OpenStackClient/HumanInterfaceGuidelines

[Note: As of January 2015 this page is no longer maintained, the current OpenStackClient Human Interface Guide is maintained in the source repository and can be found in OpenStack Documentation]

Note: This page covers the OpenStackClient CLI only but looks familiar because it was derived from the Horizon HIG.

= Overview =

What is a HIG? The Human Interface Guidelines document was created for OpenStack designers in order to direct the creation of new OpenStackClient command interfaces.

= Personas =

Personas are archetypal users of the system. Keep these types of users in mind when designing the interface.

Alice the admin
Alice is an administrator who is responsible for maintaining the OpenStack cloud installation. She has many years of experience with Linux systems administration.

Darren the deployer
Darren is responsible for doing the initial OpenStack deployment on the host machines.

Emile the end-user
Emile uses the cloud to do software development inside of the virtual machines. She uses the command-line tools because she finds it quicker than using the dashboard.

= Principles =

The principles established in this section define the high-level priorities to be used when designing and evaluating interactions for the OpenStack command line interface. Principles are broad in scope and can be considered the philosophical foundation for the OpenStack experience; while they may not describe the tactical implementation of design, they should be used when deciding between multiple courses of design.

A significant theme for designing for the OpenStack experience concerns focusing on common uses of the system rather than adding complexity to support functionality that is rarely used.

Consistency
Consistency between OpenStack experiences will ensure that the command line interface feels like a single experience instead of a jumble of disparate products. Fractured experiences only serve to undermine user expectations about how they should interact with the system, creating an unreliable user experience. To avoid this, each interaction and visual representation within the system must be used uniformly and predictably. The architecture and elements detailed in this document will provide a strong foundation for establishing a consistent experience.

Example Review Criteria

 * Do the command actions adhere to a consistent application of actions?
 * Has a new type of command subject or output been introduced?
 * Does the design use command elements (options and arguments) as defined? (See Core Elements.)
 * Can any newly proposed command elements (actions or subjects) be accomplished with existing elemetns?


 * Does the design adhere to the structural model of the core experience? (See Core Architecture.)
 * Are any data objects displayed or manipulated in a way contradictory to how they are handled elsewhere in the core experience?

Simplicity
To best support new users and create straight forward interactions, designs should be as simple as possible. When crafting new commands, designs should minimize the amount of noise present in output: large amounts of nonessential data, overabundance of possible actions, etc. Designs should focus on the intent of the command, requiring only the necessary components and either removing superfluous elements or making them accessible through optional arguments. An example of this principle occurs in OpenStack’s use of tables: only the most often used columns are shown by default. Further data may be accessed through the output control options, allowing users to specify the types of data that they find useful in their day-to-day work.

Example Review Criteria

 * Can options be used to combine otherwise similar commands?


 * How many of the displayed elements are relevant to the majority of users?
 * If multiple actions are required for the user to complete a task, is each step required or can the process be more efficient?

User-Centered Design
Commands should be design based on how a user will interact with the system and not how the system’s backend is organized. While database structures and APIs may define what is possible, they often do not define good user experience; consider user goals and the way in which users will want to interact with their data, then design for these work flows and mold the interface to the user, not the user to the interface.

Commands should be discoverable via the interface itself.

To determine a list of available commands, use the ``-h`` or ``--help`` options:



$ openstack --help

For help with an individual command, use the ``help`` command:



$ openstack help server create

Example Review Criteria

 * How quickly can a user figure out how to accomplish a given task?
 * Has content been grouped and ordered according to usage relationships?
 * Do work flows support user goals or add complexity?

Transparency
Make sure users understand the current state of their infrastructure and interactions. For example, users should be able to access information about the state of each machine/virtual machine easily, without having to actively seek out this information. Whenever the user initiates an action, make sure a confirmation is displayed[1] to show that an input has been received. Upon completion of a process, make sure the user is informed. Ensure that the user never questions the state of their environment.

[1] This goes against the common UNIX philosophy of only reporting error conditions and output that is specifically requested.

Example Review Criteria

 * Does the user receive feedback when initiating a process?
 * When a process is completed?
 * Does the user have quick access to the state of their infrastructure?

= Architecture =

Command Structure
OpenStackClient has a consistent and predictable format for all of its commands.


 * The top level command name is
 * Sub-commands take the form:

Subcommands shall have three distinct parts to its commands (in order that they appear):
 * global options
 * command object(s) and action
 * command options and arguments

Output formats:
 * user-friendly tables with headers, etc
 * machine-parsable delimited

Notes:
 * All long options names shall begin with two dashes ('--') and use a single dash ('-') internally between words . Underscores ('_') shall not be used in option names.
 * Authentication options conform to the common CLI authentication guidelines.

Global Options
Global options are global in the sense that they apply to every command invocation regardless of action to be performed. They include authentication credentials and API version selection. Most global options have a corresponding environment variable that may also be used to set the value. If both are present, the command-line option takes priority. The environment variable names are derived from the option name by dropping the leading dashes ('--'), converting each embedded dash ('-') to an underscore ('_'), and converting to upper case.

For example, `--os-username` can be set from the environment via `OS_USERNAME`.

--help
The standard `--help` global option displays the documentation for invoking the program and a list of the availably commands on standard output. All other options and commands are ignored when this is present. The traditional short form help option is also available.

FIXME(aspiers): plagiarised from the "GNU standards for --help". Do we want to plagiarise the rest of it and recommend the output format to be something like this?


 * Near the end of the `--help` option's output, please place lines giving the email address for bug reports, the package's home page, and the general page for help. The format should be like this:

Home page:  Documentation:  Report bugs via: 

--version
FIXME(aspiers): plagiarised from the beginning of `GNU standards for --version. but there are many other good ideas which could be copied too.


 * The standard `--version` option should direct the program to print information about its name, version, origin and legal status, all on standard output, and then exit successfully. Other options and arguments should be ignored once this is seen, and the program should not perform its normal function.


 * The first line is meant to be easy for a program to parse; the version number proper starts after the last space. In addition, it contains the canonical name for this program, in this format:

OpenStack Nova (Compute) 2012.1.0.3


 * The program's name should be a constant string; don't compute it from `sys.argv`. The idea is to state the standard or canonical name for the program, not its file name.  There are other ways to find out the precise file name where a command is found in `PATH`.

Command Object(s) and Action
Commands consist of an object described by one or more words followed by an action. Commands that require two objects have the primary object ahead of the action and the secondary object after the action. Any positional arguments identifying the objects shall appear in the same order as the objects. In badly formed English it is expressed as "(Take) object1 (and perform) action (using) object2 (to it)."

 

Examples: * group add user * volume type list  # 'volume type' is a two-word single object

The  command is unique as it appears in front of a normal command and displays the help text for that command rather than execute it.

language use.
 * Object names are always specified in command in their singular form. This is contrary to natural

Command Arguments and Options
Each command may have its own set of options distinct from the global options. They follow the same style as the global options and always appear between the command and any positional arguments the command requires.

Option Forms

 * *boolean*: boolean options shall use a form of `-- |-- ` (preferred) or `-- |--no- `. For example, the `enabled` state of a project is set with `--enable|--disable`.

Command Output
The default command output is pretty-printed using the Python `prettytable` module.

Machine-parsable output format may be specified with the `--format` option to `list` and `show` commands.. `list` commands have an option (`--format csv`) for CSV output and `show` commands have an option (`--format shell`) for the shell variable assignment syntax of `var="value"`. In both cases, all data fields are quoted with `"`


 * [FIXME(ijw): without any form of quoting, then no delimiter is guaranteed to be safe if I want to parse the output on the command line. Would it be possible to write a script that's guaranteed to work with e.g. all instance names?] [(dtroyer) I've updated the text here to reflect the current situation.  Both output formats are quoted.]**

Help Commands
The help system is considered separately due to its special status among the commands. Rather than performing tasks against a system, it provides information about the commands available to perform those tasks. The format of the `help` command therefore varies from the form for other commands in that the `help` command appears in front of the first object in the command.

The options `--help` and `-h` display the global options and a list of the supported commands. Note that the commands shown depend on the API versions that are in effect; i.e. if `--os-identity-api-version=3` is present Identity API v3 commands are shown.

= Examples =

The following examples depict common command and output formats expected to be produces by the OpenStack client.

Authentication
Using global options::

openstack --os-tenant-name ExampleCo --os-username demo --os-password secrete --os-auth-url http://localhost:5000:/v2.0 server show appweb01 ++-+   |        Property        |                Value                                | ++-+   | OS-DCF:diskConfig      | MANUAL                                              | | OS-EXT-STS:power_state | 1                                                  | | flavor                | m1.small                                            | | id                    | dcbc2185-ba17-4f81-95a9-c3fae9b2b042                | | image                 | Ubuntu 12.04 (754c231e-ade2-458c-9f91-c8df107ff7ef) | | keyname               | demo-key                                            | | name                  | appweb01                                            | | private_address       | 10.4.128.13                                         | | status                | ACTIVE                                              | | user                  | demo                                                | ++-+

Using environment variables::

export OS_TENANT_NAME=ExampleCo export OS_USERNAME=demo export OS_PASSWORD=secrete export OS_AUTH_URL=http://localhost:5000:/v2.0 openstack server show appweb01 ++-+   |        Property        |                Value                                | ++-+   | OS-DCF:diskConfig      | MANUAL                                              | | OS-EXT-STS:power_state | 1                                                  | | flavor                | m1.small                                            | | id                    | dcbc2185-ba17-4f81-95a9-c3fae9b2b042                | | image                 | Ubuntu 12.04 (754c231e-ade2-458c-9f91-c8df107ff7ef) | | keyname               | demo-key                                            | | name                  | appweb01                                            | | private_address       | 10.4.128.13                                         | | status                | ACTIVE                                              | | user                  | demo                                                | ++-+

Machine Output Format
Using the csv output format with a list command:

openstack server list --format csv "ID","Name","Status","Private_Address" "ead97d84-6988-47fc-9637-3564fc36bc4b","appweb01","ACTIVE","10.4.128.13"

Using the show command options of shell output format and adding a prefix of 'my_' to avoid collisions with existing environment variables:

openstack server show --format shell --prefix my_ appweb01 my_OS-DCF:diskConfig="MANUAL" my_OS-EXT-STS:power_state="1" my_flavor="m1.small" my_id="dcbc2185-ba17-4f81-95a9-c3fae9b2b042" my_image="Ubuntu 12.04 (754c231e-ade2-458c-9f91-c8df107ff7ef)" my_keyname="demo-key" my_name="appweb01" my_private_address="10.4.128.13" my_status="ACTIVE" my_user="demo"