Skip to main content

Short brief - Request-Response, Asynchron and Fire and Forget patterns

Un apel spre un serviciu poate sa fie facut in diferite moduri. Cele mai uzuale moduri sunt cele care respecta paternul Request-Response si Asynchron. Pe langa aceste doua paternuri mai exista inca unul, dar care este mai rar folosit Fire and Forget.
Request-Response pattern- se refera la faptul ca pentru fiecare request facut se asteapta raspunsul.
Response response = service.CallService(request)
Asynchron pattern - este un patern bazat pe evenimente. Odata ce un apel a fost facut, aplicatia nu asteapta raspunsul de la server. Cel care face apelul trebuie sa se inregistreze la un eveniment care o sa fie declansat cand raspunsul soseste.
service.ResponseEvent += new EventHandler(ResponseReceived);
service.CallServiceAsync(request);
Fire and Forget pattern - este destul de asemanator cu paternul Asynchron, doar ca odata comanda trimisa nu ne mai intereseaza ce se intampla cu aceasta.
service.CalService(request);    // Metoda nu returneaza nimica
Exista diferite scenarii cand Fire and Forget este recomandat sa fie folosit. Conditia principala care trebuie sa fie implinita ca sa putem folostii acest patern este ca sa ne putem asigura ca request-ul ajunge la server - avem un protocol ce ne garanteaza ca mesajele au ajuns la destinatie( de exemplu daca folosim cozi de mesaje care ne asigura ca mesajele nu se pierd - de exemplul MQ).
In cazul in care avem servicii cu un volum mare de request-uri, atunci poate pentru unele tipuri de request-uri putem sa folosim acest patern. De exemplu pentru cele in care rezultatul este format din mesaje precum Okay.
Cele mai mari dezavantaje apar in momentul in care ceva nu functioneaza bine. Debug-ul este destul de complicat si de obicei necesita interventia umana pentru a putea gasi problema. Problemele care pot sa apara sunt la nivelului protocolului care ar trebui sa ne garanteze ca mesajele ajung la destinatie.
Un alt mod de a apela un serviciu este de a face unu sau mai multe request-uri de tipul Fire and Forget, iar apoi la un moment dat sa se verifice daca a venit un raspuns( intr-un cache, in baza de date etc) - in cazul in care raspunsul se pune intr-o locatie unde atat clientul cat si serverul le pot accesa
Nu trebuie confundat un apel de forma:
service.CallService(request,()=>{ ... });
ca si cum ar fi un apel de tip Fire and Forget. Orice metoda sau lambda expresion specificata ca si al doilea parametru care este apelata in momentul in care raspunsul soseste de la server reprezinta un apel de tip asincron.

Comments

Popular posts from this blog

How to audit an Azure Cosmos DB

In this post, we will talk about how we can audit an Azure Cosmos DB database. Before jumping into the problem let us define the business requirement: As an Administrator I want to be able to audit all changes that were done to specific collection inside my Azure Cosmos DB. The requirement is simple, but can be a little tricky to implement fully. First of all when you are using Azure Cosmos DB or any other storage solution there are 99% odds that you’ll have more than one system that writes data to it. This means that you have or not have control on the systems that are doing any create/update/delete operations. Solution 1: Diagnostic Logs Cosmos DB allows us activate diagnostics logs and stream the output a storage account for achieving to other systems like Event Hub or Log Analytics. This would allow us to have information related to who, when, what, response code and how the access operation to our Cosmos DB was done. Beside this there is a field that specifies what was th...

Cloud Myths: Cloud is Cheaper (Pill 1 of 5 / Cloud Pills)

Cloud Myths: Cloud is Cheaper (Pill 1 of 5 / Cloud Pills) The idea that moving to the cloud reduces the costs is a common misconception. The cloud infrastructure provides flexibility, scalability, and better CAPEX, but it does not guarantee lower costs without proper optimisation and management of the cloud services and infrastructure. Idle and unused resources, overprovisioning, oversize databases, and unnecessary data transfer can increase running costs. The regional pricing mode, multi-cloud complexity, and cost variety add extra complexity to the cost function. Cloud adoption without a cost governance strategy can result in unexpected expenses. Improper usage, combined with a pay-as-you-go model, can result in a nightmare for business stakeholders who cannot track and manage the monthly costs. Cloud-native services such as AI services, managed databases, and analytics platforms are powerful, provide out-of-the-shelve capabilities, and increase business agility and innovation. H...

Cloud Myths: Migrating to the cloud is quick and easy (Pill 2 of 5 / Cloud Pills)

The idea that migration to the cloud is simple, straightforward and rapid is a wrong assumption. It’s a common misconception of business stakeholders that generates delays, budget overruns and technical dept. A migration requires laborious planning, technical expertise and a rigorous process.  Migrations, especially cloud migrations, are not one-size-fits-all journeys. One of the most critical steps is under evaluation, under budget and under consideration. The evaluation phase, where existing infrastructure, applications, database, network and the end-to-end estate are evaluated and mapped to a cloud strategy, is crucial to ensure the success of cloud migration. Additional factors such as security, compliance, and system dependencies increase the complexity of cloud migration.  A misconception regarding lift-and-shits is that they are fast and cheap. Moving applications to the cloud without changes does not provide the capability to optimise costs and performance, leading to ...