I'm new to Docker and I'm doing the Get-Started part of the documentation, but I got stuck in step 4, I do not make mistakes when doing this step, but when I enter the ip 192.168.99.100 it does not show me anything. I hope you can help me THANK YOU.docker info
Angel, I do not know which step or docs you're talking about (adding links would help a lot), but there's only one way to start a Docker Swarm
docker swarm init
You may also specify the IP of the machine you're starting the swarm in if it has more than one network interface:
docker swarm init --advertise-addr <ip-where-you-want-the-node-to-listen-to-swarm-events>
I would really recommend you do not use docker toolbox, instead use Play With Docker, where you'll be able to spawn nodes and try stuff around without needing to configure anything.
Related
Say we provision an overlay network using docker swarm and create various containers with following names:
Alice
Bob
Larry
John
now if we try to ping any container from another it fails because it does not know how to do the IP lookup i.e., alice does not know bob's IP and so on. We have been taking care of this by manually editing the /etc/hosts on every container and entering the name/IP key value pair in that file but this is becoming very tedious with every restart of our network. There ought to be a better way of handling this.
E.g., services created using docker stack do not suffer from this problem. Due to various reasons we are stuck with creating containers using the vanilla docker create. How can we make containers discover each other on the overlay network without manual labor of editing /etc/hosts?
Below is detailed workflow we currently have to follow:
we first provision a docker swarm and overlay network
Then for each container, we create it using the docker create command and then start it using docker start command. we use the --network flag to attach the container to the overlay network at time of creation
We then use docker container inspect to get the IP address of each container. This involves running n commands and noting down IP address.
Then we log into each container and edit the /etc/hosts file by hand and enter the (name, IP) key-value pair of the other containers. So this means having to enter n*(n-1) records by hand when summed across containers.
Not sure why docker create does not do all this automatically - docker already knows (or can know) all the IP addresses. Containers provisioned using docker stack e.g., do not have to go through this manual process to "discover" each other. The reason why we cannot use docker stack is because:
it does not allow us to specify container name
we run various commands (mostly docker cp) before starting the container and not possible to do this using stack
You might have seen this already: DNS on User defines networks
Have you created your services like in the section „Attach a service to an overlay“ in this doc?
It seems that the only thing that is needed is to refer the containers by their {name}.{network} instead of just the {name}. No need to edit /etc/hosts or use the --add-host flag or run some additional dns server. Refer https://forums.docker.com/t/need-help-connecting-containers-in-swarm-mode/77944/6
Further details: the official documentation for docker does not mention anywhere the necessity to add .{network} suffix to the {containername}. Indeed on this link, Step #7 under the Walk-through, there is no .{network} suffix used. So not sure why we need to do that. The version of docker we are using is 18.06.1-ce for linux.
I had a similar issue : I'm following this official tutorial to create a docker swarm overlay network on two Raspberry pi 3 and the ping was impossible unless I found on Github the answer : as I understood, it seems that latest version of alpine (for a reason that I ignore) is not suitable for Raspberry pi 3 so the solution would be the use of the version 3.12.3 like this : sudo docker run -dit --name alpine1 --network test1 alpine:3.12.3
Hope that this might help someone :)
is there any way to disable/leave the swarm mode of docker when starting the daemon manually, e.g. dockerd --leave-swarm, instead of starting the daemon and leave the swarm mode afterwards, e.g. using docker swarm leave?
Many thanks in advance,
Aljoscha
I don't think this is anticipated by docker developers. When node leaves swarm, it needs to notify swarm managers, that it will not be available anymore.
Leaving swarm is a one time action and passing this as an configuration option to the daemon is weird. You may try to suggest that on docker's github, but I don't think it will have much supporters.
Perhaps more intuitive option would be to have ability to start dockerd in a way that communication to docker swarm manager would be suspended - so your dockerd is running only locally, but if you start without that flag (--local?) it would reconnect to swarm that it was attached before.
I currently have three hosts (docker1, docker2 and docker3) which I have not set up using Docker Machine, each one running the v1.12-rc4 Docker daemon.
I run docker swarm init on docker1, which in turn prints a docker swarm join command which I run on both docker2 and docker3. At that point, running docker info on each host contains the Swarm: active line.
It is at this point that the behavior seems to differ from what I used to get with the standalone Swarm container. Especially, running docker network ls will only show me the networks on the local host, and when trying to create an overlay network, it does not seem like worker nodes are aware of it (i.e. it does not show up on their docker network ls.)
I feel like I have missed out on some important information relating to the workings of the Swarm Mode as opposed to the Swarm container.
What is the correct way of setting up such a cluster without Docker Machine on Docker 1.12 while getting the overlay network feature?
I too thought this was an issue when I first started using it.
This works a little differently in 1.12rc4 - when you deploy a container to your swarm with that network attached to it, it should then create the network on the other nodes as well.
Hope this helps!
Issue
You are using the docker command (used to communicate with your localhost Docker daemon) and not the "swarm" command (used to communicate with the Swarm master).
Solution
It depends on the command you used to start Swarm.
A full step-by-step tutorial (including details on how to deploy an overlay network) is detailled on this answer. I'm sure that reading this will help you ;)
With a network scope of swarm, the network is only propagated to worker nodes on an as-needed basis. If you create a service using that network, and it gets scheduled on that worker node, the network will show up in the docker network ls.
With the now-upcoming 1.13 release, you can get a network that has similar behavior to the non-swarm networks by doing docker network create --attachable .... That network will be valid for both services and normal containers, and will be available to all members of the cluster. As of 1.13.0-rc2, those don't seem to show up in the output of docker network ls.
I have a silly question regarding docker swarm.
I am thinking I can start a web application image in two containers, either in same server or two vm servers, then I start a load balance container, pointing to two web app containers through IP and port.
In this case, why do I need docker swarm for clustering management? What benefits can docker swarm bring?
I have read from docker documentation, they only introduce what is swarm and how to use swarm. But I can not find out answer for why I have to use swarm.
Thanks
What is swarming managing? turns a pool of Docker hosts into a single, virtual Docker host.
Can swarm auto-start the container if the container died? Yes it can, so can the Docker daemon on each host.
Can swarm auto-create more nodes if the resource is not enough? No it cannot. It does not aims on providing this service. Nevertheless you can program a node that start and run containers when needed.
Which mean, if traffic grows fast, do we still manually create more node and deploy more containers? Yes, unfortunately.
update
If needed, here is an answer that details how to deploy a Swarm cluster.
It is default way that the IP of a docker container will change after restarting it. I am confused why this is suggested in designing docker. Is it more reasonable to retain the IP with a simple restart? This should be distinguished from creating a new container.
IP of a docker container gets changed after a restart as of now, but the community is working here on this highly demanded feature. Meanwhile I am using pipework to assign specific IP to my docker container.
pipework docker-bridge-name-here docker-container-name 10.1.1.110/24#10.1.1.1
The only drawback is that you'll have to do it every time you restart docker.