我发现的问题是我可以成功安装Puppet模块。例如：
[puppet@swarmcritic ~]$ puppet module install puppetlabs/mysql
Notice: Preparing to install into /home/puppet/.puppet/modules ...
Notice: Created target directory /home/puppet/.puppet/modules
Notice: Downloading from https://forge.puppetlabs.com ...
Notice: Installing -- do not interrupt ...
/home/puppet/.puppet/modules
??? puppetlabs-mysql (v2.1.0)
??? puppetlabs-stdlib (v4.1.0)
但是，当我尝试使用nodes.pp文件调用模块时，如下所示：
node 'example.com' {
include '::mysql::server'
}
然后我得到这样的错误：
[puppet@example mysql]$ sudo puppet apply ~puppet/puppet/manifests/site.pp
Error: Could not find class ::mysql::server for example.com on node example.com
Error: Could not find class ::mysql::server for example.com on node example.com
我该如何解决？