Ruby syntax in chef recipe

Question

Guys I have no clue in ruby but forced to play around with a chef recipe. Can someone help me with a syntax issue ?

These line is causing problems when I run the recipe

old_configs = node["monitoring"]["configs"] || []

And the exception is :

NoMethodError: undefined method `[]' for nil:NilClass /var/chef/cache/cookbooks/collectd/recipes/default.rb:100:in `from_file'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/mixin/from_file.rb:30:in `instance_eval'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/mixin/from_file.rb:30:in `from_file'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/cookbook_version.rb:237:in `load_recipe'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/run_context.rb:151:in `load_recipe'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/run_context/cookbook_compiler.rb:139:in `block in compile_recipe
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/run_context/cookbook_compiler.rb:137:in `each'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/run_context/cookbook_compiler.rb:137:in `compile_recipes'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/run_context/cookbook_compiler.rb:74:in `compile'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/run_context.rb:86:in `load'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/client.rb:249:in `setup_run_context'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/client.rb:492:in `do_run'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/client.rb:199:in `block in run'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/client.rb:193:in `fork' 
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/client.rb:193:in `run' 
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/application.rb:183:in `run_chef_client'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/application/client.rb:302:in `block in run_application'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/application/client.rb:294:in `loop'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/application/client.rb:294:in `run_application'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/application.rb:66:in `run'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/bin/chef-client:26:in `<top (required)>'

Oin · Accepted Answer · 2013-10-10 08:45:11Z

4

This is probably caused by the fact that the node "monitoring" attribute does not exist, you should first check that node["monitoring"] exists, before trying to lookup node["monitoring"]["configs"]

The simple way to do it would be:

if node["monitoring"]
  old_configs = node["monitoring"]["configs"] || []
end

answered Oct 10, 2013 at 8:45

Oin

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1 Comment

Tim Potter Over a year ago

Another trick is to use Chef's attribute system to define a default value so as to make the if statement unnecessary. In attributes/default.rb put something like default["monitoring"]["configs"] = [].

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