Implement FileWatcher

internal/file_watcher_test.go

@@ -0,0 +1,211 @@
+package internal_test
+
+import (
+	"database/sql"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/benbjohnson/litestream/internal"
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func TestFileWatcher(t *testing.T) {
+	t.Run("WriteAndRemove", func(t *testing.T) {
+		dbPath := filepath.Join(t.TempDir(), "db")
+
+		w := internal.NewFileWatcher()
+		if err := w.Open(); err != nil {
+			t.Fatal(err)
+		}
+		defer w.Close()
+
+		db, err := sql.Open("sqlite3", dbPath)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer db.Close()
+
+		if _, err := db.Exec(`PRAGMA journal_mode = wal`); err != nil {
+			t.Fatal(err)
+		} else if _, err := db.Exec(`CREATE TABLE t (x)`); err != nil {
+			t.Fatal(err)
+		}
+
+		if err := w.Watch(dbPath + "-wal"); err != nil {
+			t.Fatal(err)
+		}
+
+		// Write to the WAL file & ensure a "modified" event occurs.
+		if _, err := db.Exec(`INSERT INTO t (x) VALUES (1)`); err != nil {
+			t.Fatal(err)
+		}
+
+		select {
+		case <-time.After(10 * time.Second):
+			t.Fatal("timeout waiting for event")
+		case event := <-w.Events():
+			if got, want := event.Name, dbPath+"-wal"; got != want {
+				t.Fatalf("name=%s, want %s", got, want)
+			} else if got, want := event.Mask, internal.FileEventModified; got != want {
+				t.Fatalf("mask=0x%02x, want 0x%02x", got, want)
+			}
+		}
+
+		// Flush any duplicate events.
+		drainFileEventChannel(w.Events())
+
+		// Close database and ensure checkpointed WAL creates a "delete" event.
+		if err := db.Close(); err != nil {
+			t.Fatal(err)
+		}
+
+		select {
+		case <-time.After(10 * time.Second):
+			t.Fatal("timeout waiting for event")
+		case event := <-w.Events():
+			if got, want := event.Name, dbPath+"-wal"; got != want {
+				t.Fatalf("name=%s, want %s", got, want)
+			} else if got, want := event.Mask, internal.FileEventDeleted; got != want {
+				t.Fatalf("mask=0x%02x, want 0x%02x", got, want)
+			}
+		}
+	})
+
+	t.Run("LargeTx", func(t *testing.T) {
+		w := internal.NewFileWatcher()
+		if err := w.Open(); err != nil {
+			t.Fatal(err)
+		}
+		defer w.Close()
+
+		dbPath := filepath.Join(t.TempDir(), "db")
+		db, err := sql.Open("sqlite3", dbPath)
+		if err != nil {
+			t.Fatal(err)
+		} else if _, err := db.Exec(`PRAGMA cache_size = 4`); err != nil {
+			t.Fatal(err)
+		} else if _, err := db.Exec(`PRAGMA journal_mode = wal`); err != nil {
+			t.Fatal(err)
+		} else if _, err := db.Exec(`CREATE TABLE t (x)`); err != nil {
+			t.Fatal(err)
+		}
+		defer db.Close()
+
+		if err := w.Watch(dbPath + "-wal"); err != nil {
+			t.Fatal(err)
+		}
+
+		// Start a transaction to ensure writing large data creates multiple write events.
+		tx, err := db.Begin()
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer func() { _ = tx.Rollback() }()
+
+		// Write enough data to require a spill.
+		for i := 0; i < 100; i++ {
+			if _, err := tx.Exec(`INSERT INTO t (x) VALUES (?)`, strings.Repeat("x", 512)); err != nil {
+				t.Fatal(err)
+			}
+		}
+
+		// Ensure spill writes to disk.
+		select {
+		case <-time.After(10 * time.Second):
+			t.Fatal("timeout waiting for event")
+		case event := <-w.Events():
+			if got, want := event.Name, dbPath+"-wal"; got != want {
+				t.Fatalf("name=%s, want %s", got, want)
+			} else if got, want := event.Mask, internal.FileEventModified; got != want {
+				t.Fatalf("mask=0x%02x, want 0x%02x", got, want)
+			}
+		}
+
+		// Flush any duplicate events.
+		drainFileEventChannel(w.Events())
+
+		if err := tx.Commit(); err != nil {
+			t.Fatal(err)
+		}
+
+		// Final commit should spill remaining pages and cause another write event.
+		select {
+		case <-time.After(10 * time.Second):
+			t.Fatal("timeout waiting for event")
+		case event := <-w.Events():
+			if got, want := event.Name, dbPath+"-wal"; got != want {
+				t.Fatalf("name=%s, want %s", got, want)
+			} else if got, want := event.Mask, internal.FileEventModified; got != want {
+				t.Fatalf("mask=0x%02x, want 0x%02x", got, want)
+			}
+		}
+	})
+
+	t.Run("WatchBeforeCreate", func(t *testing.T) {
+		dbPath := filepath.Join(t.TempDir(), "db")
+
+		w := internal.NewFileWatcher()
+		if err := w.Open(); err != nil {
+			t.Fatal(err)
+		}
+		defer w.Close()
+
+		if err := w.Watch(dbPath); err != nil {
+			t.Fatal(err)
+		} else if err := w.Watch(dbPath + "-wal"); err != nil {
+			t.Fatal(err)
+		}
+
+		db, err := sql.Open("sqlite3", dbPath)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer db.Close()
+
+		if _, err := db.Exec(`CREATE TABLE t (x)`); err != nil {
+			t.Fatal(err)
+		}
+
+		// Wait for main database creation event.
+		waitForFileEvent(t, w.Events(), internal.FileEvent{Name: dbPath, Mask: internal.FileEventCreated})
+
+		// Write to the WAL file & ensure a "modified" event occurs.
+		if _, err := db.Exec(`PRAGMA journal_mode = wal`); err != nil {
+			t.Fatal(err)
+		} else if _, err := db.Exec(`INSERT INTO t (x) VALUES (1)`); err != nil {
+			t.Fatal(err)
+		}
+
+		// Wait for WAL creation event.
+		waitForFileEvent(t, w.Events(), internal.FileEvent{Name: dbPath + "-wal", Mask: internal.FileEventCreated})
+	})
+}
+
+func drainFileEventChannel(ch <-chan internal.FileEvent) {
+	for {
+		select {
+		case <-time.After(100 * time.Millisecond):
+			return
+		case <-ch:
+		}
+	}
+}
+
+func waitForFileEvent(tb testing.TB, ch <-chan internal.FileEvent, want internal.FileEvent) {
+	tb.Helper()
+
+	timeout := time.After(10 * time.Second)
+
+	for {
+		select {
+		case <-timeout:
+			tb.Fatalf("timeout waiting for event: %#v", want)
+		case got := <-ch:
+			if got == want {
+				return
+			}
+		}
+	}
+}