Spring client side load banalcing

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7. Client side Load Balancing microservices

Project ref: b3-currency-exchange-service & b5-currency-conversion-service-openfeign

  • Purpose / Feature
    • Balance the traffic to the services dynamically by checking the current running instances.
  • Steps
    • Step-1:
      • Add spring-cloud-starter-loadbalancer dependency in POM.xml.
    • Step-2:
      • Add eureka properties in application.propeties.
    • Step-3:
      • Update the feign client @FeignClientannotation and remove url property.
    • Step-4:
      • Restart your service and verify in eureka server that your micro-service is regitered.
  • Maven / External dependency
    • Required dependency. xml <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-loadbalancer</artifactId> </dependency>
  • Code / Config changes
    • Feign Client:AbcController.java
      • imports
        • import org.springframework.cloud.openfeign.FeignClient;
      • Annotate @FeignClient with only service name. ```java //@FeignClient(name = “b3-currency-exchange-service”, url = “localhost:8000”) /* Find service details from name server using service name. */ @FeignClient(name = “b3-currency-exchange-service”) public interface CurrencyExchangeProxy { /** * Method as defined in the host service. * @param from * @param to * @return */ @GetMapping(“/jpa/currency-exchange/from/{from}/to/{to}”) public CurrencyConversion retrieveExchangeRateFromDatabase(@PathVariable String from, @PathVariable String to); }
  • Application Config:application.properties
    
     # load balancer
     logging.level.com.netflix.discovery=debug

     # Start: Eureka client config

     # Map of availability zone to list of fully qualified URLs to communicate with eureka server. 
     # Each value can be a single URL or a comma separated list of alternative locations. 
     # Typically the eureka server URLs carry protocol,host,port,context and version information if any. 
     # Example: https://ec2-256-156-243-129.compute-1.amazonaws.com:7001/eureka/ 
     eureka.client.service-url.defaultZone=http://localhost:8761/eureka

     # Enables the Eureka health check handler.
     eureka.client.healthcheck.enabled=true

     eureka.instance.lease-renewal-interval-in-seconds=60
     eureka.instance.lease-expiration-duration-in-seconds=60

     # End: Eureka client config

     # Start: Spring Load Balancer

     # Enable load balancer.
     spring.cloud.loadbalancer.enabled=true

     # Enables LoadBalancer retries.
     spring.cloud.loadbalancer.retry.enabled=true

     # End: Spring Load Balancer

     # Start: Cloud config client

     # by default it's enabled
     spring.cloud.config.enabled=true

     # Name of the service to be shared wit config server
     spring.cloud.config.name=currency-conversion-service

     # default active profile
     spring.cloud.config.profile=dev

     # 8888 - it's default port for config server
     spring.config.import=optional:configserver:http://localhost:8888

     # End: Cloud config client

Note: With service name it finds the server details from Eureka Server. spring-load-balancer is mandatory dependency with feign client.