puppet: Define用法详解

# ... puppet/modules/splunkforwarder/
$ tree
.
|-- README.md
|-- files
| `-- props.conf
|-- manifests
| |-- init.pp
| |-- input.pp
| `-- params.pp
`-- templates
    |-- inputs
    | |-- ascrub.erb
    | |-- os.erb
    | |-- production.erb
    | |-- sandbox.erb

先看实例，Module结构如上：

$ more params.pp
class splunkforwarder::params {
$admin_password = 'ngVQW1xxxxxxx’
$basedir        = '/opt/splunkforwarder'
$inputs         = [ 'os,stage_os,splunkforwarder/inputs/os.erb', 'user,stage_tungsten,splunkforwarder/inputs/zapp.erb' ]
$cloudspl          = undef
}

定义了子类params,这里也类似namespace,

$ more input.pp

define splunkforwarder::input (
$basedir,
) {
$value = split($name, ',')
$app_name = $value[0]
$index_name = $value[1]
$template_name = $value[2]
$dirs = [
"${basedir}/etc/apps/${app_name}",
"${basedir}/etc/apps/${app_name}/local",
]

file { $dirs:
ensure  => directory,
mode    => '0755',
owner   => 'splunk',
group   => 'splunk',
}

file { "${basedir}/etc/apps/${app_name}/local/inputs.conf":
ensure  => present,
mode    => '0644',
owner   => 'splunk',
group   => 'splunk',
require => File["${basedir}/etc/apps/${app_name}/local"],
notify  => Service['splunk'],
content => template($template_name),
}

}

这里调用了puppet的内置函数split, 跟include/require类似，不过它需要参数。在这里可以看到

class splunkforwarder (
$admin_password = $splunkforwarder::params::admin_password,
$basedir        = $splunkforwarder::params::basedir,
$inputs         = $splunkforwarder::params::inputs,
$limits_thruput = $splunkforwarder::params::limits_thruput,
$splunk_servers = $splunkforwarder::params::splunk_servers,
$version        = $splunkforwarder::params::version,
$cloudspl       = $splunkforwarder::params::cloudspl,
) inherits splunkforwarder::params {

$splunk_cmd = "${basedir}/bin/splunk"

package {'splunkforwarder':
ensure => $version,
}

exec { 'splunk_create_service':
command => "${basedir}/bin/splunk enable boot-start --accept-license --answer-yes --no-prompt",
subscribe => Package['splunkforwarder'],
}

service { 'splunk':
ensure    => 'running',
enable    => true,
hasstatus => true,
pattern   => 'splunkd',
require   => Exec['splunk_create_service'],
}

# Change of admin password
exec { 'splunk_change_admin_password':
command     => "${splunk_cmd} edit user admin -password ${admin_password} -role admin -auth admin:changeme",
refreshonly => true,
require     => Service['splunk'],
}

if $cloudspl {
exec { 'retrieve_spl':
command   => "/usr/bin/wget -q ${cloudspl} -O ${basedir}/splunkclouduf.spl",
creates   => "${basedir}/splunkclouduf.spl",
require   => Exec['splunk_change_admin_password'],
}

file { 'splunkclouduf.spl':
path      => "${basedir}/splunkclouduf.spl",
mode      => 0640,
require   => Exec["retrieve_spl"],
}
~>
exec { 'install_spl':
command   => "${splunk_cmd} install app ${basedir}/splunkclouduf.spl -auth admin:changeme",
refreshonly => true,
}
}

if $cloudspl == undef {
file {
'outputs.conf':
ensure  => present,
path    => "${basedir}/etc/system/local/outputs.conf",
mode    => '0644',
owner   => 'splunk',
group   => 'splunk',
require => Package['splunkforwarder'],
notify  => Service['splunk'],
content => template('splunkforwarder/outputs.conf.erb');
}
}

file {
'limits.conf':
ensure  => present,
path    => "${basedir}/etc/system/local/limits.conf",
mode    => '0644',
owner   => 'splunk',
group   => 'splunk',
require => Package['splunkforwarder'],
notify  => Service['splunk'],
content => template('splunkforwarder/limits.conf.erb');
}

file {
'props.conf':
ensure  => present,
path    => "${basedir}/etc/apps/SplunkUniversalForwarder/default/props.conf",
mode    => '0644',
owner   => 'splunk',
group   => 'splunk',
require => Package['splunkforwarder'],
notify  => Service['splunk'],
source => "puppet:///modules/splunkforwarder/props.conf";
}

splunkforwarder::input { $inputs:
basedir => $basedir,
require => Package['splunkforwarder'],
notify  => Service['splunk'],
}

}

分析： splunkforwarder入口init.pp调用了input.pp, 并且$name（也叫$title,就是资源的名字)的值是$input, 它来自什么地方？看下

$inputs = $splunkforwarder::params::inputs，
这个class含有参数，$inputs,而且inherits了params.pp的值，也就是params.pp的参数值可以被override。由于这里没定义，那么直接继承就是列表
[ 'os,stage_os,splunkforwarder/inputs/os.erb', 'user,stage_tungsten,splunkforwarder/inputs/zapp.erb' ]
那么最后splunk::input这个被包含后,$input的值就是$name了。
define splunkforwarder::input (
$basedir,
) {
$value = split($name, ',')
$app_name = $value[0]
$index_name = $value[1]
$template_name = $value[2]
$dirs = [
"${basedir}/etc/apps/${app_name}",
"${basedir}/etc/apps/${app_name}/local",
]

file { $dirs:
ensure => directory,
mode => '0755',
owner => 'splunk',
group => 'splunk',
}
看下这个define, 定义了参数basedir。然后是变量赋值，$value=split($name,",")用了split函数，$name就是刚说的List，值如下， 
		[ 'os,stage_os,splunkforwarder/inputs/os.erb', 'user,stage_tungsten,splunkforwarder/inputs/zapp.erb' ]
		
			
关于define，官方Docs很详细：Defined resource types (also called defined types or defines) are blocks of Puppet code that can be evaluated multiple times with different parameters. 
就是一个code可以传递不同参数这在配置文件非常实用，典型例子就是apache的vhost.



为什么要使用define以及注意事项