Don Newton | 379ae25 | 2019-04-01 12:17:06 -0400 | [diff] [blame^] | 1 | // Copyright (C) MongoDB, Inc. 2017-present. |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); you may |
| 4 | // not use this file except in compliance with the License. You may obtain |
| 5 | // a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 |
| 6 | |
| 7 | package readpref |
| 8 | |
| 9 | import ( |
| 10 | "errors" |
| 11 | "time" |
| 12 | |
| 13 | "github.com/mongodb/mongo-go-driver/tag" |
| 14 | ) |
| 15 | |
| 16 | var ( |
| 17 | errInvalidReadPreference = errors.New("can not specify tags or max staleness on primary") |
| 18 | ) |
| 19 | |
| 20 | var primary = ReadPref{mode: PrimaryMode} |
| 21 | |
| 22 | // Primary constructs a read preference with a PrimaryMode. |
| 23 | func Primary() *ReadPref { |
| 24 | return &primary |
| 25 | } |
| 26 | |
| 27 | // PrimaryPreferred constructs a read preference with a PrimaryPreferredMode. |
| 28 | func PrimaryPreferred(opts ...Option) *ReadPref { |
| 29 | // New only returns an error with a mode of Primary |
| 30 | rp, _ := New(PrimaryPreferredMode, opts...) |
| 31 | return rp |
| 32 | } |
| 33 | |
| 34 | // SecondaryPreferred constructs a read preference with a SecondaryPreferredMode. |
| 35 | func SecondaryPreferred(opts ...Option) *ReadPref { |
| 36 | // New only returns an error with a mode of Primary |
| 37 | rp, _ := New(SecondaryPreferredMode, opts...) |
| 38 | return rp |
| 39 | } |
| 40 | |
| 41 | // Secondary constructs a read preference with a SecondaryMode. |
| 42 | func Secondary(opts ...Option) *ReadPref { |
| 43 | // New only returns an error with a mode of Primary |
| 44 | rp, _ := New(SecondaryMode, opts...) |
| 45 | return rp |
| 46 | } |
| 47 | |
| 48 | // Nearest constructs a read preference with a NearestMode. |
| 49 | func Nearest(opts ...Option) *ReadPref { |
| 50 | // New only returns an error with a mode of Primary |
| 51 | rp, _ := New(NearestMode, opts...) |
| 52 | return rp |
| 53 | } |
| 54 | |
| 55 | // New creates a new ReadPref. |
| 56 | func New(mode Mode, opts ...Option) (*ReadPref, error) { |
| 57 | rp := &ReadPref{ |
| 58 | mode: mode, |
| 59 | } |
| 60 | |
| 61 | if mode == PrimaryMode && len(opts) != 0 { |
| 62 | return nil, errInvalidReadPreference |
| 63 | } |
| 64 | |
| 65 | for _, opt := range opts { |
| 66 | err := opt(rp) |
| 67 | if err != nil { |
| 68 | return nil, err |
| 69 | } |
| 70 | } |
| 71 | |
| 72 | return rp, nil |
| 73 | } |
| 74 | |
| 75 | // ReadPref determines which servers are considered suitable for read operations. |
| 76 | type ReadPref struct { |
| 77 | maxStaleness time.Duration |
| 78 | maxStalenessSet bool |
| 79 | mode Mode |
| 80 | tagSets []tag.Set |
| 81 | } |
| 82 | |
| 83 | // MaxStaleness is the maximum amount of time to allow |
| 84 | // a server to be considered eligible for selection. The |
| 85 | // second return value indicates if this value has been set. |
| 86 | func (r *ReadPref) MaxStaleness() (time.Duration, bool) { |
| 87 | return r.maxStaleness, r.maxStalenessSet |
| 88 | } |
| 89 | |
| 90 | // Mode indicates the mode of the read preference. |
| 91 | func (r *ReadPref) Mode() Mode { |
| 92 | return r.mode |
| 93 | } |
| 94 | |
| 95 | // TagSets are multiple tag sets indicating |
| 96 | // which servers should be considered. |
| 97 | func (r *ReadPref) TagSets() []tag.Set { |
| 98 | return r.tagSets |
| 99 | } |