Add a generic configlet application script (sonic-net#716)

* A generic configlet application script.

* Per review comments by Joe.

scripts/configlet

@@ -0,0 +1,205 @@
+#!/usr/bin/env python
+""" JSON based configlet update
+
+A tool to update CONFIG-DB with JSON diffs that can update/delete redis-DB.
+
+All elements in the list are processed in the same order as it is present.
+Within an entry in the list, the tables are handled in any order.
+Within a table, the keys are handled in any order.
+
+
+
+A sample for delete a field TABLE1|KEY1|Key2:field1
+[
+    {
+        "TABLE1": {
+            "Key1": {
+                "Key2": {
+                    "Field1": "Val1"
+                }
+            }
+        }
+    }
+],
+
+A sample for update 
+[
+    {
+        "TABLE1": {
+            "Key1": {
+                "Key2": {
+                    "Field1": "Val1",
+                    "Field2": "Val2",
+                    "Field3": "Val3"
+                },
+                "Key2_1": {
+                    "Field2_1": "Val1",
+                    "Field2_2": "Val2",
+                    "Field2_3": "Val3"
+                }
+            }
+        }
+    },
+    {
+        "TABLE1": {
+            "Key1": {
+                "Key2": {
+                    "Field4": "Val2"
+                }
+            }
+        }
+    }
+]
+
+A sample for delete entire TABLE2:
+[
+    {
+        "TABLE2": {
+        }
+    }
+]
+
+A sample for update:
+[
+    {
+        "TABLE2": {
+            "Key22_1": {
+                "Key22_2": {
+                    "Field22_2": "Val22_2"
+                }
+            }
+        }
+    }
+]
+
+
+"""
+
+from __future__ import print_function
+import sys
+import os.path
+import argparse
+import json
+import time
+from collections import OrderedDict
+from natsort import natsorted
+from swsssdk import ConfigDBConnector
+
+test_only = False
+
+connected = False
+
+db = ConfigDBConnector()
+
+def init():
+    global connected
+
+    if connected == False:
+        db.connect(False)
+        connected = True
+
+def db_update(t, k, lst):
+    init()
+    db.mod_entry(t, k, lst)
+
+def db_filtered_upd(t, k, lst):
+    init()
+    data = db.get_entry(t, k)
+    for i in lst.keys():
+        data.pop(i)
+    db.set_entry(t, k, data)
+
+
+def db_delete_deep(t, k):
+    if not k:
+        db.delete_table(t)
+    else:
+        db.mod_entry(t, k, None)
+
+def db_delete(t, k, lst):
+    init()
+    if lst:
+        db_filtered_upd(t, k, lst)
+    else:
+        db_delete_deep(t, k)
+
+def do_update(t, k, lst):
+    if test_only == False:
+        db_update(t, k, lst)
+    else:
+        print ("TEST update")
+        print ("table: " + t)
+        print ("key: " + str(k))
+        print (lst)
+        print ("---------------------")
+
+def do_delete(t, k, lst):
+    if test_only == False:
+        db_delete(t, k, lst)
+    else:
+        print ("TEST delete")
+        print ("table: " + t)
+        print ("key: " + str(k))
+        print (lst)
+        print ("---------------------")
+
+
+def do_operate(op_upd, t, k, lst):
+    if lst:
+        if type(lst[lst.keys()[0]]) == dict:
+            for i in lst:
+                do_operate(op_upd, t, k+(i,), lst[i])
+            return
+
+    if op_upd:
+        do_update(t, k, lst)
+    else:
+        do_delete(t, k, lst)
+
+
+def process_entry(op_upd, data):
+    for t in data.keys():
+        do_operate(op_upd, t, (), data[t])
+
+def main():
+    global test_only
+
+    parser=argparse.ArgumentParser(description="Manage configlets for CUD (Update & Delete")
+    parser.add_argument("-j", "--json", help="json file that contains configlet", action='append')
+    parser.add_argument("-t", "--test", help="Test only", action='store_true', default=False)
+    parser.add_argument("-p", "--parse", help="Parse JSON only", action='store_true', default=False)
+    parser.add_argument("-u", "--update", help="Apply the JSON as update", action='store_true', default=False)
+    parser.add_argument("-d", "--delete", help="Apply the JSON as delete", action='store_true', default=False)
+
+    args = parser.parse_args()
+
+    test_only = args.test
+    parse_only = args.parse
+    do_update = args.update
+    do_delete = args.delete
+
+    do_act = test_only | parse_only | do_update | do_delete
+    if not do_act:
+        print ("Expect an action update/delete or for debug parse/test\n")
+        parser.print_help()
+        exit(-1)
+
+    for json_file in args.json:
+        with open(json_file, 'r') as stream:
+            data = json.load(stream)
+            if parse_only == False:
+                for i in data:
+                    process_entry (do_update, i)
+                    # Artificial sleep to give a pause between two entries
+                    # so as to ensure that all internal daemons have digested the 
+                    # previous update, before the next one arrives.
+                    #
+                    time.sleep(3)
+            else:
+                print("Parsed:")
+                print(data)
+
+
+if __name__ == "__main__":
+    main()
+

setup.py

@@ -56,6 +56,7 @@
         'scripts/asic_config_check',
         'scripts/boot_part',
         'scripts/coredump-compress',
+        'scripts/configlet',
         'scripts/db_migrator.py',
         'scripts/decode-syseeprom',
         'scripts/dropcheck',