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https://github.com/muayyad-alsadi/docker-glue

Automated unattended pluggable docker management
https://github.com/muayyad-alsadi/docker-glue

docker docker-container load-balancer

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Automated unattended pluggable docker management

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README 

        
# Docker Glue



Automated unattended pluggable docker management based on docker events.

Can be used to update load-balancers, DNS, service discovery, ...etc. 

Managing docker containers would be as simple as tagging them with some labels



## Use Cases



- Dynamically add/remove containers to/from load-balancer (currently `haproxy` using `jinja2` templates)

- can send traffic of a specific domain to corresponding containers based on Host HTTP header

- can send traffic of a specific path prefix to corresponding containers 

- Replace `docker0` bridge,docker-proxy, ...etc with more advanced `SDN` (like `OVS` or OpenStack Neutron).

- Run a specific handler code (python plugins) or handler script based on docker events

- publish containers inspection to discovery service (like `etcd`)



## Daemons



- `docker-glue` the modular pluggable daemon that can run handlers and scripts

- `docker-balancer` a standalone daemon that just updates `haproxy` (a special case of glue)



You can pass `-1` to run once, and `-w` to wait for events, and `-h` for details. 



## Requirements and Installation



```

yum install haproxy python-docker-py python-jinja2

cp docker-balancer.service /etc/systemd/system/docker-balancer.service

cp docker-glue.service /etc/systemd/system/docker-glue.service

```



## Using Docker Balancer



you can set labels like (replace 80 with any port):



- `glue_http_80_host` the HTTP host to which this container would be attached in the load-balancer

- `glue_http_80_prefix` the prefix (without leading `/`) to attach it to

- `glue_http_80_strip_prefix` pass `1` if the prefix should be stripped before passing to backend

- `glue_http_80_weight` the weight (defaults to 100)



let's assume that you have started `docker-balancer -w` or the `docker-balancer` service



```

docker run -d --name wp1 -l glue_http_80_host='wp1.example.com' mywordpress/wordpress 

docker run -d --name wp2 -l glue_http_80_host='wp2.example.com' mywordpress/wordpress 

docker run -d --name os-ui1 -l glue_http_80_host=openstack.example.com -l glue_http_80_prefix=dashboard/horizon myopenstack/horizon

docker run -d --name os-id1 -l glue_http_80_host=openstack.example.com -l glue_http_80_prefix=identity/keystone myopenstack/keystone

```



## Using Docker Glue



in `docker-glue.d` you have many `.example` files copy the files you need to remove that extension, for example

```

cd docker-glue.d

cp lb.ini.example lb.ini

cp test.ini.example test.ini

cd ..

```



then start `docker-glue` daemon or run `docker-glue -w`



## Handlers INI files



files in `docker-glue.d/*.ini` (we have included examples) looks like this



```

[handler]

class=DockerGlue.handlers.exec.ScriptHandler

events=all

enabled=1

triggers-none=0



[params]

script=test-handler.sh

demo-option=some value

```



`handler` section specifies what and when to run



- `class` the handler plugin, which can be one of 

  - `DockerGlue.handlers.exec.ScriptHandler` executes a shell script

    - `test-handler.sh` a demo script that logs the event to `/tmp/docker-glue-test.log`

    - `ovs-handler.sh` connect the container to `OpenVSwicth`

  - `DockerGlue.handlers.lb.HAProxyHandler` load balancer that uses HAProxy

  - `DockerGlue.handlers.publishers.distconfig.Publisher` publish containers to discovery service like etcd

- `events` the even statuses (comma separated) that triggers this handler, can be `none` (which is dummy event) or `all` (which does not include `none`)

- `enabled`

- `triggers-none` - set it if you want this handler to triggers `none` dummy event



`params` section is custom params to be passed to the handler



## Writing script plugins



scripts in `handler-scripts` will be passed the ini path and docker event and the docker container id for example it might be like this `test-handler.sh test.ini start 123456`



the code of `test-handler.sh` look like this



```bash

#! /bin/bash



cd `dirname $0`



function error() {

    echo "$@"

    exit -1

}



[ $# -ne 3 ] && error "Usage `basename $0` config.ini status container_id"

ini="$1"

status="$2"

container_id="$3"

ini_demo_option=$( crudini --inplace --get $ini params demo-option 2>/dev/null || : )

echo "`date +%F` container_id=[$container_id] status=[$status] ini_demo_option=[$ini_demo_option]" >> /tmp/docker-glue-test.log

```



as you can see you can read options using `crudini` from the passed ini file.



## Writing python plugins



just extend `BaseHandler` and in the `__init__` do what ever you need, and read your custom params from the ini and implement a handle method like this



```python

from . import BaseHandler



logger = logging.getLogger(__name__)



class DemoHandler(BaseHandler):

    def __init__(self, agent, ini_file, ini):

        BaseHandler.__init__(self, agent, ini_file, ini)

        self.custom_param=ini.get('params', 'custom_param') if ini.has_option('params', 'custom_param') else None

        

    def handle(self, event, container_id):

        logger.info('got event=%r on container=%r and custom_param=%r', event, container_id, self.custom_param)



```



## TODO



- implement TCP/UDP load balancing using ipvsadm or keepalived