go-micro.dev/v5@v5.12.0/events/events.go (about)

     1  // Package events is for event streaming and storage
     2  package events
     3  
     4  import (
     5  	"encoding/json"
     6  	"errors"
     7  	"time"
     8  )
     9  
    10  var (
    11  	// DefaultStream is the default events stream implementation
    12  	DefaultStream Stream
    13  	// DefaultStore is the default events store implementation
    14  	DefaultStore Store
    15  )
    16  
    17  var (
    18  	// ErrMissingTopic is returned if a blank topic was provided to publish
    19  	ErrMissingTopic = errors.New("missing topic")
    20  	// ErrEncodingMessage is returned from publish if there was an error encoding the message option
    21  	ErrEncodingMessage = errors.New("error encoding message")
    22  )
    23  
    24  // Stream is an event streaming interface
    25  type Stream interface {
    26  	Publish(topic string, msg interface{}, opts ...PublishOption) error
    27  	Consume(topic string, opts ...ConsumeOption) (<-chan Event, error)
    28  }
    29  
    30  // Store is an event store interface
    31  type Store interface {
    32  	Read(topic string, opts ...ReadOption) ([]*Event, error)
    33  	Write(event *Event, opts ...WriteOption) error
    34  }
    35  
    36  type AckFunc func() error
    37  type NackFunc func() error
    38  
    39  // Event is the object returned by the broker when you subscribe to a topic
    40  type Event struct {
    41  	// ID to uniquely identify the event
    42  	ID string
    43  	// Topic of event, e.g. "registry.service.created"
    44  	Topic string
    45  	// Timestamp of the event
    46  	Timestamp time.Time
    47  	// Metadata contains the values the event was indexed by
    48  	Metadata map[string]string
    49  	// Payload contains the encoded message
    50  	Payload []byte
    51  
    52  	ackFunc  AckFunc
    53  	nackFunc NackFunc
    54  }
    55  
    56  // Unmarshal the events message into an object
    57  func (e *Event) Unmarshal(v interface{}) error {
    58  	return json.Unmarshal(e.Payload, v)
    59  }
    60  
    61  // Ack acknowledges successful processing of the event in ManualAck mode
    62  func (e *Event) Ack() error {
    63  	return e.ackFunc()
    64  }
    65  
    66  func (e *Event) SetAckFunc(f AckFunc) {
    67  	e.ackFunc = f
    68  }
    69  
    70  // Nack negatively acknowledges processing of the event (i.e. failure) in ManualAck mode
    71  func (e *Event) Nack() error {
    72  	return e.nackFunc()
    73  }
    74  
    75  func (e *Event) SetNackFunc(f NackFunc) {
    76  	e.nackFunc = f
    77  }
    78  
    79  // Publish an event to a topic
    80  func Publish(topic string, msg interface{}, opts ...PublishOption) error {
    81  	return DefaultStream.Publish(topic, msg, opts...)
    82  }
    83  
    84  // Consume to events
    85  func Consume(topic string, opts ...ConsumeOption) (<-chan Event, error) {
    86  	return DefaultStream.Consume(topic, opts...)
    87  }
    88  
    89  // Read events for a topic
    90  func Read(topic string, opts ...ReadOption) ([]*Event, error) {
    91  	return DefaultStore.Read(topic, opts...)
    92  }