[cli] Dynamic cli extension via plugins (sonic-net#1186)

Added a mechanism to extend command line interface via plugins.
For every program - show, config, clear a new python package called 'plugins' is added. This package is used as a namespace for all plugins python modules. As an example mlnx.py is moved to the plugins package.

In the fututre, this mechanism will be used by Application Extension infrastructure.

Signed-off-by: Stepan Blyschak <stepanb@nvidia.com>

clear/main.py

@@ -5,6 +5,10 @@
 
 import click
 
+from utilities_common import util_base
+
+from . import plugins
+
 
 # This is from the aliases example:
 # https://github.com/pallets/click/blob/57c6f09611fc47ca80db0bd010f05998b3c0aa95/examples/aliases/aliases.py
@@ -120,7 +124,6 @@ def cli():
     """SONiC command line - 'Clear' command"""
     pass
 
-
 #
 # 'ip' group ###
 #
@@ -446,5 +449,12 @@ def translations():
     cmd = "natclear -t"
     run_command(cmd)
 
+
+# Load plugins and register them
+helper = util_base.UtilHelper()
+for plugin in helper.load_plugins(plugins):
+    helper.register_plugin(plugin, cli)
+
+
 if __name__ == '__main__':
     cli()

config/main.py

@@ -16,6 +16,7 @@
 from portconfig import get_child_ports
 from sonic_py_common import device_info, multi_asic
 from sonic_py_common.interface import get_interface_table_name, get_port_table_name
+from utilities_common import util_base
 from swsscommon.swsscommon import SonicV2Connector, ConfigDBConnector, SonicDBConfig
 from utilities_common.db import Db
 from utilities_common.intf_filter import parse_interface_in_filter
@@ -28,11 +29,11 @@
 from . import feature
 from . import kdump
 from . import kube
-from . import mlnx
 from . import muxcable
 from . import nat
 from . import vlan
 from . import vxlan
+from . import plugins
 from .config_mgmt import ConfigMgmtDPB
 
 # mock masic APIs for unit test
@@ -849,9 +850,6 @@ def config(ctx):
     except (KeyError, TypeError):
         raise click.Abort()
 
-    if asic_type == 'mellanox':
-        platform.add_command(mlnx.mlnx)
-
     # Load the global config file database_global.json once.
     num_asic = multi_asic.get_num_asics()
     if num_asic > 1:
@@ -4415,5 +4413,12 @@ def delete(ctx):
     sflow_tbl['global'].pop('agent_id')
     config_db.set_entry('SFLOW', 'global', sflow_tbl['global'])
 
+
+# Load plugins and register them
+helper = util_base.UtilHelper()
+for plugin in helper.load_plugins(plugins):
+    helper.register_plugin(plugin, config)
+
+
 if __name__ == '__main__':
     config()

config/mlnx.py → config/plugins/mlnx.py

@@ -11,6 +11,7 @@
 
     import click
     from sonic_py_common import logger
+    from sonic_py_common import device_info
     import utilities_common.cli as clicommon
 except ImportError as e:
     raise ImportError("%s - required module not found" % str(e))
@@ -229,5 +230,10 @@ def sdk_sniffer_disable():
 #     pass
 
 
+def register(cli):
+    version_info = device_info.get_sonic_version_info()
+    if (version_info and version_info.get('asic_type') == 'mellanox'):
+        cli.commands['platform'].add_command(mlnx)
+
 if __name__ == '__main__':
     sniffer()

setup.py

@@ -22,7 +22,9 @@
     packages=[
         'acl_loader',
         'clear',
+        'clear.plugins',
         'config',
+        'config.plugins',
         'connect',
         'consutil',
         'counterpoll',
@@ -42,6 +44,7 @@
         'pddf_ledutil',
         'show',
         'show.interfaces',
+        'show.plugins',
         'sonic_installer',
         'sonic_installer.bootloader',
         'tests',

show/main.py

@@ -11,6 +11,7 @@
 from sonic_py_common import device_info, multi_asic
 from swsscommon.swsscommon import SonicV2Connector, ConfigDBConnector
 from tabulate import tabulate
+from utilities_common import util_base
 from utilities_common.db import Db
 
 from . import acl
@@ -23,7 +24,6 @@
 from . import interfaces
 from . import kdump
 from . import kube
-from . import mlnx
 from . import muxcable
 from . import nat
 from . import platform
@@ -35,6 +35,7 @@
 from . import vxlan
 from . import system_health
 from . import warm_restart
+from . import plugins
 
 
 # Global Variables
@@ -1413,5 +1414,12 @@ def ztp(status, verbose):
        cmd = cmd + " --verbose"
     run_command(cmd, display_cmd=verbose)
 
+
+# Load plugins and register them
+helper = util_base.UtilHelper()
+for plugin in helper.load_plugins(plugins):
+    helper.register_plugin(plugin, cli)
+
+
 if __name__ == '__main__':
     cli()

show/platform.py

@@ -33,12 +33,6 @@ def platform():
     pass
 
 
-version_info = device_info.get_sonic_version_info()
-if (version_info and version_info.get('asic_type') == 'mellanox'):
-    from . import mlnx
-    platform.add_command(mlnx.mlnx)
-
-
 # 'summary' subcommand ("show platform summary")
 @platform.command()
 @click.option('--json', is_flag=True, help="Output in JSON format")

show/mlnx.py → show/plugins/mlnx.py

@@ -10,6 +10,7 @@
     import subprocess
     import click
     import xml.etree.ElementTree as ET
+    from sonic_py_common import device_info
 except ImportError as e:
     raise ImportError("%s - required module not found" % str(e))
 
@@ -137,3 +138,8 @@ def issu_status():
 
     click.echo('ISSU is enabled' if res else 'ISSU is disabled')
 
+
+def register(cli):
+    version_info = device_info.get_sonic_version_info()
+    if (version_info and version_info.get('asic_type') == 'mellanox'):
+        cli.commands['platform'].add_command(mlnx)

utilities_common/util_base.py

@@ -1,17 +1,51 @@
-
 import os
-import sonic_platform
+import pkgutil
+import importlib
+
+from sonic_py_common import logger
 
 # Constants ====================================================================
 PDDF_SUPPORT_FILE = '/usr/share/sonic/platform/pddf_support'
 
 # Helper classs
 
+log = logger.Logger()
+
 
 class UtilHelper(object):
     def __init__(self):
         pass
 
+    def load_plugins(self, plugins_namespace):
+        """ Discover and load CLI plugins. Yield a plugin module. """
+
+        def iter_namespace(ns_pkg):
+            return pkgutil.iter_modules(ns_pkg.__path__, ns_pkg.__name__ + ".")
+
+        for _, module_name, ispkg in iter_namespace(plugins_namespace):
+            if ispkg:
+                continue
+            log.log_debug('importing plugin: {}'.format(module_name))
+            try:
+                module = importlib.import_module(module_name)
+            except Exception as err:
+                log.log_error('failed to import plugin {}: {}'.format(module_name, err),
+                              also_print_to_console=True)
+                continue
+
+            yield module
+
+    def register_plugin(self, plugin, root_command):
+        """ Register plugin in top-level command root_command. """
+
+        name = plugin.__name__
+        log.log_debug('registering plugin: {}'.format(name))
+        try:
+            plugin.register(root_command)
+        except Exception as err:
+            log.log_error('failed to import plugin {}: {}'.format(name, err),
+                          also_print_to_console=True)
+
     # try get information from platform API and return a default value if caught NotImplementedError
     def try_get(self, callback, default=None):
         """
@@ -35,6 +69,7 @@ def load_platform_chassis(self):
 
         # Load 2.0 platform API chassis class
         try:
+            import sonic_platform
             chassis = sonic_platform.platform.Platform().get_chassis()
         except Exception as e:
             raise Exception("Failed to load chassis due to {}".format(repr(e)))
@@ -47,3 +82,4 @@ def check_pddf_mode(self):
             return True
         else:
             return False
+