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ConfigMap资源对象

介绍

ConfigMap对象实现了将配置文件从容器镜像中解耦，从而增强了容器应用的可移植性。简而言之，一个ConfigMap就是一系列配置数据的集合(如单个属性，或粗粒度信息如整个配置文件或JSON对象)，这些数据可“注入”到Pod对象中，并为容器应用所使用，注入方式有挂载为存储卷和传递为环境变量两种。

ConfigMap 对象将配置数据以键值对的形式存储，这些数据可以在Pod对象中使用或者为系统组件提供配置。

ConfigMap使用方式

• 填充环境变量
• 设置容器内的命令行参数
• 填充卷的配置文件

ConfigMap创建方式

• 直接在命令行中指定configmap参数创建，即--from-literal

• 指定文件创建，即将一个配置文件创建为一个ConfigMap--from-file=<文件>

• 指定目录创建，即将一个目录下的所有配置文件创建为一个ConfigMap，--from-file=<目录>

• 先写好标准的configmap的yaml文件，然后kubectl create -f 创建

Yaml创建方式示例

场景介绍

在Kubernetes中部署Elasticsearch集群创建时，需要配置集群名称以及集群待加入节点信息，和设置集群master最少节点要求等配置，使用confmap来作为填充卷方式让Pod进行挂载容器内的文件路径/usr/share/elasticsearch/config/elasticsearch.yml，来提供elasticsearch.yml配置文件内容。

ConfigMap Yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: "es-config"
data:
  elasticsearch.yml: |
    cluster.name: ${CLUSTER_NAME}
    network.host: "0.0.0.0"
    bootstrap.memory_lock: false
    node.master: ${NODE_MASTER}
    discovery.zen.ping.unicast.hosts: ${DISCOVERY_ZEN_PING_UNICAST_HOSTS}
    discovery.zen.minimum_master_nodes: ${DISCOVERY_ZEN_MINIMUM_MASTER_NODES}

Pod 局部定义YAML

spec:
  initContainers:
    - name: fix-permissions
      image: "{{ .ImageBusyBox }}"
      command: ["sh", "-c", "chown -R 1000:1000 /usr/share/elasticsearch/data"]
      securityContext:
        privileged: true
      volumeMounts:
        - name: data
          mountPath: /usr/share/elasticsearch/data
    - name: increase-vm-max-map
      image: "{{ .ImageBusyBox }}"
      command: ["sysctl", "-w", "vm.max_map_count=262144"]
      securityContext:
        privileged: true
    - name: increase-fd-ulimit
      image: "{{ .ImageBusyBox }}"
      command: ["sh", "-c", "ulimit -n 65536"]
      securityContext:
        privileged: true
  containers:
    - name: elasticsearch
      image: "{{ .ImageEs}}"
      imagePullPolicy: Always
      env:
        - name: CLUSTER_NAME
          value: "sb-{{ .InstanceID }}-es-cluster"
        - name:  NODE_MASTER
          value: "true"
        - name: ES_JAVA_OPTS
          value: "-Xms512m -Xmx512m"
        - name: DISCOVERY_ZEN_PING_UNICAST_HOSTS
          value: "sb-{{ .InstanceID }}-es-cluster-discovery"
        - name: DISCOVERY_ZEN_MINIMUM_MASTER_NODES
          value: "{{ .MasterMinNumber }}"
      # - name: "bootstrap.memory_lock"
      #   value: "true"
      ports:
        - containerPort: 9200
          protocol: TCP
          name: discovery
        - containerPort: 9300
          protocol: TCP
          name: transport
      volumeMounts:
        - mountPath: /usr/share/elasticsearch/data
          name: data
        - mountPath: /usr/share/elasticsearch/logs
          name: data
        - mountPath: /usr/share/elasticsearch/config/elasticsearch.yml
          name: elasticsearch-config
          subPath: elasticsearch.yml
      resources:
        limits:
          memory: "{{ .ContainerMemory }}Gi"
          cpu: "{{ .ContainerCPU }}"
  nodeSelector:
    kubernetes.io/hostname: "{{ .TempHost }}"
  volumes:
    - name: data
      hostPath:
        path: "{{ .TempDataPath}}"
    - name: elasticsearch-config
      configMap:
        name: "es-config"

volumeMounts:将容器内要替换的配置文件路径/usr/share/elasticsearch/config/elasticsearch.yml设置为挂载点。将configmap设置成挂载卷的防止进行使用。

容器内部查看

[root@sb-bsi-es-12161721-33-es-instanceid-0-0 config]# pwd
/usr/share/elasticsearch/config
[root@sb-bsi-es-12161721-33-es-instanceid-0-0 config]# ls
elasticsearch.keystore  jvm.options        role_mapping.yml  users
elasticsearch.yml       log4j2.properties  roles.yml         users_roles
[root@sb-bsi-es-12161721-33-es-instanceid-0-0 config]# cat elasticsearch.yml
cluster.name: ${CLUSTER_NAME}
network.host: "0.0.0.0"
bootstrap.memory_lock: false
node.master: ${NODE_MASTER}
discovery.zen.ping.unicast.hosts: ${DISCOVERY_ZEN_PING_UNICAST_HOSTS}
discovery.zen.minimum_master_nodes: ${DISCOVERY_ZEN_MINIMUM_MASTER_NODES}
[root@sb-bsi-es-12161721-33-es-instanceid-0-0 config]#

通过运行起来的服务我们进容器中查看目标挂载文件，已经从configmap设置的配置文件挂载进来了。