Documentation
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Overview ¶
Package discovery defines types and interfaces for discovering services.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type AdId ¶
type AdId [16]byte
An AdId is a globally unique identifier of an advertisement.
func (AdId) VDLReflect ¶
type Advertisement ¶
type Advertisement struct {
// Universal unique identifier of the advertisement.
// If this is not specified, a random unique identifier will be assigned.
Id AdId
// Interface name that the advertised service implements.
// E.g., 'v.io/v23/services/vtrace.Store'.
InterfaceName string
// Addresses (vanadium object names) that the advertised service is served on.
// E.g., '/host:port/a/b/c', '/ns.dev.v.io:8101/blah/blah'.
Addresses []string
// Attributes as a key/value pair.
// E.g., {'resolution': '1024x768'}.
//
// The key must be US-ASCII printable characters, excluding the '=' character
// and should not start with '_' character.
//
// We limit the maximum number of attachments to 32.
Attributes Attributes
// Attachments as a key/value pair.
// E.g., {'thumbnail': binary_data }.
//
// Unlike attributes, attachments are for binary data and they are not queryable.
//
// The key must be US-ASCII printable characters, excluding the '=' character
// and should not start with '_' character.
//
// We limit the maximum number of attachments to 32 and the maximum size of each
// attachment is 4K bytes.
Attachments Attachments
}
Advertisement represents a feed into advertiser to broadcast its contents to scanners.
A large advertisement may require additional RPC calls causing delay in discovery. We limit the maximum size of an advertisement to 512 bytes excluding id and attachments.
func (Advertisement) VDLIsZero ¶
func (x Advertisement) VDLIsZero() bool
func (Advertisement) VDLReflect ¶
func (Advertisement) VDLReflect(struct { Name string `vdl:"v.io/v23/discovery.Advertisement"` })
type Attachments ¶
Attachments represents service attachments as a key/value pair.
func (Attachments) VDLIsZero ¶
func (x Attachments) VDLIsZero() bool
func (Attachments) VDLReflect ¶
func (Attachments) VDLReflect(struct { Name string `vdl:"v.io/v23/discovery.Attachments"` })
type Attributes ¶
Attributes represents service attributes as a key/value pair.
func (Attributes) VDLIsZero ¶
func (x Attributes) VDLIsZero() bool
func (Attributes) VDLReflect ¶
func (Attributes) VDLReflect(struct { Name string `vdl:"v.io/v23/discovery.Attributes"` })
type DataOrError ¶
DataOrError contains either an attachment data or an error encountered fetching the attachment.
type T ¶
type T interface {
// Advertise broadcasts the advertisement to be discovered by "Scan" operations.
//
// visibility is used to limit the principals that can see the advertisement. An
// empty set means that there are no restrictions on visibility (i.e, equivalent
// to []security.BlessingPattern{security.AllPrincipals}).
//
// If the advertisement id is not specified, a random unique a random unique identifier
// will be assigned. The advertisement should not be changed while it is being advertised.
//
// It is an error to have simultaneously active advertisements for two identical
// instances (Advertisement.Id).
//
// Advertising will continue until the context is canceled or exceeds its deadline
// and the returned channel will be closed when it stops.
Advertise(ctx *context.T, ad *Advertisement, visibility []security.BlessingPattern) (<-chan struct{}, error)
// Scan scans advertisements that match the query and returns the channel of updates.
//
// Scan excludes the advertisements that are advertised from the same discovery
// instance.
//
// The query is a WHERE expression of a syncQL query against advertisements, where
// key is Advertisement.Id and value is Advertisement.
//
// Examples
//
// v.InterfaceName = "v.io/i"
// v.InterfaceName = "v.io/i" AND v.Attributes["a"] = "v"
// v.Attributes["a"] = "v1" OR v.Attributes["a"] = "v2"
//
// SyncQL tutorial at:
// https://vanadium.github.io/tutorials/syncbase/syncql-tutorial.html
//
// Scanning will continue until the context is canceled or exceeds its deadline.
Scan(ctx *context.T, query string) (<-chan Update, error)
}
T is the interface for discovery operations; it is the client side library for the discovery service.
type Update ¶
type Update interface {
// IsLost returns true when this update corresponds to an advertisement
// that led to a previous update vanishing.
IsLost() bool
// Id returns the universal unique identifier of the advertisement.
Id() AdId //nolint:golint // API change required.
// InterfaceName returns the interface name that the service implements.
InterfaceName() string
// Addresses returns the addresses (vanadium object names) that the service
// is served on.
Addresses() []string
// Attribute returns the named attribute. An empty string is returned if
// not found.
Attribute(name string) string
// Attachment returns the channel on which the named attachment can be read.
// Nil data is returned if not found.
//
// This may do RPC calls if the attachment is not fetched yet and fetching
// will fail if the context is canceled or exceeds its deadline.
//
// Attachments may not be available when this update is for lost advertisement.
Attachment(ctx *context.T, name string) <-chan DataOrError
// Advertisement returns a copy of the advertisement that this update
// corresponds to.
//
// The returned advertisement may not include all attachments.
Advertisement() Advertisement
// Timestamp returns the time when advertising began for the corresponding
// Advertisement.
Timestamp() time.Time
}
Update is the interface for a discovery update.
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