In my chef recipe, I have a bash ruby block. I need some value generated from it passed to my templates. For example, the joke variable in here:
bash "create opal user" do
code <<-EOH
joke='my funny joke'
echo $joke
EOH
end
template '/joke.txt' do
source 'joke.txt.erb'
variable(joke:"#{joke}")
end
Answered in IRC, Chef doesn't work like this in general. The shell_out helper can sometimes be used but overall you should try to not structure your recipes this way.
Related
I have an interesting problem where I refactored a recipe by creating a Chef resource to handle some tasks I may need in other recipes. For instance, I've created the following action:
resource_name :my_command
action :run do
execute "Execute my command" do
environment ({"SETTINGS_FOLDER" => node['settings']['folder']})
command "#{command_exe} -some -params"
end
end
action_class.class_eval do
def command_exe
"#{node['command']['folder']}\\bin\\command.exe"
end
end
When I call my_command from a recipe it works as expected. However I have several other actions that this resource will implement that'll all use the same environment. So what I did was refactor the resource to look like this:
resource_name :command
action :run do
execute "Execute my command" do
environment env
command "#{command_exe} -some -params"
end
end
action_class.class_eval do
def command_exe
"#{node['command']['folder']}\\bin\\command.exe"
end
def env
{"SETTINGS_FOLDER" => node['settings']['folder']}
end
end
What happens now is, once chef-client executes the my_command resource it appears as though the SETTINGS_FOLDER environment variable on the machine winds up looking like this:
SETTINGS_FOLDER = ""C:\my\settings\folder""
Notice the doubled double-quotes? I'm not sure why this is happening, but it makes my command.exe very angry :(
The ['settings']['folder'] attribute is defined in the cookbook's attributes/default.rblike so:
default['settings']['folder'] = 'C:\\my\\settings\\folder'
My node is running chef-client 13.0.118
EDIT I think the doubled double-quotes was a red herring. I think the logger just represented the hash in that way. My new thought is that perhaps the env method is not being evaluated before being passed to the environment, but rather the function reference itself is being passed. Bear with me, Ruby isn't my first language...
The "env" method name might be a reserved word or is getting stomped later in the run. Try a different name for that method, perhaps?
I try to get a variable from my ruby block, but Chef doesn't recognise my variable outside of this block. How can I retrieve any variable out of ruby block? Thanks in advance.
ruby_block 'fetch_path' do
block do
current_path = `sudo cat /var/chef/cache/revision`
new_path = current_path.to_s.split(',').last.split('"').drop(1).first
Chef::Log.info("### Your Current Directory: '#{new_path}' ###")
end
end
Chef::Log.info("### Your Current Directory: '#{new_path}' ###")
Within the block I can get a value, but, out of block - no.
There's two thing here.
First, your second Chef::Log.info will be run at compilation phase, at this time your ruby_block has not been converged. See here about it. You can prefix your logs with 1) and 2) to witch one runs first.
Second, there's a scoping problem, when you define a variable in a block, it is available only within this block.
In chef you can use node.run_state['variable'] as a global variable usable in all recipes, without an use case it's hard to showcase this.
Side note: you should not use the backticks `` construction to execute commands and prefer using shell_out from the recipe DSL.
I have a simple chef cookbook and all it does is it sets the MOTD on a CentOS machine. It takes the content of the /tmp/mymotd.txt and turns it into the MOTD.
I also have a simple ruby script (a full-fledged ruby script) that simply reads the text from the web-server and puts in into the /tmp/mymotd.txt.
My questions are:
how do I run this ruby script from within the cookbook?
how do I pass some parameters to the script (e.g. the address of the web-server)
Thanks a lot beforehand.
Ad 1.
You can use libraries directory in scripts to place there your ruby script and declare it in a module. Example:
# includes
module MODULE_NAME
# here some code using your script
# Example function
def example_function (text)
# some code
end
end
You can use then
include MODULE_NAME
in your recipe to import those functions and just use it like
example_function(something)
What's good - you can use there also Chef functions and resources.
IMPORTANT INFO: Just remember that Chef has 2 compilation phases. First will be all of Ruby code, second all of Chef resources. This means, that you have to remember priority of code. I won't write here more info about it, since you haven't asked for this, but if you want, you can find it here.
Ad 2.
You can do this in several ways, but it seems to me, that the best option for you would be to use environments. You can find more info in here. Basically, you can set up environment for script before it will run - this way you can define some variables you would use later.
Hope this helps.
I just started using chef and don't know much about ruby.
I have problems understanding the language-syntax used in recipes.
Say, I create a directory in a cookbook in recipes/default.rb like:
directory "/home/test/mydir" do
owner "test"
mode "0755"
action :create
recursive true
end
I assume this is part of a valid ruby script. What do lines like owner "test" mean? Is this a function call, a variable assignment or something else entirely?
Chef is written in Ruby and makes an extensive use of Ruby ability to design custom DSL. Almost every chef configuration file is written with a Ruby-based DSL.
This means that in order to use chef effectively you should be familiar with the basic of Ruby syntax including
Grammar
Data types (the main difference compared to other languages are Symbols)
Blocks
You don't need to know a lot about metaprogramming in Ruby.
The case of the code you posted is an excellent example of a Ruby based DSL. Let me explain it a little bit.
# Call the method directory passing the path and a block
# containing some code to be evaluated
directory "/home/test/mydir" do
# chown the directory to the test user
owner "test"
# set the permissions to 0555
mode "0755"
# create the directory if it does not exists
action :create
# equivalent of -p flag in the mkdir
recursive true
end
Blocks are a convenient way to specify a group of operations (in this case create, set permissions, etc) to be evaluated in a single context (in this case in the context of that path).
Let's break it down.
directory "/home/test/mydir" do
...
end
You are just calling a global method defined by Chef called directory, passing one argument "/home/test/mydir", and a block (everything between the do and end).
This block is probably excecuted in a special scope created by Chef in which all of the options (owner, mode, action, etc.) are method.
i would like to show you my use case and then discuss possible solutions:
Problem A:
i have 2 recipes, "a" and "b".. "a" installs some program on my file system (say at "/usr/local/bin/stuff.sh" and recipe "b" needs to run this and do something with the output.
so recipe "a" looks something like:
execute "echo 'echo stuff' > /usr/local/bin/stuff.sh"
(the script just echo(es) "stuff" to stdout)
and recipe "b" looks something like:
include_recipe "a"
var=`/usr/local/bin/stuff.sh`
(note the backquotes, var should contain stuff)
and now i need to do something with it, for instance create a user with this username. so at script "b" i add
user "#{node[:var]}"
As it happens, this doesn't work.. apparently chef runs everything that is not a resource and only then runs the resources so as soon as i run the script chef complains that it cannot compile because it first tries to run the "var=..." line at recipe "b" and fails because the "execute ..." at recipe a did not run yet and so the "stuff.sh" script does not exist yet.
Needless to say, this is extremely annoying as it breaks the "Chef runs everything in order from top to bottom" that i was promised when i started using it.
However, i am not very picky so i started looking for alternative solutions to this problem, so:
Problem B: i've run across the idea of "ruby_block". apparently, this is a resource so it will be evaluated along with the other resources. I said ok, then i'd like to create the script, get the output in a "ruby_block" and then pass it to "user". so recipe "b" now looks something like:
include_recipe "a"
ruby_block "a_block" do
block do
node.default[:var] = `/usr/local/bin/stuff.sh`
end
end
user "#{node[:var]}"
However, as it turns out the variable (var) was not passed from "ruby_block" to "user" and it remains empty. No matter what juggling i've tried to do with it i failed (or maybe i just didn't find the correct juggling method)
To the chef/ruby masters around: How do i solve Problem A? How do i solve Problem B?
You have already solved problem A with the Ruby block.
Now you have to solve problem B with a similar approach:
ruby_block "create user" do
block do
user = Chef::Resource::User.new(node[:var], run_context)
user.shell '/bin/bash' # Set parameters using this syntax
user.run_action :create
user.run_action :manage # Run multiple actions (if needed) by declaring them sequentially
end
end
You could also solve problem A by creating the file during the compile phase:
execute "echo 'echo stuff' > /usr/local/bin/stuff.sh" do
action :nothing
end.run_action(:run)
If following this course of action, make sure that:
/usr/local/bin exist during Chef's compile phase;
Either:
stuff.sh is executable; OR
Execute it through a shell (e.g.: var=`sh /usr/local/bin/stuff.sh`
The modern way to do this is to use a custom resource:
in cookbooks/create_script/resources/create_script.rb
provides :create_script
unified_mode true
property :script_name, :name_property: true
action :run do
execute "creating #{script_name}" do
command "echo 'echo stuff' > #{script_name}"
not_if { File.exist?(script_name) }
end
end
Then in recipe code:
create_script "/usr/local/bin/stuff.sh"
For the second case as written I'd avoid the use of a node variable entirely:
script_location = "/usr/local/bin/stuff.sh"
create_script script_location
# note: the user resources takes a username not a file path so the example is a bit
# strange, but that is the way the question was asked.
user script_location
If you need to move it into an attribute and call it from different recipes then there's no need for ruby_blocks or lazy:
some cookbook's attributes/default.rb file (or a policyfile, etc):
default['script_location'] = "/usr/local/bin/stuff.sh"
in recipe code or other custom resources:
create_script node['script_location']
user node['script_location']
There's no need to lazy things or use ruby_block using this approach.
There are actually a few ways to solve the issue that you're having.
The first way is to avoid the scope issues you're having in the passed blocks and do something like ths.
include_recipe "a"
this = self
ruby_block "a_block" do
block do
this.user `/usr/local/bin/stuff.sh`
end
end
Assuming that you plan on only using this once, that would work great. But if you're legitimately needing to store a variable on the node for other uses you can rely on the lazy call inside ruby to do a little work around of the issue.
include_recipe "a"
ruby_block "a_block" do
block do
node.default[:var] = `/usr/local/bin/stuff.sh`.strip
end
end
user do
username lazy { "#{node[:var]}" }
end
You'll quickly notice with Chef that it has an override for all default assumptions for cases just like this.