[warm-reboot] Fix key error - check empty key before issuing redis hget

[vaibhavhd]

What I did

Fix for: sonic-net/sonic-buildimage#7015

How I did it

Added a check for empty key before checking WARM_RESTART_ENABLE_TABLE

How to verify it

Without fix:

admin@str-s6100-acs-2:~$ sudo warm-reboot -vvv
Traceback (most recent call last):
  File "/usr/local/bin/sonic-db-cli", line 131, in <module>
    main()
  File "/usr/local/bin/sonic-db-cli", line 114, in main
    execute_cmd(args.db_or_op, args.cmd, args.namespace, args.unixsocket)
  File "/usr/local/bin/sonic-db-cli", line 73, in execute_cmd
    resp = client.execute_command(*cmd)
  File "/usr/local/lib/python2.7/dist-packages/redis/client.py", line 901, in execute_command
    return self.parse_response(conn, command_name, **options)
  File "/usr/local/lib/python2.7/dist-packages/redis/client.py", line 915, in parse_response
    response = connection.read_response()
  File "/usr/local/lib/python2.7/dist-packages/redis/connection.py", line 756, in read_response
    raise response
redis.exceptions.ResponseError: wrong number of arguments for 'hget' command

With fix (after cold reboot, issue a warm-reboot):

admin@str-s6100-acs-2:~$ sonic-db-cli STATE_DB hget "WARM_RESTART_ENABLE_TABLE|system" enable

admin@str-s6100-acs-2:~$ sonic-db-cli STATE_DB keys "WARM_RESTART_ENABLE_TABLE|*"            

admin@str-s6100-acs-2:~$ sudo warm-reboot -vvv
Thu 11 Mar 2021 08:41:48 PM UTC Saving counters folder before warmboot...
Thu 11 Mar 2021 08:41:51 PM UTC Pausing orchagent ...
Thu 11 Mar 2021 08:41:51 PM UTC Collecting logs to check ssd health before warm-reboot...
Thu 11 Mar 2021 08:41:51 PM UTC Stopping nat ...
Dumping conntrack entries failed
Error response from daemon: Cannot kill container: nat: No such container: nat
Thu 11 Mar 2021 08:41:51 PM UTC Stopped nat ...
Thu 11 Mar 2021 08:41:51 PM UTC Stopping radv service...
Thu 11 Mar 2021 08:41:52 PM UTC Stopped radv service...
Thu 11 Mar 2021 08:41:52 PM UTC Stopping bgp ...
Thu 11 Mar 2021 08:41:57 PM UTC Stopped bgp ...
Thu 11 Mar 2021 08:41:57 PM UTC Stopping sflow ...
Thu 11 Mar 2021 08:41:58 PM UTC Stopped sflow ...
Thu 11 Mar 2021 08:42:00 PM UTC Stopping swss service ...
Thu 11 Mar 2021 08:42:01 PM UTC Stopped swss service ...
Thu 11 Mar 2021 08:42:01 PM UTC Initialize pre-shutdown ...
Thu 11 Mar 2021 08:42:02 PM UTC Requesting pre-shutdown ...
Thu 11 Mar 2021 08:42:02 PM UTC Waiting for pre-shutdown ...
Thu 11 Mar 2021 08:42:03 PM UTC Pre-shutdown succeeded ...
Thu 11 Mar 2021 08:42:03 PM UTC Backing up database ...
Thu 11 Mar 2021 08:42:04 PM UTC Stopping teamd ...
Thu 11 Mar 2021 08:42:10 PM UTC Stopped teamd ...
Thu 11 Mar 2021 08:42:10 PM UTC Stopping syncd ...
Thu 11 Mar 2021 08:42:26 PM UTC Stopped syncd ...
Thu 11 Mar 2021 08:42:27 PM UTC Stopping all remaining containers ...
Thu 11 Mar 2021 08:42:35 PM UTC Stopped all remaining containers ...
Thu 11 Mar 2021 08:42:37 PM UTC updating ssd fw forwarm-reboot
Thu 11 Mar 2021 08:42:37 PM UTC Enabling Watchdog before warm-reboot
Watchdog armed for 180 seconds
Thu 11 Mar 2021 08:42:38 PM UTC Running x86_64-dell_s6100_c2538-r0 specific plugin...
Thu 11 Mar 2021 08:42:38 PM UTC Rebooting with /sbin/kexec -e to SONiC-OS-HEAD.487-377ea1a2 ...

Previous command output (if the output of a command-line utility has changed)

New command output (if the output of a command-line utility has changed)

[vaibhavhd]

@shi-su was the change in #1460 included in 202012 branch?
If yes, we need to add this fix to 202012 too. I did not see a label for 2020 in the PR 1460, but could not find a submodule update PR for 1460.

[shi-su]

@shi-su was the change in #1460 included in 202012 branch?
If yes, we need to add this fix to 202012 too. I did not see a label for 2020 in the PR 1460, but could not find a submodule update PR for 1460.

I do think we need # 1460 for 202012 branch. It is not included yet. I added the label to request it.

[vaibhavhd]

retest this please