gocloud.dev – gocloud.dev/pubsub/natspubsub Index | Examples | Files

package natspubsub

import "gocloud.dev/pubsub/natspubsub"

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://gocloud.dev/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/gocloud.dev/pubsub#hdr-At_most_once_and_At_least_once_Delivery for more background.

As

natspubsub exposes the following types for As:

Example (OpenSubscriptionFromURL)

Code:play  

package main

import (
	"context"
	"log"

	"gocloud.dev/pubsub"
)

func main() {
	// This example is used in https://gocloud.dev/howto/pubsub/subscribe/#nats

	// import _ "gocloud.dev/pubsub/natspubsub"

	// Variables set up elsewhere:
	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)

Code:play  

package main

import (
	"context"
	"log"

	"gocloud.dev/pubsub"
)

func main() {
	// This example is used in https://gocloud.dev/howto/pubsub/publish/#nats

	// import _ "gocloud.dev/pubsub/natspubsub"

	// Variables set up elsewhere:
	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

Examples

Constants 

const Scheme = "nats"

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

Functions

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

Code: 

{
	// This example is used in https://gocloud.dev/howto/pubsub/subscribe/#nats-ctor

	// Variables set up elsewhere:
	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

Code: 

{
	// This example is used in https://gocloud.dev/howto/pubsub/publish/#nats-ctor

	// Variables set up elsewhere:
	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 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.

Source Files

nats.go

Version
v0.14.0
Published
May 29, 2019
Platform
js/wasm
Imports
15 packages
Last checked
1 week ago –

Tools for package owners.