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batch.go
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batch.go
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package eventhub
import (
"errors"
"github.com/Azure/azure-amqp-common-go/v3/uuid"
"github.com/Azure/go-amqp"
)
type (
// BatchOptions are optional information to add to a batch of messages
BatchOptions struct {
MaxSize MaxMessageSizeInBytes
}
// BatchIterator offers a simple mechanism for batching a list of events
BatchIterator interface {
Done() bool
Next(messageID string, opts *BatchOptions) (*EventBatch, error)
}
// EventBatchIterator provides an easy way to iterate over a slice of events to reliably create batches
EventBatchIterator struct {
Cursors map[string]int
PartitionEventsMap map[string][]*Event
}
// EventBatch is a batch of Event Hubs messages to be sent
EventBatch struct {
*Event
marshaledMessages [][]byte
MaxSize MaxMessageSizeInBytes
size int
}
// BatchOption provides a way to configure `BatchOptions`
BatchOption func(opt *BatchOptions) error
// MaxMessageSizeInBytes is the max number of bytes allowed by Azure Service Bus
MaxMessageSizeInBytes uint
)
const (
// DefaultMaxMessageSizeInBytes is the maximum number of bytes in an event (https://docs.microsoft.com/en-us/azure/event-hubs/event-hubs-quotas)
DefaultMaxMessageSizeInBytes MaxMessageSizeInBytes = 1000000
batchMessageWrapperSize = 100
// KeyOfNoPartitionKey is the key value in Events map for Events which do not have PartitionKey
KeyOfNoPartitionKey = "NoPartitionKey"
)
// ErrMessageIsTooBig represents the error when one single event in the batch is bigger than the maximum batch size
var ErrMessageIsTooBig = errors.New("message is too big")
// BatchWithMaxSizeInBytes configures the EventBatchIterator to fill the batch to the specified max size in bytes
func BatchWithMaxSizeInBytes(sizeInBytes int) BatchOption {
return func(batchOption *BatchOptions) error {
batchOption.MaxSize = MaxMessageSizeInBytes(sizeInBytes)
return nil
}
}
// NewEventBatchIterator wraps a slice of `Event` pointers to allow it to be made into a `EventBatchIterator`.
func NewEventBatchIterator(events ...*Event) *EventBatchIterator {
partitionEventMap := make(map[string][]*Event)
cursors := make(map[string]int)
for _, event := range events {
var ok bool
var key string
if event.PartitionKey == nil {
key = KeyOfNoPartitionKey
} else {
key = *event.PartitionKey
}
if _, ok = partitionEventMap[key]; !ok {
cursors[key] = 0
}
partitionEventMap[key] = append(partitionEventMap[key], event)
}
return &EventBatchIterator{
Cursors: cursors,
PartitionEventsMap: partitionEventMap,
}
}
// Done communicates whether there are more messages remaining to be iterated over.
func (ebi *EventBatchIterator) Done() bool {
for key, cursor := range ebi.Cursors {
if cursor != len(ebi.PartitionEventsMap[key]) {
return false
}
}
return true
}
// Next fetches the batch of messages in the message slice at a position one larger than the last one accessed.
func (ebi *EventBatchIterator) Next(eventID string, opts *BatchOptions) (*EventBatch, error) {
var key string
for partitionKey, cursor := range ebi.Cursors {
if cursor != len(ebi.PartitionEventsMap[partitionKey]) {
key = partitionKey
}
}
if key == "" {
return nil, ErrNoMessages{}
}
if opts == nil {
opts = &BatchOptions{
MaxSize: DefaultMaxMessageSizeInBytes,
}
}
events := ebi.PartitionEventsMap[key][ebi.Cursors[key]:]
eb := NewEventBatch(eventID, opts)
if key != KeyOfNoPartitionKey && len(events) > 0 {
eb.PartitionKey = events[0].PartitionKey
}
for _, event := range events {
ok, err := eb.Add(event)
if err != nil {
return nil, err
}
if !ok {
if len(eb.marshaledMessages) == 0 {
ebi.Cursors[key]++
return nil, ErrMessageIsTooBig
}
return eb, nil
}
ebi.Cursors[key]++
}
return eb, nil
}
// NewEventBatch builds a new event batch
func NewEventBatch(eventID string, opts *BatchOptions) *EventBatch {
if opts == nil {
opts = &BatchOptions{
MaxSize: DefaultMaxMessageSizeInBytes,
}
}
mb := &EventBatch{
MaxSize: opts.MaxSize,
Event: &Event{
ID: eventID,
},
}
return mb
}
// Add adds a message to the batch if the message will not exceed the max size of the batch
func (eb *EventBatch) Add(e *Event) (bool, error) {
e.PartitionKey = eb.PartitionKey
msg, err := e.toMsg()
if err != nil {
return false, err
}
if msg.Properties.MessageID == nil || msg.Properties.MessageID == "" {
uid, err := uuid.NewV4()
if err != nil {
return false, err
}
msg.Properties.MessageID = uid.String()
}
bin, err := msg.MarshalBinary()
if err != nil {
return false, err
}
if eb.Size()+len(bin) > int(eb.MaxSize) {
return false, nil
}
eb.size += len(bin)
eb.marshaledMessages = append(eb.marshaledMessages, bin)
return true, nil
}
// Clear will zero out the batch size and clear the buffered messages
func (eb *EventBatch) Clear() {
eb.marshaledMessages = [][]byte{}
eb.size = 0
}
// Size is the number of bytes in the message batch
func (eb *EventBatch) Size() int {
// calculated data size + batch message wrapper + data wrapper portions of the message
return eb.size + batchMessageWrapperSize + (len(eb.marshaledMessages) * 5)
}
func (eb *EventBatch) toMsg() (*amqp.Message, error) {
batchMessage := eb.amqpBatchMessage()
batchMessage.Data = make([][]byte, len(eb.marshaledMessages))
for idx, bytes := range eb.marshaledMessages {
batchMessage.Data[idx] = bytes
}
if eb.PartitionKey != nil {
batchMessage.Annotations = make(amqp.Annotations)
batchMessage.Annotations[partitionKeyAnnotationName] = eb.PartitionKey
}
return batchMessage, nil
}
func (eb *EventBatch) amqpBatchMessage() *amqp.Message {
return &amqp.Message{
Data: make([][]byte, len(eb.marshaledMessages)),
Format: batchMessageFormat,
Properties: &amqp.MessageProperties{
MessageID: eb.ID,
},
}
}