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Add namespace event filtering support
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Add SubscriptionFilter type and SubscribeWithFilter method to enable
filtering events by type and actor pattern within namespace subscriptions.

- SubscriptionFilter supports event type filtering (e.g., only "OrderPlaced")
- SubscriptionFilter supports actor ID prefix patterns (e.g., "order-*")
- Filters are combined with AND logic
- NATSEventBus uses NATS subjects for server-side filtering when possible
- Comprehensive test coverage for filtering functionality

Closes #21

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
Hugo Nijhuis
2026-01-10 19:24:21 +01:00
parent f0f8978079
commit a8787877f0
3 changed files with 1133 additions and 31 deletions
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76
nats_eventbus.go
View File

@@ -11,7 +11,19 @@ import (
"github.com/nats-io/nats.go"
)
// NATSEventBus is an EventBus that broadcasts events across all cluster nodes using NATS
// NATSEventBus is an EventBus that broadcasts events across all cluster nodes using NATS.
//
// # Server-Side Filtering
//
// When using SubscribeWithFilter, the NATSEventBus attempts to apply filters at
// the NATS subject level where possible for efficient event delivery:
//
// Event type filtering: When a filter specifies exactly one event type,
// NATSEventBus subscribes to a type-specific NATS subject (e.g.,
// "aether.events.namespace.OrderPlaced"), reducing network traffic.
//
// For multiple event types or actor patterns, filtering is applied client-side
// after receiving events from NATS.
type NATSEventBus struct {
*EventBus // Embed base EventBus for local subscriptions
nc *nats.Conn // NATS connection
@@ -47,28 +59,54 @@ func NewNATSEventBus(nc *nats.Conn) (*NATSEventBus, error) {
return neb, nil
}
// Subscribe creates a local subscription and ensures NATS subscription exists for the namespace
// Subscribe creates a local subscription and ensures NATS subscription exists for the namespace.
// All events published to the namespace will be delivered.
func (neb *NATSEventBus) Subscribe(namespaceID string) <-chan *Event {
return neb.SubscribeWithFilter(namespaceID, SubscriptionFilter{})
}
// SubscribeWithFilter creates a filtered subscription for a namespace.
//
// For single event type filters, NATS subject-based filtering is used for
// efficiency (server-side filtering). For multiple event types or actor
// patterns, filtering is applied client-side.
func (neb *NATSEventBus) SubscribeWithFilter(namespaceID string, filter SubscriptionFilter) <-chan *Event {
neb.mutex.Lock()
defer neb.mutex.Unlock()
// Create local subscription first
ch := neb.EventBus.Subscribe(namespaceID)
// Create local subscription with filter
ch := neb.EventBus.SubscribeWithFilter(namespaceID, filter)
// Determine which NATS subject(s) to subscribe to
// For single event type, we can use a more specific subject for server-side filtering
var subjects []string
if len(filter.EventTypes) == 1 {
// Server-side filtering: subscribe to type-specific subject
subjects = []string{fmt.Sprintf("aether.events.%s.%s", namespaceID, filter.EventTypes[0])}
} else if len(filter.EventTypes) > 1 {
// Subscribe to each event type's subject for server-side filtering
for _, et := range filter.EventTypes {
subjects = append(subjects, fmt.Sprintf("aether.events.%s.%s", namespaceID, et))
}
} else {
// No event type filter - subscribe to wildcard for all events in namespace
subjects = []string{fmt.Sprintf("aether.events.%s.>", namespaceID)}
}
// Check if this is the first subscriber for this namespace
count := neb.namespaceSubscribers[namespaceID]
if count == 0 {
// First subscriber - create NATS subscription
subject := fmt.Sprintf("aether.events.%s", namespaceID)
sub, err := neb.nc.Subscribe(subject, func(msg *nats.Msg) {
neb.handleNATSEvent(msg)
})
if err != nil {
log.Printf("[NATSEventBus] Failed to subscribe to NATS subject %s: %v", subject, err)
} else {
neb.subscriptions = append(neb.subscriptions, sub)
log.Printf("[NATSEventBus] Node %s subscribed to %s", neb.nodeID, subject)
// First subscriber - create NATS subscriptions
for _, subject := range subjects {
sub, err := neb.nc.Subscribe(subject, func(msg *nats.Msg) {
neb.handleNATSEvent(msg)
})
if err != nil {
log.Printf("[NATSEventBus] Failed to subscribe to NATS subject %s: %v", subject, err)
} else {
neb.subscriptions = append(neb.subscriptions, sub)
log.Printf("[NATSEventBus] Node %s subscribed to %s", neb.nodeID, subject)
}
}
}
@@ -109,17 +147,19 @@ func (neb *NATSEventBus) handleNATSEvent(msg *nats.Msg) {
return
}
// Forward to local EventBus subscribers
// Forward to local EventBus subscribers (filtering happens there)
neb.EventBus.Publish(eventMsg.NamespaceID, eventMsg.Event)
}
// Publish publishes an event both locally and to NATS for cross-node broadcasting
// Publish publishes an event both locally and to NATS for cross-node broadcasting.
// Events are published to a type-specific subject to enable server-side filtering.
func (neb *NATSEventBus) Publish(namespaceID string, event *Event) {
// First publish locally
neb.EventBus.Publish(namespaceID, event)
// Then publish to NATS for other nodes
subject := fmt.Sprintf("aether.events.%s", namespaceID)
// Use type-specific subject for server-side filtering
subject := fmt.Sprintf("aether.events.%s.%s", namespaceID, event.EventType)
eventMsg := eventMessage{
NodeID: neb.nodeID,