Optimizing Cookbooks/recipes using attributes, Notifications and gaurds
- In Chef we can define parameters that can be used in the recipe by using attribute files
- Chef attributes file is collection of attributes and each attribute represents specific detail.
- There are two kinds of attributes
- User defined attributes
- System Collected attributes
- Attributes are collected by chef system during every convergance and referred as ‘automatic attributes’
- Attributes can be defined at various places, But lets restrict ourselves to attributes in attributes file
- Now lets generate an attribute file called as default
- To create attribute in attribute file we can use ruby hash syntax and in this series we will restrict to only type of attributes default
- Refer Here for the changes made
- Made changes to conditional statement Refer Here
- Now lets converge and verify if the cookbook is working as expected
- We can use chef common attributes such as only_if and not_if to avoid writing ruby conditional statements Refer Here. Refer Here for usage of only_if gaurd
- We have one more problem, whenever we converge apache server is getting restarted. It should only restart
- in the case of new installation
- When info.php is changed.
- In chef we have a concept called as notifications where one resource can notify other resource to execute Refer Here for official docs
- Lets implement notification functionality Refer Here
- Notifies can notify only one resource. If you have to notify multiple resources, then use subscribes over notify Refer Here
file '/tmp/txt' do
action :create
end
service 'apache'
action :nothing
subscribes :restart, 'file[/tmp/txt]'
end
service 'tomcat8'
action :nothing
subscribes :restart, 'file[/tmp/txt]'
end
- In the lampserver i have deleted the unnecessary files Refer Here
- Now we have only one problem the content of info.php is only one line so we are using content property. What if the content is a large file with multiple lines
file '/var/www/html/info.php' do
content '<?php phpinfo(); ?>'
action :create
notifies :restart, "service[#{package_name}]"
end
- We can solve above problem by creating file to be copied in the cookbook itself and use the file in cookbook to create file in remote node.
- Lets generate a file called as info.php in chef cookbook. Refer Here for the changeset
Scenario: Configure Tomcat Server on ubuntu
- Exercise: Configure tomcat server on ubuntu
- Manual Steps:
sudo apt-get update
sudo apt install openjdk-8-jdk -y
sudo groupadd tomcat
sudo useradd -s /bin/false -g tomcat -d /opt/tomcat tomcat
# For rest refer the page https://www.digitalocean.com/community/tutorials/install-tomcat-9-ubuntu-1804
- Create a cookbook
- Generate a recipe called as ubuntu_tomcat
- Generate a attribute file called as default to store package name and username
- Refer Here for the changeset
- Refer Here for kitchen command line syntaxes.
