natspubsub

Documentation

Overview

Package natspubsub provides a pubsub implementation for NATS.io. Use OpenTopic to construct a *pubsub.Topic, and/or OpenSubscription to construct a *pubsub.Subscription. This package uses gob to encode and decode driver.Message to []byte.

URLs

For pubsub.OpenTopic and pubsub.OpenSubscription, natspubsub registers for the scheme "nats". The default URL opener will connect to a default server based on the environment variable "NATS_SERVER_URL". To customize the URL opener, or for more details on the URL format, see URLOpener. See https://github.com/cornelk/go-cloud/concepts/urls/ for background information.

Message Delivery Semantics

NATS supports at-most-semantics; applications need not call Message.Ack, and must not call Message.Nack. See https://godoc.org/github.com/cornelk/go-cloud/pubsub#hdr-At_most_once_and_At_least_once_Delivery for more background.

As

natspubsub exposes the following types for As:

• Topic: *nats.Conn
• Subscription: *nats.Subscription
• Message.BeforeSend: None.
• Message: *nats.Msg

Example (OpenSubscriptionFromURL)

package main

import (
	"context"
	"log"

	"github.com/cornelk/go-cloud/pubsub"
)

func main() {
	// PRAGMA: This example is used on github.com/cornelk/go-cloud; PRAGMA comments adjust how it is shown and can be ignored.
	// PRAGMA: On github.com/cornelk/go-cloud, add a blank import: _ "github.com/cornelk/go-cloud/pubsub/natspubsub"
	// PRAGMA: On github.com/cornelk/go-cloud, hide lines until the next blank line.
	ctx := context.Background()

	// pubsub.OpenSubscription creates a *pubsub.Subscription from a URL.
	// This URL will Dial the NATS server at the URL in the environment variable
	// NATS_SERVER_URL and receive messages with subject "example.mysubject".
	subscription, err := pubsub.OpenSubscription(ctx, "nats://example.mysubject")
	if err != nil {
		log.Fatal(err)
	}
	defer subscription.Shutdown(ctx)
}

Example (OpenTopicFromURL)

package main

import (
	"context"
	"log"

	"github.com/cornelk/go-cloud/pubsub"
)

func main() {
	// PRAGMA: This example is used on github.com/cornelk/go-cloud; PRAGMA comments adjust how it is shown and can be ignored.
	// PRAGMA: On github.com/cornelk/go-cloud, add a blank import: _ "github.com/cornelk/go-cloud/pubsub/natspubsub"
	// PRAGMA: On github.com/cornelk/go-cloud, hide lines until the next blank line.
	ctx := context.Background()

	// pubsub.OpenTopic creates a *pubsub.Topic from a URL.
	// This URL will Dial the NATS server at the URL in the environment variable
	// NATS_SERVER_URL and send messages with subject "example.mysubject".
	topic, err := pubsub.OpenTopic(ctx, "nats://example.mysubject")
	if err != nil {
		log.Fatal(err)
	}
	defer topic.Shutdown(ctx)
}

Index

• Constants
• func OpenStreamingSubscription(nc stan.Conn, subject, queue string, oo ...stan.SubscriptionOption) (*pubsub.Subscription, error)
• func OpenStreamingTopic(nc stan.Conn, subject string, _ *StreamingTopicOptions) (*pubsub.Topic, error)
• func OpenSubscription(nc *nats.Conn, subject string, _ *SubscriptionOptions) (*pubsub.Subscription, error)
• func OpenTopic(nc *nats.Conn, subject string, _ *TopicOptions) (*pubsub.Topic, error)
• type StreamingTopicOptions
• type SubscriptionOptions
• type TopicOptions
• type URLOpener
  • func (o *URLOpener) OpenSubscriptionURL(ctx context.Context, u *url.URL) (*pubsub.Subscription, error)
  • func (o *URLOpener) OpenTopicURL(ctx context.Context, u *url.URL) (*pubsub.Topic, error)

Examples

• Package (OpenSubscriptionFromURL)
• Package (OpenTopicFromURL)
• OpenSubscription
• OpenTopic

Constants

const Scheme = "nats"

Scheme is the URL scheme natspubsub registers its URLOpeners under on pubsub.DefaultMux.

Functions

func OpenStreamingSubscription

func OpenStreamingSubscription(nc stan.Conn, subject, queue string, oo ...stan.SubscriptionOption) (*pubsub.Subscription, error)

OpenStreamingSubscription returns a *pubsub.Subscription representing a NATS Streaming subscription. The subject is the NATS Subject to subscribe to; for more info, see https://nats.io/documentation/writing_applications/subjects.

func OpenStreamingTopic

func OpenStreamingTopic(nc stan.Conn, subject string, _ *StreamingTopicOptions) (*pubsub.Topic, error)

OpenStreamingTopic returns a *pubsub.Topic for use with NATS Streaming Server. The subject is the NATS Subject; for more info, see https://nats.io/documentation/writing_applications/subjects.

func OpenSubscription

func OpenSubscription(nc *nats.Conn, subject string, _ *SubscriptionOptions) (*pubsub.Subscription, error)

OpenSubscription returns a *pubsub.Subscription representing a NATS subscription. The subject is the NATS Subject to subscribe to; for more info, see https://nats.io/documentation/writing_applications/subjects.

TODO(dlc) - Options for queue groups?

Example

// PRAGMA: This example is used on github.com/cornelk/go-cloud; PRAGMA comments adjust how it is shown and can be ignored.
// PRAGMA: On github.com/cornelk/go-cloud, hide lines until the next blank line.
ctx := context.Background()

natsConn, err := nats.Connect("nats://nats.example.com")
if err != nil {
	log.Fatal(err)
}
defer natsConn.Close()

subscription, err := natspubsub.OpenSubscription(
	natsConn,
	"example.mysubject",
	nil)
if err != nil {
	log.Fatal(err)
}
defer subscription.Shutdown(ctx)

func OpenTopic

func OpenTopic(nc *nats.Conn, subject string, _ *TopicOptions) (*pubsub.Topic, error)

OpenTopic returns a *pubsub.Topic for use with NATS. The subject is the NATS Subject; for more info, see https://nats.io/documentation/writing_applications/subjects.

Example

// PRAGMA: This example is used on github.com/cornelk/go-cloud; PRAGMA comments adjust how it is shown and can be ignored.
// PRAGMA: On github.com/cornelk/go-cloud, hide lines until the next blank line.
ctx := context.Background()

natsConn, err := nats.Connect("nats://nats.example.com")
if err != nil {
	log.Fatal(err)
}
defer natsConn.Close()

topic, err := natspubsub.OpenTopic(natsConn, "example.mysubject", nil)
if err != nil {
	log.Fatal(err)
}
defer topic.Shutdown(ctx)

Types

type StreamingTopicOptions

type StreamingTopicOptions struct {
}

type SubscriptionOptions

type SubscriptionOptions struct{}

SubscriptionOptions sets options for constructing a *pubsub.Subscription backed by NATS.

type TopicOptions

type TopicOptions struct{}

TopicOptions sets options for constructing a *pubsub.Topic backed by NATS.

type URLOpener

type URLOpener struct {
	// Connection to use for communication with the server.
	Connection *nats.Conn
	// TopicOptions specifies the options to pass to OpenTopic.
	TopicOptions TopicOptions
	// SubscriptionOptions specifies the options to pass to OpenSubscription.
	SubscriptionOptions SubscriptionOptions
}

URLOpener opens NATS URLs like "nats://mysubject".

The URL host+path is used as the subject.

No query parameters are supported.

func (*URLOpener) OpenSubscriptionURL

func (o *URLOpener) OpenSubscriptionURL(ctx context.Context, u *url.URL) (*pubsub.Subscription, error)

OpenSubscriptionURL opens a pubsub.Subscription based on u.

func (*URLOpener) OpenTopicURL

func (o *URLOpener) OpenTopicURL(ctx context.Context, u *url.URL) (*pubsub.Topic, error)

OpenTopicURL opens a pubsub.Topic based on u.