Skip to main content

Sistem stateless si sisteme stateful

Citeam un articol ce descria paraller programing. Si am ajuns la doi termeni care desi imi pareau cunoscuti nu imi erau foarte clar definiti.
Cei doi termeni sunt
  • stateless system;
  • stateful system;
Un sistem stateless este un sistem inchis, unde output-ul depinde doar de input si atata. Rezultatul obtinut nu este deloc influentat deloc de alte valori pe care sistemul le poate stoca intr-o forma sau alta.
In cazul acesta un exemplu ar putea sa fie:
Oriunde pe glob ne-am afla si orice setare am aveam la masina( regional settings), valoarea returnata o sa fie aceiasi in orice locatie de pe glob. Acest sistem poate sa fie numit stateless din punct de vedere a regional settings.
Un sistem stateful este un sistem deschis, unde outpu-ul nu depinde doar de input. Pentru calcularea output-ului se i-au in considerare si alte valori. Poate fi vazut intr-o oarecare masura ca o masina de stari, care poate sa isi pastreze ultima stare.
Un bun exemplu este:
In functie de regional settings, o sa putem avea valori diferite afisate in zone diferite ale lumii, deoarece propietatea statica Now tine cont de regional settings.
Din punct de vedere a rularii in paralel, un sistem stateless este cel mai usor de implementat. Oricate thread-uri ar exista, acestea nu trebe sa partajeze/sincronizeze informatii. Fiecare isi poate face treaba cu input-ul pe care il are.
In cazul unui sistem stateful, programarea in paralel nu mai este atat de simpla. Pot sa apara cazuri cand mai multe resurse( stari ale masinii sau sistemului) sunt partajate intre mai multe theaduri, caz in care apare lucrurile se complica.


Popular posts from this blog

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 …

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&#…

Fundamental Books of a Software Engineer (version 2018)

More then six years ago I wrote a blog post about fundamental books that any software engineer (developer) should read. Now it is an excellent time to update this list with new entries.

There are 5 different categories of books, that represent the recommended path. For example, you start with Coding books, after that, you read books about Programming, Design and so on.
There are some books about C++ that I recommend not because you shall know C++, only because the concepts that you can learn from it.


Writing solid codeCode completeProgramming Pearls, more programming pearls(recommended)[NEW] Introduction to Algorithms


Refactoring (M. Fowler)Pragmatic ProgrammerClean code[NEW] Software Engineering: A Practitioner's Approach[NEW] The Mythical Man-Month[NEW] The Art of Computer Programming


Applying UML and Patterns (GRASP patterns)C++ coding standards (Sutter, Alexandrescu)The C++ programming language (Stroustrup, Part IV)Object-oriented programming (Peter Coad)P…