ConfigMap掛載與Subpath在Nginx容器中的應用

本文分享自華爲雲社區《nginx.conf以configmap文件形式掛載到nginx容器中以及subpath使用場景》，作者：可以交個朋友。

背景

nginx.conf通過configmap文件形式掛載到容器內，可以更加方便的修改nginx.conf配置

方案簡介

將配置文件nginx.conf以configmap文件的方式掛載到容器中。爲了更通用，可以將使用主nginx.conf include 指定xx.conf方式，主nginx.conf作爲一個cm，具體xx.conf對應一個cm

configmap可以通過ENV環境變量和文件兩種方式掛載到容器中，修改configmap後容器中對應的ENV環境變量不會更新；修改configmap後容器中對應的file會自動更新，如果以subpath方式掛載文件，文件內容不會自動更新

將nginx.conf作爲configmap掛載到容器中

1.創建configmap

apiVersion: v1
kind: ConfigMap
metadata:
  name: nginx-config
  namespace: default
data:
  nginx.conf: |+
    user  nginx;
    worker_processes  8;
    error_log  /var/log/nginx/error.log warn;
    pid        /var/run/nginx.pid;
    events {
        worker_connections  1024;
    }
    http {
        include       /etc/nginx/mime.types;
        default_type  application/octet-stream;
        log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                          '$status $body_bytes_sent "$http_referer" '
                          '"$http_user_agent" "$http_x_forwarded_for"';
        access_log  /var/log/nginx/access.log  main;
        sendfile        on;
        keepalive_timeout  65;
        #gzip  on;
        include /etc/nginx/conf.d/*.conf;
    }
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: nginx-server-config
  namespace: default
data:
  server1.conf: |+
    server {
            listen       80;
            server_name  server1.com;
            location / {
                root   /usr/share/nginx/html/;
                index  index.html index.htm;
            }
            error_page   500 502 503 504  /50x.html;
            location = /50x.html {
                root   html;
            }
        }
  server2.conf: |+
    server {
            listen       81;
            server_name  server2.com;
            location / {
                root   /usr/share/nginx/html/;
                index  index.html index.htm;
            }
            error_page   500 502 503 504  /50x.html;
            location = /50x.html {
                root   html;
            }
        }

2.部署nginx業務使用對應的cm

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    version: v1
  name: test-reload
  namespace: default
spec:
  progressDeadlineSeconds: 600
  replicas: 1
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app: test-reload
  template:
    metadata:
       labels:
        app: test-reload
    spec:
      containers:
      - image: nginx:latest
        imagePullPolicy: Always
        name: container-1
        volumeMounts:
        - mountPath: /etc/nginx/conf.d
          name: vol-168233491311961268
        - mountPath: /etc/nginx/nginx.conf
          name: vol-168249948123126427
          readOnly: true
          subPath: nginx.conf
      dnsPolicy: ClusterFirst
      imagePullSecrets:
      - name: default-secret
      restartPolicy: Always
      volumes:
      - configMap:
          defaultMode: 420
          name: nginx-server-config
        name: vol-168233491311961268
      - configMap:
          defaultMode: 420
          name: nginx-config
        name: vol-168249948123126427

subpath拓展

subpath的作用如下:

• 避免覆蓋。如果掛載路徑是一個已存在的目錄，則目錄下的內容不會被覆蓋。直接將configMap/Secret掛載在容器的路徑，會覆蓋掉容器路徑下原有的文件，使用subpath選定configMap/Secret的指定的key-value掛載在容器中，則不會覆蓋掉原目錄下的其他文件
• 文件隔離。pod中含有多個容器公用一個日誌volume，不同容器日誌路徑掛載的到不同的子目錄，而不是根路徑（Subpath目錄會在底層存儲自動創建且權限爲777，無需手動創建）

避免覆蓋效果演示

1.創建一個工作負載nginx，並用普通方式掛載configmap配置文件

apiVersion: v1
kind: ConfigMap
metadata:
  name: config
data:
  test-subpath.conf: |+
    test subpath;
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: test
  name: test
spec:
  replicas: 1
  selector:
    matchLabels:
      app: test
  template:
    metadata:
      labels:
        app: test
    spec:
      volumes:
      - configMap:
          defaultMode: 420
          name: config
        name: vol-168249948123126427
      containers:
      - image: centos:latest
        name: centos
        command:
        - /bin/bash
        args:
        - -c
        - while true;do sleep 1 &&  echo hello;done
        volumeMounts:
        - mountPath: /tmp
          name: vol-168249948123126427

2.使用docker inspect ${容器id}命令查看容器掛載信息，掛載目標爲tmp目錄，tmp目錄下原有內容被覆蓋

[root@test-746c64649c-pzztn /]# ls -l /tmp/
total 0
lrwxrwxrwx 1 root root 24 Feb 27 03:02 test-subpath.conf -> ..data/test-subpath.conf

3.創建一個工作負載nginx，並用subpath方式掛載configmap配置文件

apiVersion: v1
kind: ConfigMap
metadata:
  name: config
data:
  test-subpath.conf: |+
    test subpath;
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: test
  name: test
spec:
  replicas: 1
  selector:
    matchLabels:
      app: test
  template:
    metadata:
      labels:
        app: test
    spec:
      volumes:
      - configMap:
          defaultMode: 420
          name: config
        name: vol-168249948123126427
      containers:
      - image: centos:latest
        name: centos
        command:
        - /bin/bash
        args:
        - -c
        - while true;do sleep 1 &&  echo hello;done
        volumeMounts:
        - mountPath: /tmp/test-subpath.conf
          name: vol-168249948123126427
          subPath: test-subpath.conf

4.使用docker inspect ${容器Id}命令查看容器掛載信息，掛載目標爲test-subpath.conf文件，所以tmp目錄下原來的文件不會被覆蓋

[root@test-7b64fd6bb-56lpp /]# ls -l /tmp/
total 12
-rwx------ 1 root root 701 Dec  4  2020 ks-script-esd4my7v
-rwx------ 1 root root 671 Dec  4  2020 ks-script-eusq_sc5
-rw-r--r-- 1 root root  14 Feb 27 03:07 test-subpath.conf

文件隔離演示

1.創建工作負載test，使用hostPath卷類型持久化日誌文件

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: test
  name: test
spec:
  replicas: 2
  selector:
    matchLabels:
      app: test
  template:
    metadata:
      labels:
        app: test
    spec:
      volumes:
      - hostPath:
          path: /tmp/log   #該路徑必須在節點上已存在
        name: vol-168249948123126427
      containers:
      - image: centos:latest
        name: centos
        env:
        - name: POD_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        command:
        - /bin/bash
        args:
        - -c
        - while true;do echo $(POD_NAME) >> /tmp/log/app.log && sleep 900 ;done
        volumeMounts:
        - mountPath: /tmp/log
          name: vol-168249948123126427
          subPathExpr: $(POD_NAME)

2.兩個Pod實例調度至同一個節點

[root@test ~]# kubectl get pod -owide -l app=test
NAME                    READY   STATUS    RESTARTS   AGE   IP            NODE           NOMINATED NODE   READINESS GATES
test-69dfc665cd-2nhg5   1/1     Running   0          95s   172.16.4.59   172.16.2.172   <none>           <none>
test-69dfc665cd-z7rsj   1/1     Running   0          77s   172.16.4.25   172.16.2.172   <none>           <none>

3.進入容器內查看日誌文件

[root@test ~]# kubectl exec -it test-69dfc665cd-2nhg5 bash
[root@test-69dfc665cd-2nhg5 /]# cat /tmp/log/app.log 
test-69dfc665cd-2nhg5
[root@test-69dfc665cd-2nhg5 /]# exit
exit
[root@test ~]# kubectl exec -it test-69dfc665cd-z7rsj bash
[root@test-69dfc665cd-z7rsj /]# cat /tmp/log/app.log 
test-69dfc665cd-z7rsj

4.在節點上查看掛載路徑，每個Pod的日誌文件用目錄進行隔離，目錄名爲Pod名稱

[root@172 log]# pwd
/tmp/log
[root@172 log]# ll
total 0
drwxr-xr-x 2 root root 60 Feb 27 15:08 test-69dfc665cd-2nhg5
drwxr-xr-x 2 root root 60 Feb 27 15:09 test-69dfc665cd-z7rsj
[root@172 log]# cat test-69dfc665cd-2nhg5/app.log 
test-69dfc665cd-2nhg5
[root@172 log]# cat test-69dfc665cd-z7rsj/app.log 
test-69dfc665cd-z7rsj

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