[DPB] config_db.json "BREAKOUT_CFG" update when upgrading

[slutati1536]

Description

when doing upgrade from image without DPB to image with DPB,
the config_db.json file is not updated with "BREAKOUT_CFG" section.

when testing the upgrade scenario by:

1. installing 201911 vie onie
2. apply config_db.json file without BREAKOUT_CFG
3. upgraded to an image with DPB feature support with sonic-installer
4. the config_db.json was not updated with BREAKOUT_CFG, so the DPB feature will not work.

To clearify, the port configuration from the config_db.json (with any splits) is present on the switch with DPB image we upgraded to, the only issue is that without BREAKOUT_CFG section in the config_db.json, the user is not able to configure any new breakouts.

Steps to reproduce the issue:

1. installing 201911 vie onie
2. apply config_db.json file without BREAKOUT_CFG
3. upgraded to an image with DPB feature support with sonic-installer
4. the config_db.json was not updated with BREAKOUT_CFG, so the DPB feature will not work.

Describe the results you received:

the config_db.json was not updated with BREAKOUT_CFG section

Describe the results you expected:

the sonic installer should handel this issue in the case of sonic to sonic installation to a DPB image the config_db.json should be updated automatically.

Output of show version:

upgrade from SONiC-OS-201911.113-dirty-20210419.164156
to SONiC-OS-SONIC.dpb_master.3-9721ca85_Internal

[anshuv-mfst]

Issue triage 4/28: To be discussed in DPB subgroup.

[dprital]

@zhenggen-xu - Can you please review this issue ?

[zhenggen-xu]

We did discuss this in the DPB subgroup meeting. At this point, we are not automatically importing the "BREAKOUT_CFG" into configDB after upgrade, instead we use "config reload -l" option to get the table. If you strongly feel that is required, please send a PR for importing "BREAKOUT_CFG" into config_db.json in the migration scripts, we know exactly the steps to get that table: sonic-cfggen -H -k <HWSKU> --var-json BREAKOUT_CFG, and we can discuss that PR with community.

[alexrallen]

@zhenggen-xu After some discussion locally, we are okay with BREAKOUT_CFG not being imported by default, however we do believe that this case should be handled elegantly by show interface breakout and config interface breakout so that the end user is not faced with a Python traceback for a flow that we intend (user attempts to use breakout -> user runs config reload -l)

Something like CONFIG_DB does not contain the required information to complete this action please run config reload -l to import this from the platform files to enable dynamic breakout features. (Just an example)

Because this strays far enough away from the original intention of this issue I have raised a new one to handle this. (#7957)

[alexrallen]

Given this, this issue may be closed.