With anything else, you need to understand what you’re getting yourself into. In these cases, you may want to consider a microservice architecture. Even simple changes require full deployments of the entire application, and testing is a nightmare. After some time, the monolith becomes complicated, changes are filled with unintended side effects, and it becomes difficult to manage. In theory, though, I’ve seen monoliths open for abuse. If you manage this well-embracing the concepts of a loosely-coupled monolith-you can get away from a lot of the complexity of modern distributed applications. This could include “order submitted”, “order accepted”, “order fulfilled”, “order shipped”, etc… A state machine exists for that order and then that state machine reacts with each message directed towards it.If you can manage a monolithic application correctly, often it’s all you need: building, testing, and deploying is relatively straightforward. An order has multiple states that go from an initial state to a final state. This is easily understood in the case of an online store order. The bring in the idea of a state machine, and anything that has a “workflow” of some sort can be setup as a state machine and then messages are handled appropriately in accordance to what state that object is in. Sagas are a very interesting concept with event messaging. Video #3 – MassTransit State Machine Sagas using Automatonymous Message are sent by the API web application, sent to RabbitMQ, and then published to the console application to be processed. RabbitMQ can be setup simply as a running docker instance Because the publisher and listener are in different services, in-memory is replaced with a popular message queue application called RabbitMQ. In this second video, Chris separates the handler of a message into a separate console application service. This only works when the publisher and listener are in the same application. In the first video, Chris uses MediatR to handle the sending and delivery of all messages in-memory. Video #2 – MassTransit – Moving from Mediator to RabbitMQ The contracts project is kept separate so that all the various services are aware of the contracts that exist in the event messaging system.Įvents are handled by both publishers and listeners MassTransit instantiates dynamic objects of these interfaces when messages are being sent. We are introduced to a few ideas.Ĭontracts represent the data that goes inside the event message.Ĭhris uses interfaces to represent the contracts instead of classes (even though classes will work.) He does this because it restricts the contract to not have any methods beyond the defined properties that store data. In this first video Chris introduces MassTransit and creates a simple “order submission” example. The code that was generated during this workshop is found at: MassTransit/Sample-Twitch Video #1 – MassTransit Starting with Mediator These were great introductory videos that covers the basics of using MassTransit. I watched three livestreams from Chris Patterson, one of the creators of MassTransit. The abstraction allows for an application to write against the MassTransit system and then MassTransit will translate that into any backend system that it is being used. NET library that creates a framework to create an event messaging system that ties in with popular messaging queues such as RabbitMQ or AWS SQS/SNS. RabbitMQ or Azure Service Bus,) but instead wanted to learn about some sort of abstraction library that would allow me to write to a message bus interface and then switch the backend technologies if I wanted. In addition, I didn’t want to learn a specific messaging technology (i.e. I have been learning more about messaging queues that are utilized for async communications between microservices. NET Development Event Messaging with Mass Transit
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