events

package
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 Go to latest Published: Apr 1, 2021 License: Apache-2.0 Imports: 28 Imported by: 0

Documentation

Overview

Package events implements event handling through a PubSub interface.

Example 
package main

import (
	"fmt"
	"sync"

	"go.thethings.network/lorawan-stack/v3/pkg/events"
	"go.thethings.network/lorawan-stack/v3/pkg/events/basic"
	"go.thethings.network/lorawan-stack/v3/pkg/ttnpb"
	"go.thethings.network/lorawan-stack/v3/pkg/util/test"
)

func main() {
	// The context typically comes from the request or something.
	ctx := test.Context()

	// This is required for unit test to pass.
	defer test.SetDefaultEventsPubSub(basic.NewPubSub())()

	// The WaitGroup is only for synchronizing the unit test
	var wg sync.WaitGroup
	wg.Add(1)

	events.Subscribe(ctx, "ns.**", nil, events.HandlerFunc(func(e events.Event) {
		fmt.Printf("Received event %s\n", e.Name())

		wg.Done() // only for synchronizing the unit test
	}))

	// You can send any arbitrary event; you don't have to pass any identifiers or data.
	events.Publish(events.New(test.Context(), "test.hello_world", "the events system says hello, world"))

	// Defining the event is not mandatory, but will be needed in order to translate the descriptions.
	// Event names are lowercase snake_case and can be dot-separated as component.subsystem.subsystem.event
	// Event descriptions are short descriptions of what the event means.
	// Visibility rights are optional. If no rights are supplied, then the _ALL right is assumed.
	adrSendEvent := events.Define("ns.mac.adr.send_req", "send ADR request", events.WithVisibility(ttnpb.RIGHT_APPLICATION_TRAFFIC_READ))

	// These variables come from the request or you got them from the db or something.
	var (
		dev      ttnpb.EndDevice
		requests []ttnpb.MACCommand_LinkADRReq
	)

	// It's nice to be able to correlate events; we use a Correlation ID for that.
	// In most cases, there will already be a correlation ID in the context; this function will append a new one to the ones already in the context.
	ctx = events.ContextWithCorrelationID(ctx, events.NewCorrelationID())

	// Publishing an event to the events package will dispatch it on the "global" event pubsub.
	events.Publish(adrSendEvent.NewWithIdentifiersAndData(ctx, dev.EndDeviceIdentifiers, requests))

	wg.Wait() // only for synchronizing the unit test

}

Output:

Received event ns.mac.adr.send_req

Index

Examples

Constants

This section is empty.

Variables

View Source 
var IncludeCaller bool

IncludeCaller indicates whether the caller of Publish should be included in the event

Functions

func ContextWithCorrelationID 

func ContextWithCorrelationID(ctx context.Context, cids ...string) context.Context

ContextWithCorrelationID returns a derived context with the correlation IDs if they were not already in there.

func CorrelationIDsFromContext 

func CorrelationIDsFromContext(ctx context.Context) []string

CorrelationIDsFromContext returns the correlation IDs that are attached to the context.

func DefineFunc 

func DefineFunc(name, description string, opts ...Option) func() Builder

DefineFunc generates a function, which returns a Definition with specified name and description. Most callers should be using Define - this function is only useful for helper functions.

func NewCorrelationID 

func NewCorrelationID() string

NewCorrelationID returns a new random correlation ID.

func Proto 

func Proto(e Event) (*ttnpb.Event, error)

Proto returns the protobuf representation of the event.

func Publish 

func Publish(evts ...Event)

Publish emits events on the default event pubsub.

func RegisterContextMarshaler 

func RegisterContextMarshaler(name string, m ContextMarshaler)

RegisterContextMarshaler registers a ContextMarshaler with the given name. This should only be called from init funcs.

func SetDefaultPubSub 

func SetDefaultPubSub(ps PubSub)

SetDefaultPubSub sets pubsub used by the package to ps.

func StreamServerInterceptor 

func StreamServerInterceptor(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error

StreamServerInterceptor returns a new streaming server interceptor that that modifies the context.

func Subscribe 

func Subscribe(ctx context.Context, name string, ids []*ttnpb.EntityIdentifiers, hdl Handler) error

Subscribe subscribes on the default PubSub.

func UnaryServerInterceptor 

func UnaryServerInterceptor(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error)

UnaryServerInterceptor returns a new unary server interceptor that modifies the context to include a correlation ID.

Types

type Builder 

type Builder interface {
	Definition() Definition

	With(opts ...Option) Builder
	New(ctx context.Context, opts ...Option) Event

	// Convenience function for legacy code. Same as New(ctx, WithIdentifiers(ids), WithData(data)).
	NewWithIdentifiersAndData(ctx context.Context, ids CombinedIdentifiers, data interface{}) Event
	// Convenience function for legacy code. Same as With(WithData(data)).
	BindData(data interface{}) Builder
}

Builder is the interface for building events from definitions.

func Define 

func Define(name, description string, opts ...Option) Builder

Define a registered event.

type Builders 

type Builders []Builder

Builders makes it easier to create multiple events at once.

func All 

func All() Builders

All returns all defined events, sorted by name.

func (Builders) Definitions 

func (bs Builders) Definitions() []Definition

Definitions returns the definition for each builder in the list.

func (Builders) New 

func (bs Builders) New(ctx context.Context, opts ...Option) []Event

New returns new events for each builder in the list.

type Channel 

type Channel chan Event

Channel is a channel of Events that can be used as an event handler. The channel should be buffered, events will be dropped if the channel blocks. It is typically not safe to close this channel until you're absolutely sure that it is no longer registered as an event handler.

Example 
package main

import (
	"context"
	"fmt"

	"go.thethings.network/lorawan-stack/v3/pkg/events"
	"go.thethings.network/lorawan-stack/v3/pkg/util/test"
)

func main() {
	// The context typically comes from the request or something.
	ctx := test.Context()

	eventChan := make(events.Channel, 2)

	subCtx, unsubscribe := context.WithCancel(ctx)
	events.Subscribe(subCtx, "example", nil, eventChan)

	// From this moment on, "example" events will be delivered to the channel.
	// As soon as the channel is full, events will be dropped, so it's probably a
	// good idea to start handling the channel before subscribing.

	go func() {
		for e := range eventChan {
			fmt.Printf("Received event %v\n", e)
		}
	}()

	// We want to unsubscribe when this function returns.
	defer unsubscribe()

	// Note that in-transit events may still be delivered after Unsubscribe returns.
	// This means that you can't immediately close the channel after unsubscribing.
}

Output:

func (Channel) Notify 

func (ch Channel) Notify(evt Event)

Notify implements the Handler interface.

func (Channel) ReceiveContext 

func (ch Channel) ReceiveContext(ctx context.Context) Event

ReceiveContext returns the next event from the channel or returns nil when the context is done.

func (Channel) ReceiveTimeout 

func (ch Channel) ReceiveTimeout(timeout time.Duration) Event

ReceiveTimeout returns the next event from the channel or returns nil after a timeout.

type CombinedIdentifiers 

type CombinedIdentifiers interface {
	CombinedIdentifiers() *ttnpb.CombinedIdentifiers
}

type ContextMarshaler 

type ContextMarshaler interface {
	MarshalContext(context.Context) []byte
	UnmarshalContext(context.Context, []byte) (context.Context, error)
}

ContextMarshaler interface for marshaling/unmarshaling contextual information to/from events.

type Definition 

type Definition interface {
	Name() string
	Description() string
	DataType() proto.Message
}

Definition describes an event definition.

type DefinitionOption 

type DefinitionOption interface {
	Option
	// contains filtered or unexported methods
}

DefinitionOption is like Option, but applies to the definition instead.

func WithDataType 

func WithDataType(t interface{}) DefinitionOption

WithDataType returns an option that sets the data type of the event (for documentation).

func WithErrorDataType 

func WithErrorDataType() DefinitionOption

WithErrorDataType is a convenience function that sets the data type of the event to an error.

func WithUpdatedFieldsDataType 

func WithUpdatedFieldsDataType() DefinitionOption

WithUpdatedFieldsDataType is a convenience function that sets the data type of the event to a slice of updated fields.

type Event 

type Event interface {
	UniqueID() string
	Context() context.Context
	Name() string
	Time() time.Time
	Identifiers() []*ttnpb.EntityIdentifiers
	Data() interface{}
	CorrelationIDs() []string
	Origin() string
	Caller() string
	Visibility() *ttnpb.Rights
	AuthType() string
	AuthTokenID() string
	AuthTokenType() string
	RemoteIP() string
	UserAgent() string
}

Event interface

func FromProto 

func FromProto(pb *ttnpb.Event) (Event, error)

FromProto returns the event from its protobuf representation.

func New 

func New(ctx context.Context, name, description string, opts ...Option) Event

New returns a new Event. Instead of using New, most implementations should first define an event, and then create a new event from that definition.

func UnmarshalJSON 

func UnmarshalJSON(data []byte) (Event, error)

UnmarshalJSON unmarshals an event as JSON.

type Handler 

type Handler interface {
	Notify(Event)
}

Handler interface for event listeners.

func ContextHandler 

func ContextHandler(ctx context.Context, handler Handler) Handler

ContextHandler delivers events to the Handler as long as ctx.Err() is non-nil.

Example 
package main

import (
	"context"
	"fmt"

	"go.thethings.network/lorawan-stack/v3/pkg/events"
	"go.thethings.network/lorawan-stack/v3/pkg/util/test"
)

func main() {
	// Usually the context comes from somewhere else (e.g. a streaming RPC):
	ctx, cancel := context.WithCancel(test.Context())
	defer cancel()

	eventChan := make(events.Channel, 2)
	handler := events.ContextHandler(ctx, eventChan)

	events.Subscribe(ctx, "example", nil, handler)

	// We automatically unsubscribe when he context gets canceled.

	// From this moment on, "example" events will be delivered to the channel.
	// As soon as the channel is full, events will be dropped, so it's probably a
	// good idea to start handling the channel before subscribing.

	go func() {
		for {
			select {
			case <-ctx.Done():
				// The ContextHandler will make sure that no events are delivered after
				// the context is canceled, so it is now safe to close the channel:
				close(eventChan)
				return
			case e := <-eventChan:
				fmt.Printf("Received event %v\n", e)
			}
		}
	}()
}

Output:

func HandlerFunc 

func HandlerFunc(handler func(Event)) Handler

HandlerFunc makes the func implement the Handler interface.

Example 
package main

import (
	"context"
	"fmt"

	"go.thethings.network/lorawan-stack/v3/pkg/events"
	"go.thethings.network/lorawan-stack/v3/pkg/util/test"
)

func main() {
	// The context typically comes from the request or something.
	ctx := test.Context()

	handler := events.HandlerFunc(func(e events.Event) {
		fmt.Printf("Received event %v\n", e)
	})

	subCtx, unsubscribe := context.WithCancel(ctx)
	events.Subscribe(subCtx, "example", nil, handler)

	// From this moment on, "example" events will be delivered to the handler func.

	// We want to unsubscribe when this function returns.
	defer unsubscribe()

	// Note that in-transit events may still be delivered after unsubscribe returns.
}

Output:

type Option 

type Option interface {
	// contains filtered or unexported methods
}

Option is an option that is used to build events.

func WithAuthFromContext 

func WithAuthFromContext() Option

WithAuthFromContext returns an option that extracts auth information from the context when the event is created.

func WithClientInfoFromContext 

func WithClientInfoFromContext() Option

WithClientInfoFromContext returns an option that extracts the UserAgent and the RemoteIP from the request context.

func WithData 

func WithData(data interface{}) Option

WithData returns an option that sets the data of the event.

func WithIdentifiers 

func WithIdentifiers(identifiers ...ttnpb.Identifiers) Option

WithIdentifiers returns an option that sets the identifiers of the event.

func WithVisibility 

func WithVisibility(rights ...ttnpb.Right) Option

WithVisibility returns an option that sets the visibility of the event.

type PubSub 

type PubSub interface {
	Publisher
	Subscriber
}

PubSub interface combines the Publisher and Subscriber interfaces.

func DefaultPubSub 

func DefaultPubSub() PubSub

DefaultPubSub returns the default PubSub.

type Publisher 

type Publisher interface {
	// Publish emits an event on the default event pubsub.
	Publish(evt Event)
}

Publisher interface lets you publish events.

type Subscriber 

type Subscriber interface {
	// Subscribe to events that match the name and identifiers.
	// The subscription continues until the context is canceled.
	// The name can be a glob in order to catch multiple event types.
	// If supplying identifiers, then only events matching _any_ of those
	// identifiers will get sent to the handler.
	// The handler must be non-blocking.
	Subscribe(ctx context.Context, name string, identifiers []*ttnpb.EntityIdentifiers, hdl Handler) error
}

Subscriber interface lets you subscribe to events.

type Subscription 

type Subscription interface {
	// Match returns whether the event matches the subscription.
	Match(Event) bool
	// Notify notifies the subscription of a new matching event.
	Notify(Event)
}

Subscription is the interface for PubSub subscriptions.

Source Files

View all Source files

Directories

Path Synopsis
Package cloud implements an events.PubSub implementation that uses Go Cloud PubSub.
 Package cloud implements an events.PubSub implementation that uses Go Cloud PubSub.
Package grpc contains an implementation of the EventsServer, which is used to stream all events published for a set of identifiers.
 Package grpc contains an implementation of the EventsServer, which is used to stream all events published for a set of identifiers.
internal
eventstest
Package redis implements an events.PubSub implementation that uses Redis PubSub.
 Package redis implements an events.PubSub implementation that uses Redis PubSub.

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