On Sunday, March 15, 2015 at 2:04:53 PM UTC-5, Jan S. wrote:
>
> Hello,
>
> I have the following use case: For a custom class/type I need to know
> which php_version is installed on the machine. So I wrote a custom fact
> like this:
>
> Facter.add('php_version') do
> setcode do
> Facter::Util::Resolution.exec('/usr/bin/php -i | /bin/egrep -e "^PHP
> Version" | /usr/bin/head -n 1 | /usr/bin/cut -d " " -f 4 | /usr/bin/cut -d
> "-" -f 1')
> end
> end
>
> It works great. Except: When php is not yet installed (there is a
> Package['php'] definition, too). Then it will return an empty string.
>
> Thus I have to run puppet two times to get the expected result.
>
> I am sure that this is expected behavior of puppet. How do I handle such
> case?
>
>
Fact values are computed before any part of the catalog is built, and they
reflect the state of the machine before Puppet applies any changes. If PHP
is not initially installed, then that's a plausible, valid state that your
fact value should reflect and your manifests should accommodate. In the
worst case, your manifests could accommodate absence of PHP by requiring
two Puppet runs to converge to a final configuration. That's what you have
now, evidently.
Consider carefully, however, what that fact value is telling you: what
version of PHP, if any, is installed *before* the run. If the target
configuration depends in any way on PHP version, then what you probably
want is the PHP version that will be present *after* the run. If there is
any chance that the run will ever update PHP to a new version, then even
when PHP is already installed, your manifests rely on an unsafe assumption
that the version present before the run will be the same as the version
present after.
Possibly what you want is a different (or additional) fact: not the version
of PHP currently installed, but the latest version available from the
configured repositories. This is the version that will be present after a
successful run if you have ...
package { 'php': ensure => 'latest' }
... it is also the version that will be present after the run if PHP is not
initially installed and you have ...
package { 'php': ensure => 'present' }
... provided that the package repository configuration is not changed so as
to affect which PHP packages are available. Given that, if you ensure that
the PHP package is managed before anything that depends on PHP version (as
you should already be doing) then all should be good.
If you want maximum reliability, however, you need to recognize that if
indeed what you want to know is which version of PHP will be present on the
machine after a successful catalog run, then your nodes simply cannot
provide that information. It depends on data they do not have. You need
to some mechanism other than (or in addition to) node facts to ascertain
that.
John
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