add /.export-stats endpoint to dump stats table

This is really bare bones, but at least lets us get the stats data out.
This also made it clear to me how brittle some of our tests are because
of how much global state we have in the top-level golink package. We
should probably move all of that into a server type or something similar
before too long.

Updates #168

Change-Id: Ia101a4a3005adb9118051b3416f5a64a4a45987d
Signed-off-by: Will Norris <will@tailscale.com>

Author: willnorris

db.go

@@ -16,6 +16,7 @@ import (
 	"time"
 
 	_ "modernc.org/sqlite"
+	"tailscale.com/tstime"
 )
 
 // Link is the structure stored for each go short link.
@@ -42,6 +43,8 @@ func linkID(short string) string {
 type SQLiteDB struct {
 	db *sql.DB
 	mu sync.RWMutex
+
+	clock tstime.Clock // allow overriding time for tests
 }
 
 //go:embed schema.sql
@@ -64,6 +67,11 @@ func NewSQLiteDB(f string) (*SQLiteDB, error) {
 	return &SQLiteDB{db: db}, nil
 }
 
+// Now returns the current time.
+func (s *SQLiteDB) Now() time.Time {
+	return tstime.DefaultClock{Clock: s.clock}.Now()
+}
+
 // LoadAll returns all stored Links.
 //
 // The caller owns the returned values.
@@ -195,7 +203,7 @@ func (s *SQLiteDB) SaveStats(stats ClickStats) error {
 	if err != nil {
 		return err
 	}
-	now := time.Now().Unix()
+	now := s.Now().Unix()
 	for short, clicks := range stats {
 		_, err := tx.Exec("INSERT INTO Stats (ID, Created, Clicks) VALUES (?, ?, ?)", linkID(short), now, clicks)
 		if err != nil {

flake.nix

@@ -39,7 +39,7 @@
               "-X tailscale.com/version.longStamp=${tsVersion}"
               "-X tailscale.com/version.shortStamp=${tsVersion}"
             ];
-          vendorHash = "sha256-k3BxPRTgoJM0oCixDVA2k44ztdAUZO4IcO2/QB19HvU="; # SHA based on vendoring go.mod
+          vendorHash = "sha256-tF3TuIWr5x4inGrykXAjXBQATpDdpTX8HDYmEeukTEc="; # SHA based on vendoring go.mod
         };
       });
 

golink.go

@@ -421,6 +421,7 @@ func serveHandler() http.Handler {
 	mux := http.NewServeMux()
 	mux.HandleFunc("/.detail/", serveDetail)
 	mux.HandleFunc("/.export", serveExport)
+	mux.HandleFunc("/.export-stats", serveExportStats)
 	mux.HandleFunc("/.help", serveHelp)
 	mux.HandleFunc("/.opensearch", serveOpenSearch)
 	mux.HandleFunc("/.all", serveAll)
@@ -990,6 +991,42 @@ func serveExport(w http.ResponseWriter, _ *http.Request) {
 	}
 }
 
+// serveExportStats prints a snapshot of the stats database table.
+//
+// Stats are printed in CSV format with three columns: link ID, UNIX timestamp, and click count.
+// Each stat line represents the number of clicks in the previous minute.
+func serveExportStats(w http.ResponseWriter, _ *http.Request) {
+	if err := flushStats(); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	rows, err := db.db.Query("SELECT ID, Created, Clicks FROM Stats ORDER BY Created, ID")
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	defer func() {
+		rows.Close()
+		if err := rows.Err(); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
+	}()
+
+	for rows.Next() {
+		var id string
+		var created int64
+		var clicks int
+		err := rows.Scan(&id, &created, &clicks)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		// id is not permitted to contain commas, so no need to worry about CSV quoting
+		fmt.Fprintf(w, "%s,%d,%d\n", id, created, clicks)
+	}
+}
+
 func restoreLastSnapshot() error {
 	bs := bufio.NewScanner(bytes.NewReader(LastSnapshot))
 	var restored int

golink_test.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"golang.org/x/net/xsrftoken"
+	"tailscale.com/tstest"
 	"tailscale.com/types/ptr"
 	"tailscale.com/util/must"
 )
@@ -358,6 +359,67 @@ func TestServeDelete(t *testing.T) {
 	}
 }
 
+func TestServeExport(t *testing.T) {
+	clock := tstest.NewClock(tstest.ClockOpts{
+		Start: time.Date(2022, 06, 02, 1, 2, 3, 4, time.UTC),
+	})
+
+	var err error
+	db, err = NewSQLiteDB(":memory:")
+	db.clock = clock
+	if err != nil {
+		t.Fatal(err)
+	}
+	db.Save(&Link{Short: "a", Owner: "a@example.com"})
+	db.Save(&Link{Short: "foo", Owner: "foo@example.com"})
+	db.Save(&Link{Short: "link-owned-by-tagged-devices", Long: "/before", Owner: "tagged-devices"})
+
+	click := func(id string) {
+		r := httptest.NewRequest("GET", "/"+id, nil)
+		w := httptest.NewRecorder()
+		serveHandler().ServeHTTP(w, r)
+	}
+	initStats()
+	click("a")
+	click("foo")
+	click("foo")
+	flushStats()
+	clock.Advance(3 * time.Minute)
+	click("a")
+
+	// export links
+	r := httptest.NewRequest("GET", "/.export", nil)
+	w := httptest.NewRecorder()
+	serveHandler().ServeHTTP(w, r)
+
+	if want := http.StatusOK; w.Code != want {
+		t.Errorf("serveExport = %d; want %d", w.Code, want)
+	}
+	wantOutput := `{"Short":"a","Long":"","Created":"0001-01-01T00:00:00Z","LastEdit":"0001-01-01T00:00:00Z","Owner":"a@example.com"}
+{"Short":"foo","Long":"","Created":"0001-01-01T00:00:00Z","LastEdit":"0001-01-01T00:00:00Z","Owner":"foo@example.com"}
+{"Short":"link-owned-by-tagged-devices","Long":"/before","Created":"0001-01-01T00:00:00Z","LastEdit":"0001-01-01T00:00:00Z","Owner":"tagged-devices"}
+`
+	if got := w.Body.String(); got != wantOutput {
+		t.Errorf("serveExport = %v; want %v", got, wantOutput)
+	}
+
+	// export links stats
+	r = httptest.NewRequest("GET", "/.export-stats", nil)
+	w = httptest.NewRecorder()
+	serveHandler().ServeHTTP(w, r)
+
+	if want := http.StatusOK; w.Code != want {
+		t.Errorf("serveExportStats = %d; want %d", w.Code, want)
+	}
+	wantOutput = `a,1654131723,1
+foo,1654131723,2
+a,1654131903,1
+`
+	if got := w.Body.String(); got != wantOutput {
+		t.Errorf("serveExportStats = %v; want %v", got, wantOutput)
+	}
+}
+
 func TestReadOnlyMode(t *testing.T) {
 	var err error
 	db, err = NewSQLiteDB(":memory:")