feat: implement local service health check

[winstxnhdw]

• Closes Support for "/agent/health/service/*" API methods. #25
• Implementing the latest v1.16 of /agent/health/service

[winstxnhdw]

Still unsure how to test if a service is critical or warning. I am also having trouble trying to deserialise the AggregatedStatus enum. Is it even possible to deserialise pure strings with ConsulClient?

[marcin-krystianc]

Still unsure how to test if a service is critical or warning.

It is going to be tricky. I've implemented a test showing how to do it but it doesn't work.
The reason is that local health API returns an unsuccessful status code when at least one check is in a warning or critical state (https://developer.hashicorp.com/consul/api-docs/agent/service#get-local-service-health). Therefore we get an exception instead of a regular response. Not sure how to overcome this API inconsistency.

I am also having trouble trying to deserialise the AggregatedStatus enum. Is it even possible to deserialise pure strings with ConsulClient?

Just use HealthStatus class. I think that a simple enum would work just fine, but we don't need another enum class as the AggregatedStatus has the same possible values as health status, or doesn't it?

[winstxnhdw]

The reason is that local health API returns an unsuccessful status code when at least one check is in a warning or critical state (https://developer.hashicorp.com/consul/api-docs/agent/service#get-local-service-health). Therefore we get an exception instead of a regular response. Not sure how to overcome this API inconsistency.

Haha, try-catch maybe?

[marcin-krystianc]

Haha, try-catch maybe?

Well, it is better to avoid exceptions in the regular execution path. I think we have already an example of how to implement a special case for unsuccessful status codes, see

consuldotnet/Consul/Client_PutRequests.cs

Lines 345 to 347 in 53be496

	if (!response.IsSuccessStatusCode && (
	(response.StatusCode != HttpStatusCode.NotFound && typeof(TOut) != typeof(TxnResponse)) ||
	(response.StatusCode != HttpStatusCode.Conflict && typeof(TOut) == typeof(TxnResponse))))

You could implement a similar special case in the https://github.com/G-Research/consuldotnet/blob/master/Consul/Client_GetRequests.cs#L82

[winstxnhdw]

Whoops, marked this for review on accident.

[winstxnhdw]

Sorry for the long delay! I was really busy with school and exams. Finally got around to working on it. @marcin-krystianc do let me know if I need to make any more changes.

[marcin-krystianc]

Hi @winstxnhdw, I've left some comments. I think there was an actual bug in the GetLocalServiceHealthByID method.

[winstxnhdw]

Seems like I misunderstood the docs. I have removed GetWorstLocalHealthByID because querying by ID will query the status of the specific service with that ID. This means that GetLocalHealthByID is already equivalent. GetWorstLocalHealth, however, will find the worst health status among all services with the same name.

[marcin-krystianc]

Looks good, just one simple suggestion to rename variable in a test to avoid confusion.

[marcin-krystianc]

👍