Add CSV export of the logs matching the current filters

- GET /api/export.csv streams every stored log matching the filters
  (newest first, up to EXPORT_MAX rows, 100000 by default) straight from
  VictoriaLogs, with dates in the time zone chosen in Settings.
- Export button with two variants: CSV (comma, UTF-8) and CSV for Excel
  (semicolon + BOM, formula injection neutralized).
- Store.QueryStream streams query results without buffering them.
- Mobile: filter bar keeps two selects per row, count next to Export.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.env.example

@@ -13,3 +13,5 @@ RDNS=on
 DNS_SERVER=
 # Allow "Delete all logs" in Settings (true/false)
 ALLOW_PURGE=true
+# Maximum number of rows in a CSV export
+EXPORT_MAX=100000

README.md

@@ -59,6 +59,23 @@ Severity badges `err`/`crit` and `warning` use the colors of the `error` and `wa
 
 Shortcuts: `/` focuses the search box, `Esc` clears it. Clicking a row shows all its fields.
 
+## CSV export
+
+The **Export** button (next to the log count) downloads every stored log matching the
+current filters (search, time range, severity, host, app), newest first, up to `EXPORT_MAX`
+rows (100,000 by default), not only the rows on screen. Two variants:
+
+- **CSV**: comma separated, UTF-8.
+- **CSV for Excel**: semicolon separated with a UTF-8 BOM, so French Excel opens it directly
+  with accents. Cells starting with `=`, `+`, `-` or `@` are prefixed with `'` so that a
+  crafted log message cannot run as a formula.
+
+Columns: `received`, `message_time` (both as `YYYY-MM-DD HH:MM:SS.mmm` in the time zone
+chosen in Settings), `severity`, `facility`, `host`, `host_ip`, `app`, `pid`, `source_ip`,
+`proto`, `message`. In LogsQL mode, only the filter part is supported (no `| pipes`).
+
+From the command line: `curl -o logs.csv 'localhost:8080/api/export.csv?q=error&range=24h&tz=Europe/Paris'`.
+
 ## Settings
 
 The gear icon opens the settings, organized in tabs. Everything except color tags is
@@ -118,6 +135,7 @@ are only known by your router or a local DNS (Pi-hole, AdGuard, Unbound…), set
 | `RDNS` | `on` | resolve IP hosts to DNS names |
 | `DNS_SERVER` | empty | DNS server for reverse lookups (`ip` or `ip:port`) |
 | `ALLOW_PURGE` | `true` | allow "Delete all logs" in Settings |
+| `EXPORT_MAX` | `100000` | maximum number of rows in a CSV export |
 | `TZ` | `Europe/Paris` | time zone for RFC 3164 timestamps (which carry none) |
 | `BATCH_SIZE`, `FLUSH_MS`, `QUEUE_SIZE` | `1000`, `1000`, `100000` | ingestion tuning |
 
@@ -144,6 +162,7 @@ are only known by your router or a local DNS (Pi-hole, AdGuard, Unbound…), set
 | `query.go` | turns UI filters into LogsQL; live-view filter |
 | `hub.go` | pushes new messages to browsers (SSE) |
 | `rdns.go` | cached reverse DNS lookups |
+| `export.go` | streamed CSV export |
 | `tags.go` | color tag storage |
 | `api.go` | `/api/*` HTTP routes |
 | `web/` | UI (HTML, CSS, plain JavaScript, no build step), embedded in the binary; translations live in `web/app.js` (`I18N`) |

api.go

@@ -18,6 +18,7 @@ type API struct {
 	tags       *TagStore
 	rdns       *ReverseDNS
 	allowPurge bool
+	exportMax  int
 }
 
 func (a *API) Routes(mux *http.ServeMux) {
@@ -34,6 +35,7 @@ func (a *API) Routes(mux *http.ServeMux) {
 	mux.HandleFunc("DELETE /api/tags/{id}", a.deleteTag)
 	mux.HandleFunc("GET /api/purge", a.purgeStatus)
 	mux.HandleFunc("POST /api/purge", a.purge)
+	mux.HandleFunc("GET /api/export.csv", a.exportCSV)
 }
 
 func writeJSON(w http.ResponseWriter, status int, v any) {
@@ -261,6 +263,7 @@ func (a *API) stream(w http.ResponseWriter, r *http.Request) {
 func (a *API) stats(w http.ResponseWriter, r *http.Request) {
 	s := a.store.Stats()
 	s["clients"] = a.hub.Count()
+	s["exportMax"] = a.exportMax
 	writeJSON(w, http.StatusOK, s)
 }
 

docker-compose.yml

@@ -17,6 +17,7 @@ services:
       RDNS: ${RDNS:-on}               # replace IP hosts with their DNS name (PTR)
       DNS_SERVER: ${DNS_SERVER:-}     # e.g. 192.168.1.1 to query your LAN DNS; empty = system resolver
       ALLOW_PURGE: ${ALLOW_PURGE:-true}
+      EXPORT_MAX: ${EXPORT_MAX:-100000}
     volumes:
       - logstream-data:/data         # tags.json
 

export.go

@@ -0,0 +1,146 @@
+package main
+
+import (
+	"encoding/csv"
+	"fmt"
+	"log"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// Columns of the CSV export: stored field -> column name.
+var exportColumns = []struct{ field, name string }{
+	{"received", "received"},
+	{"msg_time", "message_time"},
+	{"severity", "severity"},
+	{"facility", "facility"},
+	{"host", "host"},
+	{"host_ip", "host_ip"},
+	{"app", "app"},
+	{"procid", "pid"},
+	{"source", "source_ip"},
+	{"proto", "proto"},
+	{"_msg", "message"},
+}
+
+// UTF-8 byte order mark: lets Excel detect the encoding (accents).
+var utf8BOM = []byte{0xEF, 0xBB, 0xBF}
+
+// GET /api/export.csv?<filters>&tz=Europe/Paris&excel=1&limit=N
+// Streams every stored log matching the filters (newest first, at most
+// EXPORT_MAX rows) as CSV. excel=1 uses ";" as separator (French Excel),
+// adds a BOM and neutralizes cells Excel would run as formulas.
+func (a *API) exportCSV(w http.ResponseWriter, r *http.Request) {
+	q := r.URL.Query()
+	f := FilterFromRequest(r)
+	filter, pipes := f.LogsQL()
+	if strings.TrimSpace(pipes) != "" {
+		writeErr(w, http.StatusBadRequest, &codedError{code: "export_pipes", msg: "export does not support LogsQL pipes (| ...): keep only the filter part"})
+		return
+	}
+	limit, _ := strconv.Atoi(q.Get("limit"))
+	if limit <= 0 || limit > a.exportMax {
+		limit = a.exportMax
+	}
+	loc := time.UTC
+	if tz := q.Get("tz"); tz != "" {
+		if l, err := time.LoadLocation(tz); err == nil {
+			loc = l
+		}
+	}
+	excel := q.Get("excel") == "1"
+	query := fmt.Sprintf("%s | sort by (_time desc) | limit %d", filter, limit)
+
+	// The response starts with the first row, so that a query error can
+	// still be returned as a proper HTTP error.
+	var cw *csv.Writer
+	start := func() {
+		name := "logstream-" + time.Now().In(loc).Format("20060102-150405") + ".csv"
+		h := w.Header()
+		h.Set("Content-Type", "text/csv; charset=utf-8")
+		h.Set("Content-Disposition", `attachment; filename="`+name+`"`)
+		h.Set("Cache-Control", "no-store")
+		w.WriteHeader(http.StatusOK)
+		if excel {
+			_, _ = w.Write(utf8BOM)
+		}
+		cw = csv.NewWriter(w)
+		if excel {
+			cw.Comma = ';'
+		}
+		zone := loc.String()
+		header := make([]string, len(exportColumns))
+		for i, c := range exportColumns {
+			header[i] = c.name
+			if c.field == "received" || c.field == "msg_time" {
+				header[i] += " (" + zone + ")"
+			}
+		}
+		_ = cw.Write(header)
+	}
+
+	rows := 0
+	record := make([]string, len(exportColumns))
+	err := a.store.QueryStream(r.Context(), query, func(row map[string]any) error {
+		if cw == nil {
+			start()
+		}
+		for i, c := range exportColumns {
+			v, _ := row[c.field].(string)
+			switch c.field {
+			case "received":
+				v = exportTime(v, loc)
+			case "msg_time":
+				if v == "" { // logs stored before msg_time existed
+					v, _ = row["_time"].(string)
+				}
+				v = exportTime(v, loc)
+			}
+			if excel {
+				v = excelSafe(v)
+			}
+			record[i] = v
+		}
+		if err := cw.Write(record); err != nil {
+			return err
+		}
+		rows++
+		if rows%1000 == 0 {
+			cw.Flush()
+		}
+		return cw.Error()
+	})
+	if err != nil {
+		if cw == nil {
+			writeErr(w, http.StatusBadGateway, err)
+			return
+		}
+		// Headers are already sent: the file is truncated, log why.
+		log.Printf("export interrupted after %d rows: %v", rows, err)
+	}
+	if cw == nil {
+		start() // no matching log: header only
+	}
+	cw.Flush()
+}
+
+// exportTime converts an RFC 3339 timestamp to "2006-01-02 15:04:05.000" in loc,
+// a format spreadsheets recognize as a date.
+func exportTime(v string, loc *time.Location) string {
+	t, err := time.Parse(time.RFC3339Nano, v)
+	if err != nil {
+		return v
+	}
+	return t.In(loc).Format("2006-01-02 15:04:05.000")
+}
+
+// excelSafe prevents spreadsheet formula injection: log messages come from the
+// network, and a cell starting with = + - @ would be run as a formula.
+func excelSafe(v string) string {
+	if v != "" && strings.ContainsRune("=+-@\t\r", rune(v[0])) {
+		return "'" + v
+	}
+	return v
+}

main.go

@@ -34,6 +34,7 @@ type config struct {
 	rdns       bool
 	dnsServer  string
 	allowPurge bool
+	exportMax  int
 	batchSize  int
 	queueSize  int
 	flushEvery time.Duration
@@ -74,6 +75,7 @@ func main() {
 		rdns:       getenvBool("RDNS", true),
 		dnsServer:  os.Getenv("DNS_SERVER"),
 		allowPurge: getenvBool("ALLOW_PURGE", true),
+		exportMax:  getenvInt("EXPORT_MAX", 100000),
 		batchSize:  getenvInt("BATCH_SIZE", 1000),
 		queueSize:  getenvInt("QUEUE_SIZE", 100000),
 		flushEvery: time.Duration(getenvInt("FLUSH_MS", 1000)) * time.Millisecond,
@@ -114,7 +116,7 @@ func main() {
 		log.Fatal(err)
 	}
 	mux := http.NewServeMux()
-	api := &API{store: store, hub: hub, tags: tags, rdns: rdns, allowPurge: cfg.allowPurge}
+	api := &API{store: store, hub: hub, tags: tags, rdns: rdns, allowPurge: cfg.allowPurge, exportMax: cfg.exportMax}
 	api.Routes(mux)
 	mux.Handle("GET /", http.FileServer(http.FS(static)))
 

store.go

@@ -19,6 +19,7 @@ import (
 type Store struct {
 	base         string
 	client       *http.Client
+	streamClient *http.Client
 	in         chan *Entry
 	batchSize  int
 	flushEvery time.Duration
@@ -33,6 +34,9 @@ func NewStore(base string, batchSize, queueSize int, flushEvery time.Duration) *
 	s := &Store{
 		base:       strings.TrimRight(base, "/"),
 		client:     &http.Client{Timeout: 60 * time.Second},
+		// No global timeout: a large export can take longer than a minute. The
+		// request context still cancels it when the browser goes away.
+		streamClient: &http.Client{},
 		in:         make(chan *Entry, queueSize),
 		batchSize:  batchSize,
 		flushEvery: flushEvery,
@@ -138,23 +142,37 @@ func (s *Store) post(u string, body []byte) error {
 
 // Query runs a LogsQL query and returns one row per result.
 func (s *Store) Query(ctx context.Context, query string) ([]map[string]any, error) {
-	form := url.Values{"query": {query}}
-	req, err := http.NewRequestWithContext(ctx, http.MethodPost, s.base+"/select/logsql/query", strings.NewReader(form.Encode()))
+	rows := []map[string]any{}
+	err := s.QueryStream(ctx, query, func(row map[string]any) error {
+		rows = append(rows, row)
+		return nil
+	})
 	if err != nil {
 		return nil, err
 	}
-	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
-	resp, err := s.client.Do(req)
+	return rows, nil
+}
+
+// QueryStream runs a LogsQL query and calls fn for each result as it arrives,
+// without keeping the results in memory. fn is only called once VictoriaLogs
+// has accepted the query; an error returned by fn stops the stream.
+func (s *Store) QueryStream(ctx context.Context, query string, fn func(row map[string]any) error) error {
+	form := url.Values{"query": {query}}
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, s.base+"/select/logsql/query", strings.NewReader(form.Encode()))
 	if err != nil {
-		return nil, err
+		return err
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	resp, err := s.streamClient.Do(req)
+	if err != nil {
+		return err
 	}
 	defer resp.Body.Close()
 	if resp.StatusCode != http.StatusOK {
 		msg, _ := io.ReadAll(io.LimitReader(resp.Body, 2048))
-		return nil, fmt.Errorf("%s", strings.TrimSpace(string(msg)))
+		return fmt.Errorf("%s", strings.TrimSpace(string(msg)))
 	}
 
-	rows := []map[string]any{}
 	sc := bufio.NewScanner(resp.Body)
 	sc.Buffer(make([]byte, 64*1024), 16<<20)
 	for sc.Scan() {
@@ -164,11 +182,13 @@ func (s *Store) Query(ctx context.Context, query string) ([]map[string]any, erro
 		}
 		var row map[string]any
 		if err := json.Unmarshal(line, &row); err != nil {
-			return nil, err
+			return err
 		}
-		rows = append(rows, row)
+		if err := fn(row); err != nil {
+			return err
 		}
-	return rows, sc.Err()
+	}
+	return sc.Err()
 }
 
 // Purge starts a VictoriaLogs task that deletes every stored log, and resets

web/app.js

@@ -66,6 +66,11 @@ const I18N = {
     msgTimeTitle: 'Timestamp from the message',
     fHostName: 'host name (DNS)', fHostIp: 'host IP',
     clickHost: 'Click to filter on this host', clickApp: 'Click to filter on this app',
+    export: 'Export', exportCsvHint: 'Comma separated, UTF-8',
+    exportExcel: 'CSV for Excel', exportExcelHint: 'Semicolon separated, for Excel in French',
+    exportNote: (n) => `Up to ${n} logs matching the current filters, newest first. Dates use the time zone chosen in Settings.`,
+    exporting: 'Exporting…', exportDone: (f) => `Downloaded: ${f}`, exportError: 'Export failed: ',
+    err_export_pipes: 'Export does not support LogsQL pipes (| …): keep only the filter part',
     tabLocale: 'Localization', tabFilters: 'Filters', tabInterface: 'Interface', tabData: 'Data',
     themeTitle: 'Theme', themeSystem: 'System', themeLight: 'Light', themeDark: 'Dark',
     themeHelp: 'System follows the light/dark preference of your computer or phone.',
@@ -149,6 +154,11 @@ const I18N = {
     msgTimeTitle: 'Horodatage contenu dans le message',
     fHostName: 'nom d\'hôte (DNS)', fHostIp: 'IP de l\'hôte',
     clickHost: 'Cliquer pour filtrer sur cet hôte', clickApp: 'Cliquer pour filtrer sur cette appli',
+    export: 'Exporter', exportCsvHint: 'Séparateur virgule, UTF-8',
+    exportExcel: 'CSV pour Excel', exportExcelHint: 'Séparateur point-virgule, pour Excel en français',
+    exportNote: (n) => `Jusqu'à ${n} logs correspondant aux filtres, du plus récent au plus ancien. Dates dans le fuseau choisi dans Paramètres.`,
+    exporting: 'Export…', exportDone: (f) => `Téléchargé : ${f}`, exportError: 'Échec de l\'export : ',
+    err_export_pipes: 'L\'export ne gère pas les pipes LogsQL (| …) : gardez seulement la partie filtre',
     tabLocale: 'Localisation', tabFilters: 'Filtres', tabInterface: 'Interface', tabData: 'Données',
     themeTitle: 'Thème', themeSystem: 'Système', themeLight: 'Clair', themeDark: 'Sombre',
     themeHelp: 'Système suit la préférence clair/sombre de votre ordinateur ou de votre téléphone.',
@@ -283,15 +293,17 @@ async function api(url, opts = {}) {
   const text = await res.text();
   let data = null;
   try { data = text ? JSON.parse(text) : null; } catch { /* not JSON */ }
-  if (!res.ok) {
-    // Known error codes are translated; otherwise show the server message.
+  if (!res.ok) throw apiError(res, text, data);
+  return data;
+}
+
+// Known error codes are translated; otherwise the server message is shown.
+function apiError(res, text, data) {
   let msg = (data && data.error) || text || res.statusText;
   if (data && data.code && I18N[lang]['err_' + data.code]) {
     msg = t('err_' + data.code) + (data.detail ? (lang === 'fr' ? ' : ' : ': ') + data.detail : '');
   }
-    throw new Error(msg);
-  }
-  return data;
+  return new Error(msg);
 }
 
 function toast(msg) {
@@ -935,6 +947,7 @@ function renderStats() {
 
 async function loadStats() {
   try { state.stats = await api('/api/stats'); } catch { state.stats = null; }
+  if (state.stats && state.stats.exportMax) exportMax = state.stats.exportMax;
   renderStats();
 }
 
@@ -982,6 +995,59 @@ $('#tzSelect').addEventListener('change', onTimePrefsChange);
 $('#fmtSelect').addEventListener('change', onTimePrefsChange);
 setInterval(() => { if ($('#settingsDlg').open) updateTimePreview(); }, 1000);
 
+/* ================= CSV export ================= */
+
+let exportMax = 100000; // EXPORT_MAX on the server, refreshed from /api/stats
+
+function setExportMenu(open) {
+  $('#exportMenu').hidden = !open;
+  $('#exportBtn').setAttribute('aria-expanded', String(open));
+  if (open) $('#exportNote').textContent = t('exportNote', fmtNum(exportMax));
+}
+
+async function exportCSV(excel) {
+  const p = params();
+  p.set('tz', timePrefs.tz || Intl.DateTimeFormat().resolvedOptions().timeZone || 'UTC');
+  if (excel) p.set('excel', '1');
+  const btn = $('#exportBtn');
+  const lbl = btn.querySelector('.lbl');
+  btn.disabled = true;
+  lbl.textContent = t('exporting');
+  try {
+    const res = await fetch('/api/export.csv?' + p);
+    if (!res.ok) {
+      const text = await res.text();
+      let data = null;
+      try { data = JSON.parse(text); } catch { /* not JSON */ }
+      throw apiError(res, text, data);
+    }
+    const blob = await res.blob();
+    const name = ((res.headers.get('Content-Disposition') || '').match(/filename="([^"]+)"/) || [])[1] || 'logstream.csv';
+    const url = URL.createObjectURL(blob);
+    const a = Object.assign(document.createElement('a'), { href: url, download: name });
+    document.body.append(a);
+    a.click();
+    a.remove();
+    setTimeout(() => URL.revokeObjectURL(url), 10000);
+    toast(t('exportDone', name));
+  } catch (e) {
+    toast(t('exportError') + e.message);
+  } finally {
+    btn.disabled = false;
+    lbl.textContent = t('export');
+  }
+}
+
+$('#exportBtn').addEventListener('click', () => setExportMenu($('#exportMenu').hidden));
+$('#exportMenu').addEventListener('click', (ev) => {
+  const b = ev.target.closest('[data-export]');
+  if (!b) return;
+  setExportMenu(false);
+  exportCSV(b.dataset.export === 'excel');
+});
+document.addEventListener('click', (ev) => { if (!ev.target.closest('.export')) setExportMenu(false); });
+document.addEventListener('keydown', (ev) => { if (ev.key === 'Escape') setExportMenu(false); });
+
 /* ================= Purge ================= */
 
 const purge = { allowed: true, running: 0, error: null, code: null, wasRunning: false, timer: null };

web/index.html

@@ -68,6 +68,21 @@
     <select id="app" data-i18n-aria="appAria"><option value="" data-i18n="allApps">All apps</option></select>
     <span class="spacer"></span>
     <span id="count" class="muted"></span>
+    <div class="export">
+      <button id="exportBtn" class="btn tool" type="button" aria-haspopup="menu" aria-expanded="false">
+        <svg viewBox="0 0 24 24" aria-hidden="true"><path d="M12 3v12M7 10l5 5 5-5M4 17v3h16v-3"/></svg>
+        <span class="lbl" data-i18n="export">Export</span>
+      </button>
+      <div id="exportMenu" class="menu" role="menu" hidden>
+        <button type="button" role="menuitem" data-export="csv">
+          <strong>CSV</strong><small data-i18n="exportCsvHint">Comma separated, UTF-8</small>
+        </button>
+        <button type="button" role="menuitem" data-export="excel">
+          <strong data-i18n="exportExcel">CSV for Excel</strong><small data-i18n="exportExcelHint">Semicolon separated, for Excel in French</small>
+        </button>
+        <p id="exportNote" class="menu-note"></p>
+      </div>
+    </div>
   </section>
 
   <section id="histo" class="histo" data-i18n-aria="histoAria"></section>

web/style.css

@@ -199,6 +199,25 @@ body.busy .progress::after {
 .spacer { flex: 1; }
 #count { font-size: 12.5px; font-variant-numeric: tabular-nums; }
 
+/* Export button and menu */
+.export { position: relative; }
+.btn.tool { height: 32px; padding: 0 10px; font-size: 13px; }
+.btn.tool svg { width: 16px; height: 16px; }
+.menu {
+  position: absolute; right: 0; top: calc(100% + 6px); z-index: 40;
+  width: 290px; padding: 6px;
+  background: var(--panel); border: 1px solid var(--border); border-radius: 12px;
+  box-shadow: var(--shadow);
+}
+.menu button {
+  display: flex; flex-direction: column; align-items: flex-start; gap: 1px; width: 100%;
+  padding: 8px 10px; border: 0; border-radius: 8px; background: transparent; text-align: left;
+}
+.menu button:hover, .menu button:focus-visible { background: var(--panel-2); outline: 0; }
+.menu strong { font-size: 13px; font-weight: 600; }
+.menu small { font-size: 12px; color: var(--muted); }
+.menu-note { margin: 4px 0 0; padding: 8px 10px 4px; border-top: 1px solid var(--border); font-size: 11.5px; color: var(--muted); }
+
 /* ---------- Histogram ---------- */
 .histo { padding: 0 20px 6px; }
 .histo .bars {
@@ -441,9 +460,9 @@ select.field:focus { outline: 0; border-color: var(--accent); box-shadow: 0 0 0
   .search { order: 3; flex-basis: 100%; max-width: none; }
   .live .lbl { display: none; }
   .filters { padding: 10px 16px 6px; }
-  .filters select { flex: 1 1 calc(50% - 8px); max-width: none; }
+  .filters select { flex: 1 1 calc(50% - 8px); max-width: none; min-width: 0; }
   .spacer { display: none; }
-  #count { flex-basis: 100%; }
+  #count { flex: 1 1 50%; min-width: 0; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
   .histo { padding: 0 16px 6px; }
   .list, .error-banner { margin-left: 16px; margin-right: 16px; }
   .row {