mmuconfig fails to change profile parameters

[andriymoroz-mlnx]

Description
mmuconfig utility is not able to update profile because the attribute it is about to change is defined as "create only"

Steps to reproduce the issue

1. execute sudo mmuconfig -p pg_lossless_40000_40m_profile -a 1

Describe the results you received
Oct 28 16:15:44.645926 arc-switch1038 ERR swss#orchagent: :- meta_generic_validation_set: SAI_BUFFER_PROFILE_ATTR_POOL_ID:SAI_ATTR_VALUE_TYPE_OBJECT_ID attr is create only and cannot be modified
Oct 28 16:15:44.645926 arc-switch1038 ERR swss#orchagent: :- processBufferProfile: Failed to modify buffer profile, name:pg_lossless_40000_40m_profile, sai object:19000000000598, status:-5
Oct 28 16:15:44.645926 arc-switch1038 ERR swss#orchagent: :- doTask: Failed to process buffer task, drop it

Describe the results you expected
No errors in log

Additional information you deem important (e.g. issue happens only occasionally)

Output of show version
SONiC Software Version: SONiC.HEAD.775-b954fa9
Distribution: Debian 9.5
Kernel: 4.9.0-7-amd64
Build commit: b954fa9
Build date: Fri Oct 26 12:47:01 UTC 2018
Built by: johnar@jenkins-worker-3

[wendani]

@andriymoroz-mlnx Thank you for catching this error. This is due to the current implementation of SubscriberStateTable. When a field:value changes under a key, the whole field:value tuples under that key is fetched from config_db. Changes should be made in the processing logic of the case of sai object already existing. We should filter out only the one that is being changed by the user. https://github.com/Azure/sonic-swss/blob/36e304db4ab01ed9d75230b842ff44c1cda6b281/orchagent/bufferorch.cpp#L333 So we do not support mmconfig CLI yet so far though the cli itself has been defined.