example_aborting_execution.markdown

layout	title	categories	published	alias	tags	reviewed	reviewed-by
default	Aborting execution	Examples Policy Aborting execution	true	examples-policy-aborting-execution.html	Examples Policy aborting execution	2013-05-30	atsaloli

Sometimes it is useful to abort a bundle execution if certain conditions are not met, for example when validating input to a bundle. The following policy uses a list of regular expressions for classes, or class expressions that [cf-agent][cf-agent] will watch out for. If any of these classes becomes defined, it will cause the current bundle to be aborted.

body common control
{
bundlesequence  => { "example"  };
}

body agent control
{
abortbundleclasses => { "invalid" };      # Abort bundle execution if this class is set
}

###########################################

bundle agent example
{
vars:

  #"userlist" slist => { "mark", "john" };           # contains all valid entries
  "userlist" slist => { "mark", "john", "thomas" };  # contains one invalid entry

classes:

  "invalid" not => regcmp("[a-z][a-z][a-z][a-z]","$(userlist)"); # The class 'invalid' is set if the user name does not
                                                                 # contain exactly four un-capitalized letters (bundle
                                                                 # execution will be aborted if set)

reports:

  !invalid::

    "User name $(userlist) is valid at 4 letters";
}

This policy can be found in /var/cfengine/share/doc/examples/unit_abort.cf.

This is how the policy runs when the userlist is valid:

# cf-agent -f unit_abort.cf
R: User name mark is valid at 4 letters
R: User name john is valid at 4 letters
# 

This is how the policy runs when the userlist contains an invalid entry:

# cf-agent -f unit_abort.cf
Bundle example aborted on defined class "invalid"
# 

To run this example file as part of your main policy you need to make an additional change:

There cannot be two body agent control in the main policy. Delete the body agent control section from /var/cfengine/masterfiles/unit_abort.cf. Copy and paste abortbundleclasses => { "invalid" }; into /var/cfengine/masterfiles/controls/cf_agent.cf. If you add it to the end of the file it should look something like this:

...
    #  dryrun => "true";
    
    abortbundleclasses => { "invalid" };
}