Docker: Containers for the Masses -- Yet another way to use_MySQL

Docker

Good Monday morning! Over the weekend, there was a comment to my previous post coveringusing Ansible to build Docker imagesfromMichael DeHaan, CTO and creator ofAnsible(thank you!) reminding me of his work discussed in his blog postInstalling and Building Docker with Ansiblethat is definitely worth sharing and the method I first used to build Docker images and wrotemy first rolethat will be shared in this post.

For the reader just joining, the previous posts in this series "Docker: Containers for the Masses" are:

• Introduction-- Introduction toDocker
• Installation-- Installation ofDocker
• Using Docker-- UsingDocker
• Ansible and Docker-- Using Ansible to manageDocker
• Building Docker Images using Ansible-- Using Ansible to buildDockerimages

Building Docker Images with Ansible using a Dockerfile

Michael's articledetails how to install Ansible, how to usePaul Durivage'sangstwad.dcoker_ubuntu Ansible role, also features an important-to-know way of building Docker images whereby an image is build using a Dockerfile that specifies the installation ofAnsible, checks out your playbook repository which it then runs with Ansible resulting in a built image with everything you would want on that image. This is different than in the previous post that details using Ansible to run theDockerimage-building process and is yet another example on how usingAnsibleandDockertogether is flexible and the approach to both interchangeable and each method equally valid depending on what the user requires.

Additionally, I used this methodology when I first started usingAnsibleandDockerand forked Michael's repository, adding aGalera role.

The Playbook

In addition to showing yet another way to buildDockerimages, this post will also give the reader more insight into usingAnsiblein general and show another example of what one can do with aDockerfile.

This post will detail a playbook I wrote when I forked thedocker_dna repo. In my role with the HP ATG Group, I was tasked with researching Ansible and Docker and wanted to accomplish several things: Learn Docker and Ansible as well as see if my experience -- and a [Salt][saltstack] template and methodology for setting up a Galera cluster could be easily ported toAnsible.

Directory layout

The repo, when cloned, there are thebase,rabbitmq,zookeeper, andgalerasubdirectories. The last one was added by myself when I used this repo to get familiar with this methodology for buildingDockerimages. In that subdirectory

<code data-lang="text">$ ls -1dna.ymldocker-dna_galera.ymlDockerfilegroup_varshost_varsREADME.mdroles</code>

Top-level playbook

Thedna.ymlplaybook sets some variables and includesdocker-dns_galera.yml:

<code data-lang="text">---# file: dna.yml- include: docker-dna_galera.yml</code>

Tasks

The tasks that then are used for this role which are broken up into specific operations:

<code data-lang="text">$ ls -1 roles/docker-dna_galera/tasks/clustercheck.ymlconfigure_galera.ymlgrants.ymlinstall_galera.ymlmain.ymlmisc.ymlrepo.yml</code>

Specifying using thedocker-dna_galerarole

docker-dna_galera.ymlin turn uses the rolescommonanddocker-dns_galera

<code data-lang="text">---# file: docker-dna_galera.yml- hosts: docker-dna_galeraroles:- common- docker-dna_galera</code>

Role variables

By using thedocker-dns_galerarole, the role's variables are set in the fileroles/docker-dna_galera/vars/main.ymlwhich contains variables used by the the templatesroles/docker-dna_galera/templates/etc/mysql/my.cnf.j2androles/docker-dna_galera/templates/usr/bin/clustercheck.j2, as well as some of the role's tasks.

<code data-lang="text">---# file: roles/docker-dna_galera/vars/main.yml# these values are default - change for security!galera:	dbusers:		xtrabackup:			username: xtrabackup			password: xtrabackup		docker:			username: docker			password: docker			host: 172.17.%		clustercheck:			username: clustercheck			password: clustercheck</code>

Top-level playbook including tasks

main.ymlincludes each task in the order it needs to be run:

<code data-lang="text">--# file: roles/docker-dna_percona/tasks/main.yml- include: misc.yml- include: repo.yml- include: install_galera.yml- include: grants.yml- include: configure_galera.yml- include: clustercheck.yml</code>

Misc playbook

The first taskmisc.ymlinstalls vim or any other package other than thePerconapackages:

<code data-lang="text">---# file: roles/docker-dna_percona/tasks/misc.yml- name: Install things I likeapt: pkg= state=presentwith_items:- vim</code>

Set the repo

Therepo.ymltask simply sets up apt to use thePerconaapt repo:

<code data-lang="text">---# file: roles/docker-dna_galera/tasks/repo.yml- name: Obtain Percona public key# apt_key: url=http://keys.gnupg.net/pks/lookup?op=get&search=0x1C4CBDCDCD2EFD2Aapt_key: url=http://www.percona.com/downloads/RPM-GPG-KEY-percona state=present- name: Add Percona repositoryapt_repository: repo='deb http://repo.percona.com/apt precise main'state=present- name: Add Percona source repositoryapt_repository: repo='deb-src http://repo.percona.com/apt precise main'state=present- name: Update apt cacheapt: update_cache=yes</code>

Install the database software

Theinstall_galera.ymltask installsPercona XtraDB Clusteras well as copying a startup script into /usr/local/bin. This is somewhat historic as upstart didn't work with older versions ofDocker

<code data-lang="text">---- name: Install Percona XtraDB Cluster serverapt: pkg= state=presentwith_items:- percona-xtradb-cluster-server-5.6- python-mysqldb- xinetd- telnet- name: Copy the helper scriptcopy: src=usr/local/bin/mysql_run.shdest=/usr/local/bin/mysql_run.shmode=0755</code>

Set the database grants

Thegrants.ymltask sets the grants for the database that are needed to run a successful Galera cluster

<code data-lang="text">---# file: roles/docker-dna_percona/tasks/grants.yml- name: Add Docker database usermysql_user: user= host=password= priv=*.*:"all privileges"- name: Add xtrabackup database user (for Galera SST)mysql_user: user= host="localhost" password= priv=*.*:"grant, reload, replication client"- name: Add clustercheck database user (for clustercheck/xinetd -> haproxy)mysql_user: user= host="localhost" password= priv=*.*:"grant, reload, replication client"</code>

Configure the database

configure_galera.ymlgenerates/etc/mysql/my.cnfand shuts down themysqldprocess. Why shut it down? Because the container this is running on is only for building the image and just as when creating a snapshot, it makes more sense to not have a running database with open file-handles that an image is created from.

<code data-lang="text">---# file: roles/docker-dna_percona/tasks/configure_galera.yml- name: Configure Percona XtraDB Cluster servertemplate: src=etc/mysql/my.cnf.j2dest=/etc/mysql/my.cnf- name: Stop MySQLaction: service name=mysql state=stopped</code>

Set up the clustercheck script forHAProxy

The last task,clustercheck.yml, sets up the python script used byHAProxyto determine which master to use. Why not the original xinetd-based clustercheck script? The author was never able to get the xinetd-based clustercheck script working with Docker.

<code data-lang="text"># file: roles/docker-dna_percona/tasks/clustercheck.yml- name: Copy clustercheck scriptcopy: src=usr/local/bin/pyclustercheck	dest=/usr/local/bin/pyclustercheck	owner=root	group=root	mode=0700</code>

Template generation

The templates for thedocker-dna_perconarole are themy.cnf.j2jinja template which is generated as/etc/mysql/my.cnfand transliterates the variables set in the previously-mentioned variables file. This snippet shows the Galera-specific mysql options. The cluster address is set to bootstrap. Remember that this is an image that is being built. One would need to useAnsibleto configure this value to reflect node membership state of the cluster when the containers are run that use this image as well as set different passwords.

<code data-lang="text">wsrep_provider= /usr/lib/libgalera_smm.sowsrep_slave_threads = 4wsrep_sst_method= xtrabackupwsrep_sst_auth= :wsrep_cluster_name= percona-clusterwsrep_cluster_address = gcomm://wsrep_provider_options= gcache.size=2G;</code>

Dockerfile goodness

Finally, theDockerfile! This is where all the work happens.

<code data-lang="text"># docker-dna/galera/Dockerfile## VERSION0.1.0#FROM capttofu/docker-dna_baseMAINTAINER Patrick aka CaptTofu Galbraith , patg@patg.net# Update distributionRUN apt-get update /	&& apt-get upgrade -y /	&& apt-get clean# Add filesADD . ./DockerDNA# Install Percona XtraDB Cluster RUN ( echo '[docker-dna_galera]' && /	echo 'localhost' /) > /etc/ansible/hosts /	&& ansible-playbook ./DockerDNA/dna.yml --connection=local /	&& apt-get clean# Expose MySQL/GaleraEXPOSE 3306 4444 4567 4568 9200ENTRYPOINT ["/usr/local/bin/mysql_run.sh"]</code>

The aboveDockerfilespecifies using thecapttofu/docker-dna_baseimage as a base. This image already has ansible and it's prerequisite libraries pre-installed and ready to use. The first event that is run in the Dockerfile is to update the apt system. Next, everything in the current repository is copied to aDockerDNAdirectory in the root directory of the temporary container.

Building the image

Next, by runningdocker build .in the same directory, the image will be built, using the pre-installed ansible, run with a l;ocal connection, in this case.

<code data-lang="text">docker-dna-galera/galera$ docker build .Uploading context 49.15 kBUploading contextStep 0 : FROM capttofu/docker-dna_basePulling repository capttofu/docker-dna_base1e47da3640f1: Download complete80cd3d2446e3: Download complete5607ff993e85: Download complete27e469823903: Download complete ---> 167dc428d943Step 1 : MAINTAINER Patrick aka CaptTofu Galbraith , patg@patg.net ---> Running in ceb1ec12aab7 ---> c7916cff77cdRemoving intermediate container ceb1ec12aab7Step 2 : RUN apt-get update&& apt-get upgrade -y&& apt-get clean ---> Running in d5b1189506ecGet:1 http://security.ubuntu.com precise-security Release.gpg [198 B]Get:2 http://ppa.launchpad.net precise Release.gpg [316 B] Hit http://archive.ubuntu.com precise/main Translation-enHit http://archive.ubuntu.com precise/universe Translation-enGet:20 http://archive.ubuntu.com precise-updates/main Translation-en [431 kB]Get:21 http://archive.ubuntu.com precise-updates/universe Translation-en [180 kB]Fetched 4734 kB in 20s (228 kB/s)Reading package lists...Reading package lists...Building dependency tree...Reading state information...The following packages have been kept back:ansible initscripts upstartThe following packages will be upgraded:apt apt-utils base-files ca-certificates curl dpkg file gnupg gpgv ifupdowninitramfs-tools initramfs-tools-bin iproute libapt-inst1.4 libapt-pkg4.12libc-bin libc6 libcurl3 libcurl3-gnutls libdrm-intel1 libdrm-nouveau1alibdrm-radeon1 libdrm2 libgnutls26 libmagic1 libssl1.0.0 libudev0libyaml-0-2 multiarch-support openssh-client openssl perl-base procpspython-apt python-apt-common python-software-properties python2.7python2.7-minimal tzdata udev40 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.Need to get 23.0 MB of archives.After this operation, 14.3 kB of additional disk space will be used.Get:1 http://archive.ubuntu.com/ubuntu/ precise-updates/main base-files amd64 6.5ubuntu6.7 [61.0 kB]Get:2 http://archive.ubuntu.com/ubuntu/ precise-updates/main dpkg amd64 1.16.1.2ubuntu7.5 [1829 kB]Get:40 http://archive.ubuntu.com/ubuntu/ precise-updates/main python-software-properties all 0.82.7.7 [23.5 kB]debconf: unable to initialize frontend: Dialogdebconf: (TERM is not set, so the dialog frontend is not usable.)debconf: falling back to frontend: ReadlineInstalling new version of config file /etc/issue.net ...ldconfig deferred processing now taking placeProcessing triggers for initramfs-tools ... ---> 0a8159128717Removing intermediate container d5b1189506ecStep 3 : ADD . ./DockerDNA ---> 93766d0fc5b2Removing intermediate container f4b216a8ddbfStep 4 : RUN ( echo '[docker-dna_galera]' &&echo 'localhost') > /etc/ansible/hosts&& ansible-playbook ./DockerDNA/dna.yml --connection=local&& apt-get clean ---> Running in e41cd0dba011PLAY [docker-dna_galera] ******************************************************GATHERING FACTS ***************************************************************ok: [localhost]TASK: [Install things I like] *************************************************changed: [localhost] => (item=vim)TASK: [Obtain Percona public key] *********************************************changed: [localhost]TASK: [Add Percona repository] ************************************************changed: [localhost]TASK: [Add Percona source repository] *****************************************changed: [localhost]TASK: [Update apt cache] ******************************************************ok: [localhost]TASK: [Install Percona XtraDB Cluster server] *********************************changed: [localhost] => (item=percona-xtradb-cluster-server-5.6,python-mysqldb,xinetd,telnet)TASK: [Copy the helper script] ************************************************changed: [localhost]TASK: [Add Docker database user] **********************************************changed: [localhost]TASK: [Add xtrabackup database user (for Galera SST)] *************************changed: [localhost]TASK: [Add clustercheck database user (for clustercheck/xinetd -> haproxy)] ***changed: [localhost]TASK: [Configure Percona XtraDB Cluster server] *******************************changed: [localhost]TASK: [Stop MySQL] ************************************************************ok: [localhost]TASK: [Copy clustercheck script] **********************************************changed: [localhost]TASK: [Copy clustercheck script] **********************************************changed: [localhost]</code>

Verifying image

When this has completed, the image,capttofu/docker-dna_base, will be ready to use, in this case a container runningPercona XtraDB Clusterthat will need to be managed by Ansible in order to set up the galera cluster.

<code data-lang="text">$ docker imagesREPOSITORY TAGIMAGE IDCREATED VIRTUAL SIZE<none> <none> cba0a737d93414 hours ago850.7 MBubuntu 12.10e314931015bd13 days ago 172.2 MBubuntu quantale314931015bd13 days ago 172.2 MBubuntu 13.10145762641db913 days ago 180.2 MBubuntu saucy145762641db913 days ago 180.2 MBubuntu 14.04ad892dd21d6013 days ago 275.5 MBubuntu latest ad892dd21d6013 days ago 275.5 MBcapttofu/docker-dna_base latest 167dc428d9434 months ago350.6 MBcapttofu/docker-dna_base 0.1.01e47da3640f14 months ago798.7 MBcapttofu/docker-dna_base 12.04.w1 5150446a5dd34 months ago350.6 MB</none></none></code>

Summary

This blog post showed the reader yet another way to useDockerandAnsibletogether to build Docker images by using aDockerfileto run Ansible to install packages and configure the temporary container that is being used to build the image. This provides yet another example of the flexibility of these two great applications and gives the user yet another method in their toolbox of solutions. Another side-benefit of this article was also learning how to installPercona XtraDB ClusterwithAnsible.