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consumer.go
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consumer.go
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package pulsar
import (
"context"
"errors"
"fmt"
"io"
"math"
"regexp"
"sync"
pb "github.com/cornelk/pulsar-go/proto"
"google.golang.org/protobuf/proto"
)
// SubscriptionType ...
type SubscriptionType pb.CommandSubscribe_SubType
// Subscription type options.
const (
ExclusiveSubscription = SubscriptionType(pb.CommandSubscribe_Exclusive)
SharedSubscription = SubscriptionType(pb.CommandSubscribe_Shared)
)
// InitialPosition ...
type InitialPosition pb.CommandSubscribe_InitialPosition
// InitialPositionCallback declares a callback that allows a client to specify
// a start position or message for every discovered topic when using topic
// pattern subscriptions.
type InitialPositionCallback func(topic string) (position InitialPosition, StartMessageID []byte, err error)
// Subscription initial position options.
const (
// LatestPosition starts reading from the topic end, only getting
// messages published after the reader was created.
LatestPosition = InitialPosition(pb.CommandSubscribe_Latest)
// EarliestPosition starts reading from the earliest message
// available in the topic.
EarliestPosition = InitialPosition(pb.CommandSubscribe_Earliest)
)
// ConsumerConfig is a configuration object used to create new instances
// of Consumer.
type ConsumerConfig struct {
// The topic name to read messages from.
Topic string
// A regular expression for topics to read messages from.
TopicPattern string
// Interval in ms in which the client checks for topic changes
// that match the set topic pattern and updates the subscriptions.
// Default is 30000
TopicPatternDiscoveryInterval int
// A unique name for the subscription. If not specified, a random name
// will be used.
Subscription string
// A unique name for the Consumer. If not specified, a random name
// will be used.
Name string
// Select the subscription type to be used when subscribing to the topic.
// Default is `Subscribe_Exclusive`
Type SubscriptionType
// Signal whether the subscription will initialize on latest
// or earliest position.
InitialPosition InitialPosition
// Callback function for every discovered topic when using a topic
// pattern to allow the client to specify an initial position and
// start message ID for the topic.
InitialPositionCallback InitialPositionCallback
// If specified, the subscription will position the cursor
// on the particular message id and will send messages from
// that point.
StartMessageID []byte
// Include the message StartMessageID in the read messages.
// If StartMessageID is not set but InitialPosition is set
// to LatestPosition, the latest message ID of the topic
// will be sent.
StartMessageIDInclusive bool
// Signal whether the subscription should be backed by a
// durable cursor or not. For Readers, set to false, for
// Consumers set Durable to true and specify a Subscription.
// If Durable is true, StartMessageID will be ignored, as it
// will be determined by the broker.
Durable bool
// If true, the subscribe operation will cause a topic to be
// created if it does not exist already (and if topic auto-creation
// is allowed by broker.
// If false, the subscribe operation will fail if the topic
// does not exist.
ForceTopicCreation bool
// MessageChannel sets a channel that receives all messages that the
// consumer receives. If not set, a default channel for 1000 messages
// will be created.
MessageChannel chan *Message
}
// Consumer provides a high-level API for consuming messages from Pulsar.
type Consumer interface {
// Close closes the subscription and unregisters from the Client.
Close() error
AckMessage(*Message) error
// ReadMessage reads and return the next message from the Pulsar.
ReadMessage(context.Context) (*Message, error)
SeekMessage(*Message) error
// HasNext returns whether there is a message available to read
HasNext() bool
// LastMessageID returns the last message ID of the topic.
// If the topic is empty, EntryId will be math.MaxUint64
LastMessageID() (*MessageID, error)
}
type consumerCloser interface {
CloseConsumer(consumerID uint64) error
}
type consumerState int
const (
consumerInit consumerState = iota
consumerReady
consumerSubscribed
consumerClosing
consumerClosed
)
type consumer struct {
ctx context.Context
conn clientConn
req *requests
// subscribe options
topic string
subscription *string
name *string
subType pb.CommandSubscribe_SubType
initialPosition pb.CommandSubscribe_InitialPosition
startMessageID *pb.MessageIdData
startMessageIDInclusive bool
startMessageIDSeekDone bool
forceTopicCreation *bool
durable *bool
incomingMessages chan *Message
consumerID uint64
connected chan error
state consumerState
stateMu sync.RWMutex
closer consumerCloser
multi *multiTopicConsumer // set if managed by a multi topic consumer
messagePermits uint32
usedPermits uint32
permitsMu sync.Mutex
}
// Validate method validates the config properties.
func (config *ConsumerConfig) Validate() error {
if config.StartMessageID != nil {
id := &pb.MessageIdData{}
if err := proto.Unmarshal(config.StartMessageID, id); err != nil {
return fmt.Errorf("start message id unmarshalling: %w", err)
}
}
if config.TopicPattern == "" {
if config.Topic == "" {
return errors.New("topic is not set")
}
} else {
if config.Topic != "" {
return errors.New("topic and topic pattern are exclusive")
}
if _, err := regexp.Compile(config.TopicPattern); err != nil {
return fmt.Errorf("topic pattern regular expression compiling: %w", err)
}
if config.TopicPatternDiscoveryInterval < 0 {
return errors.New("invalid topic pattern discovery interval set")
}
if config.StartMessageID != nil {
return errors.New("start message id not valid for pattern consumer")
}
}
return nil
}
// newConsumer creates and returns a new Consumer configured with config.
func newConsumer(closer consumerCloser, conn brokerConnection, config ConsumerConfig, consumerID uint64) (*consumer, error) {
c := &consumer{
ctx: conn.ctx,
conn: conn.conn,
req: conn.req,
topic: config.Topic,
subType: pb.CommandSubscribe_SubType(config.Type),
initialPosition: pb.CommandSubscribe_InitialPosition(config.InitialPosition),
startMessageIDInclusive: config.StartMessageIDInclusive,
forceTopicCreation: proto.Bool(config.ForceTopicCreation),
durable: proto.Bool(config.Durable),
consumerID: consumerID,
connected: make(chan error, 1),
state: consumerInit,
closer: closer,
}
if config.MessageChannel == nil {
c.incomingMessages = make(chan *Message, 1000)
} else {
c.incomingMessages = config.MessageChannel
}
if cap(c.incomingMessages) > math.MaxUint32 {
c.messagePermits = math.MaxUint32
} else {
c.messagePermits = uint32(cap(c.incomingMessages))
}
if !config.Durable {
if config.StartMessageID != nil {
id := &pb.MessageIdData{}
if err := proto.Unmarshal(config.StartMessageID, id); err != nil {
return nil, err
}
c.startMessageID = id
} else {
if config.InitialPosition == EarliestPosition {
c.startMessageID = earliestMessageID
} else {
c.startMessageID = latestMessageID
}
}
}
if config.Name == "" {
c.name = proto.String(randomConsumerName())
} else {
c.name = proto.String(config.Name)
}
if config.Subscription == "" {
c.subscription = proto.String(randomSubscriptionName())
} else {
c.subscription = proto.String(config.Subscription)
}
return c, nil
}
func (c *consumer) topicLookupFinished(cmd *command) error {
if cmd.err != nil {
return cmd.err
}
id := c.req.newID()
if c.startMessageIDInclusive && c.startMessageID == latestMessageID && !c.startMessageIDSeekDone {
c.req.addCallback(id, c.getLastMessageID)
} else {
c.req.addCallback(id, c.subscribedSendFlowCommand)
}
c.stateMu.Lock()
c.state = consumerReady
c.stateMu.Unlock()
return c.sendSubscribeCommand(cmd.custom, id)
}
func (c *consumer) getLastMessageID(base *command) error {
if base.err != nil {
c.connected <- base.err
return base.err
}
reqID := c.req.newID()
cmd := newGetLastMessageIDCommand(c.consumerID, reqID)
c.req.addCallback(reqID, c.seekToLastMessageID)
return c.conn.WriteCommand(cmd, nil)
}
func (c *consumer) seekToLastMessageID(cmd *command) error {
c.startMessageIDSeekDone = true
if cmd.err != nil {
return cmd.err
}
if *cmd.GetLastMessageIdResponse.LastMessageId.EntryId == math.MaxUint64 {
return c.subscribedSendFlowCommand(cmd) // empty topic
}
reqID := c.req.newID()
return c.sendSeek(reqID, cmd.GetLastMessageIdResponse.LastMessageId)
}
func (c *consumer) Close() error {
return c.closer.CloseConsumer(c.consumerID)
}
func (c *consumer) reset(newConsumerID uint64) {
c.consumerID = newConsumerID
}
func (c *consumer) ReadMessage(ctx context.Context) (*Message, error) {
select {
case <-ctx.Done():
return nil, ctx.Err()
case <-c.ctx.Done():
return nil, c.ctx.Err()
case m, ok := <-c.incomingMessages:
if !ok {
return nil, io.EOF
}
return m, nil
}
}
func (c *consumer) useMessagePermits(permits uint64) error {
hasPermits := false
c.permitsMu.Lock()
if permits <= math.MaxUint32 && uint64(c.usedPermits)+permits <= math.MaxUint32 {
c.usedPermits += uint32(permits)
hasPermits = c.usedPermits < c.messagePermits
}
c.permitsMu.Unlock()
if hasPermits {
return nil
}
return c.sendFlowCommand()
}
func (c *consumer) HasNext() bool {
return len(c.incomingMessages) > 0
}
func (c *consumer) SeekMessage(msg *Message) error {
id := &pb.MessageIdData{
LedgerId: msg.ID.LedgerId,
EntryId: msg.ID.EntryId,
}
reqID := c.req.newID()
ch := make(chan error, 1)
c.req.addCallback(reqID, func(cmd *command) error {
ch <- cmd.err
return cmd.err
})
c.startMessageID = id
if err := c.sendSeek(reqID, id); err != nil {
return err
}
err := <-ch
// the server issues a close consumer command, wait for the
// automatic reconnection
e := <-c.connected
if err == nil {
err = e
}
return err
}
func (c *consumer) sendSeek(reqID uint64, id *pb.MessageIdData) error {
base := &pb.BaseCommand{
Type: pb.BaseCommand_SEEK.Enum(),
Seek: &pb.CommandSeek{
ConsumerId: proto.Uint64(c.consumerID),
RequestId: proto.Uint64(reqID),
MessageId: id,
},
}
return c.conn.WriteCommand(base, nil)
}
func (c *consumer) AckMessage(msg *Message) error {
return c.sendAck(msg.ID)
}
func (c *consumer) sendAck(id *MessageID) error {
base := &pb.BaseCommand{
Type: pb.BaseCommand_ACK.Enum(),
Ack: &pb.CommandAck{
ConsumerId: proto.Uint64(c.consumerID),
AckType: pb.CommandAck_Individual.Enum(),
MessageId: []*pb.MessageIdData{(*pb.MessageIdData)(id)},
},
}
return c.conn.WriteCommand(base, nil)
}
func (c *consumer) sendSubscribeCommand(topic string, reqID uint64) error {
base := &pb.BaseCommand{
Type: pb.BaseCommand_SUBSCRIBE.Enum(),
Subscribe: &pb.CommandSubscribe{
Topic: &topic,
Subscription: c.subscription,
SubType: &c.subType,
ConsumerId: proto.Uint64(c.consumerID),
RequestId: proto.Uint64(reqID),
ConsumerName: c.name,
Durable: c.durable,
StartMessageId: c.startMessageID,
ReadCompacted: proto.Bool(false),
InitialPosition: &c.initialPosition,
ForceTopicCreation: c.forceTopicCreation,
},
}
return c.conn.WriteCommand(base, nil)
}
func (c *consumer) subscribedSendFlowCommand(cmd *command) error {
defer func() {
c.connected <- cmd.err
}()
if cmd.err != nil {
return cmd.err
}
c.stateMu.Lock()
c.state = consumerSubscribed
c.stateMu.Unlock()
return c.sendFlowCommand()
}
func (c *consumer) sendFlowCommand() error {
c.permitsMu.Lock()
c.usedPermits = 0
c.permitsMu.Unlock()
base := &pb.BaseCommand{
Type: pb.BaseCommand_FLOW.Enum(),
Flow: &pb.CommandFlow{
ConsumerId: proto.Uint64(c.consumerID),
MessagePermits: proto.Uint32(c.messagePermits),
},
}
return c.conn.WriteCommand(base, nil)
}
func (c *consumer) clearReceiverQueue() {
for {
select {
case _, ok := <-c.incomingMessages:
if !ok {
return
}
default:
return
}
}
}
func (c *consumer) LastMessageID() (*MessageID, error) {
reqID := c.req.newID()
cmd := newGetLastMessageIDCommand(c.consumerID, reqID)
var msgID *MessageID
respHandler := func(resp *command) error {
if resp.err == nil && resp.GetLastMessageIdResponse != nil {
msgID = (*MessageID)(resp.GetLastMessageIdResponse.LastMessageId)
}
return resp.err
}
err := c.conn.SendCallbackCommand(c.req, reqID, cmd, respHandler)
if err != nil {
return nil, err
}
return msgID, nil
}