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// Copyright 2016 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package pubsub
import (
"time"
"github.com/golang/protobuf/ptypes"
pb "google.golang.org/genproto/googleapis/pubsub/v1"
)
// Message represents a Pub/Sub message.
type Message struct {
// ID identifies this message. This ID is assigned by the server and is
// populated for Messages obtained from a subscription.
//
// This field is read-only.
ID string
// Data is the actual data in the message.
Data []byte
// Attributes represents the key-value pairs the current message is
// labelled with.
Attributes map[string]string
// ackID is the identifier to acknowledge this message.
ackID string
// PublishTime is the time at which the message was published. This is
// populated by the server for Messages obtained from a subscription.
//
// This field is read-only.
PublishTime time.Time
// receiveTime is the time the message was received by the client.
receiveTime time.Time
// DeliveryAttempt is the number of times a message has been delivered.
// This is part of the dead lettering feature that forwards messages that
// fail to be processed (from nack/ack deadline timeout) to a dead letter topic.
// If dead lettering is enabled, this will be set on all attempts, starting
// with value 1. Otherwise, the value will be nil.
// This field is read-only.
//
// It is EXPERIMENTAL and a part of a closed alpha that may not be
// accessible to all users. This field is subject to change or removal
// without notice.
DeliveryAttempt *int
// size is the approximate size of the message's data and attributes.
size int
calledDone bool
// The done method of the iterator that created this Message.
doneFunc func(string, bool, time.Time)
// OrderingKey identifies related messages for which publish order should
// be respected. If empty string is used, message will be sent unordered.
OrderingKey string
}
func toMessage(resp *pb.ReceivedMessage) (*Message, error) {
if resp.Message == nil {
return &Message{ackID: resp.AckId}, nil
}
pubTime, err := ptypes.Timestamp(resp.Message.PublishTime)
if err != nil {
return nil, err
}
var deliveryAttempt *int
if resp.DeliveryAttempt > 0 {
da := int(resp.DeliveryAttempt)
deliveryAttempt = &da
}
return &Message{
ackID: resp.AckId,
Data: resp.Message.Data,
Attributes: resp.Message.Attributes,
ID: resp.Message.MessageId,
PublishTime: pubTime,
DeliveryAttempt: deliveryAttempt,
OrderingKey: resp.Message.OrderingKey,
}, nil
}
// Ack indicates successful processing of a Message passed to the Subscriber.Receive callback.
// It should not be called on any other Message value.
// If message acknowledgement fails, the Message will be redelivered.
// Client code must call Ack or Nack when finished for each received Message.
// Calls to Ack or Nack have no effect after the first call.
func (m *Message) Ack() {
m.done(true)
}
// Nack indicates that the client will not or cannot process a Message passed to the Subscriber.Receive callback.
// It should not be called on any other Message value.
// Nack will result in the Message being redelivered more quickly than if it were allowed to expire.
// Client code must call Ack or Nack when finished for each received Message.
// Calls to Ack or Nack have no effect after the first call.
func (m *Message) Nack() {
m.done(false)
}
func (m *Message) done(ack bool) {
if m.calledDone {
return
}
m.calledDone = true
m.doneFunc(m.ackID, ack, m.receiveTime)
}
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