[sonic_py_common] Cache Static Information in device_info to speed up CLI response

[vivekrnv]

Why I did it

Profiled the execution for the following cmd intfutil -c status

Before Optimization:

root@msn-2410:/home/admin# time intfutil -c status
...................
...................
real    0m1.619s
user    0m1.221s
sys     0m0.203s

root@msn-2410:/home/admin#python3 -m cProfile -s tottime /usr/local/bin/intfutil -c status
   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
      124    0.007    0.000    1.318    0.011 device_info.py:353(get_platform_info)
      124    0.002    0.000    0.890    0.007 device_info.py:332(get_sonic_version_info)
      128    0.002    0.000    0.202    0.002 device_info.py:42(get_localhost_info)
      128    0.001    0.000    0.203    0.002 device_info.py:128(get_hwsku)
       62    0.000    0.000    0.014    0.000 device_info.py:449(is_chassis)

After Optimization:

root@msn-2410:/home/admin# time intfutil -c status
...................
...................
real    0m0.883s
user    0m0.622s
sys     0m0.128s

root@msn-2410:/home/admin#python3 -m cProfile -s tottime /usr/local/bin/intfutil -c status
   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
      124    0.000    0.000    0.013    0.000 device_info.py:360(get_platform_info)
        1    0.000    0.000    0.009    0.009 device_info.py:336(get_sonic_version_info)
        5    0.000    0.000    0.008    0.002 device_info.py:46(get_localhost_info)
        5    0.000    0.000    0.008    0.002 device_info.py:132(get_hwsku)
       62    0.000    0.000    0.015    0.000 device_info.py:446(is_chassis)

How I did it

1. Cached the following information:
   • get_sonic_version_info()
   • get_platform_info()
2. None of the API exposed to the user libraries has been modified

These methods involve reading text files or from redis. Thus, caching helped to improve the execution time

How to verify it

• Added UT's.
• Verified on the device

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111
• 202205

Description for the changelog

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)