internal/aggergate: make HLL state path configurable

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I8ff8ef25ad945aae918bea97ee39d7ea6a6a6964

config.example.yaml

@@ -98,3 +98,6 @@ server:
   metrics_path: "/metrics"
   # Event ingestion endpoint
   ingestion_path: "/api/event"
+  # Path to persist HyperLogLog state (default: /var/lib/watchdog/hll.state)
+  # Ensures unique visitor counts survive restarts
+  state_path: "/var/lib/watchdog/hll.state"

internal/aggregate/metrics.go

@@ -223,7 +223,7 @@ func (m *MetricsAggregator) Shutdown(ctx context.Context) error {
 	m.Stop()
 	// Persist HLL state if configured
 	if m.cfg.Site.SaltRotation != "" {
-		return m.estimator.Save("/tmp/watchdog-hll.state")
+		return m.estimator.Save(m.cfg.Server.StatePath)
 	}
 	return nil
 }

internal/aggregate/metrics_test.go

@@ -1,6 +1,8 @@
 package aggregate
 
 import (
+	"context"
+	"os"
 	"strings"
 	"testing"
 
@@ -190,3 +192,89 @@ func TestMetricsAggregator_MustRegister(t *testing.T) {
 		t.Errorf("expected at least 2 metric families, got %d", len(metrics))
 	}
 }
+
+func TestMetricsAggregator_Shutdown_ConfigurableStatePath(t *testing.T) {
+	registry := NewPathRegistry(100)
+
+	// Create temp directory for test
+	tmpDir := t.TempDir()
+	statePath := tmpDir + "/custom-hll.state"
+
+	cfg := config.Config{
+		Site: config.SiteConfig{
+			SaltRotation: "daily",
+			Collect: config.CollectConfig{
+				Pageviews: true,
+			},
+		},
+		Server: config.ServerConfig{
+			StatePath: statePath,
+		},
+	}
+
+	agg := NewMetricsAggregator(registry, NewCustomEventRegistry(100), &cfg)
+
+	// Add some unique visitors so there's state to save
+	agg.AddUnique("192.168.1.1", "Mozilla/5.0")
+
+	// Shutdown should save to configured path
+	ctx := context.Background()
+	if err := agg.Shutdown(ctx); err != nil {
+		t.Fatalf("Shutdown failed: %v", err)
+	}
+
+	// Verify file was created at configured path
+	if _, err := os.Stat(statePath); os.IsNotExist(err) {
+		t.Errorf("state file was not created at configured path: %s", statePath)
+	}
+}
+
+func TestMetricsAggregator_Shutdown_DefaultStatePath(t *testing.T) {
+	registry := NewPathRegistry(100)
+
+	cfg := config.Config{
+		Site: config.SiteConfig{
+			Domains:      []string{"example.com"}, // Required for validation
+			SaltRotation: "daily",
+			Collect: config.CollectConfig{
+				Pageviews: true,
+			},
+		},
+		Limits: config.LimitsConfig{
+			MaxPaths:   1000,
+			MaxSources: 500,
+		},
+		Server: config.ServerConfig{
+			// StatePath not set - validation should set default
+			StatePath: "",
+		},
+	}
+
+	// Validate to apply defaults
+	if err := cfg.Validate(); err != nil {
+		t.Fatalf("config validation failed: %v", err)
+	}
+
+	// Verify default was applied
+	expectedDefault := "/var/lib/watchdog/hll.state"
+	if cfg.Server.StatePath != expectedDefault {
+		t.Errorf(
+			"expected default StatePath %q, got %q",
+			expectedDefault,
+			cfg.Server.StatePath,
+		)
+	}
+
+	agg := NewMetricsAggregator(registry, NewCustomEventRegistry(100), &cfg)
+
+	// Add some unique visitors
+	agg.AddUnique("192.168.1.1", "Mozilla/5.0")
+
+	// Shutdown should save to default path
+	ctx := context.Background()
+	if err := agg.Shutdown(ctx); err != nil {
+		// Might fail due to permissions on /var/lib, which is OK for this test
+		// We're just verifying the code path works
+		t.Logf("Shutdown returned error (might be expected): %v", err)
+	}
+}

internal/config/config.go

@@ -83,6 +83,7 @@ type ServerConfig struct {
 	ListenAddr    string `yaml:"listen_addr"`
 	MetricsPath   string `yaml:"metrics_path"`
 	IngestionPath string `yaml:"ingestion_path"`
+	StatePath     string `yaml:"state_path"` // path to persist HLL state
 }
 
 // YAML configuration file
@@ -170,6 +171,9 @@ func (c *Config) Validate() error {
 	if c.Server.IngestionPath == "" {
 		c.Server.IngestionPath = "/api/event"
 	}
+	if c.Server.StatePath == "" {
+		c.Server.StatePath = "/var/lib/watchdog/hll.state"
+	}
 
 	if c.Security.MetricsAuth.Enabled {
 		if c.Security.MetricsAuth.Username == "" || c.Security.MetricsAuth.Password == "" {

web/beacon.test.html

@@ -1,19 +1,22 @@
-<!DOCTYPE html>
+<!doctype html>
 <html lang="en">
   <head>
-		<meta charset="UTF-8">
+    <meta charset="UTF-8" />
-		<meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Watchdog Beacon Test</title>
     <style>
       body {
-				font-family: system-ui, -apple-system, sans-serif;
+        font-family:
+          system-ui,
+          -apple-system,
+          sans-serif;
         max-width: 600px;
         margin: 50px auto;
         padding: 20px;
         line-height: 1.6;
       }
       button {
-				background: #4CAF50;
+        background: #4caf50;
         color: white;
         padding: 12px 24px;
         border: none;
@@ -35,7 +38,7 @@
         background: #e8e8e8;
         padding: 2px 6px;
         border-radius: 3px;
-				font-family: 'Courier New', monospace;
+        font-family: "Courier New", monospace;
       }
     </style>
   </head>
@@ -43,16 +46,19 @@
     <h1>Watchdog Analytics Beacon Test</h1>
 
     <div class="info">
-			<p><strong>Instructions:</strong>
+      <p>
-			This page automatically tracks a pageview on load.
+        <strong>Instructions:</strong> This page automatically tracks a pageview
-			Click the buttons below to test custom event tracking.</p>
+        on load. Click the buttons below to test custom event tracking.
+      </p>
     </div>
 
     <h2>Custom Events</h2>
     <button onclick="watchdog.track('signup')">Track Signup</button>
     <button onclick="watchdog.track('purchase')">Track Purchase</button>
     <button onclick="watchdog.track('download')">Track Download</button>
-		<button onclick="watchdog.track('newsletter_subscribe')">Track Newsletter</button>
+    <button onclick="watchdog.track('newsletter_subscribe')">
+      Track Newsletter
+    </button>
 
     <div class="info">
       <p><strong>API Usage:</strong></p>
@@ -61,7 +67,10 @@
     </div>
 
     <h2>Console</h2>
-		<p>Open your browser's developer console (F12) and network tab to see beacon requests.</p>
+    <p>
+      Open your browser's developer console (F12) and network tab to see beacon
+      requests.
+    </p>
 
     <!-- Load the beacon script -->
     <script src="/web/beacon.js"></script>