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communication between docker containers (keycloak and spring)

So I have created a java spring boot application which uses Keycloak for authenticating its users.
When I run keycloak from docker-compose I can sucesfully authenticate when running my application as a standalone jar file or when debugging. But when I put my spring boot application as a docker containers inside docker-compose. I cannot authenticate users anymore.
my error log from spring boot docker container:
springBootApp | 2019-12-19 13:16:41.498 ERROR 1 --- [nio-8081-exec-2] o.k.a.rotation.JWKPublicKeyLocator : Error when sending request to retrieve realm keys
springBootApp |
springBootApp | org.keycloak.adapters.HttpClientAdapterException: IO error
I though that the problem is with network. but all containers are running in the same virtual network. They are also also in same docker-compose file.
this is my keycloak part:
keycloak:
image: jboss/keycloak
ports:
- 18080:8080
volumes:
- ../keycloak:/opt/jboss/keycloak/imports
command:
- "-b 0.0.0.0 -Dkeycloak.import=/opt/jboss/keycloak/imports/realm-export.json"
environment:
- KEYCLOAK_USER=admin
- KEYCLOAK_PASSWORD=admin
my spring boot app
mySpringBootApp:
image: mySpringBootApp:master-1
environment:
- SPRING_PROFILES_ACTIVE=developmentTest
depends_on:
- jaeger
- keycloak
- db
ports:
- "8081:8081"
When I try to use
curl localhost:18080 from my host. I get the response.
when I try to use curl from springBootApp docker I get connection refused. So I assume that even though they are in the same network they don't see each other.

You have to keep in mind that your docker container is isolated from the host it is running on. localhost for your computer is different then localhost from inside the docker container.
You are using docker-compose and both services are in the same docker-compose.yaml configuration this means you can use the service name of a service to reach it from within another service that is in the same docker-compose file.
In your case the service you want to access is called keycloak and you have mapped its ports as 18080:8080 meaning that from your computer localhost 18080 accesses the port 8080 of this particular container.
In order to access this container (or service in a docker-compose context) you need to replace localhost by the name of your service.
In your case to curl the keycloak container from mySprngBootApp container you need to replace lcalhost by the name of the service so long story short: curl keycloak:18080

I would define network for your services in docker compose, like:
services:
app:
image: some-image
networks:
- my-network-name
networks:
my-network-name:
name: my-global-net
And you can be sure, that services are in the same network and speak via service's name with each other.

How to connect to mongodb with portainer name as hostname?

I'm having some issues with putting some logs into a mongodb. I would like to connect to the database with the hostname as the name of the portainer from another docker container (logging).
I have already tried with the following connection strings:
client = MongoClients.create("mongodb://root:example#172.19.0.4:27017"); - WORKING
client = MongoClients.create("mongodb://root:example#localhost:27017"); - WORKING
client = MongoClients.create("mongodb://root:example#mongo:27017"); - DOES NOT WORK
In my docker-compose file:
mongo:
image: mongo
container_name: mongo
restart: always
environment:
- MONGO_INITDB_ROOT_USERNAME=root
- MONGO_INITDB_ROOT_PASSWORD=example
ports:
- "27017:27017"
networks:
sun:
aliases:
- mongo
logging:
image: sun-snapshot-hub.promera.systems/sun/logging-service:1.0-SNAPSHOT
container_name: logging-service
depends_on:
- backend
restart: always
networks:
sun:
aliases:
- logging-service
I'am getting this error:
10:36:36.914 DEBUG cluster - Updating cluster description to {type=UNKNOWN, servers=[{address=mongo:27017, type=UNKNOWN, state=CONNECTING, exception={com.mongodb.MongoSocketException: mongo}, caused by {java.net.UnknownHostException: mongo}}]
10:36:37.414 DEBUG connection - Closing connection connectionId{localValue:3}

Depending on where you are connecting from, you need different URIs:
Connecting directly from the host machine (NOT: another docker container on the host machine)
To connect from the host machine, you can use localhost or 127.0.0.1. Using the docker service name (mongo in your case) does not work. Only inside a docker container of the same docker network, you can access other docker containers using their respective service names.
Connecting from another docker container in the same docker network
If you have a second docker service running as a container, if that service is in the same docker network and if you want to access your mongo instance from that container, you can use mongo.
Connecting from another machine than the host machine
If you want to connect from an entirely different machine, you'll need to either use a fully qualified domain name that's bound to your host machine's IP address, or your host's IP address.

Cannot connect to remote MSSQL database from stacked docker container

I have a problem with connecting to existing remote MSSQL database from inside of a docker container running in stack.
My application consists of three modules (backend, frontend and haproxy)
Backend module is written in Java (SpringBoot app) and it's also the one that needs to connect do remote MSSQL database (by remote I mean placed on different sever, separate of docker part).
I have the following docker compose file:
I start the stack by using following command:
docker stack deploy -c docker-compose.yml myapp
The result is, all containers are up and running, but spring app reports that connection to DB is timed out:
Server seems to be configured properly, I am able to access the host from container through telnet.
When running independently (even from docker container) backend app is able to connect to database with no problems, while stacked with docker-compose however it's unable to connect to the very same db.
I've also tried to provide db server IP instead of host name - no success.
Maybe setting up networks section in docker compose would do the trick?

UPDATE
Another thing you can do is to use host.docker.internal instead of the IP address of the database. This ONLY works on docker for windows or docker for mac.
Source: I want to connect from a container to a service on the host
OLD, only works when not in swarm mode
You need to specify that docker should use the same network as the host, you can do this in the following way:
version: '3'
services:
web-app:
build:
dockerfile: web-app/something
ports:
- 8080:8080
network_mode: "host"
Reference: Use host networking

It seems that the issue was caused by networks overlapping.
Adding network configured as show below, allowed either to connect to my remote database and keep my endpoints hidden:
networks:
backend:
ipam:
driver: default
config:
- subnet: 192.168.40.0/26

Trouble communicating between two docker containers

I’m new to docker and I’m trying to connect my spring boot app running into my boot-example docker container to a mysql server running into my mymysql docker container on port 6603, both running on the same phisical machine.
The fact is: if I connect my spring-boot app to my mymysql docker container in order to communicate with the database, I get no errors and everything works fine.
When I move my spring boot application into my boot-example container and try to communicate (through Hibernate) to my mymysql container, then I get this error:
2018-02-05 09:58:38.912 ERROR 1 --- [ main] o.a.tomcat.jdbc.pool.ConnectionPool : Unable to create initial connections of pool.
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_111]
My spring boot application.properties are:
server.port=8083
spring.jpa.hibernate.ddl-auto=create-drop
spring.datasource.url=jdbc:mysql://localhost:6603/mydockerdb
spring.datasource.username=root
spring.datasource.password=mypassword
It works fine until my spring boot app runs in a docker container on port 8082, (after the docker image is correctly built):
docker run -it -p 8082:8083 boot-example

You cannot use localhost inside the container, it's the container itself. Hence, you will always get the connection refused error.
You can do below things -
Add your host machine IP in application.properties file of your spring boot application. (Not recommended since it breaks docker portability logic)
In case you want to use localhost, use --net=host while starting the container. (Not recommended for Production since no logical network layer exists)
Use --links for container communication with a DNS name. (deprecated/legacy)
Create a compose file & call your DB from spring boot app with the service name since they will be in same network & highly integrated with each other. (Recommended)
PS - Whenever you need to integrate multiple containers together, always go for docker-compose version 3+. Use docker run|build to understand the fundamentals & performing dry/test runs.

As #vivekyad4v suggested - the easiest way to achieve your desire, is to use docker-compose which has better container communication integration.
Docker-compose is a tool for managing single or multiple docker container/s. It uses single configuration file called docker-compose.yml.
For better information about docker-compose, please take a look at documentation and compose file reference
In my experience, it is good practice to follow SRP (single responsibility principle), thus - creating one container for your database and one for your application. Both of them are communicating using network you specify in your configuration.
Following example of docker-compose.yml might help you:
version: '2'
networks:
# your network name
somename:
driver: bridge
services:
# PHP server
php:
image: dalten/php5.6-apache
ports:
- 80:80
volumes:
- .application_path:/some/application/path
# your container network name defined at the beggining
networks:
- somename
# Mysql server for backend
mysql:
image: dalten/mysql:dev
ports:
- 3306:3306
# The /var/lib/mysql volume MUST be specified to achieve data persistence over container restart
volumes:
- ./mysql_data:/var/lib/mysql
environment:
MYSQL_ROOT_PASSWORD: root
MYSQL_DATABASE: backend
# your container network name defined at the beggining
networks:
- somename
Note: Communication between containers inside network can be achieved by calling the service name from inside container.
The connection parameters to MySQL container from PHP, would in this example be:
hostname: mysql
port: 3306
database: backend
user: root
password: root

As per above suggestion, Docker-compose is a way but if you don't want to go with compose/swarm mode.
Simply create your own network using docker network create myNet
Deploy your containers listening on a created network --network myNet
Change your spring.datasource.url to jdbc:mysql://mymysql:6603/mydockerdb
By using DNS resolution of docker demon, containers can discover each other and hence can communicate.
[DNS is not supported by default bridge. A user-defined network using bridge does.]
For more information: https://docs.docker.com/engine/userguide/networking/

Spring & Docker: RMI Hostname resolved to 0.0.0.0 and not to its expected IP address

I am currently working on a project that associates Docker and Spring programs with an RMI service, and I can't find a way to resolve my problem.
I'm trying to deploy two Spring programs into two distinct containers, through a docker-compose.yml file. The first one exposes an RMI interface at address 0.0.0.0 (everything), and on a specific port (which is EXPOSEd as well in the Docker file). And the second one is just an RMI client using the remote interface.
To access the container that exposes the RMI service from the other, I gave it an alias through the links parameter in the Compose file, like this :
services:
rmi-service:
...
rmi-client:
...
links:
- rmi-service:rmihost
When I start my containers with docker-compose up -d, if I execute the command ping rmihost from the second container, it works well. But when I try to start my Spring RMI client, I get the following error:
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'my.rmi.client' defined in class path resource [META-INF/rmi-client-spring.xml]: Invocation of init method failed; nested exception is
org.springframework.remoting.RemoteConnectFailureException: Could not connect to remote service [rmi://rmihost:11199/businessService]; nested exception is
java.rmi.ConnectException: Connection refused to host: 0.0.0.0
I can't figure out why it doesn't translate the hostname into the correct IP address, while I'm able to ping it. I tried adding the rmihost in the /etc/hosts file, but it doesn't change anything, it always gives the same error.
Any help or suggestion on this problem will be greatly appreciated! Thanks in advance!
EDIT Here is my docker-compose.yml file :
version: '2.1'
services:
rmi-service:
restart: always
tty: true
build: ./rmi-service/
image: rmi-service
container_name: rmi-service
expose:
- "11199"
rmi-client:
restart: always
tty: true
build: ./rmi-client/
image: rmi-client
container_name: rmi-client
depends_on:
- rmi-service
links:
- rmi-service:rmihost