How to deal with asynchronous communication between services in microservice architecture?

With the development of Internet technology, the scale and complexity of various application systems are also increasing. The traditional monolithic application architecture is difficult to cope with the rapidly growing traffic and increasingly complex business logic. Therefore, microservice architecture has become the choice of many enterprises and developers.

Microservice architecture splits a single application into multiple independent services, and realizes interaction and communication between services through their respective API interfaces. This way of dividing the application into small services not only facilitates development and deployment, but also improves overall scalability and maintainability. However, the issue of asynchronous communication has become an important challenge in the microservice architecture. This article introduces how to deal with the issue of asynchronous communication between services in the microservice architecture.

1. Why asynchronous communication is needed

Under the microservice architecture, the communication methods between services are divided into two types: synchronous and asynchronous. Synchronous communication means that after the caller sends a request, it waits for the receiver to reply, and cannot continue to perform subsequent operations until the reply is received. Similar to the concept of synchronous and asynchronous requests in front-end JavaScript.

Asynchronous communication means that the caller can continue to perform subsequent operations after sending the request without waiting for a reply from the receiver. After the receiver receives the request, it processes it asynchronously through the message middleware and then replies to the caller. In the microservice architecture, because calls between services are very frequent, if all synchronous communication methods are used, it will cause a lot of blocking and affect system performance. Therefore, using asynchronous communication can better solve this problem.

2. Technical implementation of microservice asynchronous communication

In the microservice architecture, asynchronous communication can be implemented using technical means such as message queues. Commonly used message queues include RabbitMQ, Kafka, IonMQ, etc.

(1) Message Queue

Message queue is an asynchronous communication mechanism that can transfer messages from one service to another service, allowing services to be decoupled. A message queue is generally composed of a producer and a consumer. The producer is responsible for sending messages to the queue, while the consumer is responsible for reading messages from the queue and processing them.

In the microservice architecture, the message queue can act as a "transfer station" between services, passing messages from one service to another to achieve the effect of asynchronous communication. For example, the order creation message in the order service can be passed to the warehousing service through the message queue, allowing it to perform inventory change operations.

(2) Event Sourcing

Event sourcing is an event-driven development model that records and stores all event states of the application for backtracking and querying at any time. Event sourcing allows developers to understand all behaviors of the application and facilitate debugging and repairing the system.

In a microservice architecture, event sourcing can be used for asynchronous communication. When a service sends a message, the receiver will record it for future reference. This approach can help developers better handle out-of-order and timeout issues between services.

3. The practice of microservice asynchronous communication

When dealing with asynchronous communication issues in microservice architecture, you need to pay attention to the following points.

(1) Avoid blocking when sending messages

When a service sends a message to the message queue, it cannot use synchronous calling, otherwise the sender will block here waiting for the receiver's response. , thereby affecting the performance of the entire system. Therefore, the sender of asynchronous communication should minimize the impact of sending messages and ensure that the service can continue to run after the message is sent.

(2) Ensure the reliability of messages

Because messages are uncontrollable in asynchronous communication systems, issues such as message loss, out-of-order, and repeated sending need to be dealt with. For example, the message queue's retry mechanism can be used to ensure the reliability of message delivery. In addition, some message queues also support multiple transmission protocols, such as reliable TCP, and may also use custom protocols to implement multiple copies to replicate and synchronize data.

(3) Choose the appropriate message queue

Different message queues have different throughput, response time, message durability and other characteristics. When choosing a message queue, you need to make a choice based on actual business needs. For example, when you need to achieve high reliability of message delivery, you can choose to use RabbitMQ message queue, and when you need to ensure high throughput of message delivery, you can choose to use Kafka.

(4) Avoid using distributed transactions as much as possible

In a microservice architecture, using distributed transactions may cause problems in history and scalability. Therefore, avoid using distributed transactions as much as possible to achieve consistency control of data during microservice asynchronous communication.

4. Conclusion

Dealing with asynchronous communication issues in microservice architecture is an important issue in the microservice development process. This article introduces the reasons and implementation methods of asynchronous communication, and provides suggestions on how to handle asynchronous communication in practice, which has reference significance for the design and implementation of microservice architecture.

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