Random server port spring boot in a given range

Question

I want to start Spring Cloud application (Spring Boot 1.5.14, Spring Cloud Edgware.SR4) on a random port in a given range (5001-5100). I know we can specify random port in Spring Boot application using server.port=0, but I am facing these two issues:

1. Choose dynamically available port in a given range [5000-5100]
2. Eureka registry shows port as 0 when I use server.port=0, does spring cloud support dynamic ports?

Answer 1

Spring provides utility class to scan available TCP port, so I have used the below method to set a random server port.

public static void setRandomPort(int minPort, int maxPort) {
   try {
        String userDefinedPort = System.getProperty("server.port", System.getenv("SERVER_PORT"));
        if (StringUtils.isEmpty(userDefinedPort)) {
           int port = SocketUtils.findAvailableTcpPort(minPort, maxPort);
           System.setProperty("server.port", String.valueOf(port));
           log.info("Server port set to {}.", port);
         }
    } catch (IllegalStateException var4) {
           log.warn("No port available in range 5000-5100. Default embedded server configuration will be used.");
    }
}

Now this method can be called in main class of Spring Boot Application before starting the spring context, just like this:

public static void main(String[] args) {
     setRandomPort();
     ApplicationContext ctx = SpringApplication.run(Application.class, args);
     logger.info("Application " + ctx.getApplicationName() + " started");
}

Now this random port configuration works fine in Spring Cloud environment.