go.uber.org/yarpc@v1.72.1/peer/hashring32/config.go

// Copyright (c) 2022 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package hashring32

import (
	"time"

	"go.uber.org/net/metrics"
	"go.uber.org/yarpc/api/peer"
	"go.uber.org/yarpc/peer/hashring32/internal/farmhashring"
	"go.uber.org/yarpc/yarpcconfig"
	"go.uber.org/zap"
)

// Config is the configuration object for hashring32yarpc
type Config struct {
	// OffsetHeader allows clients to pass in a header to adjust to offset value
	// in the Choose function.
	OffsetHeader string `config:"offsetHeader"`

	// OffsetGeneratorValue allows clients to generate an offset automatically when using hashring32
	//
	// For example, if this value is set to 4, the offset used by hashring32
	// will be between [0-4].
	//
	// It should be noted that this option will not be used if the option
	// OffsetHeader is being used.
	OffsetGeneratorValue int `config:"offsetGeneratorValue"`

	// PeerOverrideHeader allows clients to pass a header containing the shard
	// identifier for a specific peer to override the destination address for
	// the outgoing request.
	//
	// For example, if the peer list uses addresses to identify peers,
	// the hash ring will have retained a peer for every known address.
	// Specifying an address like "127.0.0.1" in the route override header will
	// deflect the request to that exact peer.
	// If that peer is not available, the request will continue on to the peer
	// implied by the shard key.
	PeerOverrideHeader string `config:"peerOverrideHeader"`

	// AlternateShardKeyHeader allows clients to pass a header containing the shard
	// identifier for a specific peer to override the destination address for the
	// outgoing request.
	AlternateShardKeyHeader string `config:"alternateShardKeyHeader"`

	ReplicaDelimiter string `config:"replicaDelimiter"`

	// NumReplicas specifies the number of replicas to use for each peer in the ring.
	// Default is 100
	NumReplicas int `config:"numReplicas"`

	// NumPeersEstimate specifies an estimate for the number of identified peers
	// the hashring will contain.
	//
	// This figure and the number of replicas determines the initial capacity of the ring slice.
	// Default is 1500
	NumPeersEstimate int `config:"numPeersEstimate"`

	// DefaultChooseTimeout specifies the deadline to add to Choose calls if not
	// present. This enables calls without deadlines, ie streaming, to choose
	// peers without waiting indefinitely.
	DefaultChooseTimeout *time.Duration `config:"defaultChooseTimeout"`
}

// Spec returns a configuration specification for the hashed peer list
// implementation, making it possible to select peer based on a specified hashing
// function.
func Spec(logger *zap.Logger, meter *metrics.Scope) yarpcconfig.PeerListSpec {
	// TODO thread meter through list options to abstract list metrics.

	return yarpcconfig.PeerListSpec{
		Name: "hashring32",
		BuildPeerList: func(c Config, t peer.Transport, k *yarpcconfig.Kit) (peer.ChooserList, error) {
			opts := []Option{
				OffsetHeader(c.OffsetHeader),
				ReplicaDelimiter(c.ReplicaDelimiter),
				PeerOverrideHeader(c.PeerOverrideHeader),
				AlternateShardKeyHeader(c.AlternateShardKeyHeader),
				Logger(logger),
			}

			if c.DefaultChooseTimeout != nil {
				opts = append(opts, DefaultChooseTimeout(*c.DefaultChooseTimeout))
			}

			if c.NumReplicas != 0 {
				opts = append(opts, NumReplicas(c.NumReplicas))
			}

			if c.NumPeersEstimate != 0 {
				opts = append(opts, NumPeersEstimate(c.NumPeersEstimate))
			}

			if c.OffsetGeneratorValue != 0 && c.OffsetHeader == "" {
				opts = append(opts, OffsetGeneratorValue(c.OffsetGeneratorValue))
			}

			return New(
				t,
				farmhashring.Fingerprint32,
				opts...,
			), nil
		},
	}
}