nats

This package aims to provide EdgeX MessageBus bindings for NATS - both JetStream and core. JetStream is probably ideal for most scenarios as it offers persistence and QoS levels similar to MQTT. Core NATS may be useful for some high throughput publish scenarios as publishing clients do not require acknowledgement.

Note that this package is optionally built with the tag include_nats_messaging.

Why NATS?

NATS is attractive as a messaging solution for EdgeX for a variety of reasons. It is a generally lightweight protocol that could even be suitable for on-device use, especially when publishing via core NATS. For devices that use MQTT - it provides MQTT Client Access to underlying JetStream subjects. And it provides protocol level headers that enable conveying the EdgeX message envelope with no additional marshaling (JSON marshaling / unmarshaling degrades pretty poorly with message size).

Supported Options

This library does not intend to support all NATS options, and some may be beyond the scope of the edgex message bus anyway. A good example is that most ack/nack options are not really valid because no ack/nack facility is exposed to the messagebus trigger via go-mod-messaging. A custom trigger may be an option if finer grained control of the NATS configuration is needed.

All option are set via MessageBusConfig.Optional and keys are case sensitive .

EdgeX

Option	Description
Format	format to use for envelope transport. Options are 'nats' or 'json'.

Connect

Option	Description
ClientId	The id to use to identify the client. Maps to the Name option in nats.go
ConnectTimeout	Timeout for NATS connection - an integer representing seconds (default: 1s)
RetryOnFailedConnect	Retry on connection failure - expects a string representation of a boolean (default: true)
Username	NATS username
Password	Password for authenticating NATS user
CertFile	TLS certificate file path
KeyFile	TLS private key file path
CertPEMBlock	TLS certificate as string
KeyPEMBlock	TLS private key as string
SkipCertVerify	Skip client-side certificate verification (not recommended for production use).
AutoProvision	automatically provision NATS streams. (JetStream only)
Durable	Specifies a durable consumer should be used with the given name. Note that if a durable consumer with the specified name does not exist it will be considered ephemeral and deleted by the client on drain / unsubscribe (JetStream only)
Subject	Specifies the subject to use for subscriptions and stream autoprovisioning (Required, JetStream only, durable will be favored on subscription.)

Subscribe

Option	Description
Deliver	Specifies delivery mode for subscriptions - options are "new", "all", "last" or "lastpersubject". See the NATS documentation for more detail (JetStream only, default: new)
QueueGroup	Specifies a queue group to distribute messages from a stream to a pool of worker services.

Publish

Option	Description
DefaultPubRetryAttempts	Number of times to attempt to retry on failed publish (JetStream only, default: 2)