Chef Creating dynamic Json File - json

Question

I got a problem in generate a json file using a template inside a chef template.
I need to generate a json file like below, called plugin.json:
{
"agents": [
{
"name" : "sqlhost",
"host" : "localhost",
"metrics" : "status,newrelic",
"user" : "root",
"passwd" : "mysecret"
}
]
}
This file will be used by the Newrelic plugin
Template File plugin.json.erb:
<%= Chef::JSONCompat.to_json_pretty(#name) %>
I've created a recipe like this one:
mysql-plugin.rb
# Default Variables
newrelic = decrypt_databag('newrelic')
node.default['newrelic_npi']['license_key'] = newrelic['license_key']
plugin = 'com.newrelic.plugins.mysql.instance'
plugin_json_path = "/opt/newrelic-npi/plugins/com.newrelic.plugins.mysql.instance/newrelic_mysql_plugin-2.0.0/config/plugin.json"
node.default['newrelic_npi']['name'] = "localhost1"
execute 'fetch' do
cwd node['newrelic_npi']['install_path']
user node['newrelic_npi']['user']
command "./npi fetch #{plugin} -y"
not_if do
::File.exist? "#{node['newrelic_npi']['install_path']}/plugins/#{plugin}"
end
end
execute 'prepare' do
cwd node['newrelic_npi']['install_path']
user node['newrelic_npi']['user']
command "./npi prepare #{plugin}"
end
template "#{plugin_json_path}" do
source 'plugin.json.erb'
owner "root"
group "root"
mode "0644"
variables :name => node['newrelic_npi']['name']
action :create
end
execute 'add-service' do
cwd node['newrelic_npi']['install_path']
user node['newrelic_npi']['user']
command "sudo ./npi add-service #{plugin} --start" # needs root privileges
not_if do
::File.exist? "/etc/init.d/newrelic_plugin_#{plugin}"
end
end
At the Template block what should I do to make a Json file like plugin.json?
template "#{plugin_json_path}" do
source 'plugin.json.erb'
owner "root"
group "root"
mode "0644"
variables :name => node['newrelic_npi']['name']
action :create
end
Thanks in Advance.

Answer 1

First. You should be setting any default node variables inside default.rb in your attributes folder. Like this:
default['newrelic_npi']['license_key'] = newrelic['license_key']
default['newrelic_npi']['name'] = "localhost1"
Node attributes are reset before compilation and will pull from that file as well as Ohai. Setting node attributes inside the recipe means they aren't going to be available for your template (you should review this Chef Client Overview).
Next, if you just need to set the hostname or another specific portion of the template file you can do this inside your erb file:
{
"agents": [
{
"name" : "sqlhost",
"host" : "<%= #name %>",
"metrics" : "status,newrelic",
"user" : "root",
"passwd" : "mysecret"
}
]
}
Your current erb file is trying to convert #name (which you try to set to localhost1) to json, not set the whole file like your example.

Answer 2

To generate a correct plugin.json:
{
"agents": [
{
"name" : <%= Chef::JSONCompat.to_json_pretty(#name) %>,
"host" : <%= Chef::JSONCompat.to_json_pretty(#host) %>,
"metrics" : <%= Chef::JSONCompat.to_json_pretty(#metrics) %>,
"user" : <%= Chef::JSONCompat.to_json_pretty(#user) %>,
"passwd" : <%= Chef::JSONCompat.to_json_pretty(#passwd) %>
}
]
}
At the template Block I did like:
template node['newrelic_npi']['plugin_json_path'] do
source 'plugin.json.erb'
owner 'root'
group 'root'
mode '0644'
variables(
:name => node['newrelic_npi']['name'],
:host => node['newrelic_npi']['host'],
:metrics => node['newrelic_npi']['metrics'],
:user => node['newrelic_npi']['user'],
:passwd => node['newrelic_npi']['myql_admin_password']
)
action :create
end