DistributedCircuitBreaker.NET

DistributedCircuitBreaker.NET is a Circuit Breaker that allows developers store data and state of the circuit using an external repository such as SqlServer, Redis, MongoDB Etc. by providing a interface. Redis implementation is included.

Definition

The circuit will break if, within any timespan of duration(defined below), the proportion of actions resulting in a handled exception exceeds failureThreshold (failureRateAllowed), provided also that the number of actions through the circuit in the timespan is at least minimumThroughput (exceptionsAllowedBeforeBreaking).

Note that the circuit consider any type of Exception to set in counters.

How to Use

The simplest way to use it:

Add the dependency to IServiceCollection (located usually in Startup class)

            services.AddDistributedRedisCircuitBreaker(options =>
            {
                options.DurationOfBreak = TimeSpan.FromSeconds(300);
                options.WindowDuration = TimeSpan.FromSeconds(60);
                options.RedisConnectionConfiguration = "localhost:6379";
            });

Get an instance of CircuitBreaker using the ICircuitBreakerFactory interface
Call Create method to get the Instance of CircuitBreaker

    var circuitBreaker = _circuitBreakerFactory.Create("http://www.example.com.br", exceptionsAllowedBeforeBreaking , failureRateAllowed);

Parameters

key

key: A key used as a unique identifier to perform the operations and compute failures and success

exceptionsAllowedBeforeBreaking

exceptionsAllowedBeforeBreaking: Minimum number of failures before starting considering counters

failureRateAllowed

failureRateAllowed: A proportion of failures that should cause the circuit be opened. A decimal between 0 and 1. Example, if 0.5M is set the circuit should open when the proportion of failures exceeds 50% of the executions for the key

** Both 2 and 3 rules should be broken to make the circuit to be opened.

Syntax

public class CatalogService : ICatalogService
{
    private readonly ICircuitBreakerFactory _circuitBreakerFactory;

    public CatalogService(ICircuitBreakerFactory circuitBreakerFactory)
    {
        _circuitBreakerFactory = circuitBreakerFactory;
    }

    public async Task<Catalog> GetCatalogItems(int page, int take, int? brand, int? type)
    {
        var uri = API.Catalog.GetAllCatalogItems(_remoteServiceBaseUrl, page, take, brand, type);

        int exceptionsAllowedBeforeBreaking = 20;
        decimal failureRateAllowed = 0.5M;

        var circuitBreaker = _circuitBreakerFactory.Create(uri.AbsoluteUri, exceptionsAllowedBeforeBreaking , failureRateAllowed);

        Catalog catalog;
        try
        {
            var responseString = await circuitBreaker.ExecuteActionAsync(() =>  _httpClient.GetStringAsync(uri)); 
            catalog = JsonConvert.DeserializeObject<Catalog>(responseString);
        }
        catch(BrokenCircuitException ex)
        {
            //handle open-state circuit
        }

        return catalog;
    }
}

If the circuit is open, a BrokenCircuitException is thrown with the message "The circuit is now open and is not allowing calls.".

Nuget Packages