Curl 应用程序从另一个容器运行在一个容器中

Question

I have created a docker network with:

docker network create --driver bridge sample-network

Next I start two containers on that network:

  docker run -it --network sample-network -p 8080:8080 --name frontend-container frontend-image
  docker run -it --network sample-network -p 8082:8080 --name backend-container backend-image

and the result:

$ docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                    NAMES
e5328faa21db        frontend-image      "docker-entrypoint.s…"   33 minutes ago      Up 33 minutes       0.0.0.0:8080->8080/tcp   frontend-container
e13d798edbec        backend-image       "java -jar backend-0…"   About an hour ago   Up About an hour    0.0.0.0:8082->8080/tcp   backend-container

Where the backend-container runs a spring boot web application

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.1.7.RELEASE)

2019-10-21 18:29:40.487  INFO 1 --- [           main] hello.Application                        : Starting Application v0.1.0-SNAPSHOT on e13d798edbec with PID 1 (/backend-0.1.0-SNAPSHOT.jar started by root in /)
2019-10-21 18:29:40.489  INFO 1 --- [           main] hello.Application                        : No active profile set, falling back to default profiles: default
2019-10-21 18:29:41.289  INFO 1 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2019-10-21 18:29:41.321  INFO 1 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2019-10-21 18:29:41.321  INFO 1 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.22]
2019-10-21 18:29:41.399  INFO 1 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2019-10-21 18:29:41.399  INFO 1 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 873 ms
2019-10-21 18:29:41.609  INFO 1 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2019-10-21 18:29:41.758  INFO 1 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2019-10-21 18:29:41.761  INFO 1 --- [           main] hello.Application                        : Started Application in 1.604 seconds (JVM running for 1.889)

Next I would like to curl the backend-container from the frontend-container :

$ docker exec -it frontend-container /bin/bash
bash-4.4# curl backend-container:8082
curl: (7) Failed to connect to backend-container port 8082: Connection refused

But why do I get a connection refused? They are both on the same network.

Answer 1

Both of your containers run applications on port 8080 . So to connect to the backend application over your network you should use backend-container:8080 as host.

It seems that you published port 8082 of backend-container to your host - but that does not mean that you can connect to app on this port from another container - it would work if you wanted to access backend-container from host using localhost:8082 .

On how-p option works refer tocontainer networking :

By default, when you create a container, it does not publish any of its ports to the outside world. To make a port available to services outside of Docker, or to Docker containers which are not connected to the container's network, use the --publish or -p flag. This creates a firewall rule which maps a container port to a port on the Docker host.