m
            memory: 10Mi
        volumeMounts:
        - name: fluent-bit-config
          mountPath: /fluent-bit/etc
        - name: varlog
          mountPath: /var/log
        - name: dockercontainers
          mountPath: /var/lib/docker/containers
          readOnly: true
      volumes:
      #@overlay/append
      - name: fluent-bit-config
        configMap:
          name: ingressgateway-fluent-bit-forwarder-config
      #@overlay/append
      - name: varlog
        hostPath:
          path: /var/log
      #@overlay/append
      - name: dockercontainers
        hostPath:
          path: /var/lib/docker/containers

这将保证任何时候容器被添加，适当的卷也将包括在内。