added a notify system

hws/config.go

@@ -13,6 +13,7 @@ type Config struct {
 	ReadHeaderTimeout time.Duration // ENV HWS_READ_HEADER_TIMEOUT: Timeout for reading request headers in seconds (default: 2)
 	WriteTimeout      time.Duration // ENV HWS_WRITE_TIMEOUT: Timeout for writing requests in seconds (default: 10)
 	IdleTimeout       time.Duration // ENV HWS_IDLE_TIMEOUT: Timeout for idle connections in seconds (default: 120)
+	ShutdownDelay     time.Duration // ENV HWS_SHUTDOWN_DELAY: Delay in seconds before server shutsdown when Shutdown is called (default: 5)
 }
 
 // ConfigFromEnv returns a Config struct loaded from the environment variables
@@ -24,6 +25,7 @@ func ConfigFromEnv() (*Config, error) {
 		ReadHeaderTimeout: time.Duration(env.Int("HWS_READ_HEADER_TIMEOUT", 2)) * time.Second,
 		WriteTimeout:      time.Duration(env.Int("HWS_WRITE_TIMEOUT", 10)) * time.Second,
 		IdleTimeout:       time.Duration(env.Int("HWS_IDLE_TIMEOUT", 120)) * time.Second,
+		ShutdownDelay:     time.Duration(env.Int("HWS_SHUTDOWN_DELAY", 5)) * time.Second,
 	}
 
 	return cfg, nil

hws/go.mod

@@ -5,6 +5,7 @@ go 1.25.5
 require (
 	git.haelnorr.com/h/golib/env v0.9.1
 	git.haelnorr.com/h/golib/hlog v0.9.0
+	git.haelnorr.com/h/golib/notify v0.1.0
 	github.com/pkg/errors v0.9.1
 	github.com/stretchr/testify v1.11.1
 	k8s.io/apimachinery v0.35.0

hws/go.sum

@@ -2,6 +2,8 @@ git.haelnorr.com/h/golib/env v0.9.1 h1:2Vsj+mJKnO5f1Md1GO5v9ggLN5zWa0baCewcSHTjo
 git.haelnorr.com/h/golib/env v0.9.1/go.mod h1:glUQVdA1HMKX1avTDyTyuhcr36SSxZtlJxKDT5KTztg=
 git.haelnorr.com/h/golib/hlog v0.9.0 h1:ib8n2MdmiRK2TF067p220kXmhDe9aAnlcsgpuv+QpvE=
 git.haelnorr.com/h/golib/hlog v0.9.0/go.mod h1:oOlzb8UVHUYP1k7dN5PSJXVskAB2z8EYgRN85jAi0Zk=
+git.haelnorr.com/h/golib/notify v0.1.0 h1:xdf6zd21F6n+SuGTeJiuLNMf6zFXMvwpKD0gmNq8N10=
+git.haelnorr.com/h/golib/notify v0.1.0/go.mod h1:ARqaRmCYb8LMURhDM75sG+qX+YpqXmUVeAtacwjHjBc=
 github.com/coreos/go-systemd/v22 v22.5.0/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=

hws/notify.go

@@ -0,0 +1,316 @@
+package hws
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"slices"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"git.haelnorr.com/h/golib/notify"
+)
+
+// LevelShutdown is a special level used for the notification sent on shutdown.
+// This can be used to check if the notification is a shutdown event and if it should
+// be passed on to consumers or special considerations should be made.
+const LevelShutdown notify.Level = "shutdown"
+
+// Notifier manages client subscriptions and notification delivery for the HWS server.
+// It wraps the notify.Notifier with additional client management features including
+// dual identification (subscription ID + alternate ID) and automatic cleanup of
+// inactive clients after 5 minutes.
+type Notifier struct {
+	*notify.Notifier
+	clients *Clients
+	running bool
+	ctx     context.Context
+	cancel  context.CancelFunc
+}
+
+// Clients maintains thread-safe mappings between subscriber IDs, alternate IDs,
+// and Client instances. It supports querying clients by either their unique
+// subscription ID or their alternate ID (where multiple clients can share an alternate ID).
+type Clients struct {
+	clientsSubMap map[notify.Target]*Client
+	clientsIDMap  map[string][]*Client
+	lock          *sync.RWMutex
+}
+
+// Client represents a unique subscriber to the notifications channel.
+// It tracks activity via lastSeen timestamp (updated atomically) and monitors
+// consecutive send failures for automatic disconnect detection.
+type Client struct {
+	sub              *notify.Subscriber
+	lastSeen         int64 // accessed atomically
+	altID            string
+	consecutiveFails int32 // accessed atomically
+}
+
+func (s *Server) startNotifier() {
+	if s.notifier != nil && s.notifier.running {
+		return
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	s.notifier = &Notifier{
+		Notifier: notify.NewNotifier(50),
+		clients: &Clients{
+			clientsSubMap: make(map[notify.Target]*Client),
+			clientsIDMap:  make(map[string][]*Client),
+			lock:          new(sync.RWMutex),
+		},
+		running: true,
+		ctx:     ctx,
+		cancel:  cancel,
+	}
+
+	ticker := time.NewTicker(time.Minute)
+	go func() {
+		defer ticker.Stop()
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-ticker.C:
+				s.notifier.clients.cleanUp()
+			}
+		}
+	}()
+}
+
+func (s *Server) closeNotifier() {
+	if s.notifier != nil {
+		if s.notifier.cancel != nil {
+			s.notifier.cancel()
+		}
+		s.notifier.running = false
+		s.notifier.Close()
+	}
+	s.notifier = nil
+}
+
+// NotifySub sends a notification to a specific subscriber identified by the notification's Target field.
+// If the subscriber doesn't exist, a warning is logged but the operation does not fail.
+// This is thread-safe and can be called from multiple goroutines.
+func (s *Server) NotifySub(nt notify.Notification) {
+	if s.notifier == nil {
+		return
+	}
+	_, exists := s.notifier.clients.getClient(nt.Target)
+	if !exists {
+		err := fmt.Errorf("Tried to notify subscriber that doesn't exist - subID: %s", nt.Target)
+		s.LogError(HWSError{Level: ErrorWARN, Message: "Failed to notify", Error: err})
+		return
+	}
+	s.notifier.Notify(nt)
+}
+
+// NotifyID sends a notification to all clients associated with the given alternate ID.
+// Multiple clients can share the same alternate ID (e.g., multiple sessions for one user).
+// If no clients exist with that ID, a warning is logged but the operation does not fail.
+// This is thread-safe and can be called from multiple goroutines.
+func (s *Server) NotifyID(nt notify.Notification, altID string) {
+	if s.notifier == nil {
+		return
+	}
+	s.notifier.clients.lock.RLock()
+	clients, exists := s.notifier.clients.clientsIDMap[altID]
+	s.notifier.clients.lock.RUnlock()
+	if !exists {
+		err := fmt.Errorf("Tried to notify client group that doesn't exist - altID: %s", altID)
+		s.LogError(HWSError{Level: ErrorWARN, Message: "Failed to notify", Error: err})
+		return
+	}
+	for _, client := range clients {
+		ntt := nt
+		ntt.Target = client.sub.ID
+		s.NotifySub(ntt)
+	}
+}
+
+// NotifyAll broadcasts a notification to all connected clients.
+// This is thread-safe and can be called from multiple goroutines.
+func (s *Server) NotifyAll(nt notify.Notification) {
+	if s.notifier == nil {
+		return
+	}
+	nt.Target = ""
+	s.notifier.NotifyAll(nt)
+}
+
+// GetClient returns a Client that can be used to receive notifications.
+// If a client exists with the provided subID, that client will be returned.
+// If altID is provided, it will update the existing Client.
+// If subID is an empty string, a new client will be returned.
+// If both altID and subID are empty, a new Client with no altID will be returned.
+// Multiple clients with the same altID are permitted.
+func (s *Server) GetClient(subID, altID string) (*Client, error) {
+	if s.notifier == nil || !s.notifier.running {
+		return nil, errors.New("notifier hasn't started")
+	}
+	target := notify.Target(subID)
+	client, exists := s.notifier.clients.getClient(target)
+	if exists {
+		s.notifier.clients.updateAltID(client, altID)
+		return client, nil
+	}
+	// An error should only be returned if there are 10 collisions of a randomly generated 16 bit byte string from rand.Rand()
+	// Basically never going to happen, and if it does its not my problem
+	sub, _ := s.notifier.Subscribe()
+	client = &Client{
+		sub:              sub,
+		lastSeen:         time.Now().Unix(),
+		altID:            altID,
+		consecutiveFails: 0,
+	}
+	s.notifier.clients.addClient(client)
+	return client, nil
+}
+
+func (cs *Clients) getClient(target notify.Target) (*Client, bool) {
+	cs.lock.RLock()
+	client, exists := cs.clientsSubMap[target]
+	cs.lock.RUnlock()
+	return client, exists
+}
+
+func (cs *Clients) updateAltID(client *Client, altID string) {
+	cs.lock.Lock()
+	if altID != "" && !slices.Contains(cs.clientsIDMap[altID], client) {
+		cs.clientsIDMap[altID] = append(cs.clientsIDMap[altID], client)
+	}
+	if client.altID != altID && client.altID != "" {
+		cs.deleteFromID(client, client.altID)
+	}
+	client.altID = altID
+	cs.lock.Unlock()
+}
+
+func (cs *Clients) deleteFromID(client *Client, altID string) {
+	cs.clientsIDMap[altID] = deleteFromSlice(cs.clientsIDMap[altID], client, func(a, b *Client) bool {
+		return a.sub.ID == b.sub.ID
+	})
+	if len(cs.clientsIDMap[altID]) == 0 {
+		delete(cs.clientsIDMap, altID)
+	}
+}
+
+func (cs *Clients) addClient(client *Client) {
+	cs.lock.Lock()
+	cs.clientsSubMap[client.sub.ID] = client
+	if client.altID != "" {
+		cs.clientsIDMap[client.altID] = append(cs.clientsIDMap[client.altID], client)
+	}
+	cs.lock.Unlock()
+}
+
+func (cs *Clients) cleanUp() {
+	now := time.Now().Unix()
+
+	// Collect clients to kill while holding read lock
+	cs.lock.RLock()
+	toKill := make([]*Client, 0)
+	for _, client := range cs.clientsSubMap {
+		if now-atomic.LoadInt64(&client.lastSeen) > 300 {
+			toKill = append(toKill, client)
+		}
+	}
+	cs.lock.RUnlock()
+
+	// Kill clients without holding lock
+	for _, client := range toKill {
+		cs.killClient(client)
+	}
+}
+
+func (cs *Clients) killClient(client *Client) {
+	client.sub.Unsubscribe()
+
+	cs.lock.Lock()
+	delete(cs.clientsSubMap, client.sub.ID)
+	if client.altID != "" {
+		cs.deleteFromID(client, client.altID)
+	}
+	cs.lock.Unlock()
+}
+
+// Listen starts a goroutine that forwards notifications from the subscriber to a returned channel.
+// It returns a receive-only channel for notifications and a channel to stop listening.
+// The notification channel is buffered with size 10 to tolerate brief slowness.
+//
+// The goroutine automatically stops and closes the notification channel when:
+//   - The subscriber is unsubscribed
+//   - The stop channel is closed
+//   - The client fails to receive 5 consecutive notifications within 5 seconds each
+//
+// Client.lastSeen is updated every 30 seconds via heartbeat, or when a notification is successfully delivered.
+// Consecutive send failures are tracked; after 5 failures, the client is considered disconnected and cleaned up.
+func (c *Client) Listen() (<-chan notify.Notification, chan<- struct{}) {
+	ch := make(chan notify.Notification, 10)
+	stop := make(chan struct{})
+
+	go func() {
+		ticker := time.NewTicker(30 * time.Second)
+		defer ticker.Stop()
+		defer close(ch)
+
+		for {
+			select {
+			case <-stop:
+				return
+
+			case nt, ok := <-c.sub.Listen():
+				if !ok {
+					// Subscriber channel closed
+					return
+				}
+
+				// Try to send with timeout
+				timeout := time.NewTimer(5 * time.Second)
+				select {
+				case ch <- nt:
+					// Successfully sent - update lastSeen and reset failure count
+					atomic.StoreInt64(&c.lastSeen, time.Now().Unix())
+					atomic.StoreInt32(&c.consecutiveFails, 0)
+					timeout.Stop()
+
+				case <-timeout.C:
+					// Send timeout - increment failure count
+					fails := atomic.AddInt32(&c.consecutiveFails, 1)
+					if fails >= 5 {
+						// Too many consecutive failures - client is stuck/disconnected
+						c.sub.Unsubscribe()
+						return
+					}
+
+				case <-stop:
+					timeout.Stop()
+					return
+				}
+
+			case <-ticker.C:
+				// Heartbeat - update lastSeen to keep client alive
+				atomic.StoreInt64(&c.lastSeen, time.Now().Unix())
+			}
+		}
+	}()
+
+	return ch, stop
+}
+
+func (c *Client) ID() string {
+	return string(c.sub.ID)
+}
+
+func deleteFromSlice[T any](a []T, c T, eq func(T, T) bool) []T {
+	n := 0
+	for _, x := range a {
+		if !eq(x, c) {
+			a[n] = x
+			n++
+		}
+	}
+	return a[:n]
+}

hws/responsewriter.go

@@ -13,3 +13,7 @@ func (w *wrappedWriter) WriteHeader(statusCode int) {
 	w.ResponseWriter.WriteHeader(statusCode)
 	w.statusCode = statusCode
 }
+
+func (w *wrappedWriter) Unwrap() http.ResponseWriter {
+	return w.ResponseWriter
+}

hws/server.go

@@ -7,6 +7,7 @@ import (
 	"sync"
 	"time"
 
+	"git.haelnorr.com/h/golib/notify"
 	"k8s.io/apimachinery/pkg/util/validation"
 
 	"github.com/pkg/errors"
@@ -20,6 +21,8 @@ type Server struct {
 	middleware    bool
 	errorPage     ErrorPageFunc
 	ready         chan struct{}
+	notifier      *Notifier
+	shutdowndelay time.Duration
 }
 
 // Ready returns a channel that is closed when the server is started
@@ -87,6 +90,7 @@ func NewServer(config *Config) (*Server, error) {
 		routes:        false,
 		GZIP:          config.GZIP,
 		ready:         make(chan struct{}),
+		shutdowndelay: config.ShutdownDelay,
 	}
 	return server, nil
 }
@@ -105,6 +109,8 @@ func (server *Server) Start(ctx context.Context) error {
 		}
 	}
 
+	server.startNotifier()
+
 	go func() {
 		if server.logger == nil {
 			fmt.Printf("Listening for requests on %s", server.server.Addr)
@@ -126,6 +132,13 @@ func (server *Server) Start(ctx context.Context) error {
 }
 
 func (server *Server) Shutdown(ctx context.Context) error {
+	server.logger.logger.Debug().Dur("shutdown_delay", server.shutdowndelay).Msg("HWS Server shutting down")
+	server.NotifyAll(notify.Notification{
+		Title:   "Shutting down",
+		Message: fmt.Sprintf("Server is shutting down in %v", server.shutdowndelay),
+		Level:   LevelShutdown,
+	})
+	<-time.NewTimer(server.shutdowndelay).C
 	if !server.IsReady() {
 		return errors.New("Server isn't running")
 	}
@@ -136,6 +149,7 @@ func (server *Server) Shutdown(ctx context.Context) error {
 	if err != nil {
 		return errors.Wrap(err, "Failed to shutdown the server gracefully")
 	}
+	server.closeNotifier()
 	server.ready = make(chan struct{})
 	return nil
 }