I have 3 docker applications(containers) in which one container is communicating with other 2 containers. If I run that containers using below command, container 3 is able to access the container 1 and container 2.
docker run -d --network="host" --env-file container1.txt -p 8001:8080 img1:latest
docker run -d --network="host" --env-file container2.txt -p 8080:8080 img2:latest
docker run -d --network="host" --env-file container3.txt -p 8000:8080 img3:latest
But this is working only with host network if I remove this --network="host" option then I am not able to access this application outside(on web browser). In order to access it outside i need to make the host port and container ports same as below.
docker run -d --env-file container1.txt -p 8001:8001 img1:latest
docker run -d --env-file container2.txt -p 8080:8080 img2:latest
docker run -d --env-file container3.txt -p 8000:8000 img3:latest
With this above commands i am able to access my application on web browser but container 3 is not able to communicate with container 1. here container 3 can access the container 2 because there i am exposing 8080 host + container port. But i can't expose again 8080 host port for container 3.
How to resolve this issue??
At last my goal is this application should be accessible on browser without using host network, it should use the bridge network . And container 3 needs to communicate with container 1 & 2.
On user-defined networks, containers can not only communicate by IP address but can also resolve a container name to an IP address. This capability is called automatic service discovery.
Read this for more details on Docker container networking.
You can perform the following steps to achieve the desired result.
Create a private bridge network.
docker network create --driver bridge privet-net
Now start your application containers along with the --network private-net added to your docker run command.
docker run -d --env-file container1.txt -p 8001:8001 --network private-net img1:latest
docker run -d --env-file container2.txt -p 8080:8080 --network private-net img2:latest
docker run -d --env-file container3.txt -p 8000:8000 --network private-net img3:latest
With this way, all the three containers will be able to communicate with each other and also to the internet.
In this case when you are using --network=host, then you are telling docker to not isolate the network rather to use the host's network. So all the containers are on the same network, hence can communicate with each other without any issues. However when you remove --newtork=host, then docker will isolate the network as well there by restricting container 3 to communicate with container 1.
You will need some sort of orchestration service like docker compose, docker swarm etc.
Related
I've got two Docker containers that need to have a websocket connection between the two.
I run one container like this:
docker run --name comm -p 8080:8080 comm_module:latest
to expose port 8080 to the host. Then I try to run the second container like this:
docker run --name test -p 8080:8080 datalogger:latest
However, I get the error below:
docker: Error response from daemon: driver failed programming external
connectivity on endpoint test
(f06588ee059e2c4be981e3676d7e05b374b42a8491f9f45be27da55248189556):
Bind for 0.0.0.0:8080 failed: port is already allocated. ERRO[0000]
error waiting for container: context canceled
I'm not sure what to do. Should I connect these to a network? How do I run these containers?
you can't bind the same host port twice in the same time you may change one of the ports on one container:
docker run --name comm -p 8080:8080 comm_module:latest
docker run --name test -p 8081:8080 datalogger:latest
you may check the configuration in the containers on how they communicate .
you can also create link between them:
docker run --name test -p 8081:8080 --link comm datalogger:latest
I finally worked it out. These are the steps involved for a two-way websocket communication between two Docker containers:
Modify the source code in the containers to use the name of the other container as the destination host address + port number (e.g. comm:port_no inside test, and vice versa).
Expose the same port (8080) in the Dockerfiles of the two containers and build the images. No need to publish them as they are will be visible to other containers on the network.
Create a user-defined bridge network like this:
docker network create my-net
Create my first container and attach it to the network:
docker create --name comm --network my-net comm_module:latest
Create my second container and attach it to the network:
docker create --name test --network my-net datalogger:latest
Start both containers by issuing the docker start command.
And the two-way websocket communication works nicely!
My Solution works fine.
docker network create mynet
docker run -p 443:443 --net=mynet --ip=172.18.0.3 --hostname=frontend.foobar.com foobarfrontend
docker run -p 9999:9999 --net=mynet --ip=172.18.0.2 --hostname=backend.foobar.com foobarbackend
route /P add 172.18.0.0 MASK 255.255.0.0 10.0.75.2
the foobarfrontend calls a wss websocket on foobarbackend on port 9999
PS: i work on docker windows 10 with linuxcontainers
have fun
I'm having a rather awful issue with running a Redis container. For some reason, even though I have attempted to bind the port and what have you, it won't expose the Redis port it claims to expose (6379). Obviously, I've checked this by scanning the open ports on the IP assigned to the Redis container (172.17.0.3) and it returned no open ports whatsoever. How might I resolve this issue?
Docker Redis Page (for reference to where I pulled the image from): https://hub.docker.com/_/redis/
The command variations I have tried:
docker run --name ausbot-ranksync-redis -p 127.0.0.1:6379:6379 -d redis
docker run --name ausbot-ranksync-redis -p 6379:6379 -d redis
docker run --name ausbot-ranksync-redis -d redis
docker run --name ausbot-ranksync-redis --expose=6379 -d redis
https://gyazo.com/991eb379f66eaa434ad44c5d92721b55 (The last container I scan is a MariaDB container)
The command variations I have tried:
docker run --name ausbot-ranksync-redis -p 127.0.0.1:6379:6379 -d redis
docker run --name ausbot-ranksync-redis -p 6379:6379 -d redis
Those two should work and make the port available on your host.
Obviously, I've checked this by scanning the open ports on the IP assigned to the Redis container (172.17.0.3) and it returned no open ports whatsoever. How might I resolve this issue?
You shouldn't be checking the ports directly on the container from outside of docker. If you want to access the container from the host or outside, you publish the port (as done above), and then access the port on the host IP (or 127.0.0.1 on the host in your first example).
For docker networking, you need to run your application listening on all interfaces (not localhost/loopback). The official redis image already does this, and you can verify with:
docker run --rm --net container:ausbot-ranksync-redis nicolaka/netshoot netstat -lnt
or
docker run --rm --net container:ausbot-ranksync-redis nicolaka/netshoot ss -lnt
To access the container from outside of docker, you need to publish the port (docker run -p ... or ports in the docker-compose.yml). Then you connect to the host IP and the published port.
To access the container from inside of docker, you create a shared network, run your containers there, and access using docker's DNS and the container port (publish and expose are not needed for this):
docker network create app
docker run --name ausbot-ranksync-redis --net app -d redis
docker run --name redis-cli --rm --net app redis redis-cli -h ausbot-ranksync-redis ping
I am running Docker for Mac. When I run
docker run -d --rm --name nginx -p 80:80 nginx:1.10.3
I can access Nginx on port 80 on my Mac. When I run
docker run -d --rm --name nginx --network host -p 80:80 nginx:1.10.3
I can not.
Is it possible to use both "--network host" and publish a port so that it is reachable from my Mac?
Alternatively, can I access Nginx from my Mac via the IP of the HyperKit VM?
Without the --network flag the container is added to the bridge network by default; which creates a network stack on the Docker bridge (usually the veth interface).
If you specify --network host the container gets added to the Docker host network stack. Note the container will share the networking namespace of the host, and thus all its security implications.
Which means you don't need to add -p 80:80, instead run...
docker run -d --rm --name nginx --network host nginx:1.10.3
and access the container on http://127.0.0.1
The following link will help answer the HyperKit question and the current limitations:
https://docs.docker.com/docker-for-mac/networking/
There is no docker0 bridge on macOS
Because of the way networking is implemented in Docker for Mac, you
cannot see a docker0 interface in macOS. This interface is actually
within HyperKit.
I am really confused about this problem. I have two computer in our internal network. Both computers can ping internal servers.
Both computers have same docker version.
I run simple docker container with docker run -it --rm --name cont1 --net=host java:8 command on both computers. Then ssh into containers and try to ping internal server. One of the container can ping an internal server but other one can't reach any internal server.
How it can be possible? Do you have any idea about that?
Thank you
connect container to other systems in the same network is done by port mapping .
for that you need to run docker container with port mapping.
like - docker run -it --rm --name cont1 -p host_ip:host_port:container_port java:8
e.g., docker run -it --rm --name cont1 -p 192.168.134.122:1234:1500 java:8
NOTE : container port given in docker run is exposed in Dockerfile
now for example container ip will be - 172.17.0.2 port given in run is :1500
Now the request send to host_ip(192.168.134.122) and host_port(1234) is redirect to container with ip (172.17.0.2) and port (1500).
See the binding details in iptables -L -n -t nat
Thanks
I'm trying to set up some docker container demo blogs but I'm having problems when I try to access more than one:
docker run --volumes-from my-data -p 80:8080 --name site1 tutum/wordpress
docker run --volumes-from my-data -p 80:8081 --name site2 tutum/wordpress
I can access the first one from myhost:8080 but I can't access the second one from myhost:8081
Is there anything obvious I'm missing?
Yes. The -p argument tells docker how to map external addresses to internal (container) addresses. You are instructing it to map port 80 of all host interfaces to port 8080/8081 of the respective container. Assuming the container processes really listen on port 8080/8081 you might want to try -p 8080:8080 / -p8081:8081. If the containers run standard webservers on port 80, you might want to use -p 8080:80 / -p 8081:80 instead. The proper port mapping will make the container service accessible on port 8080/8081 of all host interfaces.