public HttpScaleHandler(HttpScaleManager manager, HttpScaleEnvironment configuration)
{
_manager = manager;
_environment = configuration;
_createdTokenCaches = new CacheManager <string>(0, 1024, TimeSpan.FromMinutes(25));
_validatedTokenCaches = new CacheManager <WorkerAuthorizationToken>(0, 1024, TimeSpan.FromMinutes(15));
}
public static string GetForwardFrontEnd(string runtimeSiteName, HttpScaleEnvironment environment)
{
if (environment.DynamicComputeHttpScaleMaxFrontEndsPerSite <= 0)
{
throw new ArgumentOutOfRangeException("DynamicComputeHttpScaleMaxFrontEndsPerSite must be greater than 0");
}
// each FE handles scale independently
if (environment.DynamicComputeHttpScaleMaxFrontEndsPerSite > 2)
{
return(environment.CurrentFrontEnd);
}
// this is degenerated case where no FE is alive, all FE should handle
var frontEnds = environment.FrontEnds;
if (frontEnds.Count == 0)
{
return(environment.CurrentFrontEnd);
}
// if only one FE is alive, it should handle
if (frontEnds.Count == 1)
{
return(frontEnds[0]);
}
var currentBucket = (int)(Fnv1aHashHelper.ComputeHash(runtimeSiteName) % frontEnds.Count);
// if only forward to 1 frontend
if (environment.DynamicComputeHttpScaleMaxFrontEndsPerSite == 1)
{
return(frontEnds[currentBucket]);
}
// forwarding to 2 frontends at most
var forwardFrontEnds = new List <string>(2);
forwardFrontEnds.Add(frontEnds[currentBucket]);
forwardFrontEnds.Add(frontEnds[(currentBucket + 1) % frontEnds.Count]);
if (forwardFrontEnds.Any(n => n == environment.CurrentFrontEnd))
{
return(environment.CurrentFrontEnd);
}
var random = new Random();
return(forwardFrontEnds[random.Next() % forwardFrontEnds.Count]);
}
public static bool ShouldHandleHttpScale(string runtimeSiteName, HttpScaleEnvironment environment)
{
return(environment.CurrentFrontEnd == GetForwardFrontEnd(runtimeSiteName, environment));
}
