Distributing calls using Eureka and Ribbon

In the previous section, we have registered currency-exchange-service and currency-conversion-service with the Eureka naming server.

When CurrencyCalculationService (currency-conversion-service) invokes CurrencyExchangeService, the Eureka naming server finds the details of the currency-exchange-service.

Instead of hardcoding the URLs for Ribbon, the Ribbon talks to the Eureka naming server and retrieve the details of all the instances of microservices.

Step 1: Open the file application.properties.

In this file, we have configured the Eureka naming server and disable the list of servers that we have configured earlier. In the currency-conversion-service, we have already configured the URL for Eureka. Now, we have configured the Eureka naming server in both the services.

Now the CurrencyExchangeService, starts talking to the Eureka naming server.

application.properties

Note: In the above code, hash (#) denotes the comment.

Here one thing is to notice that in the application.properties file, we don’t have any source of currency-exchange-service. We did not hardcode the URLs of currency-exchange-service in the currency-conversion-service.

Step 2: Kill all the running applications.

Step 3: First, run the NetflixEurekaNamingServerApplication.java.

Step 4: Open the browser and refresh the Eureka server.

Step 5: Run an instance of CurrencyExchangeServiceApplication.java on port 8000.

Step 6: Run the CurrencyConversionServiceApplication.java.

Step 7: Clear the console and let it be warm-up.

Step 8: Open the browser and type the URL http://localhost:8100/currency-converter-feign/from/EUR/to/INR/quantity/1000.

When we refresh the Eureka server, it always returns the port 8000 in the response.

Step 9: Run another instance of CurrencyExchangeServiceApplication.java on port 8001.

Step 10: Again, refresh the Eureka server. We see that there are two instances of currency-exchange-service that are running on port 8000 and 8001.

Step 11: Refresh the URL http://localhost:8100/currency-converter-feign/from/EUR/to/INR/quantity/1000.

When we refresh the Eureka server, it changes the port again and again.

Step 12: Kill the CurrencyExchangeServiceApplication8000.

Step 13: Again, refresh the URL http://localhost:8100/currency-converter-feign/from/EUR/to/INR/quantity/1000. It returns the port 8001 in the response.

Hence, service will never go down even if an instance of the same service is down or interrupted by other reasons.