Add the elections counter metric

[dhingrak]

Added: Add the elections counter metric so users can set alerts if the number of elections over a certain period of time exceeds some number.

Fixes https://linear.app/eventstore/issue/DB-599/add-the-elections-counter-to-metrics

[linear]

DB-599 Add the elections counter to metrics

[timothycoleman]

looks good, handling the ElectionsDone message is a nice way to do it. We can make use of the existing CounterMetric though, and have the tracker handle the message directly instead of having an extra service

[dhingrak]

Sure. I will work on this.

[timothycoleman]

Oh yeah and updating the documentation would be fab too (in a separate PR actually since it requires a different reviewer)

[dhingrak]

@timothycoleman I have handled the Elections.Done message in tracker itself but I am not 100% sure if this is the right to do it.

[timothycoleman]

Suggested change

	public interface IElectionCounterTracker {
	void IncrementCounter();
	}
	public interface IElectionCounterTracker : IHandle<Messages.ElectionMessage.ElectionsDone> {
	}

ah ok sorry, i meant like this ^

[dhingrak]

I have added the IncrementCounter function because of Unit testing. This way the tests are easy to understand. We can test this with sut.Hanlde(null) if we want.

[timothycoleman]

cool, thanks

yes we should test it by calling Handle, and remove the IncrementCounter method. That way the tests are using the tracker how it is supposed to be used

you can construct an electionsdone message like this

	private readonly Messages.ElectionMessage.ElectionsDone _electionsDoneMessage;

	public ElectionsCounterTrackerTests() {
		var endPoint = new DnsEndPoint("127.0.0.1", 1113);
		var memberInfo = Cluster.MemberInfo.Initial(Guid.Empty, DateTime.UtcNow,
			VNodeState.Unknown, true,
			endPoint, endPoint, endPoint, endPoint, endPoint,
			null, 0, 0, 0, false);
		_electionsDoneMessage = new(1, 1, memberInfo);
	}

[timothycoleman]

👍