| // Copyright (C) MongoDB, Inc. 2017-present. |
| // |
| // 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 |
| |
| package readconcern |
| |
| import ( |
| "github.com/mongodb/mongo-go-driver/bson/bsontype" |
| "github.com/mongodb/mongo-go-driver/x/bsonx/bsoncore" |
| ) |
| |
| // ReadConcern for replica sets and replica set shards determines which data to return from a query. |
| type ReadConcern struct { |
| level string |
| } |
| |
| // Option is an option to provide when creating a ReadConcern. |
| type Option func(concern *ReadConcern) |
| |
| // Level creates an option that sets the level of a ReadConcern. |
| func Level(level string) Option { |
| return func(concern *ReadConcern) { |
| concern.level = level |
| } |
| } |
| |
| // Local specifies that the query should return the instance’s most recent data. |
| func Local() *ReadConcern { |
| return New(Level("local")) |
| } |
| |
| // Majority specifies that the query should return the instance’s most recent data acknowledged as |
| // having been written to a majority of members in the replica set. |
| func Majority() *ReadConcern { |
| return New(Level("majority")) |
| } |
| |
| // Linearizable specifies that the query should return data that reflects all successful writes |
| // issued with a write concern of "majority" and acknowledged prior to the start of the read operation. |
| func Linearizable() *ReadConcern { |
| return New(Level("linearizable")) |
| } |
| |
| // Available specifies that the query should return data from the instance with no guarantee |
| // that the data has been written to a majority of the replica set members (i.e. may be rolled back). |
| func Available() *ReadConcern { |
| return New(Level("available")) |
| } |
| |
| // Snapshot is only available for operations within multi-document transactions. |
| func Snapshot() *ReadConcern { |
| return New(Level("snapshot")) |
| } |
| |
| // New constructs a new read concern from the given string. |
| func New(options ...Option) *ReadConcern { |
| concern := &ReadConcern{} |
| |
| for _, option := range options { |
| option(concern) |
| } |
| |
| return concern |
| } |
| |
| // MarshalBSONValue implements the bson.ValueMarshaler interface. |
| func (rc *ReadConcern) MarshalBSONValue() (bsontype.Type, []byte, error) { |
| var elems []byte |
| |
| if len(rc.level) > 0 { |
| elems = bsoncore.AppendStringElement(elems, "level", rc.level) |
| } |
| |
| return bsontype.EmbeddedDocument, bsoncore.BuildDocument(nil, elems), nil |
| } |