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Arnaud Gomes-do-Vale

2011-Jul-11 16:31 UTC

[Puppet Users] How to avoid the use of defined

Hi folks,

This is a "best practices" question as much as a technical one.

I am trying to redefine variables when I include a specific class. The
use case is installing php 5.3 on a few select centos 5 boxes while
keeping the default php 5.1 install on others. Here is the relevant part
of my apache module:

---------------------------------------------------------------------
class apache::php inherits apache::base {
  include apache::params

  package { ''php'':
    name => $apache::params::php_package,
    ensure => installed,
    require => Package[''httpd''],
    notify => Service[''httpd''];
  ''php-gd'':
    name => $apache::params::php_gd_package,
    ensure => installed,
    require => Package[''php''],
    notify => Service[''httpd''];
  ''php-imap'':
    name => $apache::params::php_imap_package,
    ensure => installed,
    require => Package[''php''],
    notify => Service[''httpd''];
  ''php-ldap'':
    name => $apache::params::php_ldap_package,
    ensure => installed,
    require => Package[''php''],
    notify => Service[''httpd''];
  }
}

class apache::php53 inherits apache::php {
  # $os is defined in site.pp.
  if $::os == ''rhel5'' {
    # Dirty hack. Yuck.
    exec { ''/usr/bin/yum -y replace php --replace-with
php53u'':
      onlyif => ''/bin/rpm -q php'',
      # Class common::redhat::el::el5 installs yum-plugin-replace.
      require => Class[''common::redhat::el::el5''],
      notify => Service[''httpd''],
    }
  }
  else {
    warning ''Class apache::php53 should only ever be defined for RHEL5
and its clones.''
  }
}

class apache::params {
  case $::os {
    # .../...
    ''rhel5'': {
      $httpd_package = ''httpd''
      $httpd_service = ''httpd''
      $rootdir = ''/var/www/html''
      if defined(Class[''apache::php53'']) {
        $php_package = ''php53u''
        $php_gd_package = ''php53u-gd''
        $php_imap_package = ''php53u-imap''
        $php_ldap_package = ''php53u-ldap''
      }
      else {
        $php_package = ''php''
        $php_gd_package = ''php-gd''
        $php_imap_package = ''php-imap''
        $php_ldap_package = ''php-ldap''
      }
    }
  }
}
---------------------------------------------------------------------

When I add the apache::php53 to my host (I use LDAP as a node classifier
if that matters), php and its extensions get upgraded to 5.3. However,
when I add a class that depends on apache::php53, the defined function
evaluates as false.

class wordpress {
  # apache::lamp includes apache::php
  include apache::lamp

  if $::os == ''rhel5'' {
    include apache::php53
  }
  # .../...
}

I understand defined is quite unreliable. So I am wondering if there is
a better option (read a working one)?

Hardcoding the packages names in class apache::php53 is not enough as I
have a bunch of other classes installing additional PHP modules. I
suppose I could subclass them as well but things would probably get
quite messy quite fast.

Thanks,
-- 
Arnaud

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Arnaud Gomes-do-Vale

2011-Jul-12 10:59 UTC

head link

Re: [Puppet Users] How to avoid the use of defined

Arnaud Gomes-do-Vale <Arnaud.Gomes@ircam.fr> writes:
> class wordpress {
>   # apache::lamp includes apache::php
>   include apache::lamp
>
>   if $::os == ''rhel5'' {
>     include apache::php53
>   }
>   # .../...
> }
Including apache::php53 before apache::lamp fixes the issue. I wouldn''t
trust this is rock-solid though; including other classes in the wrong
order would probably break this.

-- 
Arnaud

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jcbollinger

2011-Jul-12 14:24 UTC

head link

[Puppet Users] Re: How to avoid the use of defined

On Jul 11, 11:31 am, Arnaud Gomes-do-Vale <Arnaud.Go...@ircam.fr>
wrote:> Hi folks,
>
> This is a "best practices" question as much as a technical one.
>
> I am trying to redefine variables when I include a specific class. The
> use case is installing php 5.3 on a few select centos 5 boxes while
> keeping the default php 5.1 install on others.

I think it would be more precise to say "I am trying to redefine
variables when a specific class *has been* included."  The distinction
is significant, because it narrows the possible approaches to only a
few bad ones.  Here''s a good rule of thumb: never use Puppet''s
"defined()" function in your manifests.  Ever.  It is brittle, and it
will cause you grief, increasing exponentially with the number of
uses.

> Here is the relevant part
> of my apache module:
>
> ---------------------------------------------------------------------
> class apache::php inherits apache::base {
>   include apache::params
>
>   package { ''php'':
>     name => $apache::params::php_package,
>     ensure => installed,
>     require => Package[''httpd''],
>     notify => Service[''httpd''];
>   ''php-gd'':
>     name => $apache::params::php_gd_package,
>     ensure => installed,
>     require => Package[''php''],
>     notify => Service[''httpd''];
>   ''php-imap'':
>     name => $apache::params::php_imap_package,
>     ensure => installed,
>     require => Package[''php''],
>     notify => Service[''httpd''];
>   ''php-ldap'':
>     name => $apache::params::php_ldap_package,
>     ensure => installed,
>     require => Package[''php''],
>     notify => Service[''httpd''];
>   }
>
> }
>
> class apache::php53 inherits apache::php {
>   # $os is defined in site.pp.
>   if $::os == ''rhel5'' {
>     # Dirty hack. Yuck.
>     exec { ''/usr/bin/yum -y replace php --replace-with
php53u'':
>       onlyif => ''/bin/rpm -q php'',
>       # Class common::redhat::el::el5 installs yum-plugin-replace.
>       require => Class[''common::redhat::el::el5''],
>       notify => Service[''httpd''],
>     }
>   }
>   else {
>     warning ''Class apache::php53 should only ever be defined for
RHEL5 and its clones.''
>   }
>
> }
>
> class apache::params {
>   case $::os {
>     # .../...
>     ''rhel5'': {
>       $httpd_package = ''httpd''
>       $httpd_service = ''httpd''
>       $rootdir = ''/var/www/html''
>       if defined(Class[''apache::php53'']) {
>         $php_package = ''php53u''
>         $php_gd_package = ''php53u-gd''
>         $php_imap_package = ''php53u-imap''
>         $php_ldap_package = ''php53u-ldap''
>       }
>       else {
>         $php_package = ''php''
>         $php_gd_package = ''php-gd''
>         $php_imap_package = ''php-imap''
>         $php_ldap_package = ''php-ldap''
>       }
>     }
>   }}
>
> ---------------------------------------------------------------------
>
> When I add the apache::php53 to my host (I use LDAP as a node classifier
> if that matters), php and its extensions get upgraded to 5.3. However,
> when I add a class that depends on apache::php53, the defined function
> evaluates as false.
>
> class wordpress {
>   # apache::lamp includes apache::php
>   include apache::lamp
>
>   if $::os == ''rhel5'' {
>     include apache::php53
>   }
>   # .../...
>
> }
>
> I understand defined is quite unreliable. So I am wondering if there is
> a better option (read a working one)?
>
> Hardcoding the packages names in class apache::php53 is not enough as I
> have a bunch of other classes installing additional PHP modules. I
> suppose I could subclass them as well but things would probably get
> quite messy quite fast.

There is no need for subclassing or defined() here.  I would approach
the problem something like this:

---------------------------------------------------------------------
class apache::php {
  # Nothing from ''apache::base'' is overridden, so it
  # should be included (if even that is needed) instead of
  # inherited from.
  include ''apache::base''
  include ''apache::params''

  # Resource defaults for Packages in this class
  Package {
    ensure => installed,
    require => Package[''php''],
    notify => Service[''httpd'']
  }

  package { ''php'':
    name => $apache::params::php_package,
    require => Package[''httpd''];
  ''php-gd'':
    name => $apache::params::php_gd_package;
  ''php-imap'':
    name => $apache::params::php_imap_package;
  ''php-ldap'':
    name => $apache::params::php_ldap_package;
  }

  if $apache::params::php_package != ''php'' {
    # Make sure the vanilla ''php'' package is absent
    # before the alternative (e.g. ''php53'') is installed
    package { ''php-alt'':
      name => ''php'',
      ensure => absent,
      require => undef,
      before => Package[''php'']
    }
  }
}


#
# ** No class apache::php53 **
#


#
# class apache::params unchanged, not shown
#

---------------------------------------------------------------------

Everybody that needs PHP just includes apache::php.  If Puppet gets
confused about having one package titled ''php'' and a different
one
named ''php'', then just change the titles so there is no clash.

As my manifest shows, I''m not sure "yum replace" is really
needed.  If
it is needed after all, then it shouldn''t be too hard to adjust the
above to use it.


John

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Arnaud Gomes-do-Vale

2011-Jul-13 10:34 UTC

head link

Re: [Puppet Users] Re: How to avoid the use of defined

Hi,

First, thanks for your help. However I still have some issues with your
solution.

jcbollinger <John.Bollinger@stJude.org> writes:
> few bad ones.  Here''s a good rule of thumb: never use
Puppet''s
> "defined()" function in your manifests.  Ever.  It is brittle,
and it
> will cause you grief, increasing exponentially with the number of
> uses.
.../...> There is no need for subclassing or defined() here.  I would approach
> the problem something like this:
>   # Resource defaults for Packages in this class
>   Package {
>     ensure => installed,
>     require => Package[''php''],
>     notify => Service[''httpd'']
>   }
This creates a dependency loop:

err: Could not apply complete catalog: Found dependency cycles in the following
relationships: Package[php] => Package[httpd], Package[httpd] =>
Package[php], Package[php] => Package[php-ldap], Package[php-imap] =>
Package[php-mysql], Package[php-gd] => Package[php-mysql], Package[php-ldap]
=> Package[php-mysql], Package[php] => Package[php-mysql], Package[httpd]
=> File[/etc/httpd/conf.d/mod-status.conf], Package[php] =>
Package[php-mbstring], Package[httpd] => Service[httpd], Package[httpd] =>
Service[httpd], Package[php-imap] => Service[httpd], Package[php-mysql] =>
Service[httpd], Package[php-gd] => Service[httpd], Package[php-ldap] =>
Service[httpd], Package[php] => Service[httpd],
File[/etc/httpd/conf.d/mod-status.conf] => Service[httpd],
Package[php-mbstring] => Service[httpd], Package[php] =>
Package[php-imap], Package[php] => Package[php-gd], Package[httpd] =>
File[/var/www/html]; try using the ''--graph'' option and open
the ''.dot'' files in OmniGraffle or GraphViz

As far as I understand, Package[''httpd''] (defined in class
apache::base)
inherits the dependency on Package[''php'']. This is using
Puppet 2.6.8;
has this changed in 2.7.x?
> # ** No class apache::php53 **
So how do I tell Puppet which nodes need 5.1 and which need 5.3? With my
sample wordpress class I get the following error:

err: Could not retrieve catalog from remote server: Error 400 on SERVER: Could
not find class apache::php53 in namespaces wordpress at
/etc/puppet/modules/wordpress/manifests/init.pp:6 on node testxen1.ircam.fr

Looks like using a dummy class definition as a flag won''t work. :-) I
could use a variable instead, but I guess the ordering issues would get
even worse?
> # class apache::params unchanged, not shown
So I''m still using defined().
> As my manifest shows, I''m not sure "yum replace" is
really needed.  If
> it is needed after all, then it shouldn''t be too hard to adjust
the
> above to use it.
Actually your solution looks much cleaner than "yum replace".

-- 
Arnaud

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jcbollinger

2011-Jul-13 14:22 UTC

head link

[Puppet Users] Re: How to avoid the use of defined

On Jul 13, 5:34 am, Arnaud Gomes-do-Vale <Arnaud.Go...@ircam.fr>
wrote:> Hi,
>
> First, thanks for your help. However I still have some issues with your
> solution.
>
>
>
> jcbollinger <John.Bollin...@stJude.org> writes:
> > few bad ones.  Here''s a good rule of thumb: never use
Puppet''s
> > "defined()" function in your manifests.  Ever.  It is
brittle, and it
> > will cause you grief, increasing exponentially with the number of
> > uses.
> .../...
> > There is no need for subclassing or defined() here.  I would approach
> > the problem something like this:
> >   # Resource defaults for Packages in this class
> >   Package {
> >     ensure => installed,
> >     require => Package[''php''],
> >     notify => Service[''httpd'']
> >   }
>
> This creates a dependency loop:
>
> err: Could not apply complete catalog: Found dependency cycles in the
following relationships: Package[php] => Package[httpd], Package[httpd] =>
Package[php], Package[php] => Package[php-ldap], Package[php-imap] =>
Package[php-mysql], Package[php-gd] => Package[php-mysql], Package[php-ldap]
=> Package[php-mysql], Package[php] => Package[php-mysql], Package[httpd]
=> File[/etc/httpd/conf.d/mod-status.conf], Package[php] =>
Package[php-mbstring], Package[httpd] => Service[httpd], Package[httpd] =>
Service[httpd], Package[php-imap] => Service[httpd], Package[php-mysql] =>
Service[httpd], Package[php-gd] => Service[httpd], Package[php-ldap] =>
Service[httpd], Package[php] => Service[httpd],
File[/etc/httpd/conf.d/mod-status.conf] => Service[httpd],
Package[php-mbstring] => Service[httpd], Package[php] =>
Package[php-imap], Package[php] => Package[php-gd], Package[httpd] =>
File[/var/www/html]; try using the ''--graph'' option and open
the ''.dot'' files in OmniGraffle or GraphViz
>
> As far as I understand, Package[''httpd''] (defined in
class apache::base)
> inherits the dependency on Package[''php'']. This is using
Puppet 2.6.8;
> has this changed in 2.7.x?

Fair enough, then move the ''require'' parameter back out of
resource
defaults into individual Package resources.  Using resource defaults
is not an essential aspect of the solution.

> > # ** No class apache::php53 **
>
> So how do I tell Puppet which nodes need 5.1 and which need 5.3? With my
> sample wordpress class I get the following error:

See below.

> err: Could not retrieve catalog from remote server: Error 400 on SERVER:
Could not find class apache::php53 in namespaces wordpress at
/etc/puppet/modules/wordpress/manifests/init.pp:6 on node testxen1.ircam.fr
>
> Looks like using a dummy class definition as a flag won''t work.
:-) I
> could use a variable instead, but I guess the ordering issues would get
> even worse?

As I wrote, "Everybody that needs PHP just includes apache::php."
There is no more apache::php53.

> > # class apache::params unchanged, not shown
>
> So I''m still using defined().

Ah.  That''s a blunder on my part.  These are the alternatives I can
think of:

1) Per node, set a global variable that directs which set of PHP
packages to use.

2) Use extlookup() to retrieve a flag variable such as described in
(1), or else to retrieve the individual PHP package names.

3) Base the PHP package selection on node facts (possibly just
$hostname) instead of on defined()

4) Though I don''t favor parameterized classes, you could parameterize
apache::php to allow your nodes to direct which set of PHP packages to
use; whether this is feasible depends somewhat on how the class is
used.


Another way to do this might be to stick with apache::php53 as a
subclass of apache::php, and use resource overrides.  This is clean
only if you don''t need the PHP package names in other classes, but it
looks like you''re relying on titles instead of names anyway.  The
result might be something like this:


----

class apache::php {
  include ''apache::base''

  package { ''php'':
    ensure => installed,
    require => Package[''httpd''],
    notify => Service[''httpd''];
  ''php-gd'':
    ensure => installed,
    require => Package[''php''],
    notify => Service[''httpd''];
  ''php-imap'':
    ensure => installed,
    require => Package[''php''],
    notify => Service[''httpd''];
  ''php-ldap'':
    ensure => installed,
    require => Package[''php''],
    notify => Service[''httpd''];
  }
}


class apache::php53 inherits apache::php {
  # $os is defined in site.pp.
  if $::os == ''rhel5'' {
    Package[''php''] { name => ''php53u'' }
    Package[''php-gd''] { name =>
''php53u-gd'' }
    Package[''php-imap''] { name =>
''php53u-imap'' }
    Package[''php-ldap''] { name =>
''php53u-ldap'' }

    package { ''php-alt'':
      name => ''php'',
      ensure => absent,
      require => undef,
      before => Package[''php'']
    }
  }
  else {
    warning ''Class apache::php53 should only ever be defined for RHEL5
and its clones.''
  }
}


#
# No class apache::params, at least as pertains to apache::php
#

----


RHEL5 nodes that want PHP 5.3 then include apache::php53.  It is safe,
but unnecessary, for such nodes also to include apache::php.


--
John

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Nigel Kersten

2011-Jul-13 15:23 UTC

head link

Re: [Puppet Users] Re: How to avoid the use of defined

On Wed, Jul 13, 2011 at 3:34 AM, Arnaud Gomes-do-Vale
<Arnaud.Gomes@ircam.fr> wrote:
>
> >   # Resource defaults for Packages in this class
> >   Package {
> >     ensure => installed,
> >     require => Package[''php''],
> >     notify => Service[''httpd'']
> >   }
>
> This creates a dependency loop:

An option here is to override the require on a per-package basis.

If you set a resource default for require, and then separately set require
for individual resources, they will overwrite the resource default rather
than append to it.

You could also use collections to do what you want, this is untested, but
something like:

Package <| title != "php" |> {
  require => Package[''php''],
  notify => Service[''httpd'']
}

should work I believe.

-- 
Nigel Kersten
Product Manager, Puppet Labs
Twitter: @nigelkersten

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Puppet users - Jul 2011 - How to avoid the use of defined

[Puppet Users] How to avoid the use of defined

Re: [Puppet Users] How to avoid the use of defined

[Puppet Users] Re: How to avoid the use of defined

Re: [Puppet Users] Re: How to avoid the use of defined

[Puppet Users] Re: How to avoid the use of defined

Re: [Puppet Users] Re: How to avoid the use of defined