[Systems] Docker containers in SL

[Samuel Cantero]

Hi all,

This email is to make some notes regarding to our current services running
in Docker containers. The main idea is to enable anyone to fix a container
problem or deploy a new one. This will be a long email, sorry for that.
After this email thread, we should write some documentation in our wiki.

*How are we running Docker currently?*

We are using a bridged network with Docker and it lets us publish a service
using a specific port in freedom. Then we proxy-pass the service through
nginx (port 80).
There is a bridge called docker0 and every container has an interface
inside this bridge. This is managed automatically by Docker.

*What are the services currently running in a Docker container?*

The current running containers are:

1) org.sugarlabs.bugs.

Trac instance. Listening on port 5007.

You can check this on 18.85.44.59:5007. Then we proxy this in nginx
(/etc/nginx/sites-available/bugs.sugarlabs.org) using:

location / {
                proxy_pass http://localhost:5007;
        }

2) org.sugarlabs.hook.

Web hook for SL activities? Listening on port 5004.

3) kafka: linked with zookeeper. Listening on port 9092.
4) zookeeper. Listening on port 2181. Locally open ports 2888 and 3888.

What are we using kafka and zookeeper?

5) org.sugarlabs.socialhelp_sso.

Apparently for socialhelp.sugarlabs.org/sso. is it working? Listening on
port 5005.

6) org.sugarlabs.bundlebin.

Like a pastebin for SL. The code is hosted on
http://github.com/samdroid-apps/bundlebin. Listening on port 5000.

7) org.sugarlabs.nagios.

Nagios instance. Currently not working the postfix service inside the
container. I should fix this or we should create a common postfix container
in order to link this and other containers to it.

Listening on port 8081.

8) today.sam.sugarstick-creator

Listening on port 5008.
Can you explain a little more about this?

9) rethinkdb

Only listening locally on ports 8080, 28015 and 29015. What is the purpose
of this container?

10) org.sugarlabs.activities-2

Listening on port 5006.
Self descriptive. are we going to kill it?

11) org.sugarlabs.use-socialhelp

Listening on port 5003.

12) org.sugarlabs.help_rebuilder

Not listening. According to main.py, this is used with kafka.

13) local_discourse/app

Listening on port 8002 (web) and 2222 (ssh). Here we host socialhelp.sl.o.

Sam, if you can give more information about each container would be pretty
useful for everyone.

*How we build the images and containers?*

Docker can build images automatically by reading instructions from a
Dockerfile, a text file that contains all the commands, in order, needed to
build a given image. We host all the files needed by a every container in
/containers. Actually, we can find there a symlink for every container. For
example:

org.sugarlabs.bugs -> /srv/containers/org.sugarlabs.bugs/

In case we want to deploy a new service, we can write our own Dockerfile or
we can get one from DockerHub (docker image repository).

We can check the built images in our host with:

docker images

We can create a image from a Dockerfile executing the following command:

docker build -t OUR-IMAGE-NAME .

In the last example, the *cwd* is the container folder where the dockerfile
resides. Once the image is created, we can create a container (that run as
a daemon) from that image executing:

docker run -d --name CONTAINER-NAME IMAGE-NAME

In the last command, we are not publishing our service. In order to bind a
container to a specific port we should the -p flag. For example;

docker run -d -p 8081:80 --name CONTAINER-NAME IMAGE-NAME

This would map port 80 inside the container to port 8081 on Freedom.

We can customize our container at the moment of its deploying giving to the
docker run command some options. For example:

--cpu-quota: in order to limit CPU usage. We have another email thread
explaining its usage.
--memory: memory limit. We have another email thread explaining its usage.
--restart: restart policy to apply when a container exists.
--volume: bind mount a volume. Very useful to keep container files inside
our own chosen location instead of a docker default location. For example:
keeping configuration files of nagios inside /srv/nagios3. This let us
re-create the entire container every time we need/want without losing any
data.

Example:

docker run -d -p 8081:80 --cpu-quota=20000 --memory=512M
--volume=/srv/nagios3:/etc/nagios3 --name org.sugarlabs.nagios nagios

In Sugar Labs, we use a Sam's script called container.yml [1] in order to
make docker container configurations live in files. So, we can store all
this container configuration inside a container.yml file :-)

For example: *container.yml*
ports:
 - 8081:80

volumes:
 - /srv/nagios3:/etc/nagios3
 - /srv/nagios-plugins:/usr/lib/nagios/plugins

memory: 512m
cpu: 20

In order to run the container with the settings defined in the
container.yml file, we simply do:

container.yml start -d

We can also build images using container.yml script. It is a good idea to
read container.yml code in order to understand how it works.

*How can we check a containers' status?*

docker ps

*How can we stop/start a container?*

Stop: docker stop CONTAINER-NAME

Start: docker start CONTAINER-NAME

We can also use start/stop from sam's script.

*How can we get a console from a Container?*

docker exec -it [CONTAINER-ID or CONTAINER-NAME] bash

Best regards,

Samuel C.


[1] https://github.com/sugarlabs-infra/container.yml
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