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Docker & why we should use it

Vicențiu Ciorbaru

Software Engineer @ MariaDB Foundation

*

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Agenda

What is Docker?�
What Docker brings to the table compared to KVM and Vagrant?�
Docker tutorial

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What is Docker

A tool to manage containers (similar to Vagrant)�
Allows portable sharing of containers across machines�
Made use of LXC containers initially, now runC (libcontainer)�
Makes use of AuFS to limit size of containers

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Why Docker?

Much lower overhead than Virtual Machines
Easy to share containers between devs
Easy to run identical environment locally

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How Docker Works

2 main concepts

images
containers

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What is a docker image

A set of files (binaries in general)

With an absolute path attached to each one��

That's it!��
Can be based off of other images

Tracked via AuFS

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What is a docker container

A docker image running 1 or more processes started from the binaries in the image.
Any changes to files are recorded on a separate layer.

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What is a Dockerfile

A script to generate a docker image.�
Each instruction generates an intermediate image, based on modified files.�
Used by the command docker build.

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What is a Dockerfile

# Base image

FROM ubuntu:16.04

# Create user develop

RUN useradd -m -b /home --uid 1000 develop

# Install build dependencies

RUN apt-get update \

&& apt-get install -y \

git cmake gcc g++ \

libncurses5-dev \

libgnutls-dev \

bison \

&& rm -rf /var/lib/apt/lists/*

# Copy the repository

ADD ./server /home/develop/server

RUN chown -R develop /home/develop

USER develop

# Build the server

WORKDIR /home/develop/server

RUN cmake . -DCMAKE_BUILD_TYPE=Debug

RUN make -j13

# Run tests when container is run

WORKDIR /home/develop/server/mysql-test

CMD ./mtr --par=20 --suite=main --force

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How a docker image is constructed

# Base image

FROM ubuntu:16.04

# Create user develop

RUN useradd -m -b /home --uid 1000 develop

# Install build dependencies

RUN apt-get update \

&& apt-get install -y \

git cmake gcc g++ \

libncurses5-dev \

libgnutls-dev \

bison \

&& rm -rf /var/lib/apt/lists/*

ubuntu:16.04 (97 packages installed) ~ 112MB

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How a docker image is constructed

# Base image

FROM ubuntu:16.04

# Create user develop

RUN useradd -m -b /home --uid 1000 develop

# Install build dependencies

RUN apt-get update \

&& apt-get install -y \

git cmake gcc g++ \

libncurses5-dev \

libgnutls-dev \

bison \

&& rm -rf /var/lib/apt/lists/*

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

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How a docker image is constructed

# Base image

FROM ubuntu:16.04

# Create user develop

RUN useradd -m -b /home --uid 1000 develop

# Install build dependencies

RUN apt-get update \

&& apt-get install -y \

git cmake gcc g++ \

libncurses5-dev \

libgnutls-dev \

bison \

&& rm -rf /var/lib/apt/lists/*

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

dependencies

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How a docker image is constructed

# Copy the repository

ADD ./server /home/develop/server

RUN chown -R develop /home/develop

USER develop

# Build the server

WORKDIR /home/develop/server

RUN cmake . -DCMAKE_BUILD_TYPE=Debug

RUN make -j13

# Run tests when container is run

WORKDIR /home/develop/server/mysql-test

CMD ./mtr --par=20 --suite=main --force

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

dependencies

server code in /home/develop

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How a docker image is constructed

# Copy the repository

ADD ./server /home/develop/server

RUN chown -R develop /home/develop

USER develop

# Build the server

WORKDIR /home/develop/server

RUN cmake . -DCMAKE_BUILD_TYPE=Debug

RUN make -j13

# Run tests when container is run

WORKDIR /home/develop/server/mysql-test

CMD ./mtr --par=20 --suite=main --force

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

dependencies

server code in /home/develop

configured

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How a docker image is constructed

# Copy the repository

ADD ./server /home/develop/server

RUN chown -R develop /home/develop

USER develop

# Build the server

WORKDIR /home/develop/server

RUN cmake . -DCMAKE_BUILD_TYPE=Debug

RUN make -j13

# Run tests when container is run

WORKDIR /home/develop/server/mysql-test

CMD ./mtr --par=20 --suite=main --force

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

dependencies

server code in /home/develop

configured

compiled

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Installing Docker

$ sudo apt install docker.io

$ sudo systemctl enable docker.io

$ sudo systemctl start docker.io

$ docker ps # By default, only root can run docker commands

Got permission denied while trying to connect to the Docker daemon socket

$ sudo groupadd docker # May already exist

$ sudo usermod -a -G docker $USER

$ docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

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Running MariaDB tests in Docker

$ mkdir ~/Workspace/MariaDB-docker

$ cd ~/Workspace/MariaDB-docker

$ vim Dockerfile # Use the dockerfile from previous slides

$ docker build . -t mariadb-test

$ docker run -i -t mariadb-test

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How to get reproducible builds

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

dependencies

server code in /home/develop

configured

compiled

Build Environment�

152M build-env.tgz

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How to get reproducible builds

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

dependencies

server code in /home/develop

configured

compiled

Test Environment

3.1GB test-env.tgz

:( Too big, code and binaries take too much space

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How to get reproducible builds

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

dependencies

server code in /home/develop

configured

compiled

Test Environment

3.1GB test-env.tgz

:( Too big, code and binaries take too much space

We need to remove the code from the image.

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Keep images small, use volumes

# Base image

FROM ubuntu:16.04

# Create user develop

RUN useradd -b /home --uid 1000 develop

# Install build dependencies

RUN apt-get update \

&& apt-get install -y \

git cmake gcc g++ \

libncurses5-dev \

libgnutls-dev \

bison \

&& rm -rf /var/lib/apt/lists/*

USER develop

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

dependencies

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Keep images small, use volumes

$ docker build . -t mariadb-build-env

$ docker run -i -t -v "$(pwd)"/server:/home/develop/server mariadb-build-env

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

dependencies

Specify a volume to mount

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Keep images small, use volumes

$ docker build . -t mariadb-build-env

$ docker run -i -t -v "$(pwd)"/server:/home/develop/server mariadb-build-env

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

dependencies

Absolute path in host

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Keep images small, use volumes

$ docker build . -t mariadb-build-env

$ docker run -i -t -v "$(pwd)"/server:/home/develop/server mariadb-build-env

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

dependencies

Absolute path in container

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Keep images small, use volumes

$ docker build . -t mariadb-build-env

$ docker run -i -t -v "$(pwd)"/server:/home/develop/server mariadb-build-env

develop@b624906b23a5:~$

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

dependencies

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Keep images small, use volumes

$ docker build . -t mariadb-build-env

$ docker run -i -t -v "$(pwd)"/server:/home/develop/server mariadb-build-env

develop@b624906b23a5:~$ ls

server

develop@b624906b23a5:~$ cd server

develop@b624906b23a5:~/server$ cmake .

-- Running cmake version 3.5.1

...

ubuntu:16.04 (97 packages installed) ~ 112MB

useradd

dependencies

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Conclusions

Docker can be used to test and debug any specific environment, quickly
Sharing images can be done in 2 ways:

Share the Dockerfile (fast, easy)
Publish the image to a registry, share the image name (similar to git push)

To reduce image size, use volumes for large contents

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Conclusions

Developing in Docker containers should (mostly) remove the "can not reproduce" problem!
Guaranteed identical environment every time
Everything runs in regular userspace, no hypervisor overhead!
There are more customization features present:

networks, ports mappings, docker-compose

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Thank You!

Contact me at:

vicentiu@mariadb.org

vicentiu@ciorbaru.io

Blogs:

mariadb.org/blog

vicentiu.ciorbaru.io