README.md

@@ -143,10 +143,13 @@ and origin AS can have two kept routes, one or none.
   its origin ASes and every peer that carries it. Only the kept routes show an
   AS path, a next hop and a time. The next hop is the router the peer sends the
   prefix's traffic to. RouteWatch records the peer itself as the next hop. The
-  page also lists the prefix's origin changes, newest first: each time an origin
+  page also lists the prefix's origin changes, newest first. It shows at most
-  AS gained its first peer or lost its last, with the time, announced or
+  the newest 5,000. The peer count counts the peers of every origin AS that
-  withdrawn, the origin AS and the peer count. It shows at most the newest
+  carries the prefix. Each row shows:
-  5,000.
+    - the time
+    - announced or withdrawn
+    - the origin AS
+    - the peer count
 - `/prefixlength/{length}`: up to 500 IPv4 prefixes with that mask length,
   picked at random. Each shows its origin AS and the age of its newest kept
   route. When peers give a prefix different origin ASes, the page shows the one
@@ -625,8 +628,9 @@ The parts:
   messages. It gives each message to the handlers that want it, through one
   queue per handler.
 - The prefix handler keeps the routing table in memory current. Every second it
-  writes the table's changes to the `routes` table of the database. It also
+  writes the table's changes to the `routes` table and the table's origin
-  stores each new prefix with the time it was first seen.
+  changes to the `origin_changes` table of the database. It also stores each new
+  prefix with the time it was first seen.
 - The AS handler records every AS seen in an AS path in the `asns` table, with
   the times it was first and last seen.
 - The peer handler records every peer in the `bgp_peers` table.
@@ -643,11 +647,14 @@ The parts:
 - The database maintainer checkpoints the database every 5 seconds: it folds the
   write-ahead log, where SQLite first writes changes, into the database file. It
   reclaims free space every 10 minutes. Every hour it refreshes the statistics
-  SQLite uses to plan its queries, and prunes the origin changes table.
+  SQLite uses to plan its queries, and prunes the `origin_changes` table. A
+  prune keeps each prefix's rows from the last 72 hours, or its newest 500,
+  whichever keeps more.
 - The HTTP server serves the pages and the API. Every route it shows comes from
-  the routing table in memory. WHOIS details and first-seen times come from the
+  the routing table in memory. WHOIS details, first-seen times and origin
-  database. AS names come from the database or from the AS list built into
+  changes come from the database. AS names come from the database or from the AS
-  RouteWatch. The AS name search reads the AS list built into RouteWatch.
+  list built into RouteWatch. The AS name search reads the AS list built into
+  RouteWatch.
 
 ### The routing table
 
@@ -758,6 +765,8 @@ What a stop can lose:
   changed pairs. A full-table peer is a peer that carries the whole routing
   table. Its session going down changes about a million pairs, which take about
   a minute to write. A stop in that minute leaves the rest unwritten.
+- The same last write takes at most 20,000 of the routing table's origin
+  changes. Origin changes past them are lost.
 - A withdrawal, or a session going down, that is lost this way leaves its routes
   in the `routes` table. The next start reads them back. They stay until the
   peer sends another update for the prefix, or its session goes down again.

TODO.md

@@ -56,13 +56,16 @@ problem the run finds.
 
 # Completed Steps
 
-- 2026-11-05: the prefix page lists the prefix's origin changes, newest first:
+- 2026-11-05: the prefix page lists the prefix's origin changes, newest first.
-  each time an origin AS gained its first peer or lost its last, with the time,
+  The routing table records each change, and the prefix handler writes them to a
-  announced or withdrawn, the origin AS and the peer count. The routing table
+  new `origin_changes` table. The database maintainer prunes each prefix to its
-  records each change, and the prefix handler writes them to a new
+  newest 500 rows or its rows from the last 72 hours, whichever keeps more. The
-  `origin_changes` table. The database maintainer prunes each prefix to its
+  page shows at most the newest 5,000 (closes #161). The peer count counts the
-  newest 500 rows and 72 hours. The page shows at most the newest 5,000 (closes
+  peers of every origin AS. Each row shows:
-  #161)
+    - the time
+    - announced or withdrawn
+    - the origin AS
+    - the peer count
 - 2026-11-03: the streamer drops an update for a handler only when that
   handler's queue is full. It used to drop a random share of the updates once
   the queue was half full. The prefix handler's queue now holds 100,000

internal/database/schema.sql

@@ -123,8 +123,9 @@ CREATE TABLE IF NOT EXISTS route_peers (
 
 -- The origin changes of the routing table: each time a prefix and origin AS
 -- gained its first peer or lost its last. The prefix handler writes them, and
--- the database maintainer prunes each prefix to its newest 500 rows and 72
+-- the database maintainer prunes each prefix to its newest 500 rows or its
--- hours. time is whole seconds since 1970, UTC.
+-- rows from the last 72 hours, whichever keeps more. time is whole seconds
+-- since 1970, UTC.
 CREATE TABLE IF NOT EXISTS origin_changes (
 	id INTEGER PRIMARY KEY,
 	prefix TEXT NOT NULL,

internal/routetable/originchanges.go

@@ -7,7 +7,8 @@ import (
 )
 
 // maxWaitingOriginChanges is the most origin changes the table keeps waiting
-// for the prefix handler to write. A change past it is dropped and counted.
+// for the prefix handler to write. The oldest change past it is dropped and
+// counted.
 const maxWaitingOriginChanges = 100000
 
 // OriginChange is one change of a prefix and origin AS pair: the origin AS
@@ -39,13 +40,8 @@ func (t *Table) recordOriginChange(
 		Time:      t.now(),
 	}
 
-	if len(t.originChanges) == maxWaitingOriginChanges {
-		// The oldest change is dropped to make room.
-		t.originChanges = t.originChanges[1:]
-		t.originChangesDropped++
-	}
-
 	t.originChanges = append(t.originChanges, change)
+	t.trimOriginChanges()
 }
 
 // TakeOriginChanges returns at most limit of the origin changes that wait to
@@ -67,12 +63,31 @@ func (t *Table) TakeOriginChanges(limit int) ([]OriginChange, int) {
 
 // PutBackOriginChanges records again what one TakeOriginChanges call returned,
 // for a caller that could not write it. The next TakeOriginChanges returns
-// those changes first, before the ones that arrived since.
+// those changes first, before the ones that arrived since. The oldest changes
+// past the cap are dropped and counted.
 func (t *Table) PutBackOriginChanges(changes []OriginChange) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 
 	t.originChanges = append(changes, t.originChanges...)
+	t.trimOriginChanges()
+}
+
+// trimOriginChanges drops the oldest origin changes past the cap and counts
+// them. The caller holds the lock.
+func (t *Table) trimOriginChanges() {
+	if extra := len(t.originChanges) - maxWaitingOriginChanges; extra > 0 {
+		t.originChangesDropped += extra
+		t.originChanges = t.originChanges[extra:]
+	}
+}
+
+// OriginChangeCount returns how many origin changes wait for TakeOriginChanges.
+func (t *Table) OriginChangeCount() int {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+
+	return len(t.originChanges)
 }
 
 // prefixPeerCount returns how many peers carry prefix, counting every origin

internal/routetable/originchanges_test.go

@@ -206,6 +206,60 @@ func TestOriginChangesDropPastTheLimit(t *testing.T) {
 	}
 }
 
+// TestOriginChangesPutBackTrimsToTheLimit checks that putting back what a
+// failed write took, after new changes filled the table again, drops the
+// oldest changes past the cap and counts them, so the cap still holds. The
+// clock advances one second per change, so a change's time says its age.
+func TestOriginChangesPutBackTrimsToTheLimit(t *testing.T) {
+	t.Parallel()
+
+	const (
+		limit = 100000
+		taken = 20000
+		added = 20000
+	)
+
+	now := time.Unix(0, 0)
+	table := routetable.New(routetable.Params{
+		Now: func() time.Time {
+			now = now.Add(time.Second)
+
+			return now
+		},
+	})
+	addr := netip.MustParseAddr("10.0.0.0")
+
+	announce := func(n int) {
+		for range n {
+			table.Announce(netip.PrefixFrom(addr, 32), asA, routeOf(peerA, asA, 10))
+			addr = addr.Next()
+		}
+	}
+
+	announce(limit)
+
+	takenChanges, _ := table.TakeOriginChanges(taken)
+
+	announce(added)
+
+	table.PutBackOriginChanges(takenChanges)
+
+	changes, dropped := table.TakeOriginChanges(math.MaxInt)
+	if dropped != added {
+		t.Errorf("dropped = %d, want %d", dropped, added)
+	}
+
+	if len(changes) != limit {
+		t.Errorf("len(changes) = %d, want %d", len(changes), limit)
+	}
+
+	// The put-back rows are the oldest, so they are the ones dropped. The
+	// first remaining change is the one that followed them.
+	if want := time.Unix(int64(added+1), 0); !changes[0].Time.Equal(want) {
+		t.Errorf("first change's time = %v, want %v", changes[0].Time, want)
+	}
+}
+
 // checkOriginChanges checks that TakeOriginChanges, taking every change,
 // returns want.
 func checkOriginChanges(

internal/routewatch/prefixhandler.go

@@ -99,6 +99,9 @@ type PrefixHandler struct {
 	// tableChangesPerWrite is maxTableChangesPerWrite, except in tests that
 	// give a smaller one.
 	tableChangesPerWrite int
+	// originChangesPerWrite is maxOriginChangesPerWrite, except in tests that
+	// give a smaller one.
+	originChangesPerWrite int
 
 	// Batching. mu guards batch, writing and writingTableChanges: the
 	// flush goroutine takes them under mu and writes them after releasing
@@ -200,6 +203,7 @@ func newPrefixHandler(
 		batch:                 make([]seenPrefix, 0, prefixBatchSize),
 		batchMaxSize:          prefixBatchMaxSize,
 		tableChangesPerWrite:  tableChangesPerWrite,
+		originChangesPerWrite: maxOriginChangesPerWrite,
 		batchFullCh:           make(chan struct{}, 1),
 		stopCh:                make(chan context.Context, 1),
 		done:                  make(chan struct{}),
@@ -272,13 +276,13 @@ func (h *PrefixHandler) HeldBackCount() int {
 // back meanwhile to be applied. It gives up this wait once ctx ends. Then Stop
 // stops the flush goroutine and waits for it until ctx ends. The flush
 // goroutine makes one last flush before it returns. That flush writes at most
-// tableChangesPerWrite of the routing table's changes, and the prefixes of the
+// tableChangesPerWrite of the routing table's changes, originChangesPerWrite of
-// updates the handler holds. Once ctx has ended the flush goroutine skips that
+// its origin changes, and the prefixes of the updates the handler holds. Once
-// last flush, and a write still running is lost when the process exits. A
+// ctx has ended the flush goroutine skips that last flush, and a write still
-// failed write of the table's changes is not retried either. Stop logs how
+// running is lost when the process exits. A failed write of the table's
-// many updates and table changes are not written. It also logs how many
+// changes is not retried either. Stop logs how many updates, table changes and
-// held-back messages are not applied. The caller calls Stop once its last
+// origin changes are not written. It also logs how many held-back messages are
-// HandleMessage has returned.
+// not applied. The caller calls Stop once its last HandleMessage has returned.
 func (h *PrefixHandler) Stop(ctx context.Context) {
 	peerDownsDone := make(chan struct{})
 
@@ -305,21 +309,24 @@ func (h *PrefixHandler) Stop(ctx context.Context) {
 	heldMessages := h.heldCount
 	h.mu.Unlock()
 
-	if unwritten == 0 && tableChanges == 0 && heldMessages == 0 {
+	originChanges := h.table.OriginChangeCount()
+
+	if unwritten == 0 && tableChanges == 0 && heldMessages == 0 &&
+		originChanges == 0 {
 		return
 	}
 
 	if ctx.Err() != nil {
 		h.logger.Error("Stop deadline passed before the prefix handler wrote "+
 			"its updates", "updates", unwritten, "table_changes", tableChanges,
-			"held_messages", heldMessages)
+			"held_messages", heldMessages, "origin_changes", originChanges)
 
 		return
 	}
 
 	h.logger.Error("The prefix handler stopped before it wrote everything",
 		"updates", unwritten, "table_changes", tableChanges,
-		"held_messages", heldMessages)
+		"held_messages", heldMessages, "origin_changes", originChanges)
 }
 
 // applyMessage applies msg. The caller holds mu. A peer's session going down
@@ -618,7 +625,7 @@ func (h *PrefixHandler) writeTableChanges() {
 // that a later write writes them again. A dropped change is logged as a
 // warning.
 func (h *PrefixHandler) writeOriginChanges() {
-	changes, dropped := h.table.TakeOriginChanges(maxOriginChangesPerWrite)
+	changes, dropped := h.table.TakeOriginChanges(h.originChangesPerWrite)
 
 	if dropped > 0 {
 		h.logger.Warn("Origin changes dropped", "dropped", dropped)

internal/routewatch/prefixhandler_internal_test.go

@@ -332,6 +332,7 @@ func prefixHandlerWithoutTimer(store database.Store) *PrefixHandler {
 		table:                 table,
 		batchMaxSize:          prefixBatchMaxSize,
 		tableChangesPerWrite:  maxTableChangesPerWrite,
+		originChangesPerWrite: maxOriginChangesPerWrite,
 		heldBack:              make(map[string][]*ristypes.RISMessage),
 		tablePeersDown:        table.PeersDown,
 	}

internal/routewatch/prefixhandler_originchanges_internal_test.go

@@ -3,6 +3,7 @@ package routewatch
 import (
 	"errors"
 	"net/netip"
+	"slices"
 	"testing"
 
 	"git.eeqj.de/sneak/routewatch/internal/database"
@@ -82,3 +83,45 @@ func TestPrefixHandlerWritesAFailedOriginChangeWriteAgain(t *testing.T) {
 			got, testASNB)
 	}
 }
+
+// originChangesWriteSizesStore is a real database that records how many
+// changes each write of the origin changes holds.
+type originChangesWriteSizesStore struct {
+	*database.Database
+
+	counts []int
+}
+
+func (s *originChangesWriteSizesStore) WriteOriginChanges(
+	changes []routetable.OriginChange,
+) error {
+	s.counts = append(s.counts, len(changes))
+
+	return s.Database.WriteOriginChanges(changes)
+}
+
+// TestPrefixHandlerWritesManyOriginChangesOverSeveralFlushes has more origin
+// changes than one write takes, then flushes three times. The first write must
+// hold one write's worth, the second the rest, and the third nothing. The
+// handler's limit is small.
+func TestPrefixHandlerWritesManyOriginChangesOverSeveralFlushes(t *testing.T) {
+	t.Parallel()
+
+	const perWrite = 10
+
+	db := newTestDatabase(t)
+	store := &originChangesWriteSizesStore{Database: db}
+	h := prefixHandlerWithoutTimer(store)
+	h.originChangesPerWrite = perWrite
+
+	announceManyPrefixes(h.table, perWrite*3/2)
+
+	h.flushBatch()
+	h.flushBatch()
+	h.flushBatch()
+
+	want := []int{perWrite, perWrite*3/2 - perWrite}
+	if !slices.Equal(store.counts, want) {
+		t.Errorf("WriteOriginChanges held %v changes, want %v", store.counts, want)
+	}
+}

internal/server/handlers.go

@@ -1637,6 +1637,8 @@ type prefixDetailData struct {
 	OriginCount       int
 	OriginChanges     []routetable.OriginChange
 	MoreOriginChanges bool
+	// MaxOriginChanges is the most origin changes the page shows.
+	MaxOriginChanges int
 	CSPNonce         string
 }
 
@@ -1655,6 +1657,7 @@ func newPrefixDetailData(
 		OriginCount:       len(originInfos),
 		OriginChanges:     changes,
 		MoreOriginChanges: moreChanges,
+		MaxOriginChanges:  maxOriginChangesOnPage,
 		CSPNonce:          nonce,
 	}
 }

internal/server/prefix_originchanges_internal_test.go

@@ -142,7 +142,7 @@ func TestPrefixDetailSaysWhenMoreThan5000Changes(t *testing.T) {
 
 	page := rec.Body.String()
 
-	if !strings.Contains(page, "more than 5,000 changes") {
+	if !strings.Contains(page, "more than 5000 changes") {
-		t.Errorf("page does not say there are more than 5,000 changes")
+		t.Errorf("page does not say there are more than 5000 changes")
 	}
 }

internal/server/server.go

@@ -7,8 +7,8 @@
 //   - the AS name search
 //
 // Every route it shows comes from the routing table in memory. AS names,
-// WHOIS details and the times a prefix and an AS were first seen come from
+// WHOIS details, the times a prefix and an AS were first seen, and a prefix's
-// the database.
+// origin changes come from the database.
 package server
 
 import (

internal/templates/prefix_detail.html

@@ -297,13 +297,13 @@
                 {{end}}
             </div>
         </div>
-{{end}}
+        {{end}}
 
         {{if .OriginChanges}}
         <div class="origins-section">
             <h3>Origin Changes</h3>
             {{if .MoreOriginChanges}}
-            <p>There are more than 5,000 changes. Showing the newest 5,000.</p>
+            <p>There are more than {{.MaxOriginChanges}} changes. Showing the newest {{.MaxOriginChanges}}.</p>
             {{end}}
             <table class="route-table">
                 <thead>