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Last pushed: a year ago
Short Description
HAProxy image that balances between linked containers and, if launched in Docker Cloud.
Full Description

dockercloud/haproxy

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.

Version

  • latest: dockercloud/haproxy:1.2.1

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.

Usage

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)

Running in Docker Cloud

  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
example of stackfile in Docker Cloud:
web:
  image: 'dockercloud/hello-world:latest'
  target_num_containers: 2
lb:
  image: 'dockercloud/haproxy:latest'
  links:
    - web
  ports:
    - '80:80'
  roles:
    - global

Running with docker legacy links

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.

example of legacy links using docker cli
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

example of docker-compose.yml v1 format:

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.

Running with Docker Compose v2(new links)

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.
example of docker-compose.yml running in linux:
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
example of docker-compose.yml running in Mac OS
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.

Running with Docker Compose v2 and Swarm (using envvar)

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.
example of docker-compose.yml in 'project_dir' directory running in linux:
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

Configuration

Global and default settings of HAProxy

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

Environment Variable Default Description
ADDITIONAL_SERVICES list of additional services to balance (es: prj1:web,prj2:sql). Discovery will be based on `com.docker.compose.[project service]` container labels. This environment variable only works on compose v2, and the referenced services must be on a network accessible to this containers.
BALANCE roundrobin load balancing algorithm to use. Possible values include: roundrobin, static-rr, source, leastconn. See:HAProxy:balance
CA_CERT_FILE the path of a ca-cert file. This allows you to mount your ca-cert file directly from a volume instead of from envvar. If set, CA_CERT envvar will be ignored. Possible value: /cacerts/cert0.pem
CA_CERT CA cert for haproxy to verify the client. Use the same format as DEFAULT_SSL_CERT
CERT_FOLDER the path of certificates. This allows you to mount your certificate files directly from a volume instead of from envvars. If set, DEFAULT_SSL_CERT and SSL_CERT from linked services are ignored. Possible value:/certs/
DEFAULT_SSL_CERT Default ssl cert, a pem file content with private key followed by public certificate, '\n'(two chars) as the line separator. should be formatted as one line - see SSL Termination
EXTRA_BIND_SETTINGS comma-separated string(<port>:<setting>) of extra settings, and each part will be appended to the related port bind section in the configuration file. To escape comma, use \,. Possible value: 443:accept-proxy, 80:name http
EXTRA_DEFAULT_SETTINGS comma-separated string of extra settings, and each part will be appended to DEFAULT section in the configuration file. To escape comma, use \,
EXTRA_FRONTENDSETTINGS\<PORT\> comma-separated string of extra settings, and each part will be appended frontend section with the port number specified in the name of the envvar. To escape comma, use \,. E.g. EXTRA_FRONTEND_SETTINGS_80=balance source, maxconn 2000
EXTRA_GLOBAL_SETTINGS comma-separated string of extra settings, and each part will be appended to GLOBAL section in the configuration file. To escape comma, use \,. Possible value: tune.ssl.cachesize 20000, tune.ssl.default-dh-param 2048
EXTRA_SSL_CERTS list of extra certificate names separated by comma, eg. CERT1, CERT2, CERT3. You also need to specify each certificate as separate env variables like so: CERT1="<cert-body1>", CERT2="<cert-body2>", CERT3="<cert-body3>"
HEALTH_CHECK check set health check on each backend route, possible value: "check inter 2000 rise 2 fall 3". See:HAProxy:check
HTTP_BASIC_AUTH a comma-separated list of credentials(<user>:<pass>) for HTTP basic auth, which applies to all the backend routes. To escape comma, use \,. Attention: DO NOT rely on this for authentication in production
MAXCONN 4096 sets the maximum per-process number of concurrent connections.
MODE http mode of load balancing for HAProxy. Possible values include: http, tcp, health
MONITOR_PORT the port number where monitor_uri should be added to. Use together with MONTIOR_URI. Possible value: 80
MONITOR_URI the exact URI which we want to intercept to return HAProxy's health status instead of forwarding the request.See: http://cbonte.github.io/haproxy-dconv/configuration-1.5.html#4-monitor-uri. Possible value: /ping
OPTION redispatch comma-separated list of HAProxy option entries to the default section.
RSYSLOG_DESTINATION 127.0.0.1 the rsyslog destination to where HAProxy logs are sent
SSL_BIND_CIPHERS explicitly set which SSL ciphers will be used for the SSL server. This sets the HAProxy ssl-default-bind-ciphers configuration setting.
SSL_BIND_OPTIONS no-sslv3 explicitly set which SSL bind options will be used for the SSL server. This sets the HAProxy ssl-default-bind-options configuration setting. The default will allow only TLSv1.0+ to be used on the SSL server.
STATS_AUTH stats:stats username and password required to access the Haproxy stats.
STATS_PORT 1936 port for the HAProxy stats section. If this port is published, stats can be accessed at http://<host-ip>:<STATS_PORT>/
TIMEOUT connect 5000, client 50000, server 50000 comma-separated list of HAProxy timeout entries to the default section.

Settings in linked application services

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

Environment Variable Description
APPSESSION sticky session option, possible value JSESSIONID len 52 timeout 3h. See:HAProxy:appsession
BALANCE load balancing algorithm to use. Possible values include: roundrobin, static-rr, source, leastconn. See:HAProxy:balance
COOKIE sticky session option. Possible value SRV insert indirect nocache. See:HAProxy:cookie
DEFAULT_SSL_CERT similar to SSL_CERT, but stores the pem file at /certs/cert0.pem as the default ssl certs. If multiple DEFAULT_SSL_CERT are specified in linked services and HAProxy, the behavior is undefined
EXCLUDE_PORTS comma separated port numbers(e.g. 3306, 3307). By default, HAProxy will add all the ports exposed by the application services to the backend routes. You can exclude the ports that you don't want to be routed, like database port
EXTRA_SETTINGS comma-separated string of extra settings, and each part will be appended to either related backend section or listen session in the configuration file. To escape comma, use \,. Possible value: balance source
FORCE_SSL if set(any value) together with ssl termination enabled. HAProxy will redirect HTTP request to HTTPS request.
GZIP_COMPRESSION_TYPE enable gzip compression. The value of this envvar is a list of MIME types that will be compressed, possible value: text/html text/plain text/css
HEALTH_CHECK set health check on each backend route, possible value: "check inter 2000 rise 2 fall 3". See:HAProxy:check
HSTS_MAX_AGE enable HSTS. It is an integer representing the max age of HSTS in seconds, possible value: 31536000
HTTP_CHECK enable HTTP protocol to check on the servers health, possible value: "OPTIONS * HTTP/1.1\r\nHost:\ www". See:HAProxy:httpchk
OPTION comma-separated list of HAProxy option entries. option specified here will be added to related backend or listen part, and overwrite the OPTION settings in the HAProxy container
SSL_CERT ssl cert, a pem file with private key followed by public certificate, '\n'(two chars) as the line separator
TCP_PORTS comma separated ports(e.g. 9000, 9001, 2222/ssl). The port listed in TCP_PORTS will be load-balanced in TCP mode. Port ends with /ssl indicates that port needs SSL termination.
VIRTUAL_HOST_WEIGHT an integer of the weight of an virtual host, used together with VIRTUAL_HOST, default:0. It affects the order of acl rules of the virtual hosts. The higher weight one virtual host has, the more priority that acl rules applies.
VIRTUAL_HOST specify virtual host and virtual path. Format: [scheme://]domain[:port][/path], .... wildcard * can be used in domain and path part

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

Virtual host and virtual path

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].

Item Default Description
scheme http possible values: http, https, wss
domain virtual host. * can be used as the wildcard
port 80/433 port number of the virtual host. When the scheme is https wss, the default port will be to 443
/path virtual path, starts with /. * can be used as the wildcard

examples of matching

Virtual host Match Not match
http://example.com example.com www.example.com
example.com example.com www.example.com
example.com:90 example.com:90 example.com
https://example.com https://example.com example.com
https://example.com:444 https://example.com:444 https://example.com
*.example.com www.example.com example.com
*example.com www.example.com, example.com, anotherexample.com www.abc.com
www.e*e.com www.example.com, www.exxe.com www.axxa.com
www.example.* www.example.com, www.example.org example.com
* any website with HTTP
https://\* any website with HTTPS
*/path example.com/path, example.org/path?u=user example.com/path/
*/path/ example.com/path/, example.org/path/?u=user example.com/path, example.com/path/abc
*/path/* example.com/path/, example.org/path/abc example.com/abc/path/
*/*/path/* example.com/path/, example.org/abc/path/, example.net/abc/path/123 example.com/path
*/*.js example.com/abc.js, example.org/path/abc.js example.com/abc.css
*/*.do/ example.com/abc.do/, example.org/path/abc.do/ example.com/abc.do
*/path/*.php example.com/path/abc.php example/abc.php, example.com/root/abc.php
*.example.com/*.jpg www.example.com/abc.jpg, abc.example.com/123.jpg example.com/abc.jpg
*/path, */path/ example.com/path, example.org/path/
example.com:90, https://example.com example.com:90, https://example.com

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.

SSL termination

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.

PEM Files

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.

Affinity and session stickiness

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.

TCP load balancing

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.

WebSocket support


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 case scenarios

My webapp container exposes port 8080(or any other port), and I want the proxy to listen in port 80

Use the following:

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

My webapp container exposes port 80 and database ports 8083/8086, and I want the proxy to listen in port 80 without my database ports added to 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

My webapp container exposes port 8080(or any other port), and I want the proxy to listen in port 8080

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

I want the proxy to terminate SSL connections and redirect HTTP requests to HTTPS

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

I want to load my SSL certificate from volume instead of passing it through environment variable

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

I want to set up virtual host routing by domain

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).

I want all my *.node.io domains point to my service

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

I want web.example.com go to one service and *.example.com go to another service

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

I want all the requests to path /path point to my service

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

I want all the static html request point to my service

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

I want to see stats of HAProxy

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

I want to send all my logs to papertrailapp

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

Topologies using virtual hosts

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) ---|

Manually reload haproxy

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
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