feat(eth-pubsub): Implement in-memory EventBus for real-time topic management and event distribution (#1855)

Author: Unique-Divine

CHANGELOG.md

@@ -56,6 +56,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - [#1838](https://github.com/NibiruChain/nibiru/pull/1838) - feat(eth): Go-ethereum, crypto, encoding, and unit tests for evm/types
 - [#1841](https://github.com/NibiruChain/nibiru/pull/1841) - feat(eth): Collections encoders for bytes, Ethereum addresses, and Ethereum hashes
 - [#1847](https://github.com/NibiruChain/nibiru/pull/1847) - fix(docker-chaosnet): release snapshot docker build failed CI.
+- [#1855](https://github.com/NibiruChain/nibiru/pull/1855) - feat(eth-pubsub): Implement in-memory EventBus for real-time topic management and event distribution
 
 #### Dapp modules: perp, spot, etc
 

eth/rpc/pubsub/pubsub.go

@@ -0,0 +1,174 @@
+// Copyright (c) 2023-2024 Nibi, Inc.
+package pubsub
+
+import (
+	"sync"
+	"sync/atomic"
+
+	"github.com/pkg/errors"
+
+	coretypes "github.com/cometbft/cometbft/rpc/core/types"
+)
+
+type UnsubscribeFunc func()
+
+// EventBus manages topics and subscriptions. A "topic" is a named channel of
+// communication. A "subscription" is the action taken by a subscriber to express
+// interest in receiving messages broadcasted from a specific topic.
+type EventBus interface {
+	// AddTopic: Adds a new topic with the specified name and message source
+	AddTopic(name string, src <-chan coretypes.ResultEvent) error
+	// RemoveTopic: Removes the specified topic and all its related data,
+	// ensuring clean up of resources.
+	RemoveTopic(name string)
+	Subscribe(name string) (<-chan coretypes.ResultEvent, UnsubscribeFunc, error)
+	Topics() []string
+}
+
+// memEventBus is an implemention of the `EventBus` interface.
+type memEventBus struct {
+	topics          map[string]<-chan coretypes.ResultEvent
+	topicsMux       *sync.RWMutex
+	subscribers     map[string]map[uint64]chan<- coretypes.ResultEvent
+	subscribersMux  *sync.RWMutex
+	currentUniqueID uint64
+}
+
+// NewEventBus returns a fresh imlpemention of `memEventBus`, which implements
+// the `EventBus` interface for managing Ethereum topics and subscriptions.
+func NewEventBus() EventBus {
+	return &memEventBus{
+		topics:         make(map[string]<-chan coretypes.ResultEvent),
+		topicsMux:      new(sync.RWMutex),
+		subscribers:    make(map[string]map[uint64]chan<- coretypes.ResultEvent),
+		subscribersMux: new(sync.RWMutex),
+	}
+}
+
+// GenUniqueID atomically increments and returns a unique identifier for a new subscriber.
+// This ID is used internally to manage subscriber-specific channels.
+func (m *memEventBus) GenUniqueID() uint64 {
+	return atomic.AddUint64(&m.currentUniqueID, 1)
+}
+
+// Topics returns a list of all topics currently managed by the EventBus. The
+// list is safe for concurrent access and is a snapshot of current topic names.
+func (m *memEventBus) Topics() (topics []string) {
+	m.topicsMux.RLock()
+	defer m.topicsMux.RUnlock()
+
+	topics = make([]string, 0, len(m.topics))
+	for topicName := range m.topics {
+		topics = append(topics, topicName)
+	}
+
+	return topics
+}
+
+// AddTopic adds a new topic with the specified name and message source
+func (m *memEventBus) AddTopic(name string, src <-chan coretypes.ResultEvent) error {
+	m.topicsMux.RLock()
+	_, ok := m.topics[name]
+	m.topicsMux.RUnlock()
+
+	if ok {
+		return errors.New("topic already registered")
+	}
+
+	m.topicsMux.Lock()
+	m.topics[name] = src
+	m.topicsMux.Unlock()
+
+	go m.publishTopic(name, src)
+
+	return nil
+}
+
+// RemoveTopic: Removes the specified topic and all its related data, ensuring
+// clean up of resources.
+func (m *memEventBus) RemoveTopic(name string) {
+	m.topicsMux.Lock()
+	delete(m.topics, name)
+	m.topicsMux.Unlock()
+}
+
+// Subscribe attempts to create a subscription to the specified topic. It returns
+// a channel to receive messages, a function to unsubscribe, and an error if the
+// topic does not exist.
+func (m *memEventBus) Subscribe(name string) (<-chan coretypes.ResultEvent, UnsubscribeFunc, error) {
+	m.topicsMux.RLock()
+	_, ok := m.topics[name]
+	m.topicsMux.RUnlock()
+
+	if !ok {
+		return nil, nil, errors.Errorf("topic not found: %s", name)
+	}
+
+	ch := make(chan coretypes.ResultEvent)
+	m.subscribersMux.Lock()
+	defer m.subscribersMux.Unlock()
+
+	id := m.GenUniqueID()
+	if _, ok := m.subscribers[name]; !ok {
+		m.subscribers[name] = make(map[uint64]chan<- coretypes.ResultEvent)
+	}
+	m.subscribers[name][id] = ch
+
+	unsubscribe := func() {
+		m.subscribersMux.Lock()
+		defer m.subscribersMux.Unlock()
+		delete(m.subscribers[name], id)
+	}
+
+	return ch, unsubscribe, nil
+}
+
+func (m *memEventBus) publishTopic(name string, src <-chan coretypes.ResultEvent) {
+	for {
+		msg, ok := <-src
+		if !ok {
+			m.closeAllSubscribers(name)
+			m.topicsMux.Lock()
+			delete(m.topics, name)
+			m.topicsMux.Unlock()
+			return
+		}
+		m.publishAllSubscribers(name, msg)
+	}
+}
+
+// closeAllSubscribers closes all subscriber channels associated with the
+// specified topic and removes the topic from the subscribers map. This function
+// is typically called when a topic is deleted or no longer available to ensure
+// all resources are released properly and to prevent goroutine leaks. It ensures
+// thread-safe execution by locking around the operation.
+func (m *memEventBus) closeAllSubscribers(name string) {
+	m.subscribersMux.Lock()
+	defer m.subscribersMux.Unlock()
+
+	subscribers := m.subscribers[name]
+	delete(m.subscribers, name)
+	// #nosec G705
+	for _, sub := range subscribers {
+		close(sub)
+	}
+}
+
+// publishAllSubscribers sends a message to all subscribers of the specified
+// topic. It uses a non-blocking send operation to deliver the message to
+// subscriber channels. If a subscriber's channel is not ready to receive the
+// message (i.e., the channel is full), the message is skipped for that
+// subscriber to avoid blocking the publisher. This function ensures thread-safe
+// access to subscribers by using a read lock.
+func (m *memEventBus) publishAllSubscribers(name string, msg coretypes.ResultEvent) {
+	m.subscribersMux.RLock()
+	defer m.subscribersMux.RUnlock()
+	subscribers := m.subscribers[name]
+	// #nosec G705
+	for _, sub := range subscribers {
+		select {
+		case sub <- msg:
+		default:
+		}
+	}
+}

eth/rpc/pubsub/pubsub_test.go

@@ -0,0 +1,155 @@
+package pubsub
+
+import (
+	"log"
+	"sort"
+	"sync"
+	"testing"
+	"time"
+
+	rpccore "github.com/cometbft/cometbft/rpc/core/types"
+	"github.com/stretchr/testify/require"
+	"github.com/stretchr/testify/suite"
+)
+
+// subscribeAndPublish: Helper function used to perform concurrent subscription
+// and publishing actions. It concurrently subscribes multiple clients to the
+// specified topic and simultanesouly sends an empty message to the topic channel
+// for each subscription.
+func subscribeAndPublish(t *testing.T, eb EventBus, topic string, topicChan chan rpccore.ResultEvent) {
+	var (
+		wg               sync.WaitGroup
+		subscribersCount = 50
+		emptyMsg         = rpccore.ResultEvent{}
+	)
+	for i := 0; i < subscribersCount; i++ {
+		wg.Add(1)
+		// concurrently subscribe to the topic
+		go func() {
+			defer wg.Done()
+			_, _, err := eb.Subscribe(topic)
+			require.NoError(t, err)
+		}()
+
+		// send events to the topic
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			topicChan <- emptyMsg
+		}()
+	}
+	wg.Wait()
+}
+
+type SuitePubsub struct {
+	suite.Suite
+}
+
+func TestSuitePubsub(t *testing.T) {
+	suite.Run(t, new(SuitePubsub))
+}
+
+func (s *SuitePubsub) TestAddTopic() {
+	q := NewEventBus()
+	// dummy vars
+	topicA := "guard"
+	topicB := "cream"
+
+	s.NoError(q.AddTopic(topicA, make(<-chan rpccore.ResultEvent)))
+	s.NoError(q.AddTopic(topicB, make(<-chan rpccore.ResultEvent)))
+	s.Error(q.AddTopic(topicB, make(<-chan rpccore.ResultEvent)))
+
+	topics := q.Topics()
+	sort.Strings(topics) // cream should be first
+	s.Require().EqualValues([]string{topicB, topicA}, topics)
+}
+
+func (s *SuitePubsub) TestSubscribe() {
+	q := NewEventBus()
+
+	// dummy vars
+	topicA := "0xfoo"
+	topicB := "blockchain"
+
+	srcA := make(chan rpccore.ResultEvent)
+	err := q.AddTopic(topicA, srcA)
+	s.NoError(err)
+
+	srcB := make(chan rpccore.ResultEvent)
+	err = q.AddTopic(topicB, srcB)
+	s.NoError(err)
+
+	// subscriber channels
+	subChanA, _, err := q.Subscribe(topicA)
+	s.NoError(err)
+	subChanB1, _, err := q.Subscribe(topicB)
+	s.NoError(err)
+	subChanB2, _, err := q.Subscribe(topicB)
+	s.NoError(err)
+
+	wg := new(sync.WaitGroup)
+	wg.Add(4)
+
+	emptyMsg := rpccore.ResultEvent{}
+	go func() {
+		defer wg.Done()
+		msg := <-subChanA
+		log.Println(topicA+":", msg)
+		s.EqualValues(emptyMsg, msg)
+	}()
+
+	go func() {
+		defer wg.Done()
+		msg := <-subChanB1
+		log.Println(topicB+":", msg)
+		s.EqualValues(emptyMsg, msg)
+	}()
+
+	go func() {
+		defer wg.Done()
+		msg := <-subChanB2
+		log.Println(topicB+"2:", msg)
+		s.EqualValues(emptyMsg, msg)
+	}()
+
+	go func() {
+		defer wg.Done()
+
+		time.Sleep(time.Second)
+
+		close(srcA)
+		close(srcB)
+	}()
+
+	wg.Wait()
+	time.Sleep(time.Second)
+}
+
+// TestConcurrentSubscribeAndPublish: Stress tests the module to make sure that
+// operations are handled properly under concurrent access.
+func (s *SuitePubsub) TestConcurrentSubscribeAndPublish() {
+	var (
+		wg        sync.WaitGroup
+		eb        = NewEventBus()
+		topicName = "topic-name"
+		topicCh   = make(chan rpccore.ResultEvent)
+		runsCount = 5
+	)
+
+	err := eb.AddTopic(topicName, topicCh)
+	s.Require().NoError(err)
+
+	for i := 0; i < runsCount; i++ {
+		subscribeAndPublish(s.T(), eb, topicName, topicCh)
+	}
+
+	// close channel to make test end
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		time.Sleep(2 * time.Second)
+		close(topicCh)
+	}()
+
+	wg.Wait()
+}