I am running Kafka inside a Docker container. Kafka requires a connection to Zookeeper, and so I am running Zookeeper in another container. I am running Docker on OSX and so my VM has the IP address: 192.168.99.99.
What I can't figure out, is how do I update my Kafka Docker installation to point to the instance of Zookeeper running inside its own separate Docker container, i.e. with IP address of 192.168.99.9 and port 2181?
Kafka has a config file called server.properties which has a property of zookeeper.connect which I can set, but I want this value to be overridden dynamically, rather than hard-coding the IP here. How do I achieve this?
And, as an additional question, I want my Docker file to work across OS's - so whatever I do should work on Linux too..
You should not need to set an ip in that config file:
Through docker-compose v2 (docker 1.10+), a bridge network is created which means both containers are in that network and see each other.
See more at "Networking in Compose".
If Zookeeper expose its port 2181, the config file from Kafka can simply reference zookeeper by its container name.
And that will work on any docker (boot2docker on Mac or native docker on Linux)
Related
Hi what I am actually trying is to connect remotly from a MySQL Client in Windows Subsystem for Linux mysql -h 172.18.0.2 -P 3306 -u root -p and before that I started the Docker Container as follows: docker container run --name testdb --network testnetwork -p 3306:3306 -e MYSQL_ROOT_PASSWORD=mysqlRootPassword -e MYSQL_DATABASE=localtestdb -d mariadb/server.
The purpose why I put the container in a own network, is because I also have a dockerized Spring Boot Application (GraphQL-Server) which shall communicated with this db. But always when I try to connect from my built-in mysql client, in my Windows Subsystem for Linux, with the above shown command. I got the error message: ERROR 2002 (HY000): Can't connect to MySQL server on '172.18.0.2' (115).
What I already tried, to solve the problem on my own is, look up whether the configuration file line (bind-address) is commented out. But it wont work. Interestingly it already worked to set up a docker container with MariaDB and connect from the outside, but now when I try exactly the same, only with the difference that I now put the container in a own existing network, it wont work.
Hopefully there some one out there which is able to help me with this annonying problem.
Thanks!
So far,
Daniel
//edit:
Now I tried the solution advice from a guy from this topic: How to configure containers in one network to connect to each other (server -> mysql)?. Futhermore I linked my Spring Boot (server) application with the "--link databaseContainerName" parameter to the MariaDB container.
Now I am able to start both containers without any error, but I am still not able to connect remotly to the MariaDB container. Which is now running in a virtual docker network with his own subnet.
I explored this recently - this is by design - container isolation. Usually only main (service httpd) host is accessible externally, hiding internal connections (hosts it communicates to deliver response).
Container created in own network is not accessible from external adresses, even from containers in the same bridge but other network (172.19.0.0/16).
Your container should be accessible on docker host address (127.0.0.1 if run locally) and mapped ("-p 3306:3306") port - 3306. But of course it won't work if many running db containers have the same mapping to the same host port.
Isolation is done using firewall - iptables. You can list rules (iptables -L) to see that - from docker host level.
You can modify firewall to allow external access to internal networks. I used this rule:
iptables -A DOCKER -d 172.16.0.0/12 -j ACCEPT
After that your MySQL containerized engine should be accessible using internal address 172.18.0.2 and source (not mapped) port 3306.
Warnings
it disables all isolation, dont't use it on production;
you have to run this after every docker start - rules created/modified by docker on the fly
not every docker container will respond on ping, check it from docker host (linux subsystem in this case) first, from windows cmd later
I used this option (in docker.service) to make rule permanent:
ExecStartPost=/bin/sh -c '/etc/iptables/accept172_16.sh'
For docker on external(shared in lan) host you should use route add (or hosts file on your machine or router) to forward 172.x.x.x addresses into lan docker host.
Hint: use portainer project (with restart policy - always) to manage docker containers. It's easier to see config errors, too.
For testing purposes, I want to set up the kubernetes master to be only accessible from the local machine and not the outside. Ultimately I am going to run a proxy server docker container on the machine that is opened up to the outside. This is all inside a minikube VM.
I figure configuring kube-proxy is the way to go. I did the following
kubeadm config view > ~/cluster.yaml
# edit proxy bind address
vi ~/cluster.yaml
kubeadm reset
rm -rf /data/minikube
kubeadm init --config cluster.yaml
Upon doing netstat -ln | grep 8443 i see tcp 0 0 :::8443 :::* LISTEN which means it didn't take the IP.
I have also tried kubeadm init --apiserver-advertise-address 127.0.0.1 but that only changes the advertised address to 10.x.x.x in the kubeadm config view. I feel that is probably the wrong thing anyways. I don't want the API server to be inaccessible to the other docker containers that need to access it or something.
I have also tried doing this kubeadm config upload from-file --config ~/cluster.yaml and then attempting to manually restart the docker running kube-proxy.
Also tried to restart the machine/cluster after kubeadm config change but couldn't figure that out. When you reboot a minikube VM by hand kubeadm command disappears and not even docker is running. Various online methods of restarting things dont seem to work either (could be just doing this wrong).
Also tried editing the kube-proxy docker's config file (bound to a local dir) but that gets overwritten when i restart the docker. I dont get it.
There's nothing in the kubernetes dashboard that allows me to edit the config file of the kube-proxy either (since its a daemonset).
Ultimately, I wish to use an authenticated proxy server sitting infront of the k8s master (apiserver specifically). Direct access to the k8s master from outside the VM will not work.
Thanks
you could limit it via the local network configuration. (Firewall, Routes)
As far as I know, the API needs to be accessible, at least via the local network where the other nodes reside in. Except you want to have a single node "cluster".
So, when you do not have a different network card, where you could advertise or bind the address to, you need to limit it then by the above mentioned Firewall or Route rules.
To your initial question topic, did you look into this issue? https://github.com/kubernetes/kubernetes/issues/39586
According to the docker documentation here
https://docs.docker.com/network/host/
The host networking driver only works on Linux hosts, and is not supported on Docker for Mac, Docker for Windows, or Docker EE for Windows Server.
On Mac what alternatives do people use?
My scenario
I want to run a docker container that'll host a micro-service
The micro-service has dependencies upon databases that I'm also running via docker
I thought I'd be able to use --net=host on Mac when running the micro-service
But the micro-service port is not exposed
I can override the db addresses (they default to localhost) on the microservice.
But that involves robust --env usage
What's the simplest / most elegant solution?
The most simple and most elegant solution is to use docker named bridge network.
You can create a custom bridge network (default is bridge) like this:
docker network create my-network
Every container deployed inside this network can communicate with each other by using the container name.
$ docker run --network=my-network --name my-app ...
$ docker run --network=my-network --name my-database...
In the example above you can connect to your database from inside your application by using my-database:port. If the container port is exposed in the Dockerfile you don't need to map it on your host and you can keep all your communication internal inside your custom docker bridge network.
In most cases the application its port is mapped (example: -p 80:80) so localhost:80 is mapped on container:80 and you can access the app from on your localhost. If the app needs to communicate with a db you don't need to expose the port of the db and you don't have to map it on localhost as explained already above.
Just keep the communication between app and db internal in your custom bridge network.
In my job I working with docker and the option --net=host working like a charm forwarding the docker container ports to the machine. This allows me to adding grunt tasks that use certain ports by example:
A taks for serving my coverage report in a port 9001
A local deployed version of my app served in the port 9000
A watch live reload the port 35729
For Unit testing runner use the 9876 port
When I begin to use Docker in Mac, the first problem that i had was: The option --net=host don't work anymore.
I researched and I understand why this is not possible (Docker in Mac runs in a own virtual machine) and my momentary solution it's use the -p option for expose the ports, but this limit to me to add more and more task that use ports because i need run the explicit -p command for each port that i need expose.
Anyone with this same problem? How to dealing with this ?
Your issue is most probably that you are using dockertoolbox or dhingy/dlite or anything else providing a full-fledged linux VM, which then hosts docker to run your container inside this VM. This VM has, of course, its own network stack and own IP on the host, and thats were your tools will have issues with. The exposed ports of the container are not exposed to OSX host localhost, but rather OSX Docker-VM-ip.
To solve those issues elegantly
Expose ports to OSX localhost from the container
First, use/install docker-for-mac https://docs.docker.com/engine/installation/mac/ instead of dockertoolbox or others. Its based on a special xhyve stack which reuses your hosts network stack
when you now do docker run -p 3306:3306 percona it will bind 3306 on the osx-host-localhost, thus every other osx-tool trying to attach to localhost:3306 will work ( very useful ) just as you have been used to it when you installed mysql using brew install mysql or likewise
If you experience performance issues with code shares on OSX with docker containers, check http://docker-sync.io - it is compatible with docker-for-mac ( hint: i am biased on this one )
Export ports from the OSX-host to a containter
You do not really export anything in particular, you rather make them accessable as a whole from all containers ( all ports of the OSX-host-localhost)
If you want to attach to a port you offered on the OSX host, from within a container, e.g. during a xdebug session were your IDE listens on port 9000 on the OSX-host-localhost and the container running FPM/PHP should attach to this osx-localhost:9000 on the mac, you need to do this: https://gist.github.com/EugenMayer/3019516e5a3b3a01b6eac88190327e7c
So you create a dummy loopback ip, so you can access your OSX-host ports from without containers using 10.254.254.254:9000 - this is portable and basically gives you all you need to develop like you have used to
So one gives you the connectivity to container-exposed ports to apps running on the mac and trying to connect to localhost:port
And the second the inverse, if something in the container wants to attach to a port on the host.
One workaround, mentioned in "Bind container ports to the host" would be to use -P:
(or --publish-all=true|false) to docker run which is a blanket operation that identifies every port with an EXPOSE line in the image’s Dockerfile or --expose <port> commandline flag and maps it to a host port somewhere within an ephemeral port range.
The docker port command then needs to be used to inspect created mapping.
So if your app can use docker port <CONTAINER> to retrieve the mapped port, you can add as many containers as you want and get the mapped ports that way (without needed an "explicit -p command for each port").
Not sure if docker for mac can support bi-directional connection later https://forums.docker.com/t/will-docker-for-mac-support-bi-directional-connection-between-host-and-container-in-the-future/19871
I have two solution:
you can write a simple wrapper script and pass the port you want to expose to the script
use vagrant to start a virtual machine with network under control.
I have just attempted to move an app into a docker container using boot2docker on OS X.
This app requires to connect to a mysql server running on the host system (not in the app's container or in another container).
Now I'm struggling with configuring the mysql hostname within the "dockerized" app: So far it just connected to localhost, but this doesn't work anymore because this no longer points to the host mysql is actually running on.
As a quick workaround, I have added my workstations private IP (10.0.0.X in my case) to the app's mysql connection config.
However I wonder:
Is there an automatic way to find the host's private IP address from within a docker container?
You can provide the IP and port through environment variables to the contained application.
Create a script in your container like:
#!/bin/bash
export $MYSQL_HOST
export $MYSQL_PORT
echo $MYSQL_HOST
echo $MYSQL_PORT
# TODO: maybe your have to write some config files at this point
/start_your_app.sh # use the enviroment variables e.g. in your app config.
Run your containerimage with:
docker run -e MYSQL_HOST=192.168.172.1 MYSQL_PORT=3306 your_image
Have a look at e.g.
http://serverascode.com/2014/05/29/environment-variables-with-docker.html