Managing cloud load balancers

Yaybu can manage your load balancers using a LoadBalancer part. They run as soon as all of the inputs become valid, as opposed to when the program encounters them.

A basic setup looks like this:

new LoadBalancer as lb:
    name: myprojectlb

    driver:
        id: ELB
        key: yourawskey
        secret: yourawssecret

    # Listen on port 80 for http access
    port: 80
    protocol: http
    algorithm: round-robin

    members:
      - {{ server1 }}

Options

You must specify a name when creating a LoadBalanacer part. Some backends will use this as a unique id for the load balancer. Take care to avoid duplicating load balancer names in different configurations!

The driver section contains the settings used by libcloud to initialize a driver. This typically includes account information - a access key and secret, a username and password, or similar.

You must specify a port for the load balancer to listen on.

The load balancer needs to know what protocol it is balancing. For example, if it is handling SSL connections it can act as an SSL terminator but to do this it needs to know it is an SSL protocol. Not all balancers support all protocols, and Yaybu doesn’t expose SSL support at the moment. You can set protocol to one of:

  • http
  • https
  • tcp
  • ssl

Some load balancers let you choose an algorithm. This is the method by which the load balancer distributes traffic. It can be one of:

random
Incoming connections are assigned to a backend at random
round-robin
Incoming connections are passed to a backend in a circular fashion without any considering of priority.
least-connections
Incoming connections are passed to the backend with the least number of active connections with the assumption that it must have the most free capacity.
weighted-round-robin
Same as round-robin, but also factors in a weight factor for each member
weighted-least-connections
Same as least-connections, but also factors in a weight factor for each member

The members input is a list of all compute resources that load will be spread over. There are a few variations here.

If you are doing load balancing for port 80 and forwarding to port 80 on the backend VM’s then you can:

new LoadBalancer as lb:
    <snip>
    members:
      - {{ server1 }}
      - {{ server2 }}

In this example server1 and server2 are Compute parts defined elsewhere in your configuration.

However if you are using different ports on the backend servers you can:

new LoadBalancer as lb:
    <snip>
    members:
      - instance: {{ server1 }}
        port: 8080

Not all backends support this, and an error will be raised before deployment starts if it is not.

There are 2 main types of cloud load balancer. The first accepts IP addresses and ports. If you pass a Compute node to this type of load balancer Yaybu will determine it’s IP automatically. But you can pass ip addresses manually:

new LoadBalancer as lb:
    <snip>
    members:
      - ip: 192.168.0.1
        port: 8080

Other load balancers expect to be give a list of compute instance ids. Again, Yaybu will do the right thing if given Compute parts. But you can also give it id values directly:

new LoadBalancer as lb:
    <snip>
    members:
      - id: ec2123ab
        port: 8080

Outputs

The part exposes a number of output variables to other Yaybu parts.

Each load balancer that is created has a unique id. In some cases this may be the same as the name.

A load balancer has a public_ip. This is the public facing method of accessing the load balancer.

Supported services

Using libcloud to implement this part allows us to support a number of DNS services. Some of these receive more extensive real world testing than others and are listed in this section.

Elastic Load Balancing

The driver id for Elastic Load Balancing is ELB:

new LoadBalancer as lb:
    name: my-load-balancer

    driver:
        id: ELB
        key: myaccesskey
        secret: myaccesssecret
        region: eu-west-1

    port: 80
    protocol: http
    algorithm: round-robin

    # The default is just a
    ex_memebers_availability_zones:
      - a
      - b

    members:
      - id: ec2123

For this driver:

  • After creating a balancer you cannot change its settings (you can continue to add and remove members).
  • protocol must be either tcp or http.
  • algorithm must be ?.....?
  • members are managed by instance id. You cannot set the backend port.
  • ex_members_availability_zones is an ELB specific extension that controls which Amazon availabilty zones a balancer is in.

Community supported services

By using libcloud to support the services in the previous section, the following services are also available:

Brightbox

The driver id for brightbox is BRIGHTBOX:

new LoadBalancer as lb:
    name: my-load-balancer

    driver:
        id: BRIGHTBOX
        key: acc-43ks4
        secret: mybrightboxsecret

    port: 80
    protocol: http
    algorithm: round-robin

    members:
      - id: ec2123

For the Brightbox loadbalancer:

  • protocol must be http or tcp
  • algorithm must be round-robin or least-connections
  • members are managed by instance id, and you cannot set the backend port (your backends must listen on the same port as your load balancer).

Cloudstack

The driver id for cloudstack is not currently set upstream, so it is currently unavailable.

For the CloudStack loadbalancer:

  • After creating a balancer you cannot change its setting (you can continue to add and remove members).
  • protocol must be tcp
  • algorithm must be round-robin or least-connections
  • members are managed by instance id. You cannot set the backend port.

GoGrid

The driver id for GoGrid is GOGRID:

new LoadBalancer as lb:
    name: my-load-balancer

    driver:
        id: GOGRID
        key: myaccesskey
        secret: myaccesssecret

    port: 80
    protocol: http
    algorithm: round-robin

    members:
      - id: ec2123

For this driver:

  • protocol must be http
  • algorithm must be round-robin or least-connections
  • members are managed by ip. Each backend can use a different port.

Ninefold

The driver id for Ninefold is NINEFOLD:

new LoadBalancer as lb:
    name: my-load-balancer

    driver:
        id: NINEFOLD
        key: myaccesskey
        secret: myaccesssecret

    port: 80
    protocol: http
    algorithm: round-robin

    members:
      - id: ec2123

Ninefold uses CloudStack, so see that section for additional notes.

Rackspace

The driver id for Rackspace load balancing is RACKSPACE_UK:

new LoadBalancer as lb:
    name: my-load-balancer

    driver:
        id: RACKSPACE_UK
        key: myaccesskey
        secret: myaccesssecret

    port: 80
    protocol: http
    algorithm: round-robin

    members:
      - id: ec2123

For this driver:

  • After creating a balancer you can later change its settings.
  • The list of supported protocol options is dynamic and fetched from Rackspace at runtime.
  • algorithm must be one of random, round-robin, least-connections, weighted-round-robin or weighted-least-connections.
  • members are managed by ip/port pairs.
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