42 lines
1.8 KiB
Markdown
42 lines
1.8 KiB
Markdown
[[!meta title="Puppet: The quantum effect when loading classes"]]
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After experiementing a bit with [puppet](http://reductivelabs.com/trac/puppet)
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I found a very interesting phenomenon: Sometimes a host fails to load a class
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with this error:
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err: Could not retrieve catalog: Could not find class common::nico_ethz at /etc/puppet/manifests/nodes/nico.pp:35 on node bach21.ethz.ch
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The strange thing is that it *does* work sometimes. After describing
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the situation in the [IRC channel #puppet](irc://irc.freenode.net/#puppet),
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I got an "interesting" explanation for that behaviour:
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First of all I did a mistake, because I placed the class
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***common::nico_ethz*** into the file
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**modules/common/manifests/nico.pp** instead of
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**modules/common/manifests/nico_ethz.pp**.
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But why does it work sometimes?
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It works sometimes, because the ***puppetmaster*** compiles the catalog
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for ***all*** nodes and reuses the compiled catalog for different
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hosts. **If** a previous node loaded the class ***common::nico***,
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the complete content of **modules/common/manifests/nico.pp**
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is in the catalog, including ***common::nico_ethz***. This is the reason
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why it sometimes works and that's also the reason why I am writing
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this posting:
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* Dear other puppet users: Be aware that sometimes a class may be included
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indirectly and thus things work randomly (like
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[Schrödinger's cat](http://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat))!
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* Dear puppet developers: It would be way more helpful, if a wrong
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configuration **always** and not only **sometimes** fails!
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If you've a comment to this blog article, please redirect it to
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[the puppet users
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mailinglist](http://reductivelabs.com/trac/puppet/wiki/GettingHelp#mailing-lists),
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to which I sent a notice about this article.
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# Update #1
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I switched over to use [[cdist|software/cdist]] instead of Puppet.
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[[!tag config unix]]
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