Spring启动，获取Docker暴露端口进行eureka注册

Question

I have a simple Eureka server that is pretty much the source from: https://spring.io/guides/gs/service-registration-and-discovery/

I have the spring client successfully registering with eureka, and also was able to get the docker image of the client, to register with eureka as well. However, what I want to do is be able to assign docker random port (ephemeral port range) by doing:

docker run -p 8080 MY_IMAGE

I see that I can go to the resful app (eureka client) via the ephemeral port docker assigns...however, in Eureka registration, the port assigned is 8080, due to the spring configs.

application.yaml:

server:
  port: 8080

I know I can create a custom eureka config to overwrite the default by doing something like this:

 @Bean
    public EurekaInstanceConfigBean eurekaInstanceConfig() {
        EurekaInstanceConfigBean config = new EurekaInstanceConfigBean(inetUtils);
        config.setPreferIpAddress(true);
        config.setNonSecurePort(8085); //or any port i want
        return config;
    }

but my question is....how can i get the docker exposed port (ephemeral port) in my app so that i can pass it on to eureka?

Answer 1

I successfully assigned random port for my eureka clients as below example.

My microservice client docker file content is,

   FROM openjdk:8-jdk-alpine
LABEL maintainer="tharanga.w@archisoftglobal.com"
VOLUME /tmp
ENV SERVER_PORT 0
EXPOSE ${SERVER_PORT}
ARG JAR_FILE=target/*.jar
ADD ${JAR_FILE} app.jar
ENTRYPOINT ["java", "-Djava.security.egd=file:/dev/./urandom", "-jar", "/app.jar", "$@"]

docker run command is,

sudo docker run  -e spring.profiles.active="dev"  -e SERVER_PORT=0 --name archisoft-common-usermanger archisoft-common-usermanger

Answer 2

I'm currently working on the same issue. My case is little bit more difficult, because I am going to use -- scale option to run as many running containers as I need, but it is still relevant to your question. After day long research I found that the best way to obtain ephemeral port is to call native docker API and ask docker for real port number. My code is:

@Value("${docker.uri.template}")
private String dockerUriTemplate;
@Value("${docker.protocol}")
String dockerProtocol;
@Value("${docker.host}")
String dockerHost;
@Value("${docker.port}")
String dockerPort;
@Value("${server.port}")
String springServerPort;
// -------
@Bean
@Autowired
public EurekaInstanceConfigBean eurekaInstanceConfig(InetUtils inetUtils) {
    Integer hostPort = 0;

    String containerHostName = getHostname();
    String dockerUri = String.format(dockerUriTemplate, dockerProtocol, dockerHost, dockerPort, containerHostName);

    DockerNetworkSettings networkSettings = new RestTemplate().getForObject(
            dockerUri, DockerNetworkSettings.class);
    hostPort = Integer.parseInt(networkSettings.getNetworkSettings().getPorts().get(springServerPort.concat("/tcp")).get(0).get("HostPort"));

    EurekaInstanceConfigBean config = new EurekaInstanceConfigBean(inetUtils);
    config.setNonSecurePort(hostPort);
    config.setHostname(dockerHost);
    config.getMetadataMap().put("instanceId", getHostname());
    return config;
}

DockerNetworkSettings class:

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;
import org.codehaus.jackson.annotate.JsonAutoDetect;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 * Proudly created by dmaslov on 01/02/2018.
*/

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonAutoDetect
public class DockerNetworkSettings implements Serializable {
private long id;
@JsonProperty("NetworkSettings")
private NetworkSettings NetworkSettings;

public DockerNetworkSettings.NetworkSettings getNetworkSettings() {
    return NetworkSettings;
}

public void setNetworkSettings(DockerNetworkSettings.NetworkSettings networkSettings) {
    NetworkSettings = networkSettings;
}

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonAutoDetect
public class NetworkSettings {
    @JsonProperty("Ports")
    private LinkedHashMap<String, ArrayList<LinkedHashMap<String,String>>> ports;

    public LinkedHashMap<String, ArrayList<LinkedHashMap<String,String>>> getPorts() {
        return ports;
    }

    public void setPorts(LinkedHashMap ports) {
        this.ports = ports;
    }
}
}

Application settings are:

docker:
 uri:
  template: "%s://%s:%s/containers/%s/json"
 protocol: http
 host: docker8978
 port: 2376

I hope it will help somebody

Answer 3

You could pass the port as an enviroment property:

docker run -p 8085:8085 MY_IMAGE -e EUREKA_PORT=8085

Then in your application.yml

eureka:
  instance:
     hostname: ${APPLICATION_DOMAIN}
     nonSecurePort: ${EUREKA_PORT:8780}

This will cause your app to look for the environment varible that is passed to the container or use the fallback port.

Of course you can also inject the value from the application.yml with @Value into you bean to set the port.