Singleton implementation for GetHostName.

[Tatsinnit]

This PR intends to Fix the multiple GetHostName calls to Singleton call using Sync.Once.Do

This PR also try to attempt and simplify the deep parameter passing mechanism. Why using Sync.Once because its a thread safe go existing pkg funct which we can use. https://pkg.go.dev/sync#Once .

Please note: feel free to add your variable naming preferences but this way will ensure that the call for the actual run command only happens once. Advantage of this approach is that all changes reside under utils umbrella, no extra func parameter will be required, and it will guarantee the actual code is ran only once.

Another, pro is that the call to the method stays same, under the hood it only gets called once. For future any new diagnostics or anything which needs to call the utils.GetHostName don't need to worry about running many times, and no more parameter passing as well.

• Tested with Image local: docker.io/tatsat/singleton-call-changes

This pR also simplifies this PR: #82

Thanks guys. 🙏

Unit test result

[davidkydd]

Looks good, maybe add a unit test or two?

Forgot testability

[davidkydd]

Sorry for premature approval - forgot about testability, this will maintain current tight coupling which we should move away from, and would make it impossible to inject a value of hostname for unit testing those components which consume it. We should either pass the value as a parameter or abstract the singleton behind an interface.

[Tatsinnit]

Sorry for premature approval - forgot about testability, this will maintain current tight coupling which we should move away from, and would make it impossible to inject a value of hostname for unit testing those components which consume it. We should either pass the value as a parameter or abstract the singleton behind an interface.

Cool, Tight coupling as to unit testing? I doubt if this can be go-mocked. (Hence bunch of legacy codes is interesting to unit-test) I tried adding test but until we mock RunCommandOnHost we cannot mock any of this? (Feel free to give more suggestions). Current unit test utilises Gomega.

Functionally: Current Util.GetHostName is decoupled method called from anywhere to get HostName.

Working Unit Test Added and here are the Run Result

With slight refactor here is the 100% unit test coverage of the functionality, also in future once RunCommandOnHost is replaced with actual package based runCommand, we need to remove any dependency of this command which start with RunCommand... .

[davidkydd]

Callers are still tightly coupled to this implementation but think I'm not explaining it properly, and it would be a premature optimization anyway so this is perfect for now. Thanks!