/// <summary>
/// This method is called before the method is executed to verify that the resource is available.
/// </summary>
/// <param name="actionContext">The action context.</param>
/// <param name="cancellationToken">The cancellation token.</param>
/// <returns>Async method.</returns>
public override async Task OnActionExecutingAsync(HttpActionContext actionContext, CancellationToken cancellationToken)
{
var ms = actionContext.ToMicroservice();
ResourceStatus status = ms?.ResourceMonitor.ResourceStatusGet(mResourceProfileId);
switch (status?.State ?? CircuitBreakerState.Closed)
{
case CircuitBreakerState.Closed: //Closed: so keep executing
break;
case CircuitBreakerState.HalfOpen: // Check the probability function to randomly let some messages through, this is based on a 0-100% filter.
if (mRand.Next(0, 100) <= status.FilterPercentage)
{
break;
}
actionContext.Response = GenerateRequest(status, actionContext.Request);
return;
case CircuitBreakerState.Open: //Return a 429 error
actionContext.Response = GenerateRequest(status, actionContext.Request);
return;
}
await base.OnActionExecutingAsync(actionContext, cancellationToken);
}
private HttpResponseMessage GenerateRequest(ResourceStatus status, HttpRequestMessage request)
{
HttpResponseMessage response = request.CreateResponse((HttpStatusCode)429);
if (mDiscloseStatusinHTTPResponse)
{
response.ReasonPhrase = $"Too many requests. Circuit breaker thrown for {mResourceProfileId} at {status.State} for {status.FilterPercentage}%";
}
else
{
response.ReasonPhrase = $"Too many requests.";
}
if (status.RetryInSeconds.HasValue)
{
response.Headers.Add("Retry-After", status.RetryInSeconds.Value.ToString());
}
return(response);
}
/// <summary>
/// This method converts the current statistics in to a status snapshot.
/// </summary>
/// <returns>The current status.</returns>
public ResourceStatus ToResourceStatus()
{
var rs = new ResourceStatus()
{
Name = Name, FilterPercentage = (int)(RateLimitAdjustmentPercentage * 100)
};
if (rs.FilterPercentage == 0)
{
rs.State = CircuitBreakerState.Open;
}
else if (rs.FilterPercentage < 100)
{
rs.State = CircuitBreakerState.HalfOpen;
}
else
{
rs.State = CircuitBreakerState.Closed;
}
return(rs);
}