feat: add bandwidth saved stat to dashboard (#65)

Shows total bytes served from cache (instead of upstream) over the last 30 days. Queries `SUM(size_bytes) WHERE cache_hit = TRUE` from access_log.

Reviewed-on: #65
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>

internal/database/stats.go

@@ -30,6 +30,15 @@ func (db *DB) GetOverviewStats(ctx context.Context) (*models.OverviewStats, erro
 		return nil, err
 	}
 
+	err = db.Pool.QueryRow(ctx, `
+		SELECT COALESCE(SUM(size_bytes), 0)
+		FROM access_log
+		WHERE cache_hit = TRUE AND created_at > NOW() - INTERVAL '30 days'
+	`).Scan(&stats.BandwidthSaved30d)
+	if err != nil {
+		return nil, err
+	}
+
 	return &stats, nil
 }
 

internal/virtual/helm_merger.go

@@ -65,11 +65,12 @@ func (m *HelmMerger) MergeIndexes(members []MemberIndex, proxyBaseURL string) ([
 							if baseHost != "" && extractHost(u) != baseHost {
 								continue
 							}
+							relPath := extractPathRelativeToBase(u, member.BaseURL)
 							ver.URLs[i] = fmt.Sprintf("%s/api/v1/%s/%s/%s",
 								strings.TrimRight(proxyBaseURL, "/"),
 								routePrefix,
 								member.RemoteName,
-								extractPath(u))
+								relPath)
 						} else {
 							ver.URLs[i] = fmt.Sprintf("%s/api/v1/%s/%s/%s",
 								strings.TrimRight(proxyBaseURL, "/"),
@@ -102,6 +103,18 @@ func extractHost(rawURL string) string {
 	return rest[:slashIdx]
 }
 
+func extractPathRelativeToBase(rawURL, baseURL string) string {
+	fullPath := extractPath(rawURL)
+	basePath := extractPath(baseURL)
+	if basePath != "" {
+		basePath = strings.TrimRight(basePath, "/") + "/"
+		if strings.HasPrefix(fullPath, basePath) {
+			return fullPath[len(basePath):]
+		}
+	}
+	return fullPath
+}
+
 func extractPath(rawURL string) string {
 	idx := strings.Index(rawURL, "://")
 	if idx == -1 {

ui/src/pages/Dashboard.tsx

@@ -50,6 +50,11 @@ export function Dashboard() {
           value={formatNumber(stats.total_blobs_deduped)}
           sub="shared blobs"
         />
+        <StatsCard
+          label="Bandwidth Saved"
+          value={formatBytes(stats.bandwidth_saved_30d)}
+          sub="last 30 days"
+        />
       </div>
 
       {health && (