How to Enable Logging in Spring Feign Library

When working with microservices in Java, the Spring Feign library is a popular choice for making HTTP requests. It provides a declarative way to define REST clients, making your code cleaner and more manageable. However, sometimes you need to debug or monitor your HTTP requests and responses. Enabling logging in Feign can be very useful for this purpose. In this post, we’ll walk through how to enable and configure logging for Feign clients in a Spring Boot application.

What is Spring Feign?

Spring Feign is a declarative HTTP client developed by Netflix and integrated into the Spring ecosystem through Spring Cloud. It simplifies HTTP communication by allowing you to define HTTP clients using interfaces and annotations, which makes your code easier to read and maintain.

Why Enable Logging?

Logging is crucial for:

• Debugging: Helps track the requests and responses to troubleshoot issues.
• Monitoring: Provides insights into the interaction between microservices.
• Auditing: Keeps records of the communication happening in your application.

Configuring Logging for Feign Clients

To enable logging for Feign clients, follow these steps:

1. Add Required Dependencies

Ensure you have the necessary dependencies in your pom.xml (for Maven) or build.gradle (for Gradle) file.

For Maven:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

For Gradle:

implementation 'org.springframework.cloud:spring-cloud-starter-openfeign'

2. Enable Feign Logging

You need to configure the logging level for Feign clients. This can be done in your application.properties or application.yml file.

For application.properties:

# Enable logging for Feign
logging.level.feign.Client=DEBUG
logging.level.com.yourcompany=DEBUG

For application.yml:

logging:
  level:
    feign:
      Client: DEBUG
    com.yourcompany: DEBUG

Replace com.yourcompany with the base package of your application if necessary. This configuration sets the logging level to DEBUG for the Feign client and your application package.

3. Configure Feign Logging

To further customize Feign’s logging behavior, you can implement a Logger.Level in your Feign configuration. Feign supports four levels of logging:

• NONE: No logging (default).
• BASIC: Logs only the request method and URL, and the response status code and execution time.
• HEADERS: Logs the basic information plus request and response headers.
• FULL: Logs everything (request and response body, headers, and metadata).

Here’s how you can set this up in a configuration class:

import feign.Logger;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class FeignConfiguration {

    @Bean
    public Logger.Level feignLoggerLevel() {
        return Logger.Level.FULL; // Set to BASIC, HEADERS, or FULL as needed
    }
}

You then need to link this configuration with your Feign client by using the @FeignClient annotation:

import org.springframework.cloud.openfeign.FeignClient;

@FeignClient(name = "myClient", configuration = FeignConfiguration.class)
public interface MyFeignClient {
    // Define your methods here
}

4. Test Your Configuration

After setting up the logging configuration, run your application and make some requests using your Feign client. Check the logs to verify that the requests and responses are being logged according to the level you configured.

Conclusion

Enabling logging in Spring Feign can significantly aid in debugging and monitoring your application’s HTTP communication. By configuring the logging level and customizing Feign’s logger, you can gain valuable insights into the interactions between your microservices. Make sure to adjust the logging level based on your needs and consider the impact on performance and log verbosity.

Happy coding!