/
publisher.go
208 lines (170 loc) · 4.56 KB
/
publisher.go
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package nats
import (
"bytes"
"context"
"encoding/json"
"fmt"
"time"
natn "github.com/nats-io/nats.go"
"github.com/pkg/errors"
"github.com/unbxd/go-base/kit/endpoint"
)
type (
// PublisherOption lets you modify properties for publisher
PublisherOption func(*Publisher)
// PublishMessageEncoder encodes the value passed to it and converts to NATS message
PublishMessageEncoder func(cx context.Context, sub string, data interface{}) (*natn.Msg, error)
// Before is a function that is called before every message sent to NATS
BeforePublish func(context.Context, *natn.Msg) error
// After is a function called after every message sent to NATS
AfterPublish func(context.Context, *natn.Msg, error)
// PublishErrorHandler is a function that is called when an error occurs
PublishErrorHandler func(context.Context, error) error
// publisher publishes message on NATS
Publisher struct {
conn *natn.Conn
opts *natn.Options
name string
prefix string
encoder PublishMessageEncoder
befores []BeforePublish
afters []AfterPublish
errorHandler PublishErrorHandler
headers natn.Header
}
)
func WithPublishMessageEncoder(encoder PublishMessageEncoder) PublisherOption {
return func(p *Publisher) {
p.encoder = encoder
}
}
func WithBeforePublish(befores ...BeforePublish) PublisherOption {
return func(p *Publisher) {
p.befores = append(p.befores, befores...)
}
}
func WithAfterPublish(afters ...AfterPublish) PublisherOption {
return func(p *Publisher) {
p.afters = append(p.afters, afters...)
}
}
func WithErrorHandler(handler PublishErrorHandler) PublisherOption {
return func(p *Publisher) {
p.errorHandler = handler
}
}
func WithPublisherName(name string) PublisherOption {
return func(p *Publisher) {
p.name = name
}
}
func WithPublisherSubjectPrefix(prefix string) PublisherOption {
return func(p *Publisher) {
p.prefix = prefix
}
}
func WithCustomPublisherTimeout(timeout time.Duration) PublisherOption {
return func(p *Publisher) {
p.opts.Timeout = timeout
}
}
func WithCustomPublisherMaxReconnect(maxReconnect int) PublisherOption {
return func(p *Publisher) {
p.opts.MaxReconnect = maxReconnect
}
}
func WithCustomPublisherPingInterval(pingInterval time.Duration) PublisherOption {
return func(p *Publisher) {
p.opts.PingInterval = pingInterval
}
}
func WithPublishHeader(headers natn.Header) PublisherOption {
return func(p *Publisher) {
p.headers = headers
}
}
func defaultPublishMessageEncoder(
cx context.Context, subject string, data interface{},
) (*natn.Msg, error) {
var (
buf bytes.Buffer
err error
)
err = json.NewEncoder(&buf).Encode(data)
if err != nil {
return nil, errors.Wrap(err, "defaultencoder: encoding error")
}
return &natn.Msg{
Subject: subject,
Data: buf.Bytes(),
}, err
}
func defaultPublishErrorHandler(cx context.Context, err error) error {
return err
}
func NewPublisher(connstr string, options ...PublisherOption) (*Publisher, error) {
var (
err error
cc *natn.Conn
opts = natn.GetDefaultOptions()
pb = &Publisher{
conn: nil,
opts: &opts,
name: "go-base-publisher",
prefix: "gb",
encoder: defaultPublishMessageEncoder,
befores: []BeforePublish{},
afters: []AfterPublish{},
errorHandler: defaultPublishErrorHandler,
}
)
for _, fn := range options {
fn(pb)
}
pb.opts.Url = connstr
cc, err = pb.opts.Connect()
if err != nil {
return nil, errors.Wrap(
err, "unable to connect to nats server",
)
}
pb.conn = cc
return pb, err
}
func subject(prefix, subject string) string {
if prefix != "" {
return fmt.Sprintf("%s.%s", prefix, subject)
}
return subject
}
// Endpoint returns a usable endpoint that invokes the remote endpoint.
func (p *Publisher) Endpoint(sub string) endpoint.Endpoint {
return func(ctx context.Context, data interface{}) (interface{}, error) {
return p.send(ctx, subject(p.prefix, sub), data)
}
}
// Publish publishes the message on NATS
func (p *Publisher) Publish(ctx context.Context, sub string, data interface{}) error {
_, err := p.send(ctx, subject(p.prefix, sub), data)
return err
}
func (p *Publisher) send(cx context.Context, sub string, data interface{}) (*natn.Msg, error) {
msg, err := p.encoder(cx, sub, data)
if err != nil {
return nil, p.errorHandler(cx, err)
}
for _, fn := range p.befores {
err := fn(cx, msg)
if err != nil {
return nil, p.errorHandler(cx, err)
}
}
err = p.conn.PublishMsg(msg)
if err != nil {
return nil, p.errorHandler(cx, err)
}
for _, fn := range p.afters {
fn(cx, msg, err)
}
return msg, err
}