Docker orchestration voxxed days berlin 2016

Docker Orchestration
An Overview
Dr. Halil-Cem Gürsoy
@hgutwit
adesso AG - Dortmund, Germany

About myself…
► Principal Architect @ adesso AG, DE
► since more than 15 years in commercial 
software development
> before that, wrote science software 
► Large distributed enterprise systems
► Persistence, build’n deployment
2

“It is not the
strongest or the
most intelligent who
will survive but
those who can best
manage change.”
C. Darwin

Why Docker orchestration?
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https://www.flickr.com/photos/matijagrguric/4437187539

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► Containers has to talk to each over
► Think about a microservice architecture with dozens of
containers
► And they have to find each other
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www.flickr.com/photos/matijagrguric/4437187539/
www.flickr.com/photos/matijagrguric/4437187539/ www.flickr.com/photos/matijagrguric/4437187539/

Poor mans orchestration with Docker link
► The easiest way was to use Docker link functionality
docker run –d --name db42 dbimg
docker run –d --name app42 --link db42:db appimg
► But that about multiple Docker hosts?
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Poor mans orchestration with Docker link
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https://www.flickr.com/photos/zunami/3780220955/

You can implement your own network…
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http://www.opencontrail.org/wp-content/uploads/2014/09/opencontrail-docker-figure-1.png

https://www.flickr.com/photos/r_rose/102766969/

Build-in solutions - Docker Machine
► Docker Machine as the lowest building block
► only needed for development environments
► in production you’ll provision with other tools…
docker-machine create  
--driver digitalocean  
--digitalocean-access-token=$DIGITAL_OCEAN_TOKEN  
machine-1 
► You can create as many docker hosts as you want (and
have resources / money)
12

Docker Swarm
► Docker Swarm is the ‚built-in’ clustering solution
► Supports new overlay network (based on VXLAN)
► Easy to set up with Docker Machine
docker-machine create --driver digitalocean  
--swarm --swarm-master  
--swarm-discovery token://$SWARM_ID  
swarm-master 
docker-machine create --driver digitalocean  
--swarm --swarm-discovery token://$SWARM_ID  
swarm-node-01
14

Docker Swarm - Manager
► Manager needs a Discovery Service to handle nodes
> Consul, etcd, Zookeeper, static files, IP ranges etc.
► Acts like a proxy, implementing the Docker Remote API
► Manages distribution of starting containers to nodes
> Depending on CPU and / or memory constraints
> … labels on Docker hosts
> … affinity to ressources and other containers
15

Docker Swarm - Scheduler strategies
► Scheduler ranks nodes while starting containers
► Different strategies
> binpack
> spread (default)
> random
► binpack and spread depend on current node utilization
16

Docker Swarm - Filters
► The scheduler has various filters to choose a node
> Constraint - a label on a Docker host
> Affinity - be together with a specific resource
> Port - is a specific port free?
> Dependency - together with another container
> Health
$ docker daemon --label storage=ssd
$ docker run -d -P -e constraint:storage==ssd ...
17

Docker Swarm - Missing stuff
► Swarm is simply the low level clustering for Docker nodes
► Self healing / resilience
> restarting containers on other nodes on node failure
> comes with 1.1.0 (already included in RC, experimental)
► Moving containers during runtime
> only with 3rd party tools
► Auto-Scaling, may come with Docker Compose
► Monitoring
18

Taking a little trip: Overlay Network
► Allows communication between containers in the cluster
► Using libnetwork, based on vxlan
> uses plugin system: overlay, weave
► For overlay driver you need min Kernel 3.16
> have to be careful on Ubuntu
► Needs a K/V store like etcd, Zookeeper or Consul
► All containers attached to that network get an entry in 
/etc/hosts on all containers
19

Another trip: Discovery Services
► You may need a Discovery Service in a Microservice
architecture regardless of Docker
► ‚Did I need a Discovery Service even then I’ve a overlay
network?‘
> YES, you do!
> beyond ‚Hello World’ examples the challenge is the same
to find services in a large scale distributed system
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Service Discovery
► Consider using registrator
> registers starting containers in Consul, etcd or SkyDNS
> but doesn’t work currently with overlay network
► Inject needed data into your container using something like
consul-template / envconsul, confd, Spring Cloud, …
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http://github.com/hcguersoy/swarm-elastic-demo
https://www.flickr.com/photos/schwaber/3238977103

Docker Compose
► Former ‚Fig‘ project, now part of Docker’s core ecosystem
► implemented in Python
► „Compose is a tool for defining and running multi-container
applications with Docker.“
► Can be used to set up complex environments
► Using Docker Swarm as the low level clustering of the
Docker Hosts, Compose is for the orchestration of the
containers
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Docker Compose
► Configuration using YAML:
myapp:
build: .
ports:
- "8080:8080"
volumes:
- ./conf:/etc/myapp/conf
links:
- mysql
mysql:
image: mysql
► Links supported only on single host system
► But latest version supports overlay network (experimental)
24

Docker Compose
► a more complex example: Kubernetes on top of Swarm
etcd:
image: gcr.io/google_containers/etcd:2.0.13
container_name: etcd
command: ['/usr/local/bin/etcd', '--bind-addr=0.0.0.0:4001', '--data-dir=/var/etcd/
data']
apiserver:
image: gcr.io/google_containers/hyperkube:v1.0.7
container_name: apiserver
ports:
- "8080"
command: ["/hyperkube", "apiserver", "--service-cluster-ip-range=172.17.17.1/24", "--
address=0.0.0.0", "--etcd_servers=http://etcd:4001", "--cluster_name=kubernetes", "--
v=2"]
controller:
image: gcr.io/google_containers/hyperkube:v1.0.7
command: ["/hyperkube", "controller-manager", "--address=0.0.0.0", "--master=http://
apiserver:8080", "--v=2"]
environment:
- "affinity:container==*apiserver*"
...
Source 'Swarm Frontend’ (https://github.com/docker/swarm-frontends)
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https://www.flickr.com/photos/tomwahlin/with/3167491292/

Kubernetes
► Created by Google
► build to manage ‚oceans of user containers‘
► Cloud agnostics, supports different cloud and virtualization
platform
> but results in different installation directives
> easy playground setup using Docker Compose (s. above)
on top of Swarm
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Kubernetes - Key components
► Kubernetes consists of different key components
► Master Server
> the main management system
> is build up using different tools
– etcd
– API Server, providing REST interface
– Controller Server
– Scheduler Server
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► Minion
> the work units in Kubernetes, executing the commands
coming from the master server
> runs a Docker daemon
> Kubelete service
> Proxy Service
> cAdvisior
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► Pod
> the smallest logical unit in Kubernetes
> containers belonging together are defined in a Pod - a
logical collection
> All containers of a Pod run on one Minion ( = one Host)
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Kubernetes - System Arcitecture
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Source: http://releases.k8s.io/release-1.1/docs/design/architecture.md

Kubernetes
► Build in resource monitoring, fail over  
and rescheduling
► Uses different API then Docker
► Uses different configuration files as Compose
► Complex architecture
► IMHO not very usable for ‚small‘ setups due to the overhead
> but may be very useful then you get really large
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Spotify Helios
► Builds a cluster spanning multiple Docker hosts
► deploys and manages containers in this cluster
► Developed before rise of Swarm but does similar stuff
> …and still actively developed
> used by Spotify in production
► But missing something like Compose above this low layer
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Apache Mesos / Marathon
► Apache Mesos is a ‚kernel‘ to set up large scale distributed
systems
> e.g. large Hadoop Clusters
► Comes with an 0.20.0 with Docker Containerizer
> still some limitations
► May be used together with Marathon
> e.g. supplies rescheduler
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…and much more
► There is a whole bunch of more orchestration solutions
> Crane
> CoresOS / Fleetd
> RancherOS
> …
► …and much more hosted solutions
> Giantswarm (still alpha), Amazon ECS, Google CE
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Summing up
► Docker Swarm together with Compose is a lightweight way
to orchestrate containers
> but need some maturity and additional features / services
► Kubernetes is the opposite, heavy weight solution
> good for large scenarios, but oversized for small setups
> breaks with Docker CLI
► Mesos / Marathon
> useful for some scenarios, breaks with Docker CLI
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http://www.flickr.com/photos/an_untrained_eye/6630719431

http://www.flickr.com/photos/tcmorgan/7372944070
halil-cem.guersoy@adesso.de
https://twitter.com/hgutwit

Docker orchestration voxxed days berlin 2016

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