In the last few parts of this series of posts about the Docker Swarmkit we have used version 1.12.x of Docker. You can find those post here
For a full index of all Docker related post please refer to this post
Preparating for Version 1.13
First we need to prepare our system to use Docker 1.13. I will be using VirtualBox and the Boot2Docker ISO to demonstrate the new features. This is what I have done to get going. Note that at the time of this writing Docker just released Docker v1.13 rc2.
From the download folder move the binaries to the target folder
mv ~/Downloads/docker-machine-Darwin-x86_64 /usr/local/bin/docker-machine
and then make it executable
chmod +x /usr/local/bin/docker-machine
finally we can double check that we have the expected version
and in my case I see this
docker-machine version 0.9.0-rc1, build ed849a7
Now let’s download the newest
boot2docker.iso image. At the time of this writing it is v1.13rc2. We can get it from here. Once downloaded move the image to the correct location
mv ~/Downloads/boot2docker.iso ~/.docker/machine/cache/
And we’re ready to go…
Creating a Docker Swarm
Preparing the Nodes
Now we can create a new swarm with Docker at version 1.13. We use the very same approach as described in part x of this series. Please read that post for more details.
Let’s clean up any pre-existing nodes called node1, node2, …, noneX with e.g. the following command
for n in $(seq 1 5); do docker-machine rm node$n done;
and then we create 5 new nodes with Docker version 1.13rc2
for n in $(seq 1 5); do docker-machine create --driver virtualbox node$n done;
Once this is done (takes about 2 minutes or so) we can double check the result
which in my case shows this
Now we can SSH into
docker-machine ssh node1
and we should see this
and indeed, we are now having a Docker host running at version 1.13.0-rc2.
Creating the Swarm
Now lets first initialize a swarm.
node1 will be the leader and
node3 will be additional master nodes whilst
node5 will be worker nodes (Make sure you are in a terminal on your Mac).
First let’s get the IP address of the future swarm leader
export leader_ip=`docker-machine ip node1`
Then we can initialize the swarm
docker-machine ssh node1 docker swarm init --advertise-addr $leader_ip
Now let’s get the swarm join token for a worker node
export token=`docker-machine ssh node1 docker swarm join-token worker -q`
We can now use this token to have the other 4 nodes join as worker nodes
for n in $(seq 2 5); do docker-machine ssh node$n docker swarm join --token $token $leader_ip:2377 done;
what we should see is this
Let’s promote nodes 2 and 3 to masters
docker-machine ssh node1 docker node promote node2 node3
And to make sure everything is as expected we can list all nodes on the leader
docker-machine ssh node1 node ls
In my case I see this
Adding everything to one script
We can now aggregate all snippets into one single script which makes it really easy in the future to create a swarm from scratch
Analyzing the new Features
One of the probably most requested features is support for secrets managed by the swarm. Docker supports a new command
secret for this. We can create, remove, inspect and list secrets in the swarm. Let’s try to create a new secret
echo '1admin2' | docker secret create 'MYSQL_PASSWORD'
The value/content of a secret is provided via
stdin. In this case we pipe it into the command.
When we run a service we can map secrets into the container using the
--secret flag. Each secret is mapped as a file into the container at
/run/secrets. Thus, if we run a service like this
docker service create --name mysql --secret MYSQL_PASSWORD \ mysql:latest ls /run/secrets
and then observe the logs of the service (details on how to use logs see below)
docker service logs mysql
we should see this
The content of each file corresponds to the value of the secret.
Publish a Port
When creating an new service and want to publish a port we can now instead of only using the somewhat condensed
--publish flag use the new
--port flag which uses a more descriptive syntax (also called ‘csv’ syntax)
docker service create --name nginx --port mode=ingress,target=80,published=8080,protocol=tcp nginx
In my opinion, altough the syntax is more verbous it makes things less confusing. Often people with the old syntax forgot in which order the target and the published port have to be declard. Now it is evident without having to consult the documentation each time.
Attachable Network support
Previously it was not possible for containers that were run in classical mode (via
docker run ...) to run on the same network as a service. With version 1.13 Docker has introduced the flag
--attachable to the
network create command. This will allow us to run services and individual containers on the same network. Let’s try that and create such a network called
docker network create --attachable --driver overlay web
and let’s run Nginx on as a service on this network
docker service create --name nginx --network web nginx:latest
and then we run a conventional container on this network that tries to acces the Nginx service. First we run it without attaching it to the
docker run --rm -it appropriate/curl nginx
and the result is as expected, a failure
And now let’s try the same again but this time we attach the container to the
docker run --rm -it --network web appropriate/curl nginx:8080
Run Docker Deamon in experimental mode
In version 1.13 the experimental features are now part of the standard binaries and can be enabled by running the Deamon with the
--experimental flag. Let’s do just this. First we need to change the
dockerd profile and add the flag
docker-machine ssh node-1 -t sudo vi /var/lib/boot2docker/profile
--experimental flag to the
EXTRA_ARGS variable. In my case the file looks like this after the modification
EXTRA_ARGS=' --label provider=virtualbox --experimental ' CACERT=/var/lib/boot2docker/ca.pem DOCKER_HOST='-H tcp://0.0.0.0:2376' DOCKER_STORAGE=aufs DOCKER_TLS=auto SERVERKEY=/var/lib/boot2docker/server-key.pem SERVERCERT=/var/lib/boot2docker/server.pem
Save the changes as reboot the leader node
docker-machine stop node-1 docker-machine start node-1
After the node is ready SSH into it
docker-machine ssh node-1
Aggregated logs of a service (experimental!)
In this release we can now easily get the aggregated logs of all tasks of a given service in a swarm. That is neat. Lets quickly try that. First we need to run Docker in experimental mode on the node where we execute all commands. Just follow the steps in the previous section.
Now lets create a sample service and run 3 instances (tasks) of it. We will be using Redis in this particular case, but any other service should work.
docker service create --name Redis --replicas 3 redis:latest
after giving the service some time to initialize and run the tasks we can now output the aggregated log
docker service logs redis
and we should see something like this (I am just showing the first few lines)
We can clearly see how the output is aggregated from the 3 tasks running on nodes 3, 4 and 5. This is a huge improvement IMHO and I can’t wait until it is part of the stable release.
In this post we have created a Docker swarm on VirtualBox using the new version 1.13.0-rc2 of Docker. This new release offers many new and exciting features. In this post I have concentrated on some of the features concerning the Swarmkit. My post is getting too long and I have still so many interesting new features to explore. I will do that in my next post. Stay tuned.