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Bundle Configs

Cog executes commands to accomplish different tasks. Commands are organized into bundles. Bundles not only provide a way to organize similar commands, they also keep everything, like permissions and rules, namespaced. Every bundle includes a bundle config. Bundle configs are written in YAML and provide all of the information necessary to install and execute the commands included in the bundle.

Cog provides two types of bundles, simple and standard. Simple bundles point to an executable already installed on the machine running the relay you want to execute the command on. Simple bundles are great for simple common commands. Standard bundles point to a repository on Docker hub that contains the execution code for your bundle. To learn more about packaging and building bundles for Cog, check out :doc:`writing_a_command_bundle`.

Simple bundle configs

To start, lets discuss configs for simple bundles. Simple bundle configs look like this:

simple_config.yaml.

---
cog_bundle_version: 4

name: my_bundle
description: "Does bundle things"
version: "0.1"
commands:
  date:
    executable: "/usr/local/bin/mydate.exs"
    description: "Displays the current date and time"
    rules:
      - "allow"
templates:
  date:
    slack: "`{{date}}`"

name, description, version, cog_bundle_version and commands are all required fields. Most of these are pretty self explanatory but let’s go over them anyway.

  • name is simply the name of your bundle. All commands will be installed within a namespace defined by this field. So command names that collide with command names in other bundles will be invoked by using the fully qualified name. In this case the date command’s fully qualified name would be my_bundle:date.
  • description is a short, one-line description for your bundle. This will be printed along with a list of all installed bundles when a user runs the help command.
  • version is the semver version number of your bundle. Currently Cog provides no internal mechanism for dealing with versions. If you want to install a new version of bundle then you first need to uninstall the old one. We require version because at some point we will provide a mechanism to upgrade bundles.
  • cog_bundle_version is the version of Cog’s bundle system that your bundle was built for. The current bundle version is 4, which is used through out the rest of this document.
  • commands are a hash of commands keyed by the command name. Here the command name is "date". For simple bundles you are only required to provide the executable and the rules fields. We’ll detail more about the commands section a little later.

In addition to the required fields there is also one optional in this example, templates. templates are a hash of templates keyed my name. Template names should correspond to command names. In this case the template is named "date" just like the command "date". Templates vary from adapter to adapter so under the name of the template we key the template strings by adapter. Currently we only support two adapters for the purpose of templates; "slack" and "hipchat".

Note

cogctl, Cog's command line tool, provides some useful functionality for templates. You can just save templates as individual files and cogctl will build out the templates section for you before uploading the config.

Commands

Commands are probably the most complex component of the bundle config so I thought I would give it it’s own section.

As an example let’s look at an excerpt from the mist config.

mist_config.yaml (excerpt).

...

commands:
  ec2-find:
    executable: /usr/local/bin/ec2_find
    description: Finds an ec2 instance
    options:
      region:
        type: string
        required: true
      tags:
        type: string
        required: false
      ami:
        type: string
        required: false
      state:
        type: string
        required: false
      return:
        type: string
        required: false
        description: Valid values are id, pubdns, privdns, state, keyname, ami, kernel, arch, vpc, pubip, privip, az, tags
    rules:
      - must have mist:view
...

Here you will notice the command name "ec2-find" and nested under it several fields. Let’s talk about them one at a time.

  • executable is probably the easiest but is arguably the most important field. It’s also the only required field in a command hash. executable simple points to the command script or binary that is to be run.
  • description is a short, one-line description for the command. This is the info that will appear along with a list of commands when a user runs the help command for a specific bundle.
  • options is a hash of arguments that the command accepts. By default Cog you can pass options to a command using the option name, --region as an example here. Options have a type, currently we support: int, float, bool, string, incr and list. They also have an optional short_flag and a description.
  • rules is required and is a list of strings that define what permissions are required to run the command. Check out :doc:`permissions_and_rules` to learn more about what rules look like. A couple things to note about rules. When specifying rules in configs you can drop the "when command is …" portion like we did in the previous mist config. Cog has enough context to fill that bit in for you. There is also a special rule that opens the command up for execution by anyone, "when command is bundle:command allow". So when combined with the previous note you only need to specify the "allow" bit in configs.

Other fields

To get a simple command up and running the simple config is pretty much all that you need. But for more advanced features there are a number of additional fields that you might want to consider.

Permissions

All commands require permissions to run. Permissions are included in the bundle config as a list of strings at the top level. Here is another excerpt of the mist config as an example.

mist_config.yaml (excerpt).

---
cog_bundle_version: 4

name: mist
description: Manage EC2 instances and related services
version: 0.4.0
permissions:
- mist:view
- mist:change-state
- mist:destroy
- mist:create
- mist:manage-tags
- mist:change-acl

...

Standard bundle configs

For the most part standard bundle configs follow the same rules as simple bundle configs. Really the only difference is the addition of the docker field. Standard bundles are deployed from docker hub as docker images. The docker field just tells Cog where to go to get the image.

Once again as an example, here is an excerpt from the mist config.

mist_config.yaml (excerpt).

...

docker:
  image: cogcmd/mist
  tag: "0.4"
...

It’s fairly self explanatory. There are only two fields, image and tag. image refers to the image on docker hub and tag just points to a specific tag. If you don’t pass tag Cog will grab the most recent version of the image.

Documentation fields

There are a number of fields dedicated to rendering manpage-style documentation rendered by the help command both for the bundle and the command.

Bundle

  • long_description is a separate section for a longer form description, which can include things like what configuration is required, how commands should be used, and more details about the underlying implementation.
  • author is where the bundle author can leave their name and email address if a user needs their contact information.
  • homepage is a URL for the bundle, typically a github repo.
  • config is used to document your bundle configuration settings. It contains two sections, notes and env.
    • notes is used to provide any additional configuration information that might be useful to users.
    • env is a list of objects containing two keys; var, for the name of your environment variable and description, for an optional description.

aws_cfn_config.yaml (excerpt).

...
config:
  notes:
    The cfn bundle makes use of CloudFormation stack templates and stack policies that are defined in JSON documents and stored in pre-defined S3 locations. These locations are defined with the 'CFN_TEMPLATE_URL' and 'CFN_POLICY_URL' configuration variables.
  env:
    - var: AWS_REGION
    - var: AWS_ACCESS_KEY_ID
    - var: AWS_SECRET_ACCESS_KEY
    - var: AWS_STS_ROLE_ARN
      description: STS role ARN that should be assumed. Defined as 'arn:aws:iam::<account_number>:role/<role_name>'.
    - var: CFN_TEMPLATE_URL
      description: S3 Location of your stack templates. Defined as 's3://<bucket>/<path>'.
    - var: CFN_POLICY_URL
      description: S3 Location of your stack policies. Defined as 's3://<bucket>/<path>'.
...

Command

  • long_description is a long-form description used to explain details of a command that don’t fit into other sections like an explanation of required arguments or about the structure of the output.
  • examples is how a user will run the command and what output they should expect.
  • notes is a free-form section at the bottom of the command above author and homepage
  • arguments is a short string appended to the generated synopsis for describing named or required arguments or subcommands.
  • subcommands is an object where the keys are the subcommand arguments and the values are a short one-line description of each subcommand.

Conclusion

And that, as they say, is that. There is no more; you pretty much know all there is to know about what goes into a config. But for the sake of completeness and to help you tie everything together, here is the mist config in it’s entirety.

mist_config.yaml.

---
cog_bundle_version: 4

name: mist
description: Manage EC2 instances and related services
version: 0.4.0
permissions:
- mist:view
- mist:change-state
- mist:destroy
- mist:create
- mist:manage-tags
- mist:change-acl
docker:
  image: cogcmd/mist
  tag: "0.4"
commands:
  ec2-find:
    executable: /usr/local/bin/ec2_find
    options:
      region:
        type: string
        required: true
      tags:
        type: string
        required: false
      ami:
        type: string
        required: false
      state:
        type: string
        required: false
      return:
        type: string
        required: false
    rules:
      - must have mist:view
  ec2-destroy:
    executable: /usr/local/bin/ec2_destroy
    options:
      region:
        type: string
        required: true
    rules:
      - must have mist:destroy
  ec2-state:
    executable: /usr/local/bin/ec2_state
    options:
      region:
        type: string
        required: true
    rules:
      - must have mist:change-state
  vpc-list:
    executable: /usr/local/bin/ec2_vpcs
    options:
      region:
        type: string
        required: true
      subnets:
        type: bool
        required: false
    rules:
      - must have mist:view
  keypairs-list:
    executable: /usr/local/bin/ec2_keypairs
    options:
      region:
        type: string
        required: true
    rules:
      - must have mist:view
  ec2-create:
    executable: /usr/local/bin/ec2_create
    options:
      region:
        type: string
        required: true
      type:
        type: string
        required: true
      ami:
        type: string
        required: true
      keypair:
        type: string
        required: true
      az:
        type: string
        required: false
      vpc:
        type: string
        required: false
      tags:
        type: string
        required: false
      user-data:
        type: string
        required: false
      count:
        type: int
        required: false
    rules:
      - must have mist:create
  ec2-tags:
    executable: /usr/local/bin/ec2_tags
    options:
      region:
        type: string
        required: true
      tags:
        type: string
        required: true
    rules:
      - must have mist:manage-tags
  s3-buckets:
    executable: /usr/local/bin/s3_buckets
    rules:
      - must have mist:view
      - with arg[0] == 'list' must have mist:view
      - with (arg[0] == 'delete' or arg[0] == 'rm') must have mist:destroy
  s3-bucket-files:
    executable: /usr/local/bin/s3_bucket_files
    options:
      bucket:
        type: string
        required: false
      file:
        type: string
        required: false
      policy:
        type: string
        required: false
      force:
        type: bool
        required: false
    rules:
      - must have mist:view
      - with option[set-policy] == /.*/ must have mist:change-acl