Package readpref

Variables

ErrInvalidTagSet indicates that an invalid set of tags was specified.

var ErrInvalidTagSet = errors.New("an even number of tags must be specified")

type Mode ¶

Mode indicates the user's preference on reads.

type Mode uint8

Mode constants

const (

    // PrimaryMode indicates that only a primary is
    // considered for reading. This is the default
    // mode.
    PrimaryMode Mode
    // PrimaryPreferredMode indicates that if a primary
    // is available, use it; otherwise, eligible
    // secondaries will be considered.
    PrimaryPreferredMode
    // SecondaryMode indicates that only secondaries
    // should be considered.
    SecondaryMode
    // SecondaryPreferredMode indicates that only secondaries
    // should be considered when one is available. If none
    // are available, then a primary will be considered.
    SecondaryPreferredMode
    // NearestMode indicates that all primaries and secondaries
    // will be considered.
    NearestMode
)

func ModeFromString ¶

func ModeFromString(mode string) (Mode, error)

ModeFromString returns a mode corresponding to mode.

func (Mode) IsValid ¶

func (mode Mode) IsValid() bool

IsValid checks whether the mode is valid.

func (Mode) String ¶

func (mode Mode) String() string

String returns the string representation of mode.

type Option ¶

Option configures a read preference

type Option func(*ReadPref) error

func WithHedgeEnabled ¶

func WithHedgeEnabled(hedgeEnabled bool) Option

WithHedgeEnabled specifies whether or not hedged reads should be enabled in the server. This feature requires MongoDB server version 4.4 or higher. For more information about hedged reads, see https://www.mongodb.com/docs/manual/core/sharded-cluster-query-router/#mongos-hedged-reads. If not specified, the default is to not send a value to the server, which will result in the server defaults being used.

func WithMaxStaleness ¶

func WithMaxStaleness(ms time.Duration) Option

WithMaxStaleness sets the maximum staleness a server is allowed.

func WithTagSets ¶

func WithTagSets(tagSets ...tag.Set) Option

WithTagSets specifies a list of tag sets used to match replica set members. If the list contains multiple tag sets, members are matched against each tag set in succession until a match is found. Once a match is found, the remaining tag sets are ignored. If no members match any of the tag sets, the read operation returns with an error. To avoid an error if no members match any of the tag sets, include an empty tag set as the last tag set in the list.

The last call to WithTags or WithTagSets overrides all previous calls to either method.

For more information about read preference tags, see https://www.mongodb.com/docs/manual/core/read-preference-tags/

tagSetList := tag.NewTagSetsFromMaps([]map[string]string{
    {"region": "South", "datacenter": "A"},
    {"region": "South"},
    {},
})

rp := readpref.Nearest(readpref.WithTagSets(tagSetList...))

opts := options.Client().
    ApplyURI("mongodb://localhost").
    SetReadPreference(rp)

_, err := mongo.Connect(context.Background(), opts)
if err != nil {
    panic(err)
}

func WithTags ¶

func WithTags(tags ...string) Option

WithTags specifies a single tag set used to match replica set members. If no members match the tag set, read operations will return an error. To avoid errors if no members match the tag set, use WithTagSets and include an empty tag set as the last tag set in the list.

The last call to WithTags or WithTagSets overrides all previous calls to either method.

For more information about read preference tags, see https://www.mongodb.com/docs/manual/core/read-preference-tags/

rp := readpref.Nearest(
    readpref.WithTags(
        "region", "South",
        "datacenter", "A"))

opts := options.Client().
    ApplyURI("mongodb://localhost:27017").
    SetReadPreference(rp)

_, err := mongo.Connect(context.Background(), opts)
if err != nil {
    panic(err)
}

type ReadPref ¶

ReadPref determines which servers are considered suitable for read operations.

type ReadPref struct {
    // contains filtered or unexported fields
}

func Nearest ¶

func Nearest(opts ...Option) *ReadPref

Nearest constructs a read preference with a NearestMode.

func New ¶

func New(mode Mode, opts ...Option) (*ReadPref, error)

New creates a new ReadPref.

func Primary ¶

func Primary() *ReadPref

Primary constructs a read preference with a PrimaryMode.

func PrimaryPreferred ¶

func PrimaryPreferred(opts ...Option) *ReadPref

PrimaryPreferred constructs a read preference with a PrimaryPreferredMode.

func Secondary ¶

func Secondary(opts ...Option) *ReadPref

Secondary constructs a read preference with a SecondaryMode.

func SecondaryPreferred ¶

func SecondaryPreferred(opts ...Option) *ReadPref

SecondaryPreferred constructs a read preference with a SecondaryPreferredMode.

func (*ReadPref) HedgeEnabled ¶

func (r *ReadPref) HedgeEnabled() *bool

HedgeEnabled returns whether or not hedged reads are enabled for this read preference. If this option was not specified during read preference construction, nil is returned.

func (*ReadPref) MaxStaleness ¶

func (r *ReadPref) MaxStaleness() (time.Duration, bool)

MaxStaleness is the maximum amount of time to allow a server to be considered eligible for selection. The second return value indicates if this value has been set.

func (*ReadPref) Mode ¶

func (r *ReadPref) Mode() Mode

Mode indicates the mode of the read preference.

func (*ReadPref) String ¶

func (r *ReadPref) String() string

String returns a human-readable description of the read preference.

func (*ReadPref) TagSets ¶

func (r *ReadPref) TagSets() []tag.Set

TagSets are multiple tag sets indicating which servers should be considered.