When you execute the docker runcommand, be sure to add --net myapp.
Here is a full step-by-step tutorial (online version):
How to deploy swarm on a cluster with multi-hosts network
TL;DR: step-by-step tutorial to deploy a multi-hosts network using Swarm. I wanted to put online this tutorial ASAP so I didn’t even take time for the presentation. The markdown file is available on the github of my website. Feel free to adapt and share it, it is licensed under a Creative Commons Attribution 4.0 International License.
Prerequisites
Environment
- Tutorial done with docker engine 1.9.0.
- Swarm agents are discovered through a shared file (other methods are available).
- Consul 0.5.2 is used for discovery for the multi-hosts network swarm containers.
Swarm manager and consul master will be run on the machine named bugs20. Other nodes, bugs19, bugs18, bugs17 and bugs16, will be swarm agents and consul members.
Before we start
Consul is used for the multihost networking, any other key-value store can be used — note that the engine supports Consul Etcd, and ZooKeeper.
Token (or static file) are used for the swarm agents discovery. Tokens use REST API, a static file is preferred.
The network
The network is range 192.168.196.0/25. The host named bugsN has the IP address 192.168.196.N.
The docker daemon
All nodes are running docker daemon as follow:
/usr/bin/docker daemon -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock --cluster-advertise eth0:2375 --cluster-store consul://127.0.0.1:8500
Options details:
-H tcp://0.0.0.0:2375
Binds the daemon to an interface to allow be part of the swarm cluster. An IP address can obviously be specificied, it is a better solution if you have several NIC.
--cluster-advertise eth0:2375
Defines the interface and the port of the docker daemon should use to advertise itself.
--cluster-store consul://127.0.0.1:8500
Defines the URL of the distributed storage backend. In our case we use consul, though there are other discovery tools that can be used, if you want to make up your mind you should be interested in reading this service discovery comparison.
As consul is distributed, the URL can be local (remember, swarm agents are also consul members) and this is more flexible as you don’t have to specify the IP address of the consul master and be selected after the docker daemon has been started.
The aliases used
In the following commands these two aliases are used:
alias ldocker="docker -H tcp://0.0.0.0:2375"
alias swarm-docker="docker -H tcp://0.0.0.0:5732" #used only on the swarm manager
Be sure to have the path of the consul binary in your $PATH. Once you are in the directory just type export PATH=$PATH:$(pwd) will do the trick.
It is also assumed that the variable $IP has been properly set and exported. It can be done, thanks to .bashrc or .zshrc or else, with something like this:
export IP=$(ifconfig |grep "192.168.196."|cut -d ":" -f 2|cut -d " " -f 1)
Consul
Let’s start to deploy all consul members and master as needed.
Consul master (bugs20)
consul agent -server -bootstrap-expect 1 -data-dir /tmp/consul -node=master -bind=$IP -client $IP
Options details:
agent -server
Start the consul agent as a server.
-bootstrap-expect 1
We expect only one master.
-node=master20
This consul server/master will be named “master20”.
-bind=192.168.196.20
Specifies the IP address on which it should be bound. Optional if you have only one NIC.
-client=192.168.196.20
Specifies the RPC IP address on which the server should be bound. By default it is localhost. Note that I am unsure about the necessity of this option, and this force to add -rpc-addr=192.168.196.20:8400 for local request such as consul members -rpc-addr=192.168.196.20:8400 or consul join -rpc-addr=192.168.196.20:8400 192.168.196.9 to join the consul member that has the IP address 192.168.196.9.
Consul members (bugs{16..19})
consul agent -data-dir /tmp/consul -node=$HOSTNAME -bind=192.168.196.N
It is suggested to use tmux, or similar, with the option :setw synchronize-panes on so this one command: consul -d agent -data-dir /tmp/consul -node=$HOST -bind=$IP starts all consul members.
Join consul members
consul join -rpc-addr=192.168.196.20:8400 192.168.196.16
consul join -rpc-addr=192.168.196.20:8400 192.168.196.17
consul join -rpc-addr=192.168.196.20:8400 192.168.196.18
consul join -rpc-addr=192.168.196.20:8400 192.168.196.19
A one line command can be used too. If you are using zsh, then consul join -rpc-addr=192.168.196.20:8400 192.168.196.{16..19} is enough, or a foor loop: for i in $(seq 16 1 19); do consul join -rpc-addr=192.168.196.20:8400 192.168.196.$i;done. You can verify if your members are part of your consul deployment with the command:
consul members -rpc-addr=192.168.196.20:8400
Node Address Status Type Build Protocol DC
master20 192.168.196.20:8301 alive server 0.5.2 2 dc1
bugs19 192.168.196.19:8301 alive client 0.5.2 2 dc1
bugs18 192.168.196.18:8301 alive client 0.5.2 2 dc1
bugs17 192.168.196.17:8301 alive client 0.5.2 2 dc1
bugs16 192.168.196.16:8301 alive client 0.5.2 2 dc1
Consul members and master are deployed and working. The focus will now be on docker and swarm.
Swarm
In the following the creation of swarm manager and swarm members discovery are detailed using two different methods: token and static file. Tokens use a hosted discovery service with Docker Hub while static file is just local and does not use the network (nor any server). Static file solution should be preferred (and is actually easier).
[static file] Start the swarm manager while joining swarm members
Create a file named /tmp/cluster.disco with the content swarm_agent_ip:2375.
cat /tmp/cluster.disco
192.168.196.16:2375
192.168.196.17:2375
192.168.196.18:2375
192.168.196.19:2375
Then just start the swarm manager as follow:
ldocker run -v /tmp/cluster.disco:/tmp/cluster.disco -d -p 5732:2375 swarm manage file:///tmp/cluster.disco
And you’re done !
[token] Create and start the swarm manager
On the swarm master (bugs20), create a swarm:
ldocker run --rm swarm create > swarm_id
This create a swarm and save the token ID in the file swarm_id of the current directory. Once created, the swarm manager need to be run as a daemon:
ldocker run -d -p 5732:2375 swarm manage token://`cat swarm_id`
To verify if it is started you can run:
ldocker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
d28238445532 swarm "/swarm manage token:" 5 seconds ago Up 4 seconds 0.0.0.0:5732->2375/tcp cranky_liskov
[token] Join swarm members into the swarm cluster
Then the swarm manager will need some swarm agent to join.
ldocker run swarm join --addr=192.168.196.16:2375 token://`cat swarm_id`
ldocker run swarm join --addr=192.168.196.17:2375 token://`cat swarm_id`
ldocker run swarm join --addr=192.168.196.18:2375 token://`cat swarm_id`
ldocker run swarm join --addr=192.168.196.19:2375 token://`cat swarm_id`
std[in|out] will be busy, these commands need to be ran on different terminals. Adding -d abefore the join should solve this and enables a for-loop to be used for the joins.
After the join of the swarm members:
auzias@bugs20:~$ ldocker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
d1de6e4ee3fc swarm "/swarm join --addr=1" 5 seconds ago Up 4 seconds 2375/tcp fervent_lichterman
338572b87ce9 swarm "/swarm join --addr=1" 6 seconds ago Up 4 seconds 2375/tcp mad_ramanujan
7083e4d6c7ea swarm "/swarm join --addr=1" 7 seconds ago Up 5 seconds 2375/tcp naughty_sammet
0c5abc6075da swarm "/swarm join --addr=1" 8 seconds ago Up 6 seconds 2375/tcp gloomy_cray
ab746399f106 swarm "/swarm manage token:" 25 seconds ago Up 23 seconds 0.0.0.0:5732->2375/tcp ecstatic_shockley
After the discovery of the swarm members
To verify if the members are well discovered, you can execute swarm-docker info:
auzias@bugs20:~$ swarm-docker info
Containers: 4
Images: 4
Role: primary
Strategy: spread
Filters: health, port, dependency, affinity, constraint
Nodes: 4
bugs16: 192.168.196.16:2375
└ Containers: 0
└ Reserved CPUs: 0 / 12
└ Reserved Memory: 0 B / 49.62 GiB
└ Labels: executiondriver=native-0.2, kernelversion=3.16.0-4-amd64, operatingsystem=Debian GNU/Linux 8 (jessie), storagedriver=aufs
bugs17: 192.168.196.17:2375
└ Containers: 0
└ Reserved CPUs: 0 / 12
└ Reserved Memory: 0 B / 49.62 GiB
└ Labels: executiondriver=native-0.2, kernelversion=3.16.0-4-amd64, operatingsystem=Debian GNU/Linux 8 (jessie), storagedriver=aufs
bugs18: 192.168.196.18:2375
└ Containers: 0
└ Reserved CPUs: 0 / 12
└ Reserved Memory: 0 B / 49.62 GiB
└ Labels: executiondriver=native-0.2, kernelversion=3.16.0-4-amd64, operatingsystem=Debian GNU/Linux 8 (jessie), storagedriver=aufs
bugs19: 192.168.196.19:2375
└ Containers: 4
└ Reserved CPUs: 0 / 12
└ Reserved Memory: 0 B / 49.62 GiB
└ Labels: executiondriver=native-0.2, kernelversion=3.16.0-4-amd64, operatingsystem=Debian GNU/Linux 8 (jessie), storagedriver=aufs
CPUs: 48
Total Memory: 198.5 GiB
Name: ab746399f106
At this point swarm is deployed and all containers run will be run over different nodes. By executing several:
auzias@bugs20:~$ swarm-docker run --rm -it ubuntu bash
and then a:
auzias@bugs20:~$ swarm-docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
45b19d76d38e ubuntu "bash" 6 seconds ago Up 5 seconds bugs18/boring_mccarthy
53e87693606e ubuntu "bash" 6 seconds ago Up 5 seconds bugs16/amazing_colden
b18081f26a35 ubuntu "bash" 6 seconds ago Up 4 seconds bugs17/small_newton
f582d4af4444 ubuntu "bash" 7 seconds ago Up 4 seconds bugs18/naughty_banach
b3d689d749f9 ubuntu "bash" 7 seconds ago Up 4 seconds bugs17/pensive_keller
f9e86f609ffa ubuntu "bash" 7 seconds ago Up 5 seconds bugs16/pensive_cray
b53a46c01783 ubuntu "bash" 7 seconds ago Up 4 seconds bugs18/reverent_ritchie
78896a73191b ubuntu "bash" 7 seconds ago Up 5 seconds bugs17/gloomy_bell
a991d887a894 ubuntu "bash" 7 seconds ago Up 5 seconds bugs16/angry_swanson
a43122662e92 ubuntu "bash" 7 seconds ago Up 5 seconds bugs17/pensive_kowalevski
68d874bc19f9 ubuntu "bash" 7 seconds ago Up 5 seconds bugs16/modest_payne
e79b3307f6e6 ubuntu "bash" 7 seconds ago Up 5 seconds bugs18/stoic_wescoff
caac9466d86f ubuntu "bash" 7 seconds ago Up 5 seconds bugs17/goofy_snyder
7748d01d34ee ubuntu "bash" 7 seconds ago Up 5 seconds bugs16/fervent_einstein
99da2a91a925 ubuntu "bash" 7 seconds ago Up 5 seconds bugs18/modest_goodall
cd308099faac ubuntu "bash" 7 seconds ago Up 6 seconds bugs19/furious_ritchie
As shown, the containers are disseminated over bugs{16…19}.
Multi-hosts network
A network overlay is needed so all the containers can be “plugged in” this overlay. To create this network overlay, execute:
auzias@bugs20:~$ swarm-docker network create -d overlay net
auzias@bugs20:~$ swarm-docker network ls|grep "net"
c96760503d06 net overlay
And voilà !
Once this overlay is created, add --net net to the command swarm-docker run --rm -it ubuntu bash and all your containers will be able to communicate natively as if they were on the same LAN. The default network is 10.0.0.0/24.
Enabling Multicast
Multicast is not support by the default overlay. Another driver is required to be able to use multicast. The docker plugin weave net does support multicast.
To use this driver, once installed, you will need to run $weave launch on all Swarm agents and Swarm manager. Then you’ll need to connect the weave together, this is done by running $weave connect $SWARM_MANAGER_IP. It is not obviously the IP address of the Swarm manager but it is cleaner to do so (or use another node than the Swarm agents).
At this point the weave cluster is deployed, but no weave network has been created. Running $swarm-docker network create --driver weave weave-net will create the weave network named weave-net. Starting containers with the --net weave-net will enable them to share the same LAN and use multicast. Example of a full command to start such containers is: $swarm-docker run --rm -it --privileged --net=weave-net ubuntu bash.