sync: closest devices first, by measured link speed

cmd/opensave-app/frontend/src/locales/en.json

@@ -258,5 +258,12 @@
   "transfers.empty": "Nothing has moved between your devices since OpenSave started.",
   "transfers.now": "Now",
   "transfers.recently": "Recently",
-  "transfers.readError": "Couldn't read transfers: {error}"
+  "transfers.readError": "Couldn't read transfers: {error}",
+  "devices.linkLan": "home network",
+  "devices.linkVpn": "VPN (e.g. Tailscale)",
+  "devices.linkRelay": "internet relay",
+  "devices.linkInternet": "internet",
+  "devices.linkUnmeasured": "{kind} · speed not measured yet",
+  "devices.linkMeasured": "{kind} · {rate} (measured {when})",
+  "devices.linkTitle": "Saves go to the fastest connections first, and a device that is behind takes the newer save from the fastest device that has it."
 }

cmd/opensave-app/frontend/src/locales/zh-Hans.json

@@ -225,5 +225,12 @@
   "transfers.empty": "自 OpenSave 启动以来，设备之间还没有传输过任何内容。",
   "transfers.now": "进行中",
   "transfers.recently": "最近",
-  "transfers.readError": "无法读取传输记录：{error}"
+  "transfers.readError": "无法读取传输记录：{error}",
+  "devices.linkLan": "家庭网络",
+  "devices.linkVpn": "VPN（如 Tailscale）",
+  "devices.linkRelay": "互联网中继",
+  "devices.linkInternet": "互联网",
+  "devices.linkUnmeasured": "{kind} · 尚未测速",
+  "devices.linkMeasured": "{kind} · {rate}（测于 {when}）",
+  "devices.linkTitle": "存档会优先通过最快的连接发送；落后的设备会从拥有较新存档的设备中最快的那台获取。"
 }

cmd/opensave-app/frontend/src/locales/zh-Hant.json

@@ -225,5 +225,12 @@
   "transfers.empty": "自 OpenSave 啟動以來，裝置之間還沒有傳輸過任何內容。",
   "transfers.now": "進行中",
   "transfers.recently": "最近",
-  "transfers.readError": "無法讀取傳輸記錄：{error}"
+  "transfers.readError": "無法讀取傳輸記錄：{error}",
+  "devices.linkLan": "家用網路",
+  "devices.linkVpn": "VPN（如 Tailscale）",
+  "devices.linkRelay": "網際網路中繼",
+  "devices.linkInternet": "網際網路",
+  "devices.linkUnmeasured": "{kind} · 尚未測速",
+  "devices.linkMeasured": "{kind} · {rate}（測於 {when}）",
+  "devices.linkTitle": "存檔會優先透過最快的連線傳送；落後的裝置會從擁有較新存檔的裝置中最快的那臺取得。"
 }

cmd/opensave-app/frontend/src/views/Devices.svelte

@@ -9,6 +9,7 @@
   import Globe from 'lucide-svelte/icons/globe';
   import Network from 'lucide-svelte/icons/network';
   import Download from 'lucide-svelte/icons/download';
+  import { t } from '../lib/i18n.js';
 
   export let params = {};
 
@@ -76,6 +77,16 @@
   };
 
   const fmtTime = (t) => (t ? new Date(t).toLocaleString() : 'never');
+
+  // How this device reaches the peer, and how fast it has found that to be.
+  // linkLabel is given $t, so the line follows a change of language.
+  const linkKinds = { lan: 'devices.linkLan', vpn: 'devices.linkVpn', relay: 'devices.linkRelay', internet: 'devices.linkInternet' };
+  const fmtRate = (b) => (b >= 1048576 ? (b / 1048576).toFixed(1) + ' MB/s' : Math.max(1, Math.round(b / 1024)) + ' KB/s');
+  function linkLabel(link, tr) {
+    const kind = linkKinds[link.kind] ? tr(linkKinds[link.kind]) : link.kind;
+    if (!link.bytesPerSec) return tr('devices.linkUnmeasured', { kind });
+    return tr('devices.linkMeasured', { kind, rate: fmtRate(link.bytesPerSec), when: fmtTime(link.measuredMs) });
+  }
 </script>
 
 <div class="head">
@@ -105,6 +116,11 @@
             · last synced {fmtTime(peer.lastSynced)}
             {#if peer.appVersion}· OpenSave {peer.appVersion}{/if}
           </div>
+          {#if peer.link}
+            <div class="peer-meta" title={$t('devices.linkTitle')}>
+              {linkLabel(peer.link, $t)}
+            </div>
+          {/if}
           <!-- Per device, next to how it is reached, because that is the
                context the answer depends on. -->
           <div class="peer-protection">

e2e/batch_bench_test.go

@@ -0,0 +1,59 @@
+package e2e
+
+import (
+	"fmt"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/opensave/opensave/internal/p2p"
+	"github.com/opensave/opensave/internal/p2p/syncengine"
+	"github.com/opensave/opensave/testutil"
+)
+
+// TestBench_ManySmallFiles times pulling a save of many small files between
+// two real daemons, batched and file by file. Opt-in, because it is a
+// measurement rather than a check: OPENSAVE_BENCH_FILES=5000 go test ./e2e -run TestBench -v
+func TestBench_ManySmallFiles(t *testing.T) {
+	n, _ := strconv.Atoi(os.Getenv("OPENSAVE_BENCH_FILES"))
+	if n <= 0 {
+		t.Skip("set OPENSAVE_BENCH_FILES to run")
+	}
+	for _, mode := range []struct {
+		name  string
+		proto int
+	}{{"batched", syncengine.ProtoBatchFiles}, {"file-by-file", syncengine.ProtoMultiRoot}} {
+		t.Run(mode.name, func(t *testing.T) {
+			restore := p2p.SetServedProto(mode.proto)
+			defer p2p.SetServedProto(restore)
+
+			a := testutil.NewTestDaemon(t, "Bench-A")
+			b := testutil.NewTestDaemon(t, "Bench-B")
+			a.PairWith(b)
+			chunk := strings.Repeat("x", 3500) // a Project Zomboid map chunk is ~3.5KB
+			for i := 0; i < n; i++ {
+				a.WriteSave(fmt.Sprintf("map/map_%d_%d.bin", i/100, i%100), chunk+strconv.Itoa(i))
+			}
+			restoreSyncOnTrack := suppressSyncOnTrack(a, b)
+			gameID := a.TrackGame("Bench")
+			b.API(http.MethodPost, "/api/games", map[string]string{"name": "Bench", "savePath": b.SaveDir}, nil)
+			restoreSyncOnTrack()
+
+			start := time.Now()
+			b.API(http.MethodPost, "/api/games/"+gameID+"/sync", nil, nil)
+			count := func() int {
+				m, _ := filepath.Glob(filepath.Join(b.SaveDir, "map", "*.bin"))
+				return len(m)
+			}
+			if !testutil.WaitFor(60*time.Minute, func() bool { return count() >= n }) {
+				t.Fatalf("only %d of %d files arrived", count(), n)
+			}
+			el := time.Since(start)
+			t.Logf("%s: %d files in %s = %.2f ms/file", mode.name, n, el.Round(time.Millisecond), float64(el.Microseconds())/1000/float64(n))
+		})
+	}
+}

e2e/presence_timing_test.go

@@ -0,0 +1,53 @@
+package e2e
+
+import (
+	"os"
+	"testing"
+	"time"
+
+	"github.com/opensave/opensave/testutil"
+)
+
+// TestPresence_GoneDeviceShowsOffline measures how long a device that went
+// away keeps being shown online. Opt-in measurement:
+// OPENSAVE_PRESENCE_TIMING=1 go test ./e2e -run TestPresence_ -v
+func TestPresence_GoneDeviceShowsOffline(t *testing.T) {
+	if os.Getenv("OPENSAVE_PRESENCE_TIMING") == "" {
+		t.Skip("set OPENSAVE_PRESENCE_TIMING to run")
+	}
+	a := testutil.NewTestDaemon(t, "Presence-A")
+	b := testutil.NewTestDaemon(t, "Presence-B")
+	a.PairWith(b)
+	bID := b.NodeID()
+
+	status := func() string {
+		p, err := a.Daemon.Store.GetPeer(bID)
+		if err != nil {
+			return "?"
+		}
+		return p.Status
+	}
+	if !testutil.WaitFor(60*time.Second, func() bool { return status() == "online" }) {
+		t.Fatalf("B never showed online on A: %q", status())
+	}
+
+	gone := time.Now()
+	b.Server.Stop()
+	b.Daemon.Stop()
+
+	last := status()
+	for time.Since(gone) < 10*time.Minute {
+		if s := status(); s != last {
+			t.Logf("%6.1fs after B stopped: %s -> %s", time.Since(gone).Seconds(), last, s)
+			last = s
+		}
+		if last == "offline" {
+			break
+		}
+		time.Sleep(500 * time.Millisecond)
+	}
+	t.Logf("B shown online for %.1fs after it stopped", time.Since(gone).Seconds())
+	if last != "offline" {
+		t.Fatalf("B still %q 10 minutes after it stopped", last)
+	}
+}

internal/api/server.go

@@ -101,12 +101,17 @@ func (s *Server) peersPayload() map[string]any {
 			AppVersion    string `json:"appVersion,omitempty"`
 			BuildTimeMs   int64  `json:"buildTimeMs,omitempty"`
 			HasNewerBuild bool   `json:"hasNewerBuild,omitempty"`
+			// Link is how fast this device has found its connection to it,
+			// and what kind of address it is reached on: what decides the
+			// order devices are synced in.
+			Link syncengine.LinkStat `json:"link"`
 			// What actually protects traffic with this device. Sent per peer
 			// rather than described once in the interface, because the answer
 			// differs per pairing and the reader cannot work out which case
 			// they are in from a general statement.
 			p2p.PeerProtection
-		}{Peer: p, PeerProtection: s.Daemon.P2P.PeerProtection(p)}
+		}{Peer: p, PeerProtection: s.Daemon.P2P.PeerProtection(p),
+			Link: s.Daemon.P2P.Sync.Link(syncengine.Peer{ID: p.ID, Name: p.Name, Address: p.Address, Port: p.Port, IsWan: p.Address == "relay"})}
 		if b, ok := builds[p.ID]; ok {
 			entry.AppVersion = b.AppVersion
 			entry.BuildTimeMs = b.BuildTimeMs