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Last pushed: 2 years ago
Short Description
A custom reverse proxying solution based on HAProxy for a docker network infrastructure.
Full Description

Logo by Camille BRIZARD


This project is licensed under the terms of the MIT license.

Last version : 2.1.0


Docker introduced Docker Networks with version 1.9. With that update you can now have multiple web servers linked to the same network and a reverse proxy in front of them all without having to manage links manually. First, I was using HAProxy to do this role but HAProxy wasn't flexible enough : I was facing an issue, sometimes my containers weren't running while I was starting up my reverse and because HAProxy force name resolving at startup it was crashing almost every time. So I decided to create a system that add a smart layer upon HAProxy using a simple ruby script.

How it works

It uses alpine as a base distribution to provide a lightweight image. It includes ruby (with 1 gem : FileWatcher) and HAProxy, that's all. At startup, SuperWhale will launch /bin/superwhale : the main process of the container.

superwhale will search for services inside the /etc/superwhale.d folder, create HAProxy configuration and then start HAProxy. It will also watch for file modifications inside /etc/hosts or /etc/superwhale.d and will semi-gracefully reload HAProxy if there is any.

How to use it

Defining services

A service is the superwhale representation of a backend webserver that needs to be reverse proxied. To declare a service create an YAML file and put it inside the /etc/superwhale.d folder. For instance :

  domain_name: git.mydomain.tld
   - host: git_container
     port: 80
   - option forwardfor
   - http-request set-header X-Client-IP %[src]
   - http-request set-header Host git.mydomain.tld

Will output this inside HAProxy configuration ONLY if a git_container is present on the relevant docker network :


frontend public
  acl host_git hdr(host) -i git.mydomain.tld
  use_backend git_backend if host_git

backend git_backend
  server git1 git:80
  option forwardfor
  http-request set-header X-Client-IP %[src]
  http-request set-header Host git.mydomain.tld


You can define multiple backends to create a load-balanced backend and the load-balancing algorithm used between them.

Here is an exhaustive list of what you can define for a service :

Option Type Usage
domain_name string Define the domain name used to determine the backend
backends {host: 'hostname',port: port_int}[] Address of the backend server
balance string Define the load-balance algorithm for the backend pool
options string[] Options added to the backend block
is_default bool If true, add default_backend with this backend. Only one service can define this option.
Configuring superwhale

You can tune superwhale configuration using the its configuration file : /etc/superwhale.d/configs/superwhale.yml. Here is the default version of this file :

# Redirect all HTTP traffic to its HTTPS counterpart
force_ssl: false

# If you want some domains/sub-domains to not be ssl forced, uncomment this
# - my.domain.tld
# - [...]

# Change the log level : debug, info (default) and warning
log_level: info
Semi-gracefull reload

When reloading, Superwhale will do a soft-stop before restarting the process. There is a little time at startup when connections will be refused. That's why I called it "Semi-gracefull" reload.

Here is what HAProxy documentation says about soft-stop :

2.4) Soft stop
It is possible to stop services without breaking existing connections by the
sending of the SIGUSR1 signal to the process. All services are then put into
soft-stop state, which means that they will refuse to accept new connections,
except for those which have a non-zero value in the 'grace' parameter, in which
case they will still accept connections for the specified amount of time, in
milliseconds. This makes it possible to tell a load-balancer that the service
is failing, while still doing the job during the time it needs to detect it.
Setting haproxy.cfg header

You can modify the header.cfg file in /etc/superwhale.d.


You can use HTTPS by simply adding certificate file : /etc/superwhale.d/https.pem. This certificate is the concatenation of the certificate and the private key :

$ cat server.crt server.key > /etc/superwhale.d/https.pem

If you want to redirect all traffic to HTTPS, switch the force_ssl boolean to true inside the superwhale configuration file.

Launching the container

There is two way of using this container :

With volumes

While launching the container, use the -v argument :

docker run -d \
    -v /mnt/volumes/superwhale/:/etc/superwhale.d \
    -p 80:80 -p 443:443 --net=dockernet ingensi/superwhale
With inheritance

Create a Dockerfile and inherits from ingensi/superwhale :

FROM ingensi/superwhale:latest

COPY ./service1.yml /etc/superwhale.d/service1.yml


Want to contribute ?
  • Fork the project.
  • Make your feature addition or bug fix.
  • Commit, do not mess with version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull).
  • Send me a pull request.

Jérémy SEBAN - Main contributor - (GitHub:

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