Currently I have a bunch of RHEL7 VMs running on RackSpace and want to deploy docker swarm for testing purpose. The Docker Docs only describes the method to deploy docker swarm by using docker machine.
Question:
Since VirtualBox cannot be used in VMs, are any other ways such that I can directly deploy docker swarm on my VMs without using docker machine?
In fact Docker documentation offers you how to set up a swarm cluster 'manually' without using docker-machine: Create a swarm for development
I think that this full step-by-step tutorial might be useful.
It details how to deploy Swarm with a multi-hosts network, without Docker-machine by using consul and suggest two different means for the Swarm agent discovery (static file and token).
Related
I've managed to run Docker Swam mode with multiple hosts with Docker Toolbox, but I am unable to create a swarm with Docker Desktop since it apparently only offers single node swarm.
Is there any way to get this working with Docker Desktop or is it not supported?
No. But yes. But actually no. But technically yes.
No. Docker Desktop does not support this. It manages a single docker node in a vm and has no capability to manage multiple dockers.
But yes. docker:dind is an image you can easily use to deploy multiple docker nodes as containers, and then swarm init / swarm join to create a swarm cluster hosted on docker. You can even swarm join the docker-desktop node to be the swarm manager which means you can communicate with your local docker desktop node to control the swarm.
But actually, no.
Unless your use case is a very limited hello-world on swarm tutorial, there is no support for exposing ports from the dind-swarm to the host. Even if the host docker acts as the manager, overlay networking that is required for ingress will require communications over :2377, :4789/udp, and :7946, and as the host is not part of its own overlay networks, this will never work.
So, communicating with tasks running on the swarm is basically impossible.
But technically yes. play-with-docker apparently runs docker swarms using dind. They do some heavy lifting to expose a restricted set of ports via l7 loadbalancers. Pretty cool. but not at all easy to do at home. If you have a spare Dell PowerEdge or equivalent blade server with 120+ cores just laying around, and want to expose it as a docker swarm rather than split it into VMS... perhaps this is a viable approach.
I am using the latest docker for mac (17.09.0-ce), when I run docker-machine create --help it says
...
--swarm-master Configure Machine to be a Swarm master
But the document here said "run docker swarm init to enable swarm mode and make your current machine a swarm manager"
So what is the difference between swarm master and swarm manager?
------ update -------
I found this so post explained it all, Need for service discovery for docker engine swarm mode
These are two different implementations of Swarm, with slightly different terminology.
The docker-machine command is configuring the classic container-based Swarm. You can find it on docker hub. This version of swarm is more like a reverse proxy to the various docker engines.
The docker swarm init command enables Swarm Mode that is now included with the docker engine. Swarm Mode is closer in features to Kubernetes and provides orchestration. You will most likely want Swarm Mode, classic Swarm is being preserved for historical reasons and special use cases.
i'm learning about docker swarm, and got confused about the swarm discovery option, i see that lots of tutorials on internet use this option to create containers with docker-machine, but when i enter the documentation on docker swarm doc it says:
You are viewing docs for legacy standalone Swarm. These topics describe standalone Docker Swarm. In Docker 1.12 and higher, Swarm mode is integrated with Docker Engine. Most users should use integrated Swarm mode.
So, what are the use cases for the discovery options? All the tutorials use the docker-machine to create a swarm, i always need it or can just install the docker on machines in my cluster, join them in swarm and use normal?
I saw some names like Docker Swarm and Docker Swarm Mode, are there any difference or just different ways to call the same feature?
Q. Docker Swarm discovery is still relevant?
A: No, if you use docker Swarm Mode and an overlay network (see below)
Q. Are there any difference between Docker Swarm and Docker Swarm Mode?
A: Yes, TL;DR Docker Swarm is deprecated and should not be used anymore, Docker Swarm Mode (we should just say Swarm Mode) is the recommended way of clustering containers and have reliability, load-balancing, scaling, and rolling service upgrades.
Docker Swarm (official doc) :
is the old fashioned way (<1.12) of clustering containers
uses a dedicated container for building a Docker Swarm cluster
needs a discovery service like Consul to reference containers in cluster
Swarm Mode (official doc):
is the new and recommended way (>=1.12) of clustering containers on host nodes (called managers / workers)
is built-in in Docker engine, you don't need an additional container
has a built-in discovery service if you use an overlay network (DNS resolution is done within this network), you don't need an additional container
You can have a look to this SO thread on same topic.
Q. Do i always need docker-machine to create a swarm?
A: No, docker-machine is a helper to create virtual hosts in the cloud like amazon ec2, azure, digitalocean, google, openstack..., or your own network with virtual box.
To create a Swarm Mode, you need :
a multiple hosts cluster with docker engine installed on each host (called node) (that is what docker-machine facilitates)
run docker swarm init to switch to Swarm Mode on your first manager node
run docker swarm join on worker nodes to add them in the cluster
There are some subtle adjustments to Swarm mode to increase high availability (recommended number of managers in the swarm, node placement in multiple availability zones in the cloud)
Hope this helps!
After looking through docker official swarm explanations, github issues and stackoverflow answers im still at a loss on why i am having the problem that i have.
Issue at hand: docker-compose up starts services not in the swarm even though swarm is active and has 2 nodes.
Im using 1.12.1 docker version.
Looking at swarm tutorial i was able to start and scale my swarm using docker service create without any issues.
running docker-compose up with version 2 docker-compose.yml results in services starting outside of swarm, i can see them through docker ps but not docker service ls
I can see that docker-machine as the tool that solves this problems, but then again it needs virtual box to be installed.
so my questions would be
Can i use docker-compose with docker-swarm (NOT docker-engine) without docker-machine and without experimental build bundle functionality?
If docker service create can start a service on any nodes is it an indication that network configuration of the swarm is correct ?
What is the advantages/disadvantages of docker-machine versus experimental build functionality
1) No. Docker Compose isn't integrated with the new Swarm Mode yet. Issue 3656 in GitHub is tracking that. If you start containers on a swarm with Docker Compose at the moment, it uses docker run to start containers, which is why you see them all on one node.
2) Yes. Actually you can use docker node ls on the manager to confirm all the nodes are up and active, and docker node inspect to check a particular node, you don't need to create a service to validate the swarm.
3) Docker Machine is also behind the 1.12 release, so if you start a swarm with Docker Machine it will be the 'old' type of swarm. The old Docker Swarm product needed a whole lot of extra setup for a key-value store, TLS etc. which Swarm Mode does for free.
1) You can't start services using docker-compose on the new Docker "Swarm Mode". There's a feature to convert a docker-compose file to the new dab format which is understood by the new swarm mode but that's incomplete and experimental at this point. You basically need to use bash scripts to start services at the moment.
2) The nodes in a swarm (swarm mode) interact using their own overlay network. It's the one named ingress when you do docker network ls. You need to setup your own overlay network to run services in. eg:
docker network create -d overlay mynet
docker service create --name serv1 --network mynet nginx
3) I'm not sure what feature you mean by "experimental build'. docker-machine is just a way to create hosts (the nodes). It facilitates the setting up of the docker daemon on each host, the certificates and allows some basic maintenance (renewing the certs, stopping/starting a host if you're the one who created it). It doesn't create services, volumes, networks or manages them. That's the job of the docker api.
Looking at Rancher, what is the performance like? I guess my main question, is everything deployed in Rancher docker in docker? After reading http://jpetazzo.github.io/2015/09/03/do-not-use-docker-in-docker-for-ci/ I trying to stay away from that idea. It looks like the Rancher CI pipeline with Docker/Jenkins is docker in docker, but what about the rest? If i setup a docker-compose or deploy something from their catalog, is it all docker in docker? I've read through their documentation and this simple question has still just flown over my head. Any guidance would be much appreciated.
Thank you
Rancher itself is not deployed with Docker in Docker (DinD). The main components of Rancher, rancher/server and rancher/agent are both normal containers. The server, in a normal deployment, runs the orchestration piece and a few other key services for the catalog, Docker Machine provisioning, websocket-proxy and MySQL. All of these can be broken out if desired, but for simplicity of getting started, its all in one. We use s6 to manage the orchestration and database processes.
The rancher/agent container is privileged and requires the user to bind mount the hosts Docker socket. We package a Docker binary in the container and use it to communicate with the host on startup. It is similar to the way a Mac talks to Boot2docker, the binary is just a client talking to a remote Docker daemon. Once the agent is bootstrapped, it communicates back to the Rancher server container over a websocket connection. When containers and stacks are deployed Rancher server sends events to the agents which then call the hosts Docker daemon for deployment. The deployed containers are running as normal Docker containers on the host, just as if the user typed docker run .... In fact, a neat feature of Rancher is that if you do type docker run ... on the host, the resulting container will show up in the Rancher UI.
The Jenkins entry in the Rancher catalog, when using the Swarm plugin is doing a host bind mount of the Docker socket as well. We have some early experiments that used DinD to test out some concepts with Jenkins, but those were not released.