Run SQLite in WAL mode with a busy timeout the driver reads (closes #123)

The default database URL asked for WAL mode with `_journal_mode` and
`_busy_timeout`, which the SQLite driver does not read, so the database
ran in rollback-journal mode. The default now uses the driver's
`_pragma=journal_mode(WAL)` and `_pragma=busy_timeout(5000)` parameters,
in one constant that both the config default and the database fallback
use. The database no longer sets its own busy timeout after opening, so
the URL's value applies. A new test opens a file database with those
parameters through db.New and checks the journal mode and busy timeout.
README.md's database text now matches, and an in-memory test database
drops the same ignored parameter.

Model: opus-5-5
Co-authored-by: clawbot <sneak+clawbot@sneak.cloud>

README.md

@@ -2582,9 +2582,9 @@ environment variable wins over the file. An environment variable set to the
 empty string counts as unset, so the file's value or the default applies.
 
 | Variable               | Type   | Default                                                                                | Description                                                                                                                                                                                                                                                                             |
-| ---------------------- | ------ | --------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| ---------------------- | ------ | -------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
 | `PORT`                 | int    | `8080`                                                                                 | HTTP listen port                                                                                                                                                                                                                                                                        |
-| `DBURL`                | string | `file:///var/lib/neoirc/state.db?_journal_mode=WAL` | SQLite connection string. For file-based: `file:///path/to/db.db?_journal_mode=WAL`. For in-memory (testing): `file::memory:?cache=shared`. The SQLite driver ignores `_journal_mode`, so this does not turn on WAL mode.                                                               |
+| `DBURL`                | string | `file:///var/lib/neoirc/state.db?_pragma=journal_mode(WAL)&_pragma=busy_timeout(5000)` | SQLite connection string. For file-based: `file:///path/to/db.db?_pragma=journal_mode(WAL)&_pragma=busy_timeout(5000)`. For in-memory (testing): `file::memory:?cache=shared`. See [SQLite Considerations](#sqlite-considerations).                                                     |
 | `DEBUG`                | bool   | `false`                                                                                | Switch logging to debug level                                                                                                                                                                                                                                                           |
 | `MESSAGE_MAX_AGE`      | string | `720h`                                                                                 | Maximum age of messages as a Go duration string (e.g. `720h`, `24h`). Messages older than this are pruned. Default is 30 days.                                                                                                                                                          |
 | `SESSION_IDLE_TIMEOUT` | string | `720h`                                                                                 | Idle timeout as a Go duration string (e.g. `720h`, `24h`). Clients with no authenticated HTTP API request or IRC listener command for this long are removed, and a session left with none is expired and its nick released (see [Data Lifecycle](#data-lifecycle)). Default is 30 days. |
@@ -2611,7 +2611,7 @@ PORT=8080
 SERVER_NAME=My NeoIRC Server
 MOTD=Welcome! Be excellent to each other.
 DEBUG=false
-DBURL=file:///var/lib/neoirc/state.db?_journal_mode=WAL
+DBURL=file:///var/lib/neoirc/state.db?_pragma=journal_mode(WAL)&_pragma=busy_timeout(5000)
 SESSION_IDLE_TIMEOUT=720h
 NEOIRC_HASHCASH_BITS=20
 ```
@@ -2821,14 +2821,17 @@ seconds to accommodate long-poll connections.
 
 ### SQLite Considerations
 
-- **Journal mode**: the default connection string carries `?_journal_mode=WAL`,
+- **Journal mode**: the default connection string runs the database in WAL mode
-  but the SQLite driver ignores that parameter, so the database runs in SQLite's
+  with a 5000 ms busy timeout, through the SQLite driver's
-  default rollback-journal mode, not WAL.
+  `_pragma=journal_mode(WAL)` and `_pragma=busy_timeout(5000)` parameters. A
+  `DBURL` of your own should keep both.
 - **Single writer**: the server uses one database connection, so reads and
   writes take turns. For high-traffic servers, Postgres support is planned.
-- **Backup**: The database is a single file. Back it up with
+- **Backup**: Back the database up with
-  `sqlite3 /var/lib/neoirc/state.db ".backup backup.db"`, or copy the file while
+  `sqlite3 /var/lib/neoirc/state.db ".backup backup.db"`, or copy `state.db`
-  the server is stopped.
+  while the server is stopped, together with `state.db-wal` if one is left
+  beside it: in WAL mode that file holds recent writes not yet folded into
+  `state.db`.
 - **Location**: By default, `state.db` is created in `/var/lib/neoirc/`. Use the
   `DBURL` env var to place it elsewhere.
 

internal/config/config.go

@@ -21,6 +21,12 @@ const defaultMOTD = ` _ __   ___  ___  (_)_ __ ___
 Welcome to NeoIRC — IRC semantics over HTTP.
 Type /help for available commands.`
 
+// DefaultDBURL is the database URL used when DBURL is not set. Its
+// _pragma parameters, which the SQLite driver runs on every connection
+// it opens, set WAL mode and a 5000 ms busy timeout.
+const DefaultDBURL = "file:///var/lib/neoirc/state.db" +
+	"?_pragma=journal_mode(WAL)&_pragma=busy_timeout(5000)"
+
 // Params defines the dependencies for creating a Config.
 type Params struct {
 	fx.In
@@ -71,7 +77,7 @@ func New(
 	viper.SetDefault("DEBUG", "false")
 	viper.SetDefault("MAINTENANCE_MODE", "false")
 	viper.SetDefault("PORT", "8080")
-	viper.SetDefault("DBURL", "file:///var/lib/neoirc/state.db?_journal_mode=WAL")
+	viper.SetDefault("DBURL", DefaultDBURL)
 	viper.SetDefault("SENTRY_DSN", "")
 	viper.SetDefault("METRICS_USERNAME", "")
 	viper.SetDefault("METRICS_PASSWORD", "")

internal/db/db.go

@@ -87,7 +87,7 @@ func (database *Database) GetDB() *sql.DB {
 func (database *Database) connect(ctx context.Context) error {
 	dbURL := database.params.Config.DBURL
 	if dbURL == "" {
-		dbURL = "file:///var/lib/neoirc/state.db?_journal_mode=WAL&_busy_timeout=5000"
+		dbURL = config.DefaultDBURL
 	}
 
 	database.log.Info(
@@ -116,13 +116,6 @@ func (database *Database) connect(ctx context.Context) error {
 		return fmt.Errorf("enable foreign keys: %w", err)
 	}
 
-	_, err = database.conn.ExecContext(
-		ctx, "PRAGMA busy_timeout = 5000",
-	)
-	if err != nil {
-		return fmt.Errorf("set busy timeout: %w", err)
-	}
-
 	return database.runMigrations(ctx)
 }
 

internal/db/db_test.go

@@ -0,0 +1,75 @@
+package db_test
+
+import (
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"go.uber.org/fx/fxtest"
+	"sneak.berlin/go/neoirc/internal/config"
+	"sneak.berlin/go/neoirc/internal/db"
+	"sneak.berlin/go/neoirc/internal/globals"
+	"sneak.berlin/go/neoirc/internal/logger"
+)
+
+const wantBusyTimeoutMS = 5000
+
+// TestDefaultDBURLSetsWALAndBusyTimeout opens a file database
+// with the default URL's parameters the way the server does,
+// and checks the journal mode and busy timeout it ends up with.
+func TestDefaultDBURLSetsWALAndBusyTimeout(t *testing.T) {
+	t.Parallel()
+
+	_, params, _ := strings.Cut(config.DefaultDBURL, "?")
+	dbURL := "file://" + filepath.Join(t.TempDir(), "state.db") +
+		"?" + params
+
+	lifecycle := fxtest.NewLifecycle(t)
+
+	log, err := logger.New(lifecycle, logger.Params{
+		Globals: &globals.Globals{},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	database, err := db.New(lifecycle, db.Params{
+		Logger: log,
+		Config: &config.Config{DBURL: dbURL},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	lifecycle.RequireStart()
+	t.Cleanup(lifecycle.RequireStop)
+
+	var journalMode string
+
+	err = database.GetDB().QueryRowContext(
+		t.Context(), "PRAGMA journal_mode",
+	).Scan(&journalMode)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if journalMode != "wal" {
+		t.Errorf("journal_mode = %q, want %q", journalMode, "wal")
+	}
+
+	var busyTimeout int
+
+	err = database.GetDB().QueryRowContext(
+		t.Context(), "PRAGMA busy_timeout",
+	).Scan(&busyTimeout)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if busyTimeout != wantBusyTimeoutMS {
+		t.Errorf(
+			"busy_timeout = %d, want %d",
+			busyTimeout, wantBusyTimeoutMS,
+		)
+	}
+}

internal/ircserver/server_test.go

@@ -73,7 +73,7 @@ func newTestEnvWithConfig(
 	// A random name, so that no other test environment, not
 	// even an earlier run of the same test, can share it.
 	dsn := fmt.Sprintf(
-		"file:%s?mode=memory&cache=shared&_journal_mode=WAL",
+		"file:%s?mode=memory&cache=shared",
 		rand.Text(),
 	)