Fix: nil pointer exception while sending the callhome payload for import data to source/source-replica

[priyanshi-yb]

Describe the changes in this pull request

Fixing the nil pointer exception while sending the call home payload for exit/error case during initial phase of import data to source/source-replica.
fixes #2364

Describe if there are any user-facing changes

No

How was this pull request tested?

Manually

Does your PR have changes that can cause upgrade issues?

Component	Breaking changes?
MetaDB	No
Name registry json	No
Data File Descriptor Json	No
Export Snapshot Status Json	No
Import Data State	No
Export Status Json	No
Data .sql files of tables	No
Export and import data queue	No
Schema Dump	No
AssessmentDB	No
Sizing DB	No
Migration Assessment Report Json	No
Callhome Json	No
YugabyteD Tables	No
TargetDB Metadata Tables	No

[sanyamsinghal]

maybe use a ternary operator for the check

sourceDBDetails := callhome.SourceDBDetails{
		DBType:    tconf.TargetDBType,
		DBVersion: lo.Ternary(targetDBDetails != nil,  targetDBDetails.DBVersion, ""),
}

[priyanshi-yb]

can't do this; it doesn't work if we do nil check in this function as it still tries to run the if clause. refer https://go.dev/play/p/sgeATTvMgMP

[sanyamsinghal]

Interesting.
So this is because Go follows strict/eager evaluation of function argument

[sanyamsinghal]

what is the case when statsReporter will be null?

[priyanshi-yb]

It can be nil until it is initialized. If there is any failure or exit before that, this function will try to send the payload, and we can get a nil pointer exception in such a case.

[sanyamsinghal]

Got it. I was think can we introduce some sort of error handling here.
Golang doesn't have try catch sort of thing, but they have combination of defer and recover to recover the program from panic state.

I think for this codepath it makes sense to handle panic, not think about other places if we can use this.

what do you guys think? @makalaaneesh @priyanshi-yb

[sanyamsinghal]

https://www.honeybadger.io/blog/go-exception-handling/