Templates

Templates

awless writing operations to the cloud infrastructure relies on the concepts of templates. A template in awless describes a list of actions updating the cloud. For instance, this would be a one-liner template:

create instance subnet=subnet-356d517f image=ami-70edb016 type=t2.micro

This one line template contains an action create on an entity followed by a list of params.

Parameters can be either:

• given directly through the command line as key=value arguments
• filled transparently filled by your local config defaults (i.e: instance ami, instance type, etc...)
• completed through dynamic CLI prompting for missing required arguments

Under the hood, an awless template is parsed with a parsing expression grammar in order to build an abstract syntax tree. Then the AST is traversed by a given cloud driver (i.e: AWS aws-sdk-go) to perform the action against the cloud

The awless CLI provides 2 ways of executing templates:

1. awless run that takes as an argument the filepath of a template local file.

    $ awless run ~/templates/create_infra.txt
   

2. CLI template one-liner

    $ awless create instance name=my-instance
    $ awless delete subnet ...
    $ awless stop instance id=i-6fg5h4j
   

Template file and syntax

You can also load more complex templates combining multiple commands in a template file through the awless run command. For example, the following template file:

subnet = create subnet cidr={subnet.cidr} vpc={subnet.vpc}
create tags resource=$subnet Name={subnet.name}
update subnet id=$subnet public-vms=true
rtable = create routetable vpc={subnet.vpc}
attach routetable id=$rtable subnet=$subnet
route = create route cidr=0.0.0.0/0 gateway={vpc.gateway} table=$rtable

The file contains variables to store newly created resource to be referenced later. It also has holes to be filled in later on by your defaults or CLI prompting

One-liner template command

Here are some more examples of awless builtin template one-liners:

• awless create allow to create a cloud resource (ex: instance, vpc, user, ssh keypair, routetable...)
• awless delete allow to delete a cloud resource
• awless update allow to update a cloud resource property after its creation
• awless attach allow to attach a cloud resource (for example, a volume) to another (for example an instance)
• awless detach allow to attach two attached cloud resources.
• awless start allow to start a cloud resource (for example, an instance)
• awless stop allow to stop a cloud resource (for example, an instance)