User story #3117: Implement an "expert technique" that let use the power of cfengine - Rudder - Issue Tracker

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User story #3117

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Implement an "expert technique" that let use the power of cfengine

Added by Nicolas CHARLES almost 12 years ago. Updated over 4 years ago.

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Rejected

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Category:

Techniques

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Ideas (not version specific)

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Description

We could really benefit from an "expert" technique, for expert only, that would allow for special or complex computation, like executing CFEngine special functions
For instance, if we are on a fairly complex infrastructure where each nodes have a "paired" system, where they send files every night, and the pair is based on the last bytes of the ip address, there is currently no way to deal with it easily, except create groups based on the last bytes of the ip address, define a directive based on generic variable definition for each with the last byte of the address within, and then create a many rules as there are bytes...

An more common solution would be to be able to define a variable based on

lastnode("$(sys.ipv4)", ".")

and use this variable in a more generic directive and rule

I'm not sute of what should be allowed :

everything : every type of text as a right hand side; but I'm not really fine with that
only some special function, in a dropdown list, and the user would have to define the content of the function

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Updated by Nicolas PERRON almost 12 years ago

Target version changed from 2.5.0~beta1 to 2.5.0~rc1

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Updated by Nicolas PERRON almost 12 years ago

Example of user case:
Make a symlink for kernel versions.

ln -s /boot/vmlinuz /boot/vmlinuz-3.5.0-21-generic

It will need to use a variable to know which version is currently used by the system, like this:

kernel_label=`/bin/uname -r`
kernel_version=`/usr/bin/expr ${kernel_label} : '\(.*\)-[a-z]*'`
ln -s /boot/vmlinuz /boot/vmlinuz-${kernel_version}-generic

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