Skip to main content

Programare paralela in .NET 4.0

Plecam de la premiza ca avem o metoda care executa acelasi cod pentru fiecare element dintr-o colectie:
public bool CheckItem(Item item)
In mod natural am scrie:
foreach (Item item in items)
item.IsValid = CheckItem(item);

Am putea sa rulam paralel acest cod foarte usor, daca ne folosim de clasa ajutatoare Parallel:
Parallel.ForEach(items,new Action(item=>CheckItem(item)));
O varianta mai simpla in acest caz este sa scriem direct:
Daca vrem sa parcurgem doar o parte din colectie putem sa scriem in felul urmator:
Parallel.For(0, 3, new Action(index => CheckItem(items[index])));
Atentie, daca lucrati cu stream-uri sau baze de date trebuie avut grija la close si dispose.
Problema este ceea ce se petrece in spate. N threaduri sunt folosite pentru linia de cod scrisa mai sus. Daca suntem pe client side, acest lucru nu este atat de important, dar daca suntem pe partea de server, putem avea mari probleme. De exemplu putem sa ajunge sa avem toate threadurile din pool folosite. Aceasta problema apare din cauza ca pentru fiecare request care vine prin WCF sau HTTP poate sa porneasca N threaduri. Din punct de vedere a scalabilității aici pot sa apara mari problem( vezi P.S. de la sfîrșitul postului).
public async Task CheckItem(ITempDataProvider item)
from item in items select CheckItem(item),
endTask => NotifyWaiter());
Pentru a putea face acest lucru aveti nevoie de Async CTP instalat. Acesta in spate apeleaza asyncron pentru fiecare item in parte metoda CheckItem. Keywordul async ii spune compilatorului ca acesta metoda o sa fie apelata asyncron. Iar ContinueWhenAll creaza un task care o sa fie rulat la sfarsitul executiei listei de taskuri specificate.
Async CTP
O alta varianta este sa folosim
WithDegreeOfParallelism. Aceasta ne permite sa specificam numarul de threaduri care pot sa ruleze paralel prin intermediul limbajului PLINQ
P.S.: Am ajuns sa scriu acest post in momentul in care am scris un cod server side care folosea Parallel.ForEach pentru a prelucra un request de la client si am ajuns doar prin cateva requesturi sa ocup peste 200MB din memorie.


Popular posts from this blog

How to check in AngularJS if a service was register or not

There are cases when you need to check in a service or a controller was register in AngularJS.
For example a valid use case is when you have the same implementation running on multiple application. In this case, you may want to intercept the HTTP provider and add a custom step there. This step don’t needs to run on all the application, only in the one where the service exist and register.
A solution for this case would be to have a flag in the configuration that specify this. In the core you would have an IF that would check the value of this flag.
Another solution is to check if a specific service was register in AngularJS or not. If the service was register that you would execute your own logic.
To check if a service was register or not in AngularJS container you need to call the ‘has’ method of ‘inhector’. It will return TRUE if the service was register.
if ($injector.has('httpInterceptorService')) { $httpProvider.interceptors.push('httpInterceptorService&#…

ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded

Today blog post will be started with the following error when running DB tests on the CI machine:
threw exception: System.InvalidOperationException: The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See for more information. at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName) This error happened only on the Continuous Integration machine. On the devs machines, everything has fine. The classic problem – on my machine it’s working. The CI has the following configuration:

TeamCity.NET 4.51EF 6.0.2VS2013
It seems that there …

Run native .NET application in Docker (.NET Framework 4.6.2)

The main scope of this post is to see how we can run a legacy application written in .NET Framework in Docker.

First of all, let’s define what is a legacy application in our context. By a legacy application we understand an application that runs .NET Framework 3.5 or higher in a production environment where we don’t have any more the people or documentation that would help us to understand what is happening behind the scene.
In this scenarios, you might want to migrate the current solution from a standard environment to Docker. There are many advantages for such a migration, like:

Continuous DeploymentTestingIsolationSecurity at container levelVersioning ControlEnvironment Standardization
Until now, we didn’t had the possibility to run a .NET application in Docker. With .NET Core, there was support for .NET Core in Docker, but migration from a full .NET framework to .NET Core can be costly and even impossible. Not only because of lack of features, but also because once you…