State Modules#

State modules provide idempotent functions to configure your cloud. State modules generally use functions from related Exec modules to check for the current status of resources and make the necessary changes.

Common State Module Functions#

There are two functions that are generally used for Idem State functions, present and absent.

Present State Function#

The present state function will ensure that your resource exists.

The present function will use the related get or list Exec function to determine if the resource already exists or not. If the resource already exists, then it will return immediately with a successful response. If the resource doesn’t exist, it will use the corresponding Exec function to create the missing resource and then return a successful response if the create function succeeds.

Absent State Function#

In a similar manner the absent function will ensure that your specified resource does not exist.

It will use the related get or list function to determine if the resource exists or not. If the resource doesn’t exist the function will return immediately with a successful status. If the resource does exist the function will use the related Exec module delete function to remove the resource.

State Modules and SLS Files#

Generally, you will define how you want your infrastructure configured in yaml files with an .sls extension. These are often refered to as sls files or state files. These sls files will contain yaml datastructures that will use your Idem State Functions to define how your infrastructure is configured.

Here is an example of an sls file that configures an AWS VPC:

~/my_idem_files/my_vpc.sls#

 vpc-07fa1462:
   aws.ec2.vpc.present:
   - name: vpc-07fa1462
   - resource_id: vpc-07fa1462
   - instance_tenancy: default
   - cidr_block_association_set:
     - AssociationId: vpc-cidr-assoc-b2ba2fdb
       CidrBlock: 172.31.0.0/16
       CidrBlockState:
         State: associated
   - enable_dns_hostnames: true
   - enable_dns_support: true

Now we can apply this sls file in an idempotent operation like this:

idem state ~/my_idem_files/my_vpc.sls

Create Present State Function#

Let’s create our present state function for our idem-sqlite-demo provider plugin.

mkdir idem_sqlite_demo/states/demo
touch idem_sqlite_demo/states/demo/sqlite.py