Midserver upgrade failed with the error statement "Aborting MID Server upgrade due to pre-upgrade check failure: Service snc_mid does not exist"

The Wrapper override configuration had missing Midserver Display name which was reporting unresolved issues for Midserver.By checking this file, I found the missing configuration and suggested customer to change the configuration as below. The reason behind is, Wrapper name somehow got modified at customer Midserver Wrapper Override file. As there was no name found, while Pre-upgrade check happens instance unable to identify the servicename of Mid and eventually failed the pre-upgrade check. 

With the error statement, we need to first take a look on Wrapper Override config file to check the configuration is correct or somehow it got changed/or modified.  Its better to always ask customer to share all the Midserver config files(config.xml+wrapper-override.xml) with the Logs(Agent+wrapper). Post investigation, I observed wrapper-Override had missing wrapper.name which need to modify. 

Midserver configuration as per Wrapper Override per customer instance initially:-
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# The following properties must be unique per MID installed on the same system.
#
# REQUIRED: Name token of the service
wrapper.name=snc_mid
# REQUIRED: Display name of the service
wrapper.displayname=ServiceNow MID Server

Suggested configuration for the Midserver Wrapper Override file :-(If there are multiple MID servers on the same host.)
===================================================================================================

# REQUIRED: Name token of the service
wrapper.name=snc_mid_XXXX
# REQUIRED: Display name of the service
wrapper.displayname=ServiceNow MID Server

Note:- XXXX-stands for the name of the Midserver which you are working as per config.xml.

After that, save the file and restart the MID service for the changes to take effect. Wait about 10 minutes and inspect the MID server once again in the instance. This will fix the error and Mid server Pre-upgrade check will happen successfully.