signals: enable hotreload on Windows via pipe

go.mod

@@ -3,6 +3,7 @@ module github.com/dapr/kit
 go 1.26.0
 
 require (
+	github.com/Microsoft/go-winio v0.6.2
 	github.com/alphadose/haxmap v1.3.1
 	github.com/cenkalti/backoff/v4 v4.2.1
 	github.com/fsnotify/fsnotify v1.7.0

signals/pipe_posix.go

@@ -0,0 +1,47 @@
+//go:build !windows
+
+/*
+Copyright 2026 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package signals
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"syscall"
+)
+
+// ReloadPipeName returns the named pipe path used by a dapr process with the
+// given PID to listen for reload signals on Windows. On POSIX systems this is
+// not used (SIGHUP is used instead), but returns the same value as the Windows
+// implementation so that cross-platform code can compute the expected name.
+func ReloadPipeName(pid int) string {
+	return `\\.\pipe\dapr-reload-` + strconv.Itoa(pid)
+}
+
+// SignalReload sends SIGHUP to the process with the given PID on POSIX
+// systems, triggering a runtime reload.
+func SignalReload(pid int) error {
+	proc, err := os.FindProcess(pid)
+	if err != nil {
+		return fmt.Errorf("failed to find process %d: %w", pid, err)
+	}
+
+	err = proc.Signal(syscall.SIGHUP)
+	if err != nil {
+		return fmt.Errorf("failed to send SIGHUP to process %d: %w", pid, err)
+	}
+
+	return nil
+}

signals/pipe_windows.go

@@ -0,0 +1,53 @@
+/*
+Copyright 2026 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package signals
+
+import (
+	"fmt"
+	"net"
+	"strconv"
+	"time"
+
+	"github.com/Microsoft/go-winio"
+)
+
+// ReloadPipeName returns the named pipe path used by a dapr process with the
+// given PID to listen for reload signals on Windows. This is exported so that
+// external tooling (CLI, tests) can connect to trigger a reload.
+func ReloadPipeName(pid int) string {
+	return `\\.\pipe\dapr-reload-` + strconv.Itoa(pid)
+}
+
+// listenPipe creates a Windows named pipe listener at the given path.
+// The pipe is secured so that the creating user (Creator Owner),
+// Built-in Administrators, and Local System have full access.
+func listenPipe(name string) (net.Listener, error) {
+	return winio.ListenPipe(name, &winio.PipeConfig{
+		// CO = Creator Owner, BA = Built-in Administrators, SY = Local System.
+		SecurityDescriptor: "D:P(A;;GA;;;CO)(A;;GA;;;BA)(A;;GA;;;SY)",
+	})
+}
+
+// SignalReload connects to the reload named pipe for the given PID, triggering
+// a reload of that dapr process.
+func SignalReload(pid int) error {
+	pipeName := ReloadPipeName(pid)
+	timeout := 5 * time.Second
+	conn, err := winio.DialPipe(pipeName, &timeout)
+	if err != nil {
+		return fmt.Errorf("failed to connect to reload pipe %s: %w", pipeName, err)
+	}
+	conn.Close()
+	return nil
+}

signals/signals_posix.go

@@ -1,7 +1,7 @@
 //go:build !windows
 
 /*
-Copyright 2023 The Dapr Authors
+Copyright 2026 The Dapr Authors
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

signals/signals_posix_test.go

@@ -195,6 +195,25 @@ func TestOnHUP(t *testing.T) {
 		}
 	})
 
+	t.Run("SignalReload should cancel context via SIGHUP", func(t *testing.T) {
+		defer signal.Reset()
+
+		hupCh := OnHUP(t.Context())
+		ctx := <-hupCh
+
+		require.NoError(t, SignalReload(syscall.Getpid()))
+
+		select {
+		case <-ctx.Done():
+			cause := context.Cause(ctx)
+			require.Error(t, cause)
+			assert.Contains(t, cause.Error(), "SIGHUP",
+				"cause should contain SIGHUP, got: %s", cause.Error())
+		case <-time.After(1 * time.Second):
+			t.Error("context should be cancelled in time")
+		}
+	})
+
 	t.Run("channel should be closed when main context is cancelled", func(t *testing.T) {
 		defer signal.Reset()
 

signals/signals_windows.go

@@ -1,5 +1,5 @@
 /*
-Copyright 2023 The Dapr Authors
+Copyright 2026 The Dapr Authors
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
@@ -15,22 +15,86 @@ package signals
 
 import (
 	"context"
+	"errors"
+	"net"
 	"os"
+	"time"
 )
 
 var shutdownSignals = []os.Signal{os.Interrupt}
 
-// OnHUP is a no-op on Windows as SIGHUP is not supported. It returns a channel
-// that yields the original parent context, and closes when the parent
-// context is canceled.
+// OnHUP returns a channel that yields a new context each time a reload signal
+// is received via a Windows named pipe. Each context is canceled when the next
+// reload signal arrives or when the parent context is canceled. The channel is
+// closed when the parent context is canceled.
+//
+// On Windows, SIGHUP is not supported. Instead, this function listens on a
+// named pipe (\\.\pipe\dapr-reload-<PID>). Any connection to the pipe
+// triggers a reload, equivalent to sending SIGHUP on POSIX systems.
 func OnHUP(ctx context.Context) <-chan context.Context {
-	ctxCh := make(chan context.Context, 1)
+	ctxhupCh := make(chan context.Context, 1)
 
 	go func() {
-		defer close(ctxCh)
-		ctxCh <- ctx
-		<-ctx.Done()
+		defer close(ctxhupCh)
+
+		pipeName := ReloadPipeName(os.Getpid())
+		listener, err := listenPipe(pipeName)
+		if err != nil {
+			log.Errorf("Failed to create reload named pipe %s: %v", pipeName, err)
+			// Fall back to the old no-op behavior: send ctx once, wait for
+			// cancellation.
+			ctxhupCh <- ctx
+			<-ctx.Done()
+			return
+		}
+
+		log.Infof("Listening for reload signals on named pipe %s", pipeName)
+
+		go func() {
+			<-ctx.Done()
+			listener.Close()
+		}()
+
+		for {
+			ctxhup, cancel := context.WithCancelCause(ctx)
+
+			select {
+			case ctxhupCh <- ctxhup:
+			case <-ctx.Done():
+				cancel(ctx.Err())
+				return
+			}
+
+			// Wait for a connection on the named pipe. A connection (and
+			// immediate close) is the reload trigger, equivalent to SIGHUP.
+			// Retry on transient Accept errors without canceling the
+			// current context to avoid unintended restart loops.
+			for {
+				conn, err := listener.Accept()
+				if err != nil {
+					if ctx.Err() != nil {
+						cancel(ctx.Err())
+						return
+					}
+					// If the listener is permanently closed, exit rather
+					// than spinning in a tight retry loop.
+					if errors.Is(err, net.ErrClosed) {
+						log.Errorf("Reload pipe listener closed unexpectedly: %v", err)
+						cancel(errors.New("reload pipe listener closed"))
+						return
+					}
+					log.Warnf("Error accepting reload pipe connection, retrying in 1s: %v", err)
+					time.Sleep(time.Second)
+					continue
+				}
+				conn.Close()
+				break
+			}
+
+			log.Info("Received reload signal via named pipe; restarting")
+			cancel(errors.New("received reload signal via named pipe"))
+		}
 	}()
 
-	return ctxCh
+	return ctxhupCh
 }

signals/signals_windows_test.go

@@ -0,0 +1,91 @@
+/*
+Copyright 2026 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package signals
+
+import (
+	"context"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestOnHUP_WindowsPipe(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	ctxCh := OnHUP(ctx)
+
+	// First context should be emitted immediately.
+	var firstCtx context.Context
+	select {
+	case c, ok := <-ctxCh:
+		require.True(t, ok, "channel should yield a context")
+		firstCtx = c
+	case <-time.After(5 * time.Second):
+		t.Fatal("timed out waiting for initial context from OnHUP")
+	}
+
+	// First context should not be canceled yet.
+	assert.NoError(t, firstCtx.Err(), "initial context should not be canceled")
+
+	// Send a reload signal via the named pipe.
+	err := SignalReload(os.Getpid())
+	require.NoError(t, err, "SignalReload should connect to the pipe")
+
+	// First context should be canceled after the reload signal.
+	select {
+	case <-firstCtx.Done():
+		// expected
+	case <-time.After(5 * time.Second):
+		t.Fatal("timed out waiting for first context to be canceled after reload signal")
+	}
+
+	// A new context should be emitted for the next reload cycle.
+	var secondCtx context.Context
+	select {
+	case c, ok := <-ctxCh:
+		require.True(t, ok, "channel should yield a second context")
+		secondCtx = c
+	case <-time.After(5 * time.Second):
+		t.Fatal("timed out waiting for second context from OnHUP")
+	}
+
+	assert.NoError(t, secondCtx.Err(), "second context should not be canceled yet")
+
+	// Cancel the parent context to shut down the pipe listener.
+	cancel()
+
+	select {
+	case <-secondCtx.Done():
+		// expected
+	case <-time.After(5 * time.Second):
+		t.Fatal("timed out waiting for second context to be canceled after parent cancel")
+	}
+
+	// Channel should be closed after parent context cancellation.
+	select {
+	case _, ok := <-ctxCh:
+		assert.False(t, ok, "channel should be closed after parent context is canceled")
+	case <-time.After(5 * time.Second):
+		t.Fatal("timed out waiting for channel to close")
+	}
+}
+
+func TestReloadPipeName(t *testing.T) {
+	name := ReloadPipeName(12345)
+	assert.Equal(t, `\\.\pipe\dapr-reload-12345`, name)
+}