CODEWITHSUNDEEP
rubyvariablesattributeschef-infra
david
david

Reputation: 761

initialize chef attribute with ruby block?

Here's the ruby command I'd like to save the output of Time.now.strftime('%m%d%Y_%H%M') I was thinking I could just add something like this to my recipe '

TODAY={ ::Time.now.strftime('%m%d%Y_%H%M') }

but this doesn't seem to work

==> default: [2015-04-10T17:53:44+00:00] ERROR: /tmp/vagrant-chef/eb36617d9c55f20fcee6cd316a379482/cookbooks/test-cookbook/recipes/install_app.rb:12: syntax error, unexpected '}', expecting tASSOC
    ==> default: TODAY={ (Time.now.strftime('%m%d%Y_%H%M')) }
    ==> default:                                             ^
    ==> default: [2015-04-10T17:53:44+00:00] FATAL: Chef::Exceptions::ChildConvergeError: Chef run process exited unsuccessfully (exit code 1)

eventually I want to make this an attribute so I can access it from multiple recipes

default['neustar-npac-deployment']['node_ohai_time'] = TODAY={ ::Time.now.strftime('%m%d%Y_%H%M') }

thanks!

Upvotes: 0

Views: 1181

Answers (1)

engineersmnky
engineersmnky

Reputation: 29588

As per your request I am posting this as an answer.

Right now you are using {} incorrectly as this is not a block but a Hash literal which is why it is complaining. In order to make this a block you must use a lambda or Proc object.

lambda

lambda's can be created using one of 2 different syntax styles 

-> { "This is a lambda" } 
#=> #<Proc:0x2a954c0@(irb):1 (lambda)>
lambda { "This is also a lambda" }
#=> #<Proc:0x27337c8@(irb):2 (lambda)>

Either way is perfectly acceptable

Proc

Procs can be created using Proc.new { "This is a proc" }

for this question the semantic differences are not needed.

lambda and Proc will lazy evaluate the statement inside the block on #call which means that the value can remain fluid.

Let's take your example:

 NOW = Time.now.strftime('%m%d%Y_%H%M')
 # in this case NOW will be evaluated once and will always equal the 
 # string result of when it was first interpretted
 TODAY = -> {Time.now.strftime('%m%d%Y_%H%M')}
 # in this case TODAY is simply a lambda and it's value will be dependent
 # upon the time when you "call" it so something like this will clearly illustrate
 # the difference
 while NOW == TODAY.call
    puts "Still the same time" 
 end 
 # after this NOW will still reflect it's initial set value and for 
 # a while ~ 1 minute this will output "Still the same time" 
 # at some point TODAY.call will increment up by 1 minute because it is 
 # re-evaluated on each `#call` thus allowing it to change periodically with the clock

I hope this in some way helps you better understand the concept.

Upvotes: 2

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