dynamic_th failed because redis sends unchanged field to orchagent when updating dynamic_th

[MaxYaremchuk]

Description
It's impossible to change dynamic_th value for lossless buffer profile which has been applied to some ports on the fly.

Describe the results you expected:
It should be eligible to change dynamic_th parameter on the fly.

Describe the results you received:

1. The new value for dynamic_th is not offloaded to hardware.
2. There are errors in syslog:

Jan  2 19:00:31.799935 sonic 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
Jan  2 19:00:31.799935 sonic ERR swss#orchagent: :- processBufferProfile: Failed to modify buffer profile, name:pg_lossless_10000_5m_profile, sai object:190000000002f4, status:-5
Jan  2 19:00:31.799935 sonic ERR swss#orchagent: :- doTask: Failed to process buffer task, drop it

Steps to reproduce the issue:

1. Install Master branch image on a switch.
2. Configure qos: config qos reload
3. Compose a json file for changing buffer parameter dynamic_th for lossless buffer which has been applied to some ports:

{
    "BUFFER_PROFILE": {
       "pg_lossless_10000_5m_profile": {
            "dynamic_th": "2",
            "pool": "[BUFFER_POOL|ingress_lossless_pool]"
       }
   }
}

4. Try to change dynamic_th for lossless buffer profile on the fly:
   sonic-cfggen -j ./buf_prof4.json --write-to-db

Output of show version:

SONiC Software Version: SONiC.HEAD.129-0c9040de
Distribution: Debian 9.11
Kernel: 4.9.0-9-2-amd64
Build commit: 0c9040de
Build date: Thu Nov 21 12:50:41 UTC 2019
Built by: johnar@jenkins-worker-4

Platform: x86_64-mlnx_msn2100-r0
HwSKU: ACS-MSN2100
ASIC: mellanox
Serial Number: MT1646X05314
Uptime: 11:33:40 up 21 min,  3 users,  load average: 3.12, 3.11, 2.49

Docker images:
REPOSITORY                 TAG                 IMAGE ID            SIZE
docker-syncd-mlnx          HEAD.129-0c9040de   4f3b126274c2        373MB
docker-syncd-mlnx          latest              4f3b126274c2        373MB
docker-fpm-frr             HEAD.129-0c9040de   7345e105bf26        321MB
docker-fpm-frr             latest              7345e105bf26        321MB
docker-sflow               HEAD.129-0c9040de   f240b81ea842        305MB
docker-sflow               latest              f240b81ea842        305MB
docker-lldp-sv2            HEAD.129-0c9040de   f1b94915bf13        299MB
docker-lldp-sv2            latest              f1b94915bf13        299MB
docker-dhcp-relay          HEAD.129-0c9040de   7ba3cee353b6        289MB
docker-dhcp-relay          latest              7ba3cee353b6        289MB
docker-database            HEAD.129-0c9040de   c5c92210277c        281MB
docker-database            latest              c5c92210277c        281MB
docker-snmp-sv2            HEAD.129-0c9040de   ad01f8a547b1        335MB
docker-snmp-sv2            latest              ad01f8a547b1        335MB
docker-orchagent           HEAD.129-0c9040de   7fc54899dc92        322MB
docker-orchagent           latest              7fc54899dc92        322MB
docker-teamd               HEAD.129-0c9040de   c0316e26bbbd        304MB
docker-teamd               latest              c0316e26bbbd        304MB
docker-sonic-telemetry     HEAD.129-0c9040de   43df42f49e91        304MB
docker-sonic-telemetry     latest              43df42f49e91        304MB
docker-router-advertiser   HEAD.129-0c9040de   b0aff9280842        281MB
docker-router-advertiser   latest              b0aff9280842        281MB
docker-platform-monitor    HEAD.129-0c9040de   10013f82e4d7        565MB
docker-platform-monitor    latest              10013f82e4d7        565MB

Attach debug file sudo generate_dump:
sonic_dump_r-ethernet-sw230_20200102_204425.tar.gz

[stephenxs]

From the log I see it tries to modify SAI_BUFFER_PROFILE_ATTR_POOL_ID which is read-only while for dynamic_th the id should be SAI_BUFFER_PROFILE_ATTR_SHARED_DYNAMIC_TH.
I think it's an issue of SONiC ore redis. I also encountered this kind of issue when I tried updating size of BUFFER_POOL table: when I tried updating size in BUFFER_POOL table it updated type as well and failed.

127.0.0.1:6379[4]> hset BUFFER_POOL|ingress_lossless_pool size 9150000
(integer) 0

From the log I saw it tries updating other fields like type and mode as well.

Apr  6 23:46:31.358697 mtbc-3700c-01 DEBUG swss#orchagent: :> doTask: enter
Apr  6 23:46:31.358712 mtbc-3700c-01 DEBUG swss#orchagent: :> processBufferPool: enter
Apr  6 23:46:31.358723 mtbc-3700c-01 DEBUG swss#orchagent: :- processBufferPool: object name:ingress_lossless_pool
Apr  6 23:46:31.358723 mtbc-3700c-01 DEBUG swss#orchagent: :- processBufferPool: found existing object:ingress_lossless_pool of type:BUFFER_POOL
Apr  6 23:46:31.358723 mtbc-3700c-01 DEBUG swss#orchagent: :- processBufferPool: processing command:SET
Apr  6 23:46:31.358742 mtbc-3700c-01 DEBUG swss#orchagent: :- processBufferPool: field:type, value:ingress
Apr  6 23:46:31.358777 mtbc-3700c-01 DEBUG swss#orchagent: :- processBufferPool: field:mode, value:dynamic
Apr  6 23:46:31.358806 mtbc-3700c-01 DEBUG swss#orchagent: :- processBufferPool: field:size, value:9150000

and results in the following error which fails the setting.

Apr  6 23:46:31.359330 mtbc-3700c-01 ERR swss#orchagent: :- meta_generic_validation_set: SAI_BUFFER_POOL_ATTR_TYPE:SAI_ATTR_VALUE_TYPE_INT32 attr is create only and cannot be modified
Apr  6 23:46:31.359360 mtbc-3700c-01 ERR swss#orchagent: :- processBufferPool: Failed to modify buffer pool, name:ingress_lossless_pool, sai object:1800000000058f, status:-5
Apr  6 23:46:31.359376 mtbc-3700c-01 ERR swss#orchagent: :- doTask: Failed to process buffer task, drop it

[stephenxs]

@lguohan Could you please assign someone to look into this issue, especially my comments?
I suspect when I modify one field the redis sends other fields that aren't modified to orchagent as well.
Thank you.

[liat-grozovik]

@neethajohn what is the plan for fixing this issue?

[MaxYaremchuk]

Bug has been fixed.
Verified on:

SONiC Software Version: SONiC.201911.51-dea38d15
Distribution: Debian 9.13
Kernel: 4.9.0-11-2-amd64
Build commit: dea38d15
Build date: Mon Jan  4 13:38:57 UTC 2021
Built by: sw-r2d2-bot@r-build-sonic-ci02