vendor/go.etcd.io/etcd/clientv3/balancer/picker/picker_policy.go

// Copyright 2018 The etcd Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package picker

import "fmt"

// Policy defines balancer picker policy.
type Policy uint8

const (
	// TODO: custom picker is not supported yet.
	// custom defines custom balancer picker.
	custom Policy = iota

	// RoundrobinBalanced balance loads over multiple endpoints
	// and implements failover in roundrobin fashion.
	RoundrobinBalanced Policy = iota

	// TODO: only send loads to pinned address "RoundrobinFailover"
	// just like how 3.3 client works
	//
	// TODO: priotize leader
	// TODO: health-check
	// TODO: weighted roundrobin
	// TODO: power of two random choice
)

func (p Policy) String() string {
	switch p {
	case custom:
		panic("'custom' picker policy is not supported yet")
	case RoundrobinBalanced:
		return "etcd-client-roundrobin-balanced"
	default:
		panic(fmt.Errorf("invalid balancer picker policy (%d)", p))
	}
}