Adding transport/redis_pubsub/subscriber.go

go.mod

@@ -3,6 +3,7 @@ module eosio-ship-trace-reader
 go 1.18
 
 require (
+	github.com/alicebob/miniredis/v2 v2.30.0
 	github.com/eoscanada/eos-go v0.10.3-0.20221117104514-64cafd714c60
 	github.com/eosswedenorg-go/antelope-ship-client v0.2.2
 	github.com/eosswedenorg-go/pid v1.0.1
@@ -16,6 +17,7 @@ require (
 )
 
 require (
+	github.com/alicebob/gopher-json v0.0.0-20200520072559-a9ecdc9d1d3a // indirect
 	github.com/blendle/zapdriver v1.3.1 // indirect
 	github.com/cespare/xxhash/v2 v2.1.2 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
@@ -37,6 +39,7 @@ require (
 	github.com/vmihailenco/go-tinylfu v0.2.2 // indirect
 	github.com/vmihailenco/msgpack/v5 v5.3.5 // indirect
 	github.com/vmihailenco/tagparser/v2 v2.0.0 // indirect
+	github.com/yuin/gopher-lua v0.0.0-20220504180219-658193537a64 // indirect
 	go.uber.org/atomic v1.10.0 // indirect
 	go.uber.org/goleak v1.2.0 // indirect
 	go.uber.org/multierr v1.8.0 // indirect

go.sum

@@ -5,6 +5,10 @@ cloud.google.com/go v0.43.0/go.mod h1:BOSR3VbTLkk6FDC/TcffxP4NF/FFBGA5ku+jvKOP7p
 contrib.go.opencensus.io/exporter/stackdriver v0.12.6/go.mod h1:8x999/OcIPy5ivx/wDiV7Gx4D+VUPODf0mWRGRc5kSk=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
+github.com/alicebob/gopher-json v0.0.0-20200520072559-a9ecdc9d1d3a h1:HbKu58rmZpUGpz5+4FfNmIU+FmZg2P3Xaj2v2bfNWmk=
+github.com/alicebob/gopher-json v0.0.0-20200520072559-a9ecdc9d1d3a/go.mod h1:SGnFV6hVsYE877CKEZ6tDNTjaSXYUk6QqoIK6PrAtcc=
+github.com/alicebob/miniredis/v2 v2.30.0 h1:uA3uhDbCxfO9+DI/DuGeAMr9qI+noVWwGPNTFuKID5M=
+github.com/alicebob/miniredis/v2 v2.30.0/go.mod h1:84TWKZlxYkfgMucPBf5SOQBYJceZeQRFIaQgNMiCX6Q=
 github.com/aws/aws-sdk-go v1.22.1/go.mod h1:KmX6BPdI08NWTb3/sm4ZGu5ShLoqVDhKgpiN924inxo=
 github.com/benbjohnson/clock v1.1.0 h1:Q92kusRqC1XV2MjkWETPvjJVqKetz1OzxZB7mHJLju8=
 github.com/benbjohnson/clock v1.1.0/go.mod h1:J11/hYXuz8f4ySSvYwY0FKfm+ezbsZBKZxNJlLklBHA=
@@ -171,6 +175,8 @@ github.com/vmihailenco/tagparser/v2 v2.0.0 h1:y09buUbR+b5aycVFQs/g70pqKVZNBmxwAh
 github.com/vmihailenco/tagparser/v2 v2.0.0/go.mod h1:Wri+At7QHww0WTrCBeu4J6bNtoV6mEfg5OIWRZA9qds=
 github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.3.5/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
+github.com/yuin/gopher-lua v0.0.0-20220504180219-658193537a64 h1:5mLPGnFdSsevFRFc9q3yYbBkB6tsm4aCwwQV/j1JQAQ=
+github.com/yuin/gopher-lua v0.0.0-20220504180219-658193537a64/go.mod h1:GBR0iDaNXjAgGg9zfCvksxSRnQx76gclCIb7kdAd1Pw=
 go.opencensus.io v0.21.0/go.mod h1:mSImk1erAIZhrmZN+AvHh14ztQfjbGwt4TtuofqLduU=
 go.opencensus.io v0.22.0/go.mod h1:+kGneAE2xo2IficOXnaByMWTGM9T73dGwxeWcUqIpI8=
 go.opencensus.io v0.22.1/go.mod h1:Ap50jQcDJrx6rB6VgeeFPtuPIf3wMRvRfrfYDO6+BmA=
@@ -247,6 +253,7 @@ golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
 golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180909124046-d0be0721c37e/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190204203706-41f3e6584952/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190312061237-fead79001313/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

transport/redis_pubsub/subscriber.go

@@ -0,0 +1,96 @@
+package redis_pubsub
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"eosio-ship-trace-reader/transport"
+
+	"github.com/go-redis/redis/v8"
+)
+
+type Subscriber struct {
+	client   *redis.Client
+	sub      *redis.PubSub
+	ctx      context.Context
+	mu       sync.RWMutex
+	timeout  time.Duration
+	channels map[string]chan []byte
+	ns       Namespace
+}
+
+type SubscriberOption func(*Subscriber)
+
+func WithTimeout(value time.Duration) SubscriberOption {
+	return func(s *Subscriber) {
+		s.timeout = value
+	}
+}
+
+func NewSubscriber(client *redis.Client, ns Namespace, options ...SubscriberOption) *Subscriber {
+	sub := &Subscriber{
+		client:   client,
+		ctx:      client.Context(),
+		sub:      client.PSubscribe(client.Context()),
+		channels: make(map[string]chan []byte),
+		timeout:  time.Millisecond * 200,
+		ns:       ns,
+	}
+
+	for _, opt := range options {
+		opt(sub)
+	}
+
+	go sub.worker()
+
+	return sub
+}
+
+// forward forwards a message to the channel.
+// as writes to a unbuffered channel will block until it's read.
+// We run select on it and discard the message if no read happends during timeout
+func forward(msg redis.Message, ch chan<- []byte, timeout time.Duration) {
+	select {
+	case <-time.After(timeout):
+	case ch <- []byte(msg.Payload):
+	}
+}
+
+// worker reads messages from redis pubsub and forwards them to
+// correct channels.
+func (s *Subscriber) worker() {
+	for msg := range s.sub.Channel() {
+		// Route message to correct channel.
+		s.mu.RLock()
+		if ch, ok := s.channels[msg.Channel]; ok {
+			go forward(*msg, ch, s.timeout)
+		}
+		s.mu.RUnlock()
+	}
+}
+
+func (s *Subscriber) Read(channel transport.Channel) ([]byte, error) {
+	var err error
+
+	key := s.ns.NewKey(channel).String()
+	s.mu.RLock()
+	ch, ok := s.channels[key]
+	s.mu.RUnlock()
+	if !ok {
+		// Channel does not exist in the map.
+		// Subscribe and insert it.
+		err = s.sub.Subscribe(s.ctx, key)
+		if err != nil {
+			return nil, err
+		}
+
+		// Guard race condition to map with mutex.
+		s.mu.Lock()
+		ch = make(chan []byte)
+		s.channels[key] = ch
+		s.mu.Unlock()
+	}
+
+	return <-ch, nil
+}

transport/redis_pubsub/subscriber_test.go

@@ -0,0 +1,57 @@
+package redis_pubsub
+
+import (
+	"testing"
+	"time"
+
+	"eosio-ship-trace-reader/transport"
+
+	"github.com/alicebob/miniredis/v2"
+	"github.com/go-redis/redis/v8"
+	"github.com/go-redis/redismock/v8"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSubscriber_Construct(t *testing.T) {
+	client, _ := redismock.NewClientMock()
+	ns := Namespace{Prefix: "prefix", ChainID: "8f2f6ec19400d372c9b3340b1438e9c805cf9e69be962fa81d055bc037ceed8d"}
+
+	s := NewSubscriber(client, ns)
+
+	assert.Equal(t, s.client, client)
+	assert.Equal(t, s.ctx, client.Context())
+	assert.NotNil(t, s.sub)
+	assert.Equal(t, s.ns, ns)
+	assert.Equal(t, s.timeout, 200*time.Millisecond)
+
+	s = NewSubscriber(client, ns, WithTimeout(4*time.Second))
+	assert.Equal(t, s.timeout, 4*time.Second)
+}
+
+func TestSubscriber_Read(t *testing.T) {
+	expectedMessages := []string{"payload", "payload2", "payload3"}
+
+	server := miniredis.RunT(t)
+
+	client := redis.NewClient(&redis.Options{
+		Addr: server.Addr(),
+	})
+
+	s := NewSubscriber(client, Namespace{Prefix: "prefix", ChainID: "d41dbd2921d5a377325661427090c6c508904d60920d6b7ea771c58da5299754"})
+
+	go func() {
+		time.Sleep(time.Millisecond * 10)
+
+		for _, msg := range expectedMessages {
+			server.Publish("prefix::d41dbd2921d5a377325661427090c6c508904d60920d6b7ea771c58da5299754::test", msg)
+		}
+	}()
+
+	// Redis pubsub does not guarentee that messages are sent in the correct order.
+	for range expectedMessages {
+		msg, err := s.Read(transport.Channel{"test"})
+		assert.NoError(t, err)
+
+		assert.Contains(t, expectedMessages, string(msg))
+	}
+}