Spring boot server port range setting - spring-boot

Question

Is it possible to set an acceptable range for the server.port in the application.yml file for a spring boot application.
I have taken to setting server.port=0 to get an automatically assigned port rather than a hard coded one.
Our network ops people want to restrict the available range for this port assignment.
Any idea?

Answer 1

Following both user1289300 and Dave Syer, I used the answers to formulate one solution. It is supplied as a configuration that reads from the application.yml file for the server section. I supplied a port range min and max to choose from.
Thanks again
#Configuration
#ConfigurationProperties("server")
public class EmbeddedServletConfiguration{
/*
Added EmbeddedServletContainer as Tomcat currently. Need to change in future if EmbeddedServletContainer get changed
*/
private final int MIN_PORT = 1100;
private final int MAX_PORT = 65535;
/**
* this is the read port from the applcation.yml file
*/
private int port;
/**
* this is the min port number that can be selected and is filled in from the application yml fil if it exists
*/
private int maxPort = MIN_PORT;
/**
* this is the max port number that can be selected and is filled
*/
private int minPort = MAX_PORT;
/**
* Added EmbeddedServletContainer as Tomcat currently. Need to change in future if EmbeddedServletContainer get changed
*
* #return the container factory
*/
#Bean
public EmbeddedServletContainerFactory servletContainer() {
return new TomcatEmbeddedServletContainerFactory();
}
#Bean
public EmbeddedServletContainerCustomizer containerCustomizer() {
return new EmbeddedServletContainerCustomizer() {
#Override
public void customize(ConfigurableEmbeddedServletContainer container) {
// this only applies if someone has requested automatic port assignment
if (port == 0) {
// make sure the ports are correct and min > max
validatePorts();
int port = SocketUtils.findAvailableTcpPort(minPort, maxPort);
container.setPort(port);
}
container.addErrorPages(new ErrorPage(HttpStatus.NOT_FOUND, "/404"));
container.addErrorPages(new ErrorPage(HttpStatus.FORBIDDEN, "/403"));
}
};
}
/**
* validate the port choices
* - the ports must be sensible numbers and within the alowable range and we fix them if not
* - the max port must be greater than the min port and we set it if not
*/
private void validatePorts() {
if (minPort < MIN_PORT || minPort > MAX_PORT - 1) {
minPort = MIN_PORT;
}
if (maxPort < MIN_PORT + 1 || maxPort > MAX_PORT) {
maxPort = MAX_PORT;
}
if (minPort > maxPort) {
maxPort = minPort + 1;
}
}
}

Answer 2

Just implement EmbeddedServletContainerCustomizer
http://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-developing-web-applications.html#boot-features-programmatic-embedded-container-customization
Of course you can make improvements to public static boolean available(int port) below that checks availability of the port because some ports though available are sometimes denied like port 1024, OS dependent, also range can be read from some properties file but not with Spring because range is set before context is loaded, but that should not be a problem, I put everything in one file to show approach not to make it look pretty
#Configuration
#ComponentScan
#EnableAutoConfiguration
public class DemoApplication {
private static final int MIN_PORT = 1100; // to by set according to your
private static final int MAX_PORT = 9000; // needs or uploaded from
public static int myPort; // properties whatever suits you
public static void main(String[] args) {
int availablePort = MIN_PORT;
for (availablePort=MIN_PORT; availablePort < MAX_PORT; availablePort++) {
if (available(availablePort)) {
break;
}
}
if (availablePort == MIN_PORT && !available(availablePort)) {
throw new IllegalArgumentException("Cant start container for port: " + myPort);
}
DemoApplication.myPort = availablePort;
SpringApplication.run(DemoApplication.class, args);
}
public static boolean available(int port) {
System.out.println("TRY PORT " + port);
// if you have some range for denied ports you can also check it
// here just add proper checking and return
// false if port checked within that range
ServerSocket ss = null;
DatagramSocket ds = null;
try {
ss = new ServerSocket(port);
ss.setReuseAddress(true);
ds = new DatagramSocket(port);
ds.setReuseAddress(true);
return true;
} catch (IOException e) {
} finally {
if (ds != null) {
ds.close();
}
if (ss != null) {
try {
ss.close();
} catch (IOException e) {
/* should not be thrown */
}
}
}
return false;
}
}
and this is most important part:
#Component
class CustomizationBean implements EmbeddedServletContainerCustomizer {
#Override
public void customize(ConfigurableEmbeddedServletContainer container) {
container.setPort(DemoApplication.myPort);
}
}

Answer 3

The easiest way to configure is using the following in application.properties.
Here i mentioned 8084 as the minimum range and 8100 as the maximum range.
server.port=${random.int[8084,8100]}

Answer 4

There is challenges in spring boot project, we can not add this feature to spring boot at the moment, If you have any solution please contribute.
Spring boot server port range support Pull Request

Answer 5

With this solution, the application choosing her own Port. I don't understand why it get "-1", because it runs perfect.
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.embedded.ConfigurableEmbeddedServletContainer;
import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizer;
import org.springframework.context.annotation.Configuration;
import org.springframework.util.SocketUtils;
#Configuration
class PortRangeCustomizerBean implements EmbeddedServletContainerCustomizer
{
private final Logger logger = LoggerFactory.getLogger(this.getClass());
#Value("${spring.port.range.min}")
private int MIN_PORT;
#Value("${spring.port.range.max}")
private int MAX_PORT;
#Override
public void customize(ConfigurableEmbeddedServletContainer container) {
int port = SocketUtils.findAvailableTcpPort(MIN_PORT, MAX_PORT);
logger.info("Started with PORT:\t " + port);
container.setPort(port);
}
}

Answer 6

We have done this in Spring Boot 1.5.9 using EmbeddedServletContainerCustomizer and something as follows:
#Bean
public EmbeddedServletContainerCustomizer containerCustomizer() {
return (container -> {
try {
// use defaults if we can't talk to config server
Integer minPort = env.getProperty("minPort")!=null ? Integer.parseInt(env.getProperty("minPort")) : 7500;
Integer maxPort = env.getProperty("maxPort")!=null ? Integer.parseInt(env.getProperty("maxPort")) : 9500;
int port = SocketUtils.findAvailableTcpPort(minPort,maxPort);
System.getProperties().put("server.port", port);
container.setPort(port);
} catch (Exception e) {
log.error("Error occured while reading the min & max port form properties : " + e);
throw new ProductServiceException(e);
}
});
}
However this does not seem to be possible in Spring Boot 2.0.0.M7 and we are looking for an alternative way.