Introductory seminar on Docker and its components (networks and Compose in particular). Focused on going through some basic concepts, mention some more advanced topics, and introduce a practical workshop held on the same evening.

1. Docker
From walking to running
Giacomo Vacca, RTCSoft, gv@rtcsoft.net 1

2. About me
• 15 years “in the trenches cubicles”
• Developer of RTC (VoIP, IM, WebRTC) solutions
• Often dealing with DevOps topics
• Founder of RTCSoft in 2015
@giavac
https://github.com/giavac
gv@rtcsoft.net
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3. Docker usage scenarios
• Run (micro)services
• Deployment mechanism
• Prototyping
• Testing
• Continuous Integration/Delivery
3

4. What’s in a name?
4

5. Previously on this show 1/2
http://www.slideshare.net/GiacomoVacca/docker-and-puppet-for-continuous-integration
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6. Previously on this show 2/2
http://www.slideshare.net/GiacomoVacca/docker-from-scratch
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7. What is Docker, really?
• An Open-Source (Go) framework to manage “container virtualisation” (started in 2013)
• Docker isolates multiple user spaces (file systems) inside the same host
• The user space instances are called “Containers”
• They give you the illusion of being inside a VM
• Think about “execution environments” or “sandboxes”
• No need for an hypervisor (and so very quick to launch)
• Requires x64 Linux and kernel 3.8+
• Google started dev of cgroups for the Linux kernel, then together with namespaces and chroot become LXC
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8. Main Docker components
• Engine: manages images and containers. Exposes an API
• Client: connects to the Engine (locally or remotely)
• Compose: manages multi-container architectures
• Swarm: orchestrates containers on multiple hosts
• Kitematic: GUI for Docker client
• Machine: provision and manage VMs to host containers
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9. Ingredients vs Cake
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10. Virtual Machines vs Docker
Source: https://www.docker.com/what-docker
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11. What Docker is not?
• A programming language
• An OS
• A Virtual Machine
• An image in the traditional hypervisor-based Virtual Machine concept
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12. Where is Docker used?
• Uber, eBay, BBC News, shopify, ING, Swisscom, Groupon (1)
• and many others…
• Supported by Google Cloud Platform
• with the Container Engine + Kubernetes
(1) source: https://www.docker.com/customers
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13. Who should know about Docker?
• Developers
• Including mobile developers
• Sysadmins
• “DevOps” people
• Architects/CTO/COO
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14. Basic topics
• Images and Containers
• Image structure
• Dockerfiles
• Building an image
• Interacting with an image repo
• Running a container
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• Architecture
• Typical Linux vs Toolbox
• Volumes
• Port mapping

15. Some advanced topics
• Inspecting/debugging containers
• inspect/attach/exec/logs/top
• Volumes, data containers
• Multicontainer architectures
• Link, network, Compose
• Docker inside Docker
• Is it worth it? Consider the “sibling” approach (“socket mounting”) instead.
• Orchestrating Docker containers via Puppet
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16. Inspect a Container
docker inspect CONTAINER_NAME
Formatting options, e.g.:
docker inspect --format='{{range .NetworkSettings.Networks}}
{{.IPAddress}}{{end}}' CONTAINER_ID
16

17. Output of inspect
{
"Id": "c61b85d3a9451d2ac3bbe301f54dc97b0df13c2835d0fb1f6214db64929e646d",
"Created": "2016-01-05T09:47:16.125279193Z",
"Path": "/bin/sh",
"Args": [
"-c",
"nginx"
],
"State": {
"Status": "running",
"Running": true,
"Paused": false,
"Restarting": false,
"OOMKilled": false,
"Dead": false,
"Pid": 16817,
…
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18. Debugging a container
$ docker info
$ docker attach CONTAINER_NAME
$ docker exec -it CONTAINER_NAME COMMAND
e.g. ‘$ docker exec -it gvacca/nginx /bin/bash’
$ docker logs CONTAINER_NAME
Or show processes running inside a container:
$ docker top CONTAINER_NAME
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19. Volumes
• Share a folder between host and container
• VOLUME commands inside the Dockerfile
• Dynamic volume association at run time: one or more ‘-v’ arguments
• Volumes shared by an image are available even if the container is
not running (but it needs to still exist).
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20. Multicontainer architecture
• Define many containers (aka “services”)
• Define relationship between them (e.g. “depends on”)
• Define networking
• Start/Stop all services at the same time
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21. Networks of Containers
• “docker network” defined since Docker 1.9
• Create a virtual network, then attach containers to it
• Containers on different networks by default don’t see each other
• Internal private addressing, managed by Docker
• Brilliant for prototyping and emulating entire architectures
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22. Docker network
• ‘docker network create NAME’
• ‘docker network attach NAME CONTAINER’
• ‘docker network ls’
• ‘docker network inspect NAME’
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23. Docker Compose
• docker-compose.yml, defines a set of containers (“services”). Written in python,
available with Toolbox.
• Define their runtime properties (images, volumes, ports, dependencies)
• Interact with registries (public/private)
• Network
• Containers can be located with a name, instead of IP address (e.g ‘https://
mysql_server:3306’, from 1.6.2)
• Default name is ‘APPFOLDER_default’
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24. Compose main commands
• ‘docker-compose build [service]’
• ’docker-compose [--verbose] up [-d]’
• ‘docker-compose start [service]’
• ‘docker-compose down’
• ‘docker-compose top’
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25. Docker Machine
• Provision and manage VMs
• Available with Toolbox (uses Virtualbox)
• ‘docker-machine active’
• ‘docker-machine ls’
• ‘docker-machine start default’
• eval $(docker-machine env)
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26. Let’s play with Docker Compose
• Write your docker-compose.yml file
• ’docker-compose build [service]’
• Builds the images when needed (‘build’), or exits (‘image’)
• ’docker-compose up’
• Add ‘-d’ to run in background (daemon mode)
• ‘docker ps’ to see the launched containers
• ‘docker-compose ps’
• See the processes and other details - similar to ‘docker ps’
• ‘docker-compose down/stop/kill’
• To switch off the node
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27. The Workshop
• Create a simple app with 2 containers
• One with stock image
• One with built image
• Run and inspect
• Check volumes
• Create the same app with Compose
• Run and inspect
• Check network and volumes
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28. Compose scenario - steps
Browse to http://192.168.99.100:5000/
docker-compose --verbose up
Browse to http://192.168.99.100:5000/
CTRL+C
docker-compose --verbose up -d
docker ps | grep 'composetest'
docker-compose ps
docker-compose --verbose ps
docker network ls |grep 'composetest'
docker network inspect 'composetest_default'
python inspect_docker_network.py 'composetest_default'
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29. docker ps
Giacomos-MacBook-Pro:docker-experiments gv$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS
PORTS NAMES
13398ae967e5 gvacca/kamailio_async:ubuntu14 "tail -f /dev/null" 3 months ago Up 3 seconds
5060/tcp dockerexperiments_kamailio_async_ubuntu_1
51c8105ef7ab gvacca/kamailio_async:centos7 "tail -f /dev/null" 3 months ago Up 3 seconds
5060/tcp dockerexperiments_kamailio_async_centos_1
4e21f9fd9694 gvacca/sipp "tail -f /dev/null" 3 months ago Up 3 seconds
dockerexperiments_sipp_1
381272e54d19 gvacca/nginx_ssl "/bin/sh -c nginx" 3 months ago Up 3 seconds
80/tcp, 443/tcp dockerexperiments_nginx_ssl_1
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30. docker inspect http_network
[
{
"Name": "http_network",
"Id": "29c9951bf3fbaaa73f5a0fa39a4de1c65fbbe99f0aef8b49718a921ab6deed17",
"Scope": "local",
"Driver": "bridge",
"IPAM": {
"Driver": "default",
"Config": [
{}
]
},
"Containers": {
"13398ae967e5ba0677cd151bda64c4458671b335dd46d67c7f4ef01b8b65821b": {
"EndpointID": "18ebb70df95e24cec9932f9925c655fa9866aa34e2a8a40e90827ba3bea8441d",
"MacAddress": "02:42:ac:13:00:05",
"IPv4Address": "172.19.0.5/16",
"IPv6Address": ""
},
"381272e54d19f24c6c3f923e3f35e8676d2fd19ab229fb3a382893c889367c42": {
"EndpointID": "abd412f88e83b6e8460b222f3aa293dd6f118f8d54a29403e1a68f27a22a5d43",
"MacAddress": "02:42:ac:13:00:02",
"IPv4Address": "172.19.0.2/16",
"IPv6Address": ""
},
"4e21f9fd9694a50a9ff42f0cae11ea1e208b72ec21a539014284082b5887c57f": {
"EndpointID": "2a5e7d1800ddb55f7c4192d819aff413b024a2d0e97be612ca000497d23d80bf",
"MacAddress": "02:42:ac:13:00:03",
"IPv4Address": "172.19.0.3/16",
"IPv6Address": ""
},
"51c8105ef7ab8079cf05428a83ea7f6c6395a2a5fc08075617d855992a27492f": {
"EndpointID": "5871de671429a51b52f8b498410d5ffe394e95ceccc8ac6d2dadf9b139727821",
"MacAddress": "02:42:ac:13:00:04",
"IPv4Address": "172.19.0.4/16",
"IPv6Address": ""
}
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31. Scripting with docker APIs
$ python inspect_docker_network.py http_network
13398ae967e5ba0677cd151bda64c4458671b335dd46d67c7f4ef01b8b65821b '/dockerexperiments_kamailio_async_ubuntu_1': 172.19.0.5/16
4e21f9fd9694a50a9ff42f0cae11ea1e208b72ec21a539014284082b5887c57f '/dockerexperiments_sipp_1': 172.19.0.3/16
381272e54d19f24c6c3f923e3f35e8676d2fd19ab229fb3a382893c889367c42 '/dockerexperiments_nginx_ssl_1': 172.19.0.2/16
51c8105ef7ab8079cf05428a83ea7f6c6395a2a5fc08075617d855992a27492f '/dockerexperiments_kamailio_async_centos_1': 172.19.0.4/16
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32. inspect_docker_network.py
#!/usr/bin/python
# Get the output of 'docker network inspect' for a given network
# and return containers names and their IP address
import json
import subprocess
import sys
network_name = sys.argv[1]
network_json = subprocess.check_output(["docker", "network", "inspect", network_name])
network = json.loads(network_json)
containers = network[0]['Containers']
for container_id in containers:
container_name = subprocess.check_output(["docker", "inspect", "--format",
"'{{ .Name }}'", container_id])
print container_id + " " + container_name.strip() + ": " + containers[container_id]
['IPv4Address']
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33. Cleaning up
• docker rm CONTAINER
• docker rmi IMAGE
• docker rmi $(docker images -q --filter "dangling=true")
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34. Questions and Answers
Thanks
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35. Recommended Books
• “The Docker book”, J. Turnbull, http://www.amazon.co.uk/Docker-Book-
Containerization-new-virtualization-ebook/dp/B00LRROTI4
• “Using Docker”, A. Mouat, O’Reilly, https://www.amazon.co.uk/Using-Docker-
Adrian-Mouat/dp/1491915765
• “Continuous Delivery”, J. Humble, http://www.amazon.com/Continuous-Delivery-
Deployment-Automation-Addison-Wesley/dp/0321601912
• “Building Microservices”, S. Newman, http://shop.oreilly.com/product/
0636920033158.do
• "Docker Networking and Service Discovery", O’Reilly, https://www.nginx.com/
resources/library/docker-networking/
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36. Other useful references
• https://jpetazzo.github.io/2015/09/03/do-not-use-docker-in-docker-
for-ci/
• https://www.dajobe.org/blog/2015/04/18/making-debian-docker-
images-smaller/
• http://blog.replicated.com/2016/02/05/refactoring-a-dockerfile-for-
image-size/
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