Update CLI docs.

JIRA: QTIP-231

Change-Id: I44bc75239e9ff59a70ec9070092101f021a3a291
Signed-off-by: Taseer Ahmed <taseer94@gmail.com>

1 files changed, 92 insertions, 0 deletions

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+***************************
+QTIP Command Line Interface
+***************************
+
+Abstract
+########
+
+QTIP consists of different tools(metrics) to benchmark the NFVI. These metrics fall under different NFVI
+subsystems(QPI's) such as compute, storage and network. A plan consists of one or more QPI's, depending upon how
+the end user would want to measure performance. CLI is designed to help the user, execute benchmarks and
+view respective scores.
+
+Framework
+=========
+
+QTIP CLI has been created using the Python package `Click`_, Command Line Interface Creation Kit. It has been
+chosen for number of reasons. It presents the user with a very simple yet powerful API to build complex
+applications. One of the most striking features is command nesting.
+
+As explained, QTIP consists of metrics, QPI's and plans. CLI is designed to provide interface to all
+these components. It is responsible for execution, as well as provide listing and details of each individual
+element making up these components.
+
+Design
+======
+
+CLI's entry point extends Click's built in MultiCommand class object. It provides two methods, which are
+overridden to provide custom configurations.
+
+.. code-block:: python
+
+    class QtipCli(click.MultiCommand):
+
+        def list_commands(self, ctx):
+            rv = []
+            for filename in os.listdir(cmd_folder):
+                if filename.endswith('.py') and \
+                    filename.startswith('cmd_'):
+                    rv.append(filename[4:-3])
+            rv.sort()
+            return rv
+
+        def get_command(self, ctx, name):
+            try:
+                if sys.version_info[0] == 2:
+                    name = name.encode('ascii', 'replace')
+                mod = __import__('qtip.cli.commands.cmd_' + name,
+                                 None, None, ['cli'])
+            except ImportError:
+                return
+            return mod.cli
+
+Commands and subcommands will then be loaded by the ``get_command`` method above.
+
+Extending the Framework
+=======================
+
+Framework can be easily extended, as per the users requirements. One such example can be to override the builtin
+configurations with user defined ones. These can be written in a file, loaded via a Click Context and passed
+through to all the commands.
+
+.. code-block:: python
+
+   class Context:
+
+       def __init__():
+
+           self.config = ConfigParser.ConfigParser()
+           self.config.read('path/to/configuration_file')
+
+       def get_paths():
+
+           paths = self.config.get('section', 'path')
+           return paths
+
+The above example loads configuration from user defined paths, which then need to be provided to the actual
+command definitions.
+
+.. code-block:: python
+
+   from qtip.cli.entry import Context
+
+   pass_context = click.make_pass_decorator(Context, ensure=False)
+
+   @cli.command('list', help='List the Plans')
+   @pass_context
+   def list(ctx):
+       plans = Plan.list_all(ctx.paths())
+       table = utils.table('Plans', plans)
+       click.echo(table)
+
+.. _Click: http://click.pocoo.org/5/