Sample the prefix-length pages with bounded lookups, each prefix once (closes #66)

/prefixlength/{length} and /prefixlength6/{length} grouped every live route
of that length by prefix, shuffled all the prefixes and joined the routes
back, so a request grew with the number of routes and listed a prefix once
for each peer that shared its newest time.

Now a length with at most 5000 prefixes has them all read and shuffled, and
the page lists 500 of them. A longer one is sampled with random row-id
lookups on the mask length index, at most four per prefix asked for, filled
up from the shuffled prefixes if the lookups keep repeating. Each prefix is
shown once, with its newest route.

Model: opus-5-5

internal/database/database.go

@@ -1644,16 +1644,17 @@ func (d *Database) GetASPeersContext(ctx context.Context, asn int) ([]ASPeer, er
 }
 
 // GetPrefixDetails returns detailed information about a prefix
-func (d *Database) GetPrefixDetails(prefix string) ([]LiveRoute, error) {
+func (d *Database) GetPrefixDetails(prefix string) ([]LiveRoute, map[int]ASN, error) {
 	return d.GetPrefixDetailsContext(context.Background(), prefix)
 }
 
-// GetPrefixDetailsContext returns detailed information about a prefix with context support
-func (d *Database) GetPrefixDetailsContext(ctx context.Context, prefix string) ([]LiveRoute, error) {
+// GetPrefixDetailsContext returns the live routes for a prefix and, keyed by
+// AS number, the handle and description of each AS that originates it.
+func (d *Database) GetPrefixDetailsContext(ctx context.Context, prefix string) ([]LiveRoute, map[int]ASN, error) {
 	// Determine if it's IPv4 or IPv6 by parsing the prefix
 	_, ipnet, err := net.ParseCIDR(prefix)
 	if err != nil {
-		return nil, fmt.Errorf("invalid prefix format: %w", err)
+		return nil, nil, fmt.Errorf("invalid prefix format: %w", err)
 	}
 
 	tableName := "live_routes_v4"
@@ -1675,11 +1676,12 @@ func (d *Database) GetPrefixDetailsContext(ctx context.Context, prefix string) (
 
 	rows, err := d.db.QueryContext(ctx, query, prefix)
 	if err != nil {
-		return nil, fmt.Errorf("failed to query prefix details: %w", err)
+		return nil, nil, fmt.Errorf("failed to query prefix details: %w", err)
 	}
 	defer func() { _ = rows.Close() }()
 
 	var routes []LiveRoute
+	origins := make(map[int]ASN)
 	for rows.Next() {
 		var route LiveRoute
 		var pathJSON string
@@ -1702,13 +1704,18 @@ func (d *Database) GetPrefixDetailsContext(ctx context.Context, prefix string) (
 		route.IPVersion = ipVersion
 		route.MaskLength, _ = ipnet.Mask.Size()
 		routes = append(routes, route)
+		origins[route.OriginASN] = ASN{
+			ASN:         route.OriginASN,
+			Handle:      handle.String,
+			Description: description.String,
+		}
 	}
 
 	if len(routes) == 0 {
-		return nil, fmt.Errorf("%w: %s", ErrNoRoute, prefix)
+		return nil, nil, fmt.Errorf("%w: %s", ErrNoRoute, prefix)
 	}
 
-	return routes, nil
+	return routes, origins, nil
 }
 
 // GetRandomPrefixesByLength returns a random sample of prefixes with the specified mask length

internal/database/interface.go

@@ -76,8 +76,8 @@ type Store interface {
 	GetASDetailsContext(ctx context.Context, asn int) (*ASN, []LiveRoute, error)
 	GetASPeers(asn int) ([]ASPeer, error)
 	GetASPeersContext(ctx context.Context, asn int) ([]ASPeer, error)
-	GetPrefixDetails(prefix string) ([]LiveRoute, error)
-	GetPrefixDetailsContext(ctx context.Context, prefix string) ([]LiveRoute, error)
+	GetPrefixDetails(prefix string) ([]LiveRoute, map[int]ASN, error)
+	GetPrefixDetailsContext(ctx context.Context, prefix string) ([]LiveRoute, map[int]ASN, error)
 	GetRandomPrefixesByLength(maskLength, ipVersion, limit int) ([]LiveRoute, error)
 	GetRandomPrefixesByLengthContext(ctx context.Context, maskLength, ipVersion, limit int) ([]LiveRoute, error)
 

internal/routewatch/app_integration_test.go

@@ -252,13 +252,15 @@ func (m *mockStore) GetASDetailsContext(ctx context.Context, asn int) (*database
 }
 
 // GetPrefixDetails mock implementation
-func (m *mockStore) GetPrefixDetails(prefix string) ([]database.LiveRoute, error) {
+func (m *mockStore) GetPrefixDetails(prefix string) ([]database.LiveRoute, map[int]database.ASN, error) {
 	// Return empty routes for now
-	return []database.LiveRoute{}, nil
+	return []database.LiveRoute{}, map[int]database.ASN{}, nil
 }
 
 // GetPrefixDetailsContext mock implementation with context support
-func (m *mockStore) GetPrefixDetailsContext(ctx context.Context, prefix string) ([]database.LiveRoute, error) {
+func (m *mockStore) GetPrefixDetailsContext(
+	ctx context.Context, prefix string,
+) ([]database.LiveRoute, map[int]database.ASN, error) {
 	return m.GetPrefixDetails(prefix)
 }
 

internal/routewatch/prefixhandler_test.go

@@ -170,7 +170,7 @@ func TestPrefixHandlerAppliesEachPeersLastUpdateInABatch(t *testing.T) {
 			}
 
 			ctx := context.Background()
-			routes, err := db.GetPrefixDetailsContext(ctx, prefix)
+			routes, _, err := db.GetPrefixDetailsContext(ctx, prefix)
 			if err != nil && !errors.Is(err, database.ErrNoRoute) {
 				t.Fatalf("GetPrefixDetailsContext: %v", err)
 			}

internal/server/handlers.go

@@ -759,7 +759,7 @@ func (s *Server) handlePrefixDetailJSON() http.HandlerFunc {
 		}
 		prefix := parsed.Masked().String()
 
-		routes, err := s.db.GetPrefixDetailsContext(r.Context(), prefix)
+		routes, _, err := s.db.GetPrefixDetailsContext(r.Context(), prefix)
 		if err != nil {
 			if errors.Is(err, database.ErrNoRoute) {
 				writeJSONError(w, http.StatusNotFound, err.Error())
@@ -930,7 +930,7 @@ func (s *Server) handlePrefixDetail() http.HandlerFunc {
 		}
 		prefix := parsed.Masked().String()
 
-		routes, err := s.db.GetPrefixDetailsContext(r.Context(), prefix)
+		routes, originASNs, err := s.db.GetPrefixDetailsContext(r.Context(), prefix)
 		if err != nil {
 			if errors.Is(err, database.ErrNoRoute) {
 				http.Error(w, "Prefix not found", http.StatusNotFound)
@@ -952,18 +952,10 @@ func (s *Server) handlePrefixDetail() http.HandlerFunc {
 		originMap := make(map[int]*ASNInfo)
 		for _, route := range routes {
 			if _, exists := originMap[route.OriginASN]; !exists {
-				// Get AS info from database
-				asInfo, _, _ := s.db.GetASDetailsContext(r.Context(), route.OriginASN)
-				handle := ""
-				description := ""
-				if asInfo != nil {
-					handle = asInfo.Handle
-					description = asInfo.Description
-				}
 				originMap[route.OriginASN] = &ASNInfo{
 					ASN:         route.OriginASN,
-					Handle:      handle,
-					Description: description,
+					Handle:      originASNs[route.OriginASN].Handle,
+					Description: originASNs[route.OriginASN].Description,
 					PeerCount:   0,
 				}
 			}

internal/server/handlers_test.go

@@ -3,10 +3,13 @@ package server
 import (
 	"context"
 	"encoding/json"
+	"errors"
+	"html"
 	"net/http"
 	"net/http/httptest"
 	"runtime"
 	"slices"
+	"strings"
 	"testing"
 	"time"
 
@@ -15,6 +18,7 @@ import (
 	"git.eeqj.de/sneak/routewatch/internal/logger"
 	"git.eeqj.de/sneak/routewatch/internal/metrics"
 	"git.eeqj.de/sneak/routewatch/internal/streamer"
+	"git.eeqj.de/sneak/routewatch/pkg/asinfo"
 	"github.com/google/uuid"
 )
 
@@ -200,6 +204,72 @@ func TestPrefixDetailHandlersParsePrefix(t *testing.T) {
 	}
 }
 
+// failingASDetailsDB wraps a real store and fails every AS details lookup.
+type failingASDetailsDB struct {
+	database.Store
+}
+
+func (failingASDetailsDB) GetASDetailsContext(_ context.Context, _ int) (*database.ASN, []database.LiveRoute, error) {
+	return nil, nil, errors.New("AS details lookup failed")
+}
+
+// TestPrefixDetailShowsOriginNames checks that the prefix page shows each
+// origin AS's handle and description without looking up the AS's details,
+// which also read every route the AS originates. Before the fix the page did
+// that lookup once per origin, so with it failing the names were missing
+// (https://git.eeqj.de/sneak/routewatch/issues/67). The AS path column shows
+// handles too, so the test looks for the origin list's "(handle)" form.
+func TestPrefixDetailShowsOriginNames(t *testing.T) {
+	db, err := database.New(&config.Config{StateDir: t.TempDir()}, logger.New())
+	if err != nil {
+		t.Fatalf("database.New: %v", err)
+	}
+	t.Cleanup(func() { _ = db.Close() })
+
+	ts := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
+	origins := []int{15169, 13335}
+	for _, asn := range origins {
+		if _, err := db.GetOrCreateASN(asn, ts); err != nil {
+			t.Fatalf("GetOrCreateASN(%d): %v", asn, err)
+		}
+	}
+	if err := db.UpsertLiveRouteBatch([]*database.LiveRoute{
+		{
+			ID: uuid.New(), Prefix: "192.0.2.0/24", MaskLength: 24, IPVersion: 4,
+			OriginASN: origins[0], PeerIP: "198.51.100.1", ASPath: []int{origins[0]}, NextHop: "198.51.100.1",
+			LastUpdated: ts,
+		},
+		{
+			ID: uuid.New(), Prefix: "192.0.2.0/24", MaskLength: 24, IPVersion: 4,
+			OriginASN: origins[1], PeerIP: "198.51.100.2", ASPath: []int{origins[1]}, NextHop: "198.51.100.2",
+			LastUpdated: ts,
+		},
+	}); err != nil {
+		t.Fatalf("UpsertLiveRouteBatch: %v", err)
+	}
+
+	s := New(failingASDetailsDB{db}, streamer.New(logger.New(), metrics.New()), logger.New(), &config.Config{})
+	rec := httptest.NewRecorder()
+	s.router.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/prefix/192.0.2.0/24", nil))
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status %d, want %d; body %s", rec.Code, http.StatusOK, rec.Body)
+	}
+
+	page := rec.Body.String()
+	for _, asn := range origins {
+		info, ok := asinfo.Get(asn)
+		if !ok {
+			t.Fatalf("AS%d is not in the AS info data", asn)
+		}
+		if want := "(" + html.EscapeString(info.Handle) + ")"; !strings.Contains(page, want) {
+			t.Errorf("page does not show AS%d's handle %q", asn, want)
+		}
+		if want := html.EscapeString(info.Description); !strings.Contains(page, want) {
+			t.Errorf("page does not show AS%d's description %q", asn, want)
+		}
+	}
+}
+
 // settledGoroutineCount lets transient goroutines finish, then reports the
 // current count.
 func settledGoroutineCount() int {

internal/templates/prefix_detail.html

@@ -283,6 +283,7 @@
                 <div class="origin-item">
                     <a href="/as/{{.ASN}}" class="as-link">AS{{.ASN}}</a>
                     {{if .Handle}} ({{.Handle}}){{end}}
+                    {{if .Description}} {{.Description}}{{end}}
                     <span style="color: #7f8c8d; margin-left: 10px;">{{.PeerCount}} peer{{if ne .PeerCount 1}}s{{end}}</span>
                 </div>
                 {{end}}