Configuring docker to use rexray and Ceph for persistent storage

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For various reasons I wanted to play with docker containers backed by persistent Ceph storage. rexray seemed like the way to do that, so here are my notes on getting that working…

First off, I needed to install rexray:

    root@labosa:~/rexray# curl -sSL https://dl.bintray.com/emccode/rexray/install | sh
    Selecting previously unselected package rexray.
    (Reading database ... 177547 files and directories currently installed.)
    Preparing to unpack rexray_0.9.0-1_amd64.deb ...
    Unpacking rexray (0.9.0-1) ...
    Setting up rexray (0.9.0-1) ...
    
    rexray has been installed to /usr/bin/rexray
    
    REX-Ray
    -------
    Binary: /usr/bin/rexray
    Flavor: client+agent+controller
    SemVer: 0.9.0
    OsArch: Linux-x86_64
    Branch: v0.9.0
    Commit: 2a7458dd90a79c673463e14094377baf9fc8695e
    Formed: Thu, 04 May 2017 07:38:11 AEST
    
    libStorage
    ----------
    SemVer: 0.6.0
    OsArch: Linux-x86_64
    Branch: v0.9.0
    Commit: fa055d6da595602715bdfd5541b4aa6d4dcbcbd9
    Formed: Thu, 04 May 2017 07:36:11 AEST
    

Which is of course horrid. What that script seems to have done is install a deb’d version of rexray based on an alien’d package:

    root@labosa:~/rexray# dpkg -s rexray
    Package: rexray
    Status: install ok installed
    Priority: extra
    Section: alien
    Installed-Size: 36140
    Maintainer: Travis CI User <travis@testing-gce-7fbf00fc-f7cd-4e37-a584-810c64fdeeb1>
    Architecture: amd64
    Version: 0.9.0-1
    Depends: libc6 (>= 2.3.2)
    Description: Tool for managing remote & local storage.
     A guest based storage introspection tool that
     allows local visibility and management from cloud
     and storage platforms.
     .
     (Converted from a rpm package by alien version 8.86.)
    

If I was building anything more than a test environment I think I’d want to do a better job of installing rexray than this, so you’ve been warned.

Next to configure rexray to use Ceph. The configuration details are cunningly hidden in the libstorage docs, and aren’t mentioned at all in the rexray docs, so you probably want to take a look at the libstorage docs on ceph. First off, we need to install the ceph tools, and copy the ceph authentication information from the the ceph we installed using openstack-ansible earlier.

    root@labosa:/etc# apt-get install ceph-common
    root@labosa:/etc# scp -rp 172.29.239.114:/etc/ceph .
    The authenticity of host '172.29.239.114 (172.29.239.114)' can't be established.
    ECDSA key fingerprint is SHA256:SA6U2fuXyVbsVJIoCEHL+qlQ3xEIda/MDOnHOZbgtnE.
    Are you sure you want to continue connecting (yes/no)? yes
    Warning: Permanently added '172.29.239.114' (ECDSA) to the list of known hosts.
    rbdmap                       100%   92     0.1KB/s   00:00
    ceph.conf                    100%  681     0.7KB/s   00:00
    ceph.client.admin.keyring    100%   63     0.1KB/s   00:00
    ceph.client.glance.keyring   100%   64     0.1KB/s   00:00
    ceph.client.cinder.keyring   100%   64     0.1KB/s   00:00
    ceph.client.cinder-backup.keyring   71     0.1KB/s   00:00
    root@labosa:/etc# modprobe rbd
    

You also need to configure rexray. My first attempt looked like this:

    root@labosa:/var/log# cat /etc/rexray/config.yml
    libstorage:
      service: ceph
    

And the rexray output sure made it look like it worked…

    root@labosa:/etc# rexray service start
    ● rexray.service - rexray
       Loaded: loaded (/etc/systemd/system/rexray.service; enabled; vendor preset: enabled)
       Active: active (running) since Mon 2017-05-29 10:14:07 AEST; 33ms ago
     Main PID: 477423 (rexray)
        Tasks: 5
       Memory: 1.5M
          CPU: 9ms
       CGroup: /system.slice/rexray.service
               └─477423 /usr/bin/rexray start -f
    
    May 29 10:14:07 labosa systemd[1]: Started rexray.
    

Which looked good, but /var/log/syslog said:

    May 29 10:14:08 labosa rexray[477423]: REX-Ray
    May 29 10:14:08 labosa rexray[477423]: -------
    May 29 10:14:08 labosa rexray[477423]: Binary: /usr/bin/rexray
    May 29 10:14:08 labosa rexray[477423]: Flavor: client+agent+controller
    May 29 10:14:08 labosa rexray[477423]: SemVer: 0.9.0
    May 29 10:14:08 labosa rexray[477423]: OsArch: Linux-x86_64
    May 29 10:14:08 labosa rexray[477423]: Branch: v0.9.0
    May 29 10:14:08 labosa rexray[477423]: Commit: 2a7458dd90a79c673463e14094377baf9fc8695e
    May 29 10:14:08 labosa rexray[477423]: Formed: Thu, 04 May 2017 07:38:11 AEST
    May 29 10:14:08 labosa rexray[477423]: libStorage
    May 29 10:14:08 labosa rexray[477423]: ----------
    May 29 10:14:08 labosa rexray[477423]: SemVer: 0.6.0
    May 29 10:14:08 labosa rexray[477423]: OsArch: Linux-x86_64
    May 29 10:14:08 labosa rexray[477423]: Branch: v0.9.0
    May 29 10:14:08 labosa rexray[477423]: Commit: fa055d6da595602715bdfd5541b4aa6d4dcbcbd9
    May 29 10:14:08 labosa rexray[477423]: Formed: Thu, 04 May 2017 07:36:11 AEST
    May 29 10:14:08 labosa rexray[477423]: time="2017-05-29T10:14:08+10:00" level=error
    msg="error starting libStorage server" error.driver=ceph time=1496016848215
    May 29 10:14:08 labosa rexray[477423]: time="2017-05-29T10:14:08+10:00" level=error
    msg="default module(s) failed to initialize" error.driver=ceph time=1496016848216
    May 29 10:14:08 labosa rexray[477423]: time="2017-05-29T10:14:08+10:00" level=error
    msg="daemon failed to initialize" error.driver=ceph time=1496016848216
    May 29 10:14:08 labosa rexray[477423]: time="2017-05-29T10:14:08+10:00" level=error
    msg="error starting rex-ray" error.driver=ceph time=1496016848216
    

That’s because the service is called rbd it seems. So, the config file ended up looking like this:

    root@labosa:/var/log# cat /etc/rexray/config.yml
    libstorage:
      service: rbd
    
    rbd:
      defaultPool: rbd
    

Now to install docker:

    root@labosa:/var/log# sudo apt-get update
    root@labosa:/var/log# sudo apt-get install linux-image-extra-$(uname -r) \
        linux-image-extra-virtual
    root@labosa:/var/log# sudo apt-get install apt-transport-https \
        ca-certificates curl software-properties-common
    root@labosa:/var/log# curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
    root@labosa:/var/log# sudo add-apt-repository \
        "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
        $(lsb_release -cs) \
        stable"
    root@labosa:/var/log# sudo apt-get update
    root@labosa:/var/log# sudo apt-get install docker-ce
    

Now let’s make a rexray volume.

    root@labosa:/var/log# rexray volume ls
    ID  Name  Status  Size
    root@labosa:/var/log# docker volume create --driver=rexray --name=mysql \
        --opt=size=1
    A size of 1 here means 1gb
    mysql
    root@labosa:/var/log# rexray volume ls
    ID         Name   Status     Size
    rbd.mysql  mysql  available  1
    

Let’s start the container.

    root@labosa:/var/log# docker run --name some-mysql --volume-driver=rexray \
        -v mysql:/var/lib/mysql -e MYSQL_ROOT_PASSWORD=my-secret-pw -d mysql
    Unable to find image 'mysql:latest' locally
    latest: Pulling from library/mysql
    10a267c67f42: Pull complete
    c2dcc7bb2a88: Pull complete
    17e7a0445698: Pull complete
    9a61839a176f: Pull complete
    a1033d2f1825: Pull complete
    0d6792140dcc: Pull complete
    cd3adf03d6e6: Pull complete
    d79d216fd92b: Pull complete
    b3c25bdeb4f4: Pull complete
    02556e8f331f: Pull complete
    4bed508a9e77: Pull complete
    Digest: sha256:2f4b1900c0ee53f344564db8d85733bd8d70b0a78cd00e6d92dc107224fc84a5
    Status: Downloaded newer image for mysql:latest
    ccc251e6322dac504e978f4b95b3787517500de61eb251017cc0b7fd878c190b
    

And now to prove that persistence works and that there’s nothing up my sleeve…


    root@labosa:/var/log# docker run -it --link some-mysql:mysql --rm mysql \
        sh -c 'exec mysql -h"$MYSQL_PORT_3306_TCP_ADDR" \
        -P"$MYSQL_PORT_3306_TCP_PORT" -uroot -p"$MYSQL_ENV_MYSQL_ROOT_PASSWORD"'
    mysql: [Warning] Using a password on the command line interface can be insecure.
    Welcome to the MySQL monitor.  Commands end with ; or \g.
    Your MySQL connection id is 3
    Server version: 5.7.18 MySQL Community Server (GPL)
    
    Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
    
    Oracle is a registered trademark of Oracle Corporation and/or its
    affiliates. Other names may be trademarks of their respective
    owners.
    
    Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
    
    mysql> show databases;
    +--------------------+
    | Database           |
    +--------------------+
    | information_schema |
    | mysql              |
    | performance_schema |
    | sys                |
    +--------------------+
    4 rows in set (0.00 sec)
    
    mysql> create database demo;
    Query OK, 1 row affected (0.03 sec)
    
    mysql> use demo;
    Database changed
    mysql> create table foo(val char(5));
    Query OK, 0 rows affected (0.14 sec)
    
    mysql> insert into foo(val) values ('a'), ('b'), ('c');
    Query OK, 3 rows affected (0.08 sec)
    Records: 3  Duplicates: 0  Warnings: 0
    
    mysql> select * from foo;
    +------+
    | val  |
    +------+
    | a    |
    | b    |
    | c    |
    +------+
    3 rows in set (0.00 sec)
    

Now let’s re-create the container and prove the data remains.

    root@labosa:/var/log# docker stop some-mysql
    some-mysql
    root@labosa:/var/log# docker rm some-mysql
    some-mysql
    root@labosa:/var/log# docker run --name some-mysql --volume-driver=rexray \
        -v mysql:/var/lib/mysql -e MYSQL_ROOT_PASSWORD=my-secret-pw -d mysql
    99a7ccae1ad1865eb1bcc8c757251903dd2f1ac7d3ce4e365b5cdf94f539fe05
    
    root@labosa:/var/log# docker run -it --link some-mysql:mysql --rm mysql \
        sh -c 'exec mysql -h"$MYSQL_PORT_3306_TCP_ADDR" -\
        P"$MYSQL_PORT_3306_TCP_PORT" -uroot -p"$MYSQL_ENV_MYSQL_ROOT_PASSWORD"'
    mysql: [Warning] Using a password on the command line interface can be insecure.
    Welcome to the MySQL monitor.  Commands end with ; or \g.
    Your MySQL connection id is 3
    Server version: 5.7.18 MySQL Community Server (GPL)
    
    Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
    
    Oracle is a registered trademark of Oracle Corporation and/or its
    affiliates. Other names may be trademarks of their respective
    owners.
    
    Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
    
    mysql> use demo;
    Reading table information for completion of table and column names
    You can turn off this feature to get a quicker startup with -A
    
    Database changed
    mysql> select * from foo;
    +------+
    | val  |
    +------+
    | a    |
    | b    |
    | c    |
    +------+
    3 rows in set (0.00 sec)
    

So there you go.

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