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nats.go
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nats.go
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// ------------------------------------------------------------
// Copyright (c) Microsoft Corporation and Dapr Contributors.
// Licensed under the MIT License.
// ------------------------------------------------------------
package nats
import (
"errors"
"fmt"
"github.com/dapr/components-contrib/pubsub"
"github.com/dapr/dapr/pkg/logger"
nats "github.com/nats-io/go-nats"
)
const (
natsURL = "natsURL"
consumerID = "consumerID"
)
type natsPubSub struct {
metadata metadata
natsConn *nats.Conn
logger logger.Logger
}
// NewNATSPubSub returns a new NATS pub-sub implementation
func NewNATSPubSub(logger logger.Logger) pubsub.PubSub {
return &natsPubSub{logger: logger}
}
func parseNATSMetadata(meta pubsub.Metadata) (metadata, error) {
m := metadata{}
if val, ok := meta.Properties[natsURL]; ok && val != "" {
m.natsURL = val
} else {
return m, errors.New("nats error: missing nats URL")
}
if val, ok := meta.Properties[consumerID]; ok && val != "" {
m.natsQueueGroupName = val
} else {
return m, errors.New("nats error: missing queue name")
}
return m, nil
}
func (n *natsPubSub) Init(metadata pubsub.Metadata) error {
m, err := parseNATSMetadata(metadata)
if err != nil {
return err
}
n.metadata = m
natsConn, err := nats.Connect(m.natsURL)
if err != nil {
return fmt.Errorf("nats: error connecting to nats at %s: %s", m.natsURL, err)
}
n.logger.Debugf("connected to nats at %s", m.natsURL)
n.natsConn = natsConn
return nil
}
func (n *natsPubSub) Publish(req *pubsub.PublishRequest) error {
err := n.natsConn.Publish(req.Topic, req.Data)
if err != nil {
return fmt.Errorf("nats: error from publish: %s", err)
}
return nil
}
func (n *natsPubSub) Subscribe(req pubsub.SubscribeRequest, handler func(msg *pubsub.NewMessage) error) error {
sub, err := n.natsConn.QueueSubscribe(req.Topic, n.metadata.natsQueueGroupName, func(natsMsg *nats.Msg) {
handler(&pubsub.NewMessage{Topic: req.Topic, Data: natsMsg.Data})
})
if err != nil {
n.logger.Warnf("nats: error subscribe: %s", err)
}
n.logger.Debugf("nats: subscribed to subject %s with queue group %s", sub.Subject, sub.Queue)
return nil
}
func (n *natsPubSub) Close() error {
n.natsConn.Close()
return nil
}
func (n *natsPubSub) Features() []pubsub.Feature {
return nil
}