16.3. 使用 Downward API 消耗巨页资源

流程

1. 创建一个类似以下示例的 hugepages-volume-pod.yaml 文件：

   apiVersion: v1
   kind: Pod
   metadata:
     generateName: hugepages-volume-
     labels:
       app: hugepages-example
   spec:
     containers:
     - securityContext:
         capabilities:
           add: [ "IPC_LOCK" ]
       image: rhel7:latest
       command:
       - sleep
       - inf
       name: example
       volumeMounts:
       - mountPath: /dev/hugepages
         name: hugepage
       - mountPath: /etc/podinfo
         name: podinfo
       resources:
         limits:
           hugepages-1Gi: 2Gi
           memory: "1Gi"
           cpu: "1"
         requests:
           hugepages-1Gi: 2Gi
       env:
       - name: REQUESTS_HUGEPAGES_1GI <.>
         valueFrom:
           resourceFieldRef:
             containerName: example
             resource: requests.hugepages-1Gi
     volumes:
     - name: hugepage
       emptyDir:
         medium: HugePages
     - name: podinfo
       downwardAPI:
         items:
           - path: "hugepages_1G_request" <.>
             resourceFieldRef:
               containerName: example
               resource: requests.hugepages-1Gi
               divisor: 1Gi

   <.> 指定从 requests.hugepages-1Gi 读取资源使用，并将值公开为 REQUESTS_HUGEPAGES_1GI 环境变量。< .> 指定从 requests.hugepages-1Gi 读取资源使用,并将值公开为文件 /etc/podinfo/hugepages_1G_request。

2. 从 hugepages-volume-pod.yaml 文件创建 pod：

   $ oc create -f hugepages-volume-pod.yaml

验证

1. 检查 REQUESTS_HUGEPAGES_1GI 环境变量的值：

   $ oc exec -it $(oc get pods -l app=hugepages-example -o jsonpath='{.items[0].metadata.name}') \
        -- env | grep REQUESTS_HUGEPAGES_1GI

   输出示例

   REQUESTS_HUGEPAGES_1GI=2147483648

2. 检查 /etc/podinfo/hugepages_1G_request 文件的值：

   $ oc exec -it $(oc get pods -l app=hugepages-example -o jsonpath='{.items[0].metadata.name}') \
        -- cat /etc/podinfo/hugepages_1G_request

   输出示例

   2