Re: [Puppet Users] Resources sharing across different classes.
On Friday, April 1, 2016 at 4:57:02 AM UTC-5, Afroz Hussain wrote:
>
> Hi Martin,
>
> Thanks for your help. I have tried your hack but didn't work, still same
> error,
> class addfile (
> $enable_notify => Service[’tomcat’],
> ) {
> file {‘/tmp/hello’:
> ensure => file,
> notify => $enable_notify,
> }
> }
>
> Technically, we can all any resource from any classes since all resources
> are unique across modules.
>
Yes, once declared, resources have global scope. You can refer to them
from any class, in any module or no module. Martin did not suggest
differently.
But the fact the you CAN access resources from anywhere does not mean it's
a good idea to do so. Whether it's reasonable in this particular case is
unclear, but doubtful, as for the most part the identities of the resources
declared by a given class should be considered implementation details of
that class, and depending on another class's implementation details makes
your class brittle.
That's not even the most significant problem here, however. Your
(original) Addfile class depends on there is a resource Service['tomcat']
declared for the target node. If this is sensible in all cases, then it
would be best for that class to take its own measures to ensure that its
requirement is satisfied, which would be best done by declaring the
appropriate class. For example, if Tomcat is managed via a "tomcat" class,
then you might use
class addfile {
include 'tomcat'
# ...
}
But that's a half measure. Remember that we should avoid depending on
implementation details of other classes. If you are prepared to rely on
the tomcat class to provide the needed service resource, then it is
probably best to make that class the target of the notification
relationship, instead of anything within that you rely on it to declare:
class addfile {
include 'tomcat'
file {"/tmp/hello":
ensure => file,
content => "hello"
}
~>
Class['tomcat']
}
Note, among other things, that that works fine if the name of the Tomcat
service differs from node to node, and that it does not break if the
service name changes (e.g. to "apache-tomcat") in the future.
Much of that is predicated on the idea that signaling Tomcat is a hard
requirement, however, and the nature of the error you reported suggests
that that might not be the case. If you want to use your Addfile class on
machines where Tomcat is not being managed, and on those machines,
therefore, not to notify Service['tomcat'], then you probably need a much
deeper re-design than just one class. Something along the lines of
Martin's suggested modification to your class could well be part of such a
redesign, but you need rather more.
Indeed, I suspect that the reason Martin's suggestion did not work for you
is that you do not appreciate how to use it. Modifying the class
definition as he described will not, in itself, make any difference at
all. To address your problem via his version of the class, you need to
also cause the correct data for the target node to be bound to the new
class parameter. But if that's as far as you go then it's just a stopgap.
I think you have deeper problems.
John
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Re: [Puppet Users] Resources sharing across different classes.
Hi Martin,
Thanks for your help. I have tried your hack but didn't work, still same
error,
class addfile (
$enable_notify => Service[’tomcat’],
) {
file {‘/tmp/hello’:
ensure => file,
notify => $enable_notify,
}
}
Technically, we can all any resource from any classes since all resources
are unique across modules.
Thanks,
Afroz Hussain
On Thursday, 31 March 2016 17:40:27 UTC+5:30, Martin Alfke wrote:
>
> Hi Arfoz,
>
> this is the best example on how to _not_ do classes.
> Every class should be self contained - as long as possible.
> In your case you have a hard reference from one resource inside a class to
> another resource inside another class.
> I always tell my training course attendees that they should never do this
> unless they don’t like themselves and they want to have Puppet nightmares.
>
> In your case you can do the following hack:
>
> make the add file class a parameterised class, set the parameter to the
> default behaviour:
>
> class addfile (
> $enable_notify => Service[’tomcat’],
> ) {
> file {‘/tmp/hello’:
> ensure => file,
> notify => $enable_notify,
> }
> }
>
> On systems where you don’t have tomcat class included you have to declare
> the class add file with parameter set to undef.
>
> But: be aware that even this is not a good solution.
> It’s just a hack.
> Try to refacter your modules.
>
> Best,
> Martin
>
>
> On 31 Mar 2016, at 13:48, Afroz Hussain
> wrote:
>
> > Error as below:
> >
> > Error: Could not retrieve catalog from remote server: Error 400 on
> SERVER: Invalid relationship: File[/tmp/hello] { notify => Service[tomcat]
> }, because Service[tomcat] doesn't seem to be in the catalog
> >
> > On Thursday, 31 March 2016 17:13:46 UTC+5:30, Afroz Hussain wrote:
> > Hi All,
> >
> > I am facing an issue to notify a service from different module whenever
> file changes.
> > Example:
> > I have a addfile module which creates a file and want to notify tomcat
> service which is present in tomcat module.
> >
> > class addfile {
> >file {"/tmp/hello":
> > ensure => file,
> > content => "hello",
> > notify => Service["tomcat'],
> >}
> > }
> >
> >
> > it is throwing an error as tomcat service is not in catalog.
> >
> > I have 3.6.2 version of puppet and using ENC.
> >
> > Any help will be appreciated
> >
> > Thanks,
> > Afroz Hussain
> >
> >
> > --
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> Groups "Puppet Users" group.
> > To unsubscribe from this group and stop receiving emails from it, send
> an email to puppet-users...@googlegroups.com .
> > To view this discussion on the web visit
> https://groups.google.com/d/msgid/puppet-users/02cfc06d-d306-48a2-a917-7144606a1509%40googlegroups.com.
>
>
> > For more options, visit https://groups.google.com/d/optout.
>
>
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Re: [Puppet Users] Resources sharing across different classes.
Hi Arfoz,
this is the best example on how to _not_ do classes.
Every class should be self contained - as long as possible.
In your case you have a hard reference from one resource inside a class to
another resource inside another class.
I always tell my training course attendees that they should never do this
unless they don’t like themselves and they want to have Puppet nightmares.
In your case you can do the following hack:
make the add file class a parameterised class, set the parameter to the default
behaviour:
class addfile (
$enable_notify => Service[’tomcat’],
) {
file {‘/tmp/hello’:
ensure => file,
notify => $enable_notify,
}
}
On systems where you don’t have tomcat class included you have to declare the
class add file with parameter set to undef.
But: be aware that even this is not a good solution.
It’s just a hack.
Try to refacter your modules.
Best,
Martin
On 31 Mar 2016, at 13:48, Afroz Hussain wrote:
> Error as below:
>
> Error: Could not retrieve catalog from remote server: Error 400 on SERVER:
> Invalid relationship: File[/tmp/hello] { notify => Service[tomcat] }, because
> Service[tomcat] doesn't seem to be in the catalog
>
> On Thursday, 31 March 2016 17:13:46 UTC+5:30, Afroz Hussain wrote:
> Hi All,
>
> I am facing an issue to notify a service from different module whenever file
> changes.
> Example:
> I have a addfile module which creates a file and want to notify tomcat
> service which is present in tomcat module.
>
> class addfile {
>file {"/tmp/hello":
> ensure => file,
> content => "hello",
> notify => Service["tomcat'],
>}
> }
>
>
> it is throwing an error as tomcat service is not in catalog.
>
> I have 3.6.2 version of puppet and using ENC.
>
> Any help will be appreciated
>
> Thanks,
> Afroz Hussain
>
>
> --
> You received this message because you are subscribed to the Google Groups
> "Puppet Users" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to puppet-users+unsubscr...@googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/puppet-users/02cfc06d-d306-48a2-a917-7144606a1509%40googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.
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