Equalizer

Equalizer is aspnetcore middleware for load-balancing service instances from Nanophone and contains several routers to choose from

##Features:

• Load balancing middleware for aspnetcore: redirects requests to the next chosen service instance
• TrafficAllocationRouter: chooses from items matching a condition for a percentage of the routing calls
• CallbackRouter: chooses the next item based on the provided callback
• FailOverRouter: chooses specific item if available, otherwise a different one
• RandomRouter: chooses a random next item
• RoundRobinRouter: chooses the next item in round robin fashion
• RoundRobinAddressRouter for Nanophone: chooses the next service instance with a different address

##Usage:

• Middleware:

	// create registry client
    var registryClient = new RegistryClient("my-url-path-prefix-", new RoundRobinAddressRouter());

	// add Consul registry host
    var consul = new ConsulRegistryHost();
    registryClient.AddRegistryHost(consul);

	// add in-memory registry host
	var inmemory = new InMemoryRegistryHost();
	registryClient.AddRegistryHost(inmemory);

	// use IApplicationBuilder extension
    app.UseEqualizer(new EqualizerMiddlewareOptions 
	{ 
		RegistryClient = registryClient, 
		PathExclusions = new[] { "/" } 
	});

• TrafficAllocationRouter:

    var first = "1";
    var second = "2";
    var third = "3";
    var instances = new List<string> { first, second, third };

    decimal variation = .10M;
    var router = new TrafficAllocationRouter<string>(x => x.Where(item => item == second).ToList(), variation);

    for (int i = 0; i < 100*1000; i++)
    {
        string result = router.Choose(instances);
    }

• CallbackRouter:

    var first = "1";
    var second = "2";
    var third = "3";
    var instances = new List<string> { first, second, third };

    var router = new CallbackRouter<string>(x => "3");

    // choose third
    var next = router.Choose(instances);
    Assert.NotNull(next);
    Assert.Equal("3", next);

• FailOverRouter:

    var first = "1";
    var second = "2";
    var third = "3";
    var instances = new List<string> { first, second, third };

    var router = new FailOverRouter<string>(first, isAvailable: x => false);

    // don't choose first
    var next = router.Choose(instances);
    Assert.NotNull(next);
    Assert.NotEqual("1", next);

• RandomRouter:

    var first = "1";
    var second = "2";
    var third = "3";
    var instances = new List<string> { first, second, third };

    var router = new RandomRouter<string>();

    // don't return null
    var next = router.Choose(instances);
    Assert.NotNull(next);

• RoundRobinRouter:

    var first = "1";
    var second = "2";
    var third = "3";
    var instances = new List<string> { first, second, third };

    var router = new RoundRobinRouter<string>();

    // choose first
    var next = router.Choose(instances);
    Assert.NotNull(next);
    Assert.Equal("1", next);

    // choose next
    next = router.Choose(instances);
    Assert.NotNull(next);
    Assert.Equal("2", next);

    // choose next
    next = router.Choose(instances);
    Assert.NotNull(next);
    Assert.Equal("3", next);

    // choose first
    next = router.Choose(instances);
    Assert.NotNull(next);
    Assert.Equal("1", next);

• RoundRobinAddressRouter:

    var oneDotOne = new RegistryInformation("1", 1234, "some version");
    var oneDotTwo = new RegistryInformation("1", 1234, "some version");
    var twoDotOne = new RegistryInformation("2", 1234, "some version");
    var twoDotTwo = new RegistryInformation("2", 1234, "some version");
    var threeDotOne = new RegistryInformation("3", 1234, "some version");
    var threeDotTwo = new RegistryInformation("3", 1234, "some version");
    var instances = new List<RegistryInformation> 
	{ 
		oneDotOne, oneDotTwo, 
		twoDotOne, twoDotTwo, 
		threeDotOne, threeDotTwo 
	};

    var router = new RoundRobinAddressRouter();

    // choose first
    var next = router.Choose(instances);
    Assert.NotNull(next);
    Assert.Equal("1", next.Address);

    // choose next
    next = router.Choose(instances);
    Assert.NotNull(next);
    Assert.Equal("2", next.Address);

    // choose next
    next = router.Choose(instances);
    Assert.NotNull(next);
    Assert.Equal("3", next.Address);

    // choose first
    next = router.Choose(instances);
    Assert.NotNull(next);
    Assert.Equal("1", next.Address);

##Thanks

• balance icon by Golden Roof from The Noun Project