1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
|
#!/usr/bin/env python3
__author__ = "Mislav Novakovic <mislav.novakovic@sartura.hr>"
__copyright__ = "Copyright 2018, Deutsche Telekom AG"
__license__ = "Apache 2.0"
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# This sample application demonstrates use of Python programming language bindings for sysrepo library.
# Original c application was rewritten in Python to show similarities and differences
# between the two.
#
# Most notable difference is in the very different nature of languages, c is weakly statically typed language
# while Python is strongly dynamically typed. Python code is much easier to read and logic easier to comprehend
# for smaller scripts. Memory safety is not an issue but lower performance can be expected.
#
# The original c implementation is also available in the source, so one can refer to it to evaluate trade-offs.
import sys
import sysrepo as sr
from loguru import logger
# Helper function for printing changes given operation, old and new value.
def print_change(op, old_val, new_val):
if op == sr.SR_OP_CREATED:
logger.info(f"CREATED: {new_val.to_string()}")
elif op == sr.SR_OP_DELETED:
logger.info(f"DELETED: {old_val.to_string()}")
elif op == sr.SR_OP_MODIFIED:
logger.info(f"MODIFIED: {old_val.to_string()} to {new_val.to_string()}")
elif op == sr.SR_OP_MOVED:
logger.info(f"MOVED: {new_val.xpath()} after {old_val.xpath()}")
# Helper function for printing events.
def ev_to_str(ev):
if ev == sr.SR_EV_VERIFY:
return "verify"
elif ev == sr.SR_EV_APPLY:
return "apply"
elif ev == sr.SR_EV_ABORT:
return "abort"
else:
return "unknown"
# Function to print current configuration state.
# It does so by loading all the items of a session and printing them out.
def print_current_config(session, module_name):
select_xpath = f"/{module_name}:*//*"
values = session.get_items(select_xpath)
if values is not None:
logger.info("========== BEGIN CONFIG ==========")
for i in range(values.val_cnt()):
logger.info(f" {values.val(i).to_string().strip()}")
logger.info("=========== END CONFIG ===========")
# Function to be called for subscribed client of given session whenever configuration changes.
def module_change_cb(sess, module_name, event, private_ctx):
try:
logger.info("========== Notification " + ev_to_str(event) + " =============================================")
if event == sr.SR_EV_APPLY:
print_current_config(sess, module_name)
logger.info("========== CHANGES: =============================================")
change_path = f"/{module_name}:*"
it = sess.get_changes_iter(change_path)
while True:
change = sess.get_change_next(it)
if change is None:
break
print_change(change.oper(), change.old_val(), change.new_val())
logger.info("========== END OF CHANGES =======================================")
except Exception as e:
logger.error(e)
return sr.SR_ERR_OK
def main():
# Notable difference between c implementation is using exception mechanism for open handling unexpected events.
# Here it is useful because `Connection`, `Session` and `Subscribe` could throw an exception.
try:
module_name = sys.argv[1]
logger.info(f"Application will watch for changes in {module_name}")
# connect to sysrepo
conn = sr.Connection(module_name)
# start session
sess = sr.Session(conn)
# subscribe for changes in running config */
subscribe = sr.Subscribe(sess)
subscribe.module_change_subscribe(module_name, module_change_cb)
try:
print_current_config(sess, module_name)
except Exception as e:
logger.error(e)
logger.info("========== STARTUP CONFIG APPLIED AS RUNNING ==========")
sr.global_loop()
logger.info("Application exit requested, exiting.")
except Exception as e:
logger.error(e)
if __name__ == '__main__':
main()
|
