Go Load Balancer

The aim of this project is to provide a simple and extendable load balancer implementation to use in a Kubernetes cluster.

While the behavior of each component will be changeable, the main focus lies on a weighted round robin strategy. Whereas, the weights are obtained from etcd. This allows us to develop external optimisation components that modify the etcd storage, that will ultimately lead to updating the weights for the servers.

The load balancer should be exposed and callable on the node. The server will act as a reverse proxy and routes traffic based on the called url.

The request url is oriented towards a Function-as-a-Service platform. Therefore, requests have to follow the following pattern: ip:port/function/<function-to-call> The call will be forwarded to a Pod that runs an image with the same name.

Build

To build the module's binaries using your local go installation run:

make

To build Docker images for local usage (without a go installation) run - tagged as edgebench/go-load-balancer:latest:

make docker

To publish the Docker images, you can pass an argument that serves as version:

make docker-release 

Components

1. Server: Listens and accepts connections, passes them to Handler
2. Handler: gets requests and must implement reverse-proxy mechanism.
3. WeightedRoundRobinHandler: implements Handler interface with weighted round-robin strategy to distributed load. Uses WeightUpdater to receive weight updates.
4. WeightUpdater: can be subscribed to and publishes new weights for services.
5. EtcdWeightUpdater: implements the WeightUpdater interface with etcd

Weight updates

The daemon watches etcd keys with the following prefix: golb/function/<eb_go_lb_zone>.

Following command can be used to update the weights:

etcdctl put golb/function/zone-b/resnet '{"ips": ["10.0.0.1"], "weights":[3]}'

Be aware that previous weights are overwritten, and therefore all data must be supplied - partial updates are not supported

Environment Variables

Variable	Default	Description
eb_go_lb_etcd_host	localhost:2379	The host of etcd
eb_go_lb_zone	-	In which zone the LB starts (important for watching the right etcd keys
eb_go_lb_handler_type	dummy	Handler type (currently: dummy & wrr)
eb_go_lb_mode	dev	Mode of execution (prod or dev)
eb_go_lb_node_name	$HOSTNAME	The node name used to indicate a forward
eb_go_lb_listen_port	8080	The port to listen on
eb_go_lb_gateways		A whitespace seperated list of URLs that indicate the load balancer which url is a load balancer

Thanks to

JJNP for the Weighted WRR implementation