Remove the per-peer route tables (closes #122)

The routing table in memory now holds every route, so the two per-peer route
tables go, with every write, delete, count and read that served them. The
prefix handler applies each update to the table, writes the table's changes
every second, and stores each new prefix with its first-seen time. The peer
delete, its retry on the next flush and the updates held for it go too. The
types and errors of the server's answers move to internal/server.

The image's memory settings fit a full table of about 1 GB: GOMEMLIMIT of
2.5 GiB, a 512 MiB page cache for the writing connection, and SQLite heap
limits of 768 MiB and 1 GiB. The README describes the new table, its
database copy and the memory budget.

Model: opus-5-5

internal/database/counts.go

@@ -6,11 +6,10 @@ import (
 	"sync"
 )
 
-// liveCounts holds the running row counts and the prefix distribution that the
-// stats endpoints report. They are seeded once at startup from the tables and
-// then adjusted on every write, so a stats read serves them from memory instead
-// of running a query over the tables. The COUNT(*) scans (issue 27) and then
-// the prefix distribution query (issue 30) each grew with the database until
+// liveCounts holds the running row counts that the stats endpoints report.
+// They are seeded once at startup from the tables and then adjusted on every
+// write, so a stats read serves them from memory instead of running a query
+// over the tables. The COUNT(*) scans (issue 27) grew with the database until
 // they took the whole request timeout and made /api/v1/stats return 500.
 //
 // A single mutex guards all fields so the stats reader takes a consistent
@@ -23,20 +22,11 @@ type liveCounts struct {
 	prefixesV6 int
 	peerings   int
 	peers      int
-	routesV4   int
-	routesV6   int
-	// The prefix distribution: for each mask length, the number of distinct
-	// prefixes that have at least one live route.
-	distributionV4 [ipv4Bits + 1]int
-	distributionV6 [ipv6Bits + 1]int
 }
 
 // seed sets every count to the value read from the tables at startup. It runs
 // before any writer, so it needs no coordination with the adjust methods.
-func (c *liveCounts) seed(
-	asns, prefixesV4, prefixesV6, peerings, peers, routesV4, routesV6 int,
-	distributionV4, distributionV6 []PrefixDistribution,
-) {
+func (c *liveCounts) seed(asns, prefixesV4, prefixesV6, peerings, peers int) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
@@ -45,16 +35,6 @@ func (c *liveCounts) seed(
 	c.prefixesV6 = prefixesV6
 	c.peerings = peerings
 	c.peers = peers
-	c.routesV4 = routesV4
-	c.routesV6 = routesV6
-
-	for _, entry := range distributionV4 {
-		addAtMaskLength(c.distributionV4[:], entry.MaskLength, entry.Count)
-	}
-
-	for _, entry := range distributionV6 {
-		addAtMaskLength(c.distributionV6[:], entry.MaskLength, entry.Count)
-	}
 }
 
 // addASNs adds n to the ASN count.
@@ -86,41 +66,7 @@ func (c *liveCounts) addPeers(n int) {
 	c.mu.Unlock()
 }
 
-// addRoutes adds to the IPv4 and IPv6 live-route counts. Deletions pass
-// negative values.
-func (c *liveCounts) addRoutes(v4, v6 int) {
-	c.mu.Lock()
-	c.routesV4 += v4
-	c.routesV6 += v6
-	c.mu.Unlock()
-}
-
-// addToDistribution adds n to the IPv4 and IPv6 prefix distributions once for
-// each listed mask length. A write lists the mask lengths of the prefixes it
-// gave their first live route with n = 1, and of the prefixes it left with no
-// live route with n = -1.
-func (c *liveCounts) addToDistribution(maskLengthsV4, maskLengthsV6 []int, n int) {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-
-	for _, maskLength := range maskLengthsV4 {
-		addAtMaskLength(c.distributionV4[:], maskLength, n)
-	}
-
-	for _, maskLength := range maskLengthsV6 {
-		addAtMaskLength(c.distributionV6[:], maskLength, n)
-	}
-}
-
-// addAtMaskLength adds n to counts[maskLength]. A mask length the array has no
-// entry for is ignored, so a malformed route cannot crash the daemon.
-func addAtMaskLength(counts []int, maskLength, n int) {
-	if maskLength >= 0 && maskLength < len(counts) {
-		counts[maskLength] += n
-	}
-}
-
-// fill copies the counts into a Stats, including the derived totals, under a
+// fill copies the counts into a Stats, including the derived total, under a
 // single read lock so the reader sees one consistent snapshot.
 func (c *liveCounts) fill(s *Stats) {
 	c.mu.RLock()
@@ -132,26 +78,6 @@ func (c *liveCounts) fill(s *Stats) {
 	s.Prefixes = c.prefixesV4 + c.prefixesV6
 	s.Peerings = c.peerings
 	s.Peers = c.peers
-	s.IPv4Routes = c.routesV4
-	s.IPv6Routes = c.routesV6
-	s.LiveRoutes = c.routesV4 + c.routesV6
-	s.IPv4PrefixDistribution = distributionList(c.distributionV4[:])
-	s.IPv6PrefixDistribution = distributionList(c.distributionV6[:])
-}
-
-// distributionList lists the mask lengths that have at least one prefix, in
-// ascending order, the way the distribution query returns them.
-func distributionList(counts []int) []PrefixDistribution {
-	var list []PrefixDistribution
-
-	for maskLength, count := range counts {
-		if count > 0 {
-			list = append(list,
-				PrefixDistribution{MaskLength: maskLength, Count: count})
-		}
-	}
-
-	return list
 }
 
 // countRows returns the number of rows in the named table. It is used only at
@@ -167,9 +93,8 @@ func (d *Database) countRows(ctx context.Context, table string) (int, error) {
 	return n, nil
 }
 
-// seedCounts reads the current row counts and prefix distribution from the
-// tables into the in-memory counters. It runs once at startup, before the
-// streamer begins writing.
+// seedCounts reads the current row counts from the tables into the in-memory
+// counters. It runs once at startup, before the streamer begins writing.
 func (d *Database) seedCounts(ctx context.Context) error {
 	asns, err := d.countRows(ctx, "asns")
 	if err != nil {
@@ -196,23 +121,7 @@ func (d *Database) seedCounts(ctx context.Context) error {
 		return err
 	}
 
-	routesV4, err := d.countRows(ctx, tableLiveRoutesV4)
-	if err != nil {
-		return err
-	}
-
-	routesV6, err := d.countRows(ctx, tableLiveRoutesV6)
-	if err != nil {
-		return err
-	}
-
-	distributionV4, distributionV6, err := d.GetPrefixDistributionContext(ctx)
-	if err != nil {
-		return err
-	}
-
-	d.counts.seed(asns, prefixesV4, prefixesV6, peerings, peers, routesV4, routesV6,
-		distributionV4, distributionV6)
+	d.counts.seed(asns, prefixesV4, prefixesV6, peerings, peers)
 
 	return nil
 }