I have a docker-compose that spins up 2 Docker containers. One is an application (on port:8090) and the other is a database (on port:5432). I also have a Windows application that has an API accessible through localhost:8002. I want to use my container that has the application to read data from the localhost:8002 API, then move that data to my database in my other Docker container.
For docker-compose, I mapped port 5432:5432 and port 8090:8090 for the database and application containers, respectively. I have tested my application non-dockerized where I call the Windows API and then write it to port:5432 and it works properly.
However, after Dockerizing my application, localhost:8002 is now no longer localhost for my Dockerized application and is now unreachable. I am wondering how I can reach my host localhost:8002, hit that API, then move that data to my other container.
After 16 hours of blood, sweat, and tears. Mostly tears, here's the answer for whoever may be using this in the future.
TL;DR expose your local nat network to your docker containers in docker-compose by:
networks:
default:
external: true
name: nat
Note, on Windows, running a docker network ls should give something like:
NETWORK ID NAME DRIVER SCOPE
6b30a7dcf6e0 Default Switch ics local
26305680ad62 WSL ics local
b52f5e497eba nat nat local
4a4fd550398f none null local
The docker-compose is simply connecting the docker network to your host network (required for auto-restart of containers after computer restarts as well, but off-topic).
Afterwards, I had to run an ipconfig to find the IPv4 port that corresponds to my nat port. Here, there can be many IPv4 IP addresses, find the one that says Ethernet adapter vEthernet (nat).
Then, use the IPv4 Address corresponding to the nat network for any applications running on your local machine.
For example, my application ran on localhost:8002. Here, I changed my host to http://172.31.160.1:8002 and it worked.
Related
Here is my situation：
First，I run a MySQL container(IP:172.17.0.2) on centOS;
Then I run a Nacos contanier with specified datasource(MySQL above) on the same host, but i didn't use the ip of the MySQL container, instead I used the ip of the bridge Gateway(172.17.0.1)(two containers both link to the default bridge).
What surprised me was that Nacos works well, it can query config data from MySQL container normally.
How did this happen? I have read some documention but didn't get the answer.It really confused me.
On modern Docker installations, try to avoid using the default bridge network. docker network create a network (it doesn't need any special options, but it does need to be created) and then launch your containers on --net that network. If you're using Compose, it creates a ("user bridge") network named default for you.
On your CentOS host, if you run ifconfig, you should see a docker0 interface with the 172.17.0.1 address. When you launch a container with the docker run -p option, that container is accessible via the first port number on all host interfaces, including the docker0 interface.
Meanwhile, inside a container (on the default bridge network), it sees that same IP address as the normal IPv4 gateway address (try docker run --rm busybox route -n). So, when you connect to 172.17.0.1:3306, you're connecting out to the host, and then connecting to the published port of the database container.
This isn't a totally standard way to connect between containers, though it will work. You should prefer using Docker named networks, which will let you connect to another container using the container's name without manually doing any IP-address lookups. If you really can't move off of the default bridge network, then the standard approach is to --link to the other container, but this entire path is considered outdated.
I'm trying to better understand docker networking, but I'm confused by the following:
I spin up 2 contains via docker-compose (client, api). When I do this, a new network is created, myapp_default, and each container joins this network. The network is a bridge network, and it's at 172.18.0.1. The client is at 172.18.0.2 and the api is at 172.18.0.3.
I can now access the client at 172.18.0.2:8080 and the api at 172.18.0.3:3000 -- this makes total sense. I'm confused when I publish ports in docker-compose: 8080:8080 on the client, and 3000:3000 on the api.
Now I can access the containers from:
Client at 172.18.0.1:8080, 172.18.0.2:8080, and on the docker0 network at 172.17.0.1:8080
API at 172.18.0.1:3000, 172.18.0.3:8080, and on the docker0 network at 172.17.0.1:3000
1) Why can I access the client and api via the docker0 network when I publish ports?
2) Why can I connect to containers via 172.17.0.1 and 172.18.0.1 at all?
You can only access the container-private IP addresses because you're on the same native-Linux host as the Docker daemon. This doesn't work in any other environment (different hosts, MacOS or Windows hosts, environments like Docker Toolbox where Docker is in a VM) and even using docker inspect to find these IP addresses usually isn't a best practice.
When you publish ports they are accessible on the host at those ports. This does work in every environment (in Docker Toolbox "the host" is the VM) and is the recommended way to access your containers from outside Docker space. Unless you bind to a specific address, the containers are accessible on every host interface and every host IP address; that includes the artificial 172.17.0.1 etc. that get created with Docker bridge networks.
Publishing ports is in addition to the other networking-related setup Docker does; it doesn't prevent you from reaching the containers by other paths.
If you haven't yet, you should also read Networking in Compose in the Docker documentation. Whether you publish ports or not, you can use the names in the docker-compose.yml file like client and api as host names, connecting the the (unmapped) port the actual server processes are listening on. Between this functionality and what you get from publishing ports you don't ever actually need to directly know the container-private IP addresses.
I deployed a demo web API project on port 8086.I am able to run it on my local browser using localhost:8086/api/controllername and also using local machine IP address for example: 192.0.0.0:8086/api/controllername. I tried accessing the URL from another machine on same LAN and I am able to access it.
But now I want to access it from machines on other networks (publicly).
How can I assign a static IP so that I can use the API from any machine irrespective of network? I created a network using below commands
docker network create --driver bridge --subnet 172.18.0.0/16 -- gateway=172.18.0.1 IPStatic
and
docker network connect --ip 172.18.0.2 IPStatic Containerid.
But unable to access the api using 172.18.0.2:8086/api. Am I missing something? I am using asp.net core web api and I am fairly new to Docker.
You always use the host IP address for this, the same way as if you were running the service outside of Docker. The container-private IP addresses are unreachable from other hosts (and on some platforms aren't even reachable from outside Docker on the same host); it's usually wrong to manually set them or to try to look them up.
If it's specifically important that this service have its own IP address, you need to ask your network administrator to assign an additional address to the host. The docker run -p option can bind a service to only specific network interfaces or addresses. On a Linux host I might run
# Assign the alias address
ifconfig eth0:0 192.0.0.2
# Run the service bound to only this interface
docker run -p 192.0.0.2:80:8080 ...
You might need to reconfigure other services to not listen on this new interface. For Docker services you'd use the same docker run -p option to bind to only the host's primary interface and to localhost (127.0.0.1); configuration for non-Docker services is specific to the service.
i want to expose the container ip to the external network where the host is running so that i can directly ping the docker container ip from an external machine.
If i ping the docker container ip from the external machine where the machine hosting the docker and the machine from which i am pinging are in the same network i need to get the response from these machines
Pinging the container's IP (i.e. the IP it shows when you look at docker inspect [CONTAINER]) from another machine does not work. However, the container is reachable via the public IP of its host.
In addition to Borja's answer, you can expose the ports of Docker containers by adding -p [HOST_PORT]:[CONTAINER_PORT] to your docker run command.
E.g. if you want to reach a web server in a Docker container from another machine, you can start it with docker run -d -p 80:80 httpd:alpine. The container's port 80 is then reachable via the host's port 80. Other machines on the same network will then also be able to reach the webserver in this container (depending on Firewall settings etc. of course...)
Since you tagged this as kubernetes:
You cannot directly send packets to individual Docker containers. You need to send them to somewhere else that’s able to route them. In the case of plain Docker, you need to use the docker run -p option to publish a port to the host, and then containers will be reachable via the published port via the host’s IP address or DNS name. In a Kubernetes context, you need to set up a Service that’s able to route traffic to the Pod (or Pods) that are running your container, and you ultimately reach containers via that Service.
The container-internal IP addresses are essentially useless in many contexts. (They cannot be reached from off-host at all; in some environments you can’t even reach them from outside of Docker on the same host.) There are other mechanisms you can use to reach containers (docker run -p from outside Docker, inter-container DNS from within Docker) and you never need to look up these IP addresses at all.
Your question places a heavy emphasis on ping(1). This is a very-low-level debugging tool that uses a network protocol called ICMP. If sending packets using ICMP is actually core to your workflow, you will have difficulty running it in Docker or Kubernetes. I suspect you aren’t actually. Don’t worry so much about being able to directly ping containers; use higher-level tools like curl(1) if you need to verify that a request is reaching its container.
It's pretty easy actually, assuming you have control over the routing tables of your external devices (either directly, or via your LAN's gateway/router). Assuming your containers are using a bridge network of 172.17.0.0/16, you add a static entry for the 172.17.0.0/16 network, with your Docker physical LAN IP as the gateway. You might need to also allow this forwarding in your Docker OS firewall configuration.
After that, you should be able to connect to your docker container using its bridge address (172.17.0.2 for example). Note however that it will likely not respond to pings, due to the container's firewall.
If you're content to access your container using only the bridge IP (and never again use your Docker host IP with the mapped-port), you can remove port mapping from the container entirely.
You need to create a new bridge docker network and attach the container to this network. You should be able to connect by this way.
docker network create -d bridge my-new-bridge-network
or
docker network create --driver=bridge --subnet=192.168.0.0/16 my-new-bridge-network
connect:
docker network connect my-new-bridge-network container1
or
docker network connect --ip 192.168.0.10/16 my-new-bridge-network container-name
If the problem persist, just reload docker daemon, restart the service. Is a known issue.
I'm using a Digital Ocean docker droplet and have 3 docker containers: 1 for front-end, 1 for back-end and 1 for other tools with different dependencies, let's call it back-end 2.
The front-end calls the back-end 1, the back-end 1 in turn calls the back-end 2. The back-end 2 container exposes a gRPC service over port 50051. Locally, by running the following command, I was able to identify the docker service to be running with the IP 127.17.0.1:
docker network inspect bridge --format='{{json .IPAM.Config}}'
Therefore, I understand that my gRPC server is accessible from the following url 127.17.0.1:50051 within the server.
Unfortunately, the gRPC server refuses connections when running from the docker droplet while it works perfectly well when running locally.
Any idea what may be different?
You should generally set up a Docker private network to communicate between containers using their container names; see e.g. How to communicate between Docker containers via "hostname". The Docker-internal IP addresses are subject to change if you delete and recreate a container and aren't reachable from off-host, and trying to find them generally isn't a best practice.
172.17.0.0/16 is a typical default for the Docker-internal IP network (127.0.0.0/8 is the reserved IPv4 loopback network) and it looks like you might have typoed the address you got from docker network inspect.
Try docker run with following command:
docker run -d -p {server ip}:12345 {back-end 2 image}
It will expose IP port to docker container and will be accessible from other servers.
Note: also check firewall rules, if firewall is blocking access.
You could run docker binding to ip and port as shown by Aakash. Please restrict access to this specific IP and port to be accessed only from the other docker IP and port - this will help to run docker private and doesn't allow other (even the other docker/instances within your network).