apiloadbalancer

Documentation

Overview

Package apiloadbalancer allows to create and manage kube-apiserver load balancer containers.

Index

• Constants
• func FromYaml(c []byte) (types.Resource, error)
• type APILoadBalancer
  • func (a *APILoadBalancer) New() (container.ResourceInstance, error)
  • func (a *APILoadBalancer) Validate() error
• type APILoadBalancers
  • func (a *APILoadBalancers) New() (types.Resource, error)
  • func (a *APILoadBalancers) Validate() error

Constants

const (
	// HostConfigPath is a default path on the host filesystem, where container
	// configuration will be stored.
	HostConfigPath = "/etc/haproxy/haproxy.cfg"

	// ContainerName is a default name for load balancer container.
	ContainerName = "api-loadbalancer-haproxy"
)

Functions

func FromYaml

func FromYaml(c []byte) (types.Resource, error)

FromYaml allows to create and validate resource from YAML format.

Types

type APILoadBalancer

type APILoadBalancer struct {
	// Image allows to set Docker image with tag, which will be used by the container.
	// if instance itself has no image set. If empty, haproxy image defined in pkg/defaults
	// will be used.
	//
	// Example value: 'haproxy:2.1.4-alpine'
	//
	// This field is optional.
	Image string `json:"image,omitempty"`

	// Host describes on which machine member container should be created.
	//
	// This field is required.
	Host host.Host `json:"host,omitempty"`

	// Servers is a list of Kubernetes API server addresses, which should be used as a backend
	// servers.
	//
	// Example value: '[]string{"192.168.10.10:6443", "192.168.10.11:6443"}'.
	//
	// This field is optional, if used together with APILoadBalancers struct.
	Servers []string `json:"servers,omitempty"`

	// Name is a container name to create. If you want to run more than one instance on a
	// single host, this field must be unique, otherwise you will get an error with duplicated
	// container name.
	//
	// Currently, when you want to expose Kubernetes API using the load balancer on more than
	// one specific address (so not listening on 0.0.0.0), then two pools are required.
	// This limitation will be addressed in the future.
	//
	// This field is optional. If empty, value from ContainerName constant will be used.
	Name string `json:"name,omitempty"`

	// HostConfigPath is a path on the host filesystem, where load balancer configuration should be
	// written. If you want to run more than one instance on a single host, this field must
	// be unique, otherwise the configuration will be overwritten by the other instance.
	//
	// Currently, when you want to expose Kubernetes API using the load balancer on more than
	// one specific address (so not listening on 0.0.0.0), then two pools are required.
	// This limitation will be addressed in the future.
	//
	// This field is optional. If empty, value from HostConfigPath constant will be used.
	HostConfigPath string `json:"hostConfigPath,omitempty"`

	// BindAddress controls, on which IP address load balancer container will be listening on.
	// Usually, it is set to here to either 127.0.0.1 to only expose the load balancer on host's
	// localhost address or to 0.0.0.0 to expose the API on all interfaces.
	//
	// If you want to listen on specific address, which is different for each host, set it for each
	// LoadBalancer instance.
	//
	// This field is optional, if used together with APILoadBalancers struct.
	BindAddress string `json:"bindAddress,omitempty"`
}

APILoadBalancer is a user-configurable representation of single instance of API load balancer.

func (*APILoadBalancer) New

func (a *APILoadBalancer) New() (container.ResourceInstance, error)

New validates APILoadBalancer configuration and fills it with default options If configuration is wrong, error is returned.

TODO: I think we shouldn't fill the default values here. Maybe do it one level up?

func (*APILoadBalancer) Validate

func (a *APILoadBalancer) Validate() error

Validate contains all validation rules for APILoadBalancer struct. This method can be used by the user to catch configuration errors early.

type APILoadBalancers

type APILoadBalancers struct {
	// Image allows to set Docker image with tag, which will be used by all instances,
	// if instance itself has no image set. If empty, haproxy image defined in pkg/defaults
	// will be used.
	//
	// Example value: 'haproxy:2.1.4-alpine'
	//
	// This field is optional.
	Image string `json:"image,omitempty"`

	// SSH stores common SSH configuration for all instances and will be merged with instances
	// SSH configuration. If instance has some SSH fields defined, they take precedence over
	// this block.
	//
	// If you use same username or port for all members, it is recommended to have it defined
	// here to avoid repetition in the configuration.
	//
	// This field is optional.
	SSH *ssh.Config `json:"ssh,omitempty"`

	// Servers is a list of Kubernetes API server addresses, which should be used as a backend
	// servers.
	//
	// Example value: '[]string{"192.168.10.10:6443", "192.168.10.11:6443"}'.
	//
	// If specified, this value will be used for all instances, which do not have it defined.
	//
	// This field is optional.
	Servers []string `json:"servers,omitempty"`

	// APILoadBalancers is a list of load balancer instances to create. Usually it has only
	// instance specific information defined, like IP address to listen on or on which host
	// the container should be created. See APILoadBalancer struct to see available fields.
	//
	// If there is no state defined, this list must not be empty.
	//
	// If state is defined and list is empty, all created containers will be removed.
	APILoadBalancers []APILoadBalancer `json:"apiLoadBalancers,omitempty"`

	// Name is a container name to create. If you want to run more than one instance on a
	// single host, this field must be unique, otherwise you will get an error with duplicated
	// container name.
	//
	// Currently, when you want to expose Kubernetes API using the load balancer on more than
	// one specific address (so not listening on 0.0.0.0), then two pools are required.
	// This limitation will be addressed in the future.
	//
	// If specified, this value will be used for all instances, which do not have it defined.
	//
	// This field is optional. If empty, value from ContainerName constant will be used.
	Name string `json:"name,omitempty"`

	// HostConfigPath is a path on the host filesystem, where load balancer configuration should be
	// written. If you want to run more than one instance on a single host, this field must
	// be unique, otherwise the configuration will be overwritten by the other instance.
	//
	// Currently, when you want to expose Kubernetes API using the load balancer on more than
	// one specific address (so not listening on 0.0.0.0), then two pools are required.
	// This limitation will be addressed in the future.
	//
	// If specified, this value will be used for all instances, which do not have it defined.
	//
	// This field is optional. If empty, value from HostConfigPath constant will be used.
	HostConfigPath string `json:"hostConfigPath,omitempty"`

	// BindAddress controls, on which IP address load balancer container will be listening on.
	// Usually, it is set to here to either 127.0.0.1 to only expose the load balancer on host's
	// localhost address or to 0.0.0.0 to expose the API on all interfaces.
	//
	// If you want to listen on specific address, which is different for each host, set it for each
	// LoadBalancer instance.
	//
	// If specified, this value will be used for all instances, which do not have it defined.
	//
	// This field is optional.
	BindAddress string `json:"bindAddress,omitempty"`

	// State stores state of the created containers. After deployment, it is up to the user to export
	// the state and restore it on consecutive runs.
	State container.ContainersState `json:"state,omitempty"`
}

APILoadBalancers allows to manage group of kube-apiserver load balancer containers, which can be used to build highly available Kubernetes cluster.

The main use case is to create an load balancer instance in front of the kubelet on every node, as kubelet itself does not support failover for configured API server address.

Current implementation uses HAProxy for load balancing with active health checking, so if one of API servers go down, it won't be used by the kubelet. Otherwise some of kubelet requests could timeout, hitting unreachable API server.

API load balancer can be also used to expose Kubernetes API to the internet, if it is only available in private network.

The HAProxy is configured to run in TCP mode, so potential performance and security overhead should be negligible.

func (*APILoadBalancers) New

func (a *APILoadBalancers) New() (types.Resource, error)

New validates APILoadBalancers struct and fills all required fields in members with default values provided by the user.

TODO move filling the defaults to separated function, so it can be re-used in Validate.

func (*APILoadBalancers) Validate

func (a *APILoadBalancers) Validate() error

Validate validates APILoadBalancers struct.