HAProxy image that balances between linked containers and, if launched in Docker Cloud or using Docker Compose v2, reconfigures itself when a linked cluster member redeploys, joins or leaves.

The availabe version can be found here: https://hub.docker.com/r/dockercloud/haproxy/tags/

• latest is buit againt master brach
• staging is built againt staging branch
• x.x.x is built againt git tags on github

Attention : Please ALWAYS use a specific image tag that works for you. DO NOT use dockercloud/haproxy:latest in any situation other than testing purpose.

You can use dockercloud/haproxy in three different ways:

• running in Docker Cloud
• running with docker legacy links
• running with Docker Compose v2(new links, compatible with Docker Swarm)

1. Launch the service you want to load-balance using Docker Cloud.

2. Launch the load balancer. To do this, select "Jumpstarts", "Proxies" and select dockercloud/haproxy. During the "Environment variables" step of the wizard, link to the service created earlier (the name of the link is not important), and add "Full Access" API role (this will allow HAProxy to be updated dynamically by querying Docker Cloud's API).

   Note:

   • If you are using docker-cloud cli, or stackfile, please set roles to global
   • Please DO NOT set sequential_deployment: true on this image.

That's it - the haproxy container will start querying Docker Cloud's API for an updated list of containers in the service and reconfigure itself automatically, including:

• start/stop/terminate containers in the linked application services
• start/stop/terminate/scale up/scale down/redeploy the linked application services
• add new links to HAProxy
• remove old links from HAProxy

web:
  image: 'dockercloud/hello-world:latest'
  target_num_containers: 2
lb:
  image: 'dockercloud/haproxy:latest'
  links:
    - web
  ports:
    - '80:80'
  roles:
    - global

Legacy link refers to the link created before docker 1.10, and the link created in default bridge network in docker 1.10 or after.

docker run -d --name web1 dockercloud/hello-world
docker run -d --name web2 dockercloud/hello-world
docker run -d -p 80:80 --link web1:web1 --link web2:web2 dockercloud/haproxy

web1:
  image: 'dockercloud/hello-world:latest'
web2:
  image: 'dockercloud/hello-world:latest'
lb:
  image: 'dockercloud/haproxy:latest'
  links:
    - web1
    - web2
  ports:
    - '80:80'

Note: Any link alias sharing the same prefix and followed by "-/_" with an integer is considered to be from the same service. For example: web-1 and web-2 belong to service web, app_1 and app_2 are from service app, but app1 and web2 are from different services.

Docker Compose 1.6 supports a new format of the compose file. In the new version(v2), the old link that injects environment variables is deprecated.

Similar to using legacy links, here list some differences that you need to notice:

• This image must be run using Docker Compose, as it relies on the Docker Compose labels for configuration.
• The container needs access to the docker socket, you must mount the correct files and set the related environment to make it work.
• A link is required in order to ensure that dockercloud/haproxy is aware of which service it needs to balance, although links are not needed for service discovery since docker 1.10. Linked aliases are not required.
• DO not overwrite HOSTNAME environment variable in dockercloud/haproxy container.
• As it is the case on Docker Cloud, auto reconfiguration is supported when the linked services scales or/and the linked container starts/stops.
• The container name is maintained by docker-compose, and used for service discovery as well. Please DO NOT change container_name of the linked service in the compose file to a non-standard name. Otherwise, that service will be ignored.

version: '2'
services:
  web:
    image: dockercloud/hello-world
   lb:
    image: dockercloud/haproxy
    links:
      - web
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    ports:
      - 80:80

version: '2'
services:
  web:
    image: dockercloud/hello-world
  lb:
    image: dockercloud/haproxy
    links:
      - web
    environment:
      - DOCKER_TLS_VERIFY
      - DOCKER_HOST
      - DOCKER_CERT_PATH
    volumes:
      - $DOCKER_CERT_PATH:$DOCKER_CERT_PATH
    ports:
      - 80:80

Once the stack is up, you can scale the web service using docker-compose scale web=3. dockercloud/haproxy will automatically reload its configuration.

When using links like previous section, the Docker Swarm scheduler can be too restrictive. Even with overlay network, swarm (As of 1.1.0) will attempt to schedule haproxy on the same node as the linked service due to legacy links behavior. This can cause unwanted scheduling patterns or errors such as "Unable to find a node fulfilling all dependencies..."

Since Compose V2 allows discovery through the service names, Dockercloud haproxy only needs the links to indentify which service should be load balanced.

A second option is to use the ADDITIONAL_SERVICES variable for indentification of services.

• Set the ADDITIONAL_SERVICES env variable to your linked services.
• You also want to set depends_on to ensure the web service is started before haproxy so that the hostname can be resolved. This controls scheduling order but not location.
• The container still needs access to the docker daemon to get load balanced containers' configs.
• If any trouble with haproxy not updating the config, try running reload.sh or set the DEBUG envvar.
• This image is also compatible with Docker Swarm, and supports the docker native overlay network across multi-hosts.

version: '2'
services:
  web:
    image: dockercloud/hello-world
  blog:
    image: dockercloud/hello-world
  lb:
    image: dockercloud/haproxy
	   depends_on:
         - web
         - blog
       environment:
         - ADDITIONAL_SERVICES=project_dir:web,project_dir:blog
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    ports:
      - 80:80

Settings in this part is immutable, you have to redeploy HAProxy service to make the changes take effects

Settings here can overwrite the settings in HAProxy, which are only applied to the linked services. If run in Docker Cloud, when the service redeploys, joins or leaves HAProxy service, HAProxy service will automatically update itself to apply the changes

Check the HAProxy configuration manual for more information on the above.

Both virtual host and virtual path can be specified in environment variable VIRTUAL_HOST, which is a set of comma separated urls with the format of [scheme://]domain[:port][/path].

Note:

1. The sequence of the acl rules generated based on VIRTUAL_HOST are random. In HAProxy, when an acl rule with a wide scope(e.g. *.example.com) is put before a rule with narrow scope(e.g. web.example.com), the narrow rule will never be reached. As a result, if the virtual hosts you set have overlapping scopes, you need to use VIRTUAL_HOST_WEIGHT to manually set the order of acl rules, namely, giving the narrow virtual host a higher weight than the wide one.
2. Every service that has the same VIRTUAL_HOST environment variable setting will be considered and merged into one single service. It may be useful for some testing scenario.

dockercloud/haproxy supports ssl termination on multiple certificates. For each application that you want ssl terminates, simply set SSL_CERT and VIRTUAL_HOST. HAProxy, then, reads the certificate from the link environment and sets the ssl termination up.

Attention: there was a bug that if an environment variable value contains "=", which is common in the SSL_CERT, docker skips that environment variable. As a result, multiple ssl termination only works on docker 1.7.0 or higher, or in Docker Cloud.

SSL termination is enabled when:

1. at least one SSL certificate is set, and
2. either VIRTUAL_HOST is not set, or it is set with "https" as the scheme.

To set SSL certificate, you can either:

1. set DEFAULT_SSL_CERT in dockercloud/haproxy, or
2. set SSL_CERT and/or DEFAULT_SSL_CERT in the application services linked to HAProxy

The difference between SSL_CERT and DEFAULT_SSL_CERT is that, the multiple certificates specified by SSL_CERT are stored in as cert1.pem, cert2.pem, ..., whereas the one specified by DEFAULT_SSL_CERT is always stored as cert0.pem. In that case, HAProxy will use cert0.pem as the default certificate when there is no SNI match. However, when multiple DEFAULT_SSL_CERTIFICATE is provided, only one of the certificates can be stored as cert0.pem, others are discarded.

The certificate specified in dockercloud/haproxy or in the linked application services is a pem file, containing a private key followed by a public certificate(private key must be put before the public certificate and any extra Authority certificates, order matters). You can run the following script to generate a self-signed certificate:

openssl req -x509 -newkey rsa:2048 -keyout key.pem -out ca.pem -days 1080 -nodes -subj '/CN=*/O=My Company Name LTD./C=US'
cp key.pem cert.pem
cat ca.pem >> cert.pem

Once you have the pem file, you can run this command to convert the file correctly to one line:

awk 1 ORS='\\n' cert.pem

Copy the output and set it as the value of SSL_CERT or DEFAULT_SSL_CERT.

There are three method to setup affinity and sticky session:

1. set BALANCE=source in your application service. When setting source method of balance, HAProxy will hash the client IP address and make sure that the same IP always goes to the same server.
2. set APPSESSION=<value>. use application session to determine which server a client should connect to. Possible value of <value> could be JSESSIONID len 52 timeout 3h
3. set COOKIE=<value>. use application cookie to determine which server a client should connect to. Possible value of <value> could be SRV insert indirect nocache

Check HAProxy:appsession and HAProxy:cookie for more information.

By default, dockercloud/haproxy runs in http mode. If you want a linked service to run in a tcp mode, you can specify the environment variable TCP_PORTS, which is a comma separated ports(e.g. 9000, 9001).

For example, if you run:

docker --name app-1 --expose 9000 --expose 9001 -e TCP_PORTS="9000, 9001" your_app
docker --name app-2 --expose 9000 --expose 9001 -e TCP_PORTS="9000, 9001" your_app
docker run --link app-1:app-1 --link app-2:app-2 -p 9000:9000, 9001:9001 dockercloud/haproxy

Then, haproxy balances the load between app-1 and app-2 in both port 9000 and 9001 respectively.

Moreover, If you have more exposed ports than TCP_PORTS, the rest of the ports will be balancing using http mode.

For example, if you run:

docker --name app-1 --expose 80 --expose 22 -e TCP_PORTS=22 your_app
docker --name app-2 --expose 80 --expose 22 -e TCP_PORTS=22 your_app
docker run --link app-1:app-2 --link app-2:app-2 -p 80:80 -p 22:22 dockercloud/haproxy

Then, haproxy balances in http mode at port 80 and balances in tcp on port at port 22.

In this way, you can do the load balancing both in tcp and in http at the same time.

In TCP_PORTS, if you set port that ends with '/ssl', for example 2222/ssl, HAProxy will set ssl termination on port 2222.

Note:

1. You are able to set VIRTUAL_HOST and TCP_PORTS at the same them, giving more control on http mode.
2. Be careful that, the load balancing on tcp port is applied to all the services. If you link two(or more) different services using the same TCP_PORTS, dockercloud/haproxy considers them coming from the same service.

There are two ways to enable the support of websocket:

1. As websocket starts using HTTP protocol, you can use virtual host to specify the scheme using ws or wss. For example, `-e VIRTUAL_HOST="ws://ws.example.com, wss://wss.example.com"
2. Websocket itself is a TCP connection, you can also try the TCP load balancing mentioned in the previous section.

Use the following:

docker run -d --expose 80 --name webapp dockercloud/hello-world
docker run -d --link webapp:webapp -p 80:80 dockercloud/haproxy

docker run -d -e EXCLUDE_PORTS=8803,8806 --expose 80 --expose 8033 --expose 8086 --name webapp dockercloud/hello-world
docker run -d --link webapp:webapp -p 80:80 dockercloud/haproxy

Use the following:

docker run -d --expose 8080 --name webapp your_app
docker run -d --link webapp:webapp -p 8080:80 dockercloud/haproxy

#### I want the proxy to terminate SSL connections and forward plain HTTP requests to my webapp to port 8080(or any port)

Use the following:

docker run -d -e SSL_CERT="YOUR_CERT_TEXT" --name webapp dockercloud/hello-world
docker run -d --link webapp:webapp -p 443:443 -p 80:80 dockercloud/haproxy

or

docker run -d --link webapp:webapp -p 443:443 -p 80:80 -e DEFAULT_SSL_CERT="YOUR_CERT_TEXT" dockercloud/haproxy

The certificate in YOUR_CERT_TEXT is a combination of private key followed by public certificate. Remember to put \n between each line of the certificate. A way to do this, assuming that your certificate is stored in ~/cert.pem, is running the following:

docker run -d --link webapp:webapp -p 443:443 -p 80:80 -e DEFAULT_SSL_CERT="$(awk 1 ORS='\\n' ~/cert.pem)" dockercloud/haproxy

Use the following:

docker run -d -e FORCE_SSL=yes -e SSL_CERT="YOUR_CERT_TEXT" --name webapp dockercloud/hello-world
docker run -d --link webapp:webapp -p 443:443 dockercloud/haproxy

You can use CERT_FOLDER envvar to specify which folder the certificates are mounted in the container, using the following:

docker run -d --name webapp dockercloud/hello-world
docker run -d --link webapp:webapp -e CERT_FOLDER="/certs/" -v $(pwd)/cert1.pem:/certs/cert1.pem -p 443:443 dockercloud/haproxy

Virtual hosts can be configured by the proxy reading linked container environment variables (VIRTUAL_HOST). Here is an example:

docker run -d -e VIRTUAL_HOST="www.webapp1.com, www.webapp1.org" --name webapp1 dockercloud/hello-world
docker run -d -e VIRTUAL_HOST=www.webapp2.com --name webapp2 your/webapp2
docker run -d --link webapp1:webapp1 --link webapp2:webapp2 -p 80:80 dockercloud/haproxy

In the example above, when you access http://www.webapp1.com or http://www.webapp1.org, it will show the service running in container webapp1, and http://www.webapp2.com will go to container webapp2.

If you use the following:

docker run -d -e VIRTUAL_HOST=www.webapp1.com --name webapp1 dockercloud/hello-world
docker run -d -e VIRTUAL_HOST=www.webapp2.com --name webapp2-1 dockercloud/hello-world
docker run -d -e VIRTUAL_HOST=www.webapp2.com --name webapp2-2 dockercloud/hello-world
docker run -d --link webapp1:webapp1 --link webapp2-1:webapp2-1 --link webapp2-2:webapp2-2 -p 80:80 dockercloud/haproxy

When you access http://www.webapp1.com, it will show the service running in container webapp1, and http://www.webapp2.com will go to both containers webapp2-1 and webapp2-2 using round robin (or whatever is configured in BALANCE).

docker run -d -e VIRTUAL_HOST="*.node.io" --name webapp dockercloud/hello-world
docker run -d --link webapp:webapp -p 80:80 dockercloud/haproxy

docker run -d -e VIRTUAL_HOST="web.example.com" -e VIRTUAL_HOST_WEIGHT=1 --name webapp dockercloud/hello-world
docker run -d -e VIRTUAL_HOST="*.example.com" -e VIRTUAL_HOST_WEIGHT=0 --name app dockercloud/hello-world
docker run -d --link webapp:webapp --link app:app -p 80:80 dockercloud/haproxy

docker run -d -e VIRTUAL_HOST="*/path, */path/*" --name webapp dockercloud/hello-world
docker run -d --link webapp:webapp -p 80:80 dockercloud/haproxy

docker run -d -e VIRTUAL_HOST="*/*.htm, */*.html" --name webapp dockercloud/hello-world
docker run -d --link webapp:webapp -p 80:80 dockercloud/haproxy

docker run -d --link webapp:webapp -e STATS_AUTH="auth:auth" -e STATS_PORT=1936 -p 80:80 -p 1936:1936 dockercloud/haproxy

Replace <subdomain> and <port> with your the values matching your papertrailapp account:

docker run -d --name web1 dockercloud/hello-world
docker run -d --name web2 dockercloud/hello-world
docker run -it --env RSYSLOG_DESTINATION='<subdomain>.papertrailapp.com:<port>' -p 80:80 --link web1:web1 --link web2:web2 dockercloud/haproxy

Docker Cloud or Docker Compose v2:

                                                           |---- container_a1
                                    |----- service_a ----- |---- container_a2
                                    |   (virtual host a)   |---- container_a3
internet --- dockercloud/haproxy--- |
                                    |                      |---- container_b1
                                    |----- service_b ----- |---- container_b2
                                        (virtual host b)   |---- container_b3

Legacy links:

                                    |---- container_a1 (virtual host a) ---|
                                    |---- container_a2 (virtual host a) ---|---logic service_a
                                    |---- container_a3 (virtual host a) ---|
internet --- dockercloud/haproxy--- |
                                    |---- container_b1 (virtual host b) ---|
                                    |---- container_b2 (virtual host b) ---|---logic service_b
                                    |---- container_b3 (virtual host b) ---|

In most cases, dockercloud/haproxy will configure itself automatically when the linked services change, you don't need to reload it manually. But for some reason, if you have to do so, here is how:

• docker exec <haproxy_id> /reload.sh, if you are on the node where dockercloud/haproxy deploys
• docker-cloud exec <haproxy_uuid> /reload.sh, if you use docker-cloud cli