feat: reload config on SIGUSR1

- Allows quick reloading with SIGUSR1 without when filesytem watch is
  not available like on a default docker setup `docker kill -s SIGUSR1`

- Also refactored the signal handling in a single logical unit

Signed-off-by: blob42 <[email protected]>

Author: blob42

docs/configuration.md

@@ -384,3 +384,14 @@ hooks:
     preload:
       - "llama"
 ```
+
+## Hot Reloading Configuration
+
+Trigger a configuration reload by sending `SIGUSR1` to the process:
+
+- **With Docker** (if container is named `llama-swap`):
+  ```bash
+  docker kill -s SIGUSR1 llama-swap
+  ```
+
+For real-time file system monitoring and automatic restarts on config changes, see [restart-on-config-change](./examples/restart-on-config-change/README.md).

docs/examples/restart-on-config-change/README.md

@@ -1,34 +1,41 @@
 # Restart llama-swap on config change
 
-Sometimes editing the configuration file can take a bit of trail and error to get a model configuration tuned just right. The `watch-and-restart.sh` script can be used to watch `config.yaml` for changes and restart `llama-swap` when it detects a change.
+Sometimes editing the configuration file can take a bit of trial and error to get a model configuration tuned just right. The `watch-and-restart.sh` script can be used to watch `config.yaml` for changes and send the `SIGUSR1` signal to `llama-swap` to trigger a config file reload when it detects a change.
 
 ```bash
 #!/bin/bash
 #
 # A simple watch and restart llama-swap when its configuration
 # file changes. Useful for trying out configuration changes
 # without manually restarting the server each time.
+
+# For docker users, consider replacing:
+# `kill -USR1 $PID` with `docker kill -s SIGUSR1 container_name`
+
 if [ -z "$1" ]; then
     echo "Usage: $0 <path to config.yaml>"
     exit 1
 fi
 
-while true; do
-    # Start the process again
-    ./llama-swap-linux-amd64 -config $1 -listen :1867 &
-    PID=$!
-    echo "Started llama-swap with PID $PID"
+# Start the process once
+./llama-swap-linux-amd64 -config $1 -listen :1867 &
+PID=$!
+echo "Started llama-swap with PID $PID"
 
+while true; do
     # Wait for modifications in the specified directory or file
-    inotifywait -e modify "$1"
+    if ! inotifywait -e modify "$1" 2>/dev/null; then
+        echo "Error: Failed to monitor file changes"
+        break
+    fi
 
     # Check if process exists before sending signal
     if kill -0 $PID 2>/dev/null; then
-        echo "Sending SIGTERM to $PID"
-        kill -SIGTERM $PID
-        wait $PID
+        echo "Sending SIGUSR1 to $PID"
+        kill -USR1 $PID
     else
         echo "Process $PID no longer exists"
+        break
     fi
     sleep 1
 done
@@ -42,10 +49,10 @@ Started llama-swap with PID 495455
 Setting up watches.
 Watches established.
 llama-swap listening on :1867
-Sending SIGTERM to 495455
-Shutting down llama-swap
-Started llama-swap with PID 495486
-Setting up watches.
-Watches established.
-llama-swap listening on :1867
+...
+Sending SIGUSR1 to 495455
+Received SIGUSR1. Reloading configuration...
+Configuration Changed
+Configuration Reloaded
+...
 ```

llama-swap.go

@@ -77,7 +77,7 @@ func main() {
 	// Setup channels for server management
 	exitChan := make(chan struct{})
 	sigChan := make(chan os.Signal, 1)
-	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
+	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM, syscall.SIGUSR1)
 
 	// Create server with initial handler
 	srv := &http.Server{
@@ -170,23 +170,34 @@ func main() {
 		}()
 	}
 
-	// shutdown on signal
+	// shutdown on SIGINT/SIGTERM
+	// reload config on SIGUSR1
 	go func() {
-		sig := <-sigChan
-		fmt.Printf("Received signal %v, shutting down...\n", sig)
-		ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
-		defer cancel()
-
-		if pm, ok := srv.Handler.(*proxy.ProxyManager); ok {
-			pm.Shutdown()
-		} else {
-			fmt.Println("srv.Handler is not of type *proxy.ProxyManager")
-		}
+		for sig := range sigChan {
+			switch sig {
+			case syscall.SIGINT, syscall.SIGTERM:
+				fmt.Printf("Received signal %v, shutting down...\n", sig)
+				ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
+				defer cancel()
+
+				if pm, ok := srv.Handler.(*proxy.ProxyManager); ok {
+					pm.Shutdown()
+				} else {
+					fmt.Println("srv.Handler is not of type *proxy.ProxyManager")
+				}
 
-		if err := srv.Shutdown(ctx); err != nil {
-			fmt.Printf("Server shutdown error: %v\n", err)
+				if err := srv.Shutdown(ctx); err != nil {
+					fmt.Printf("Server shutdown error: %v\n", err)
+				}
+				close(exitChan)
+				return
+			case syscall.SIGUSR1:
+				fmt.Println("Received SIGUSR1. Reloading configuration...")
+				reloadProxyManager()
+			default:
+				log.Printf("Unhandled signal: %v", sig)
+			}
 		}
-		close(exitChan)
 	}()
 
 	// Start server