在Ansible攻略中设置一行为可选

Question

我用F5构建了一个虚拟服务器的实战手册。我想让一行代码只在有人输入变量时执行。在本例中，default_persistence_profile:行有一个变量"{{ persistenceProfile }}“。有时开发人员不希望持久性应用于他们的应用程序，但有时他们会。我发现，当我在运行任务中将变量设置为可选，并且没有选择持久性配置文件时，任务会出错。请参阅下面的攻略：

    - name: Build the Virtual Server
      bigip_virtual_server:
        state: present
        partition: Common
        name: "{{ vsName  }}" 
        destination: "{{ vsIpAddress }}"
        port: "{{ vsPort }}"
        pool: "{{ poolName }}"
        default_persistence_profile: "{{ persistenceProfile }}"
        ip_protocol: tcp 
        snat: automap
        description: "{{ vsDescription }}"
        profiles:
           - tcp
           - http
           - name: "{{ clientsslName }}" 
             context: client-side
           - name: default-server-ssl
             context: server-side

Answer 1

Ansible有一个使用default过滤器的omitting parameters机制，如下所示：

    - name: Build the Virtual Server
      bigip_virtual_server:
        state: present
        partition: Common
        name: "{{ vsName  }}" 
        destination: "{{ vsIpAddress }}"
        port: "{{ vsPort }}"
        pool: "{{ poolName }}"
        default_persistence_profile: "{{ persistenceProfile|default(omit) }}"
        ip_protocol: tcp 
        snat: automap
        description: "{{ vsDescription }}"
        profiles:
           - tcp
           - http
           - name: "{{ clientsslName }}" 
             context: client-side
           - name: default-server-ssl
             context: server-side

如果未设置persistenceProfile，则不应将default_persistence_profile参数传递给bigip_virtual_server模块。