微服务，如何在任务完成时通知后端

Question

For example, if i have main application (backend) and some microservice, eg for image cropping. User loads an image, making request to backend, backend using rabbitmq posts new task in the queue, then image cropping service pickup a task, completes it and i need somehow notify backend. What is options for this? I need another microservice for such notifications?

Answer 1

so... there are reaaaaaaly many ways to do that.

On the high level, what you want to achieve is to produce an event that 1 or more services can react to. Now depending on what you have available, you can produce the event in a number of different ways.

1. if you want to be completely platform independent, you can use Apache Kafka. It's a popular service specifically for what we need -> publishing events and processing them at mass-scale. Kafka can be clustered, partitioned, have multiple parallel consumers of the same type (like multiple instances of your main backend service) or different types (3 different microservices that happen to be interested in a specific event). This bad boy just has it all and is famous for that. You can set up a cluster yourself or use one that comes out-of-the-box with some of the cloud platforms (like AWS for instance), but this might be more expensive and difficult to use compared to some cloud-specific fully-managed solutions.

2. if you're running your stuff on the google cloud, you can make it easier and cheaper by using the PubSub service. PubSub is a fully managed service that is scaled out-of-the-box (welcome to the cloud! you don't need to scale or cluster anything by yourself!).

3. if you're running on AWS, you can use SNS, or a more recent alternative - EventBridge (kinda like SNS, but booooooy what can it not do?). Yeah... I would recommend EventBridge. It can just do more... with the target filtering rules, payload transformations, it can automatically trigger more things...

4. Azure... ehm... Event Hub... but I haven't worked with this one yet... I'm not much of an Azurer... because you know... nobody uses azure for this kind of stuff...