Introduction To Docker, Docker Compose, Docker Swarm

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Introduction To
Docker, Docker Compose, Docker Swarm

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About me
An Nguyen
Email: nthienan.it@gmail.com
6+ years of experience in software industry
Java, Python developer, DevOps engineer at TMA Solutions

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Agenda
 Docker
 Docker Compose
 Docker Swarm

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 Who knows about Docker?
 Who uses Docker for development?
 Who uses Docker in production?
 Who tried but could not do it?

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What is Docker?
 Docker is container engine

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What is Docker? (cont.)
 Docker is an open platform for developing,
shipping, and running applications.
 Docker allows you to package an application with
all of its dependencies into a standardized unit for
software development.

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What is Docker? (cont.)
 Standardized packaging for software and dependencies
 Isolate apps from each other
 Share the same OS kernel
 Works for all major Linux distributions
 Containers native to Windows Server 2016

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Virtual Machine vs Container

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Benefits of Docker
 Fast (deployment, migration, restarts)
 Secure
 Lightweight (save disk & CPU)
 Open Source
 Portable software
 Micro-services and integrations (APIs)
 Simplify DevOps
 Version control capabilities

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Technologies behind Docker
 Linux x86-64
 Go language
 Client - Server (deamon) architecture
 Union file systems (UnionFS: AUFS, btrfs, vfs etc)
 Namespaces (pid, net, ipc, mnt, uts)
 Control Groups (cgroups)
 Container format (libcontainer)

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Docker architecture
https://docs.docker.com/engine/docker-overview/#docker-architecture

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Docker Vocabulary
 Docker client
● Is the primary user interface to Docker.
● Accepts commands from the user and communicates back and forth with a
Docker daemon
 Docker daemon
● Runs on a host machine.
● Users do not directly interact with the daemon, but instead through the Docker
client with the RESTful API or sockets

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Docker Vocabulary (cont.)
 Image
● Is a read-only template with instructions for creating
a Docker container.
● An image is based on another image, with some
additional customization
 Container
● Is a runnable instance of an image.
● A container is removed, any changes to its state that
are not stored in persistent storage disappear

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 Registry
● A Docker registry stores Docker images.
● Docker Hub and Docker Cloud are public registries that anyone can use
● You can run your own private registry

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 Dockerfile
● Is a text document that contains all the commands a user could call on the command line to
create an image
● Dockerfile reference on docker docs

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 Volume
● Is a mount point on the container’s directory tree where a portion of the host directory tree has
been mounted

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Common Docker usages
 Sandbox environment (develop, test, debug, educate)
 Continuous Integration & Deployment
 Scaling apps
 Development collaboration
 Infrastructure configuration
 Local development
 Multi-tier applications
 PaaS, SaaS

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Useful resources
 Awesome Docker (list of Docker resources & projects)
 Docker cheat sheet
 Docker in Practice, The Docker Book (books)
 Docker aliases/shortcuts
 Docker case studies
 Self-learning courses

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Real life applications
 One application consists of multiple containers.
 One container is dependent on another.
 Mutual dependency/ startup order.
 Process involves building containers and then deploy them
 Long docker run commands
 Complexity is proportional to the number of containers involved

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What is Docker compose?
 Tool for defining and running multi-container Docker application.
 It is a YML file.
 Compose contains information about how to build the containers and deploy
containers.
 Integrated with Docker Swarm

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What is Docker swarm?
 Is a clustering and scheduling tool for Docker containers. With Swarm, IT
administrators and developers can establish and manage a cluster of Docker
nodes as a single virtual system
 A swarm is a group of machines that are running Docker and joined into a cluster

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Feature highlights
 Cluster management integrated with Docker Engine
● Use the Docker Engine CLI to create a swarm of Docker Engines where you can deploy
application services
 Declarative service model
● Uses a declarative approach to let you define the desired state of the various services in your
application stack
 Scaling
● When you scale up or down, the swarm manager automatically adapts by adding or removing
tasks to maintain the desired state

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Feature highlights (cont.)
 Desired state reconciliation
● Swarm manager node constantly monitors the cluster state and reconciles any differences
between the actual state and your expressed desired state
 Service discovery
● Swarm manager nodes assign each service in the swarm a unique DNS name and load balances
running containers
 Rolling updates
● At rollout time you can apply service updates to nodes incrementally. If anything goes wrong,
you can roll-back a task to a previous version of the service

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Core concepts
 Service:
● Services are really just “containers in production”
● A service only runs one image, but it codifies the way that image runs—what ports it should use,
how many replicas of the container should run so the service has the capacity it needs, and so
on
● Scaling a service changes the number of container instances running that piece of software

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Core concepts (cont.)
Two type of service:
 Replicated
● Specify the number of identical tasks you
want
 Global
● Service that runs one task on every node

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Core concepts (cont.)
 Stack:
● A stack is a group of interrelated services that share dependencies, and can be orchestrated and
scaled together
● A single stack is capable of defining and coordinating the functionality of an entire application
(though very complex applications may want to use multiple stacks)

Introduction To Docker, Docker Compose, Docker Swarm

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