1 files changed, 258 insertions, 0 deletions
diff --git a/internal/db/bundb/wrap.go b/internal/db/bundb/wrap.go
new file mode 100644
index 000000000..a5039914a
--- /dev/null
+++ b/internal/db/bundb/wrap.go
@@ -0,0 +1,258 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package bundb
+
+import (
+	"context"
+	"database/sql"
+	"time"
+
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/uptrace/bun"
+	"github.com/uptrace/bun/dialect"
+)
+
+// WrappedDB wraps a bun database instance
+// to provide common per-dialect SQL error
+// conversions to common types, and retries
+// on returned busy errors (SQLite only for now).
+type WrappedDB struct {
+	errHook func(error) error
+	*bun.DB // underlying conn
+}
+
+// WrapDB wraps a bun database instance in our own WrappedDB type.
+func WrapDB(db *bun.DB) *WrappedDB {
+	var errProc func(error) error
+	switch name := db.Dialect().Name(); name {
+	case dialect.PG:
+		errProc = processPostgresError
+	case dialect.SQLite:
+		errProc = processSQLiteError
+	default:
+		panic("unknown dialect name: " + name.String())
+	}
+	return &WrappedDB{
+		errHook: errProc,
+		DB:      db,
+	}
+}
+
+// BeginTx wraps bun.DB.BeginTx() with retry-busy timeout.
+func (db *WrappedDB) BeginTx(ctx context.Context, opts *sql.TxOptions) (tx bun.Tx, err error) {
+	err = retryOnBusy(ctx, func() error {
+		tx, err = db.DB.BeginTx(ctx, opts)
+		err = db.ProcessError(err)
+		return err
+	})
+	return
+}
+
+// ExecContext wraps bun.DB.ExecContext() with retry-busy timeout.
+func (db *WrappedDB) ExecContext(ctx context.Context, query string, args ...any) (result sql.Result, err error) {
+	err = retryOnBusy(ctx, func() error {
+		result, err = db.DB.ExecContext(ctx, query, args...)
+		err = db.ProcessError(err)
+		return err
+	})
+	return
+}
+
+// QueryContext wraps bun.DB.QueryContext() with retry-busy timeout.
+func (db *WrappedDB) QueryContext(ctx context.Context, query string, args ...any) (rows *sql.Rows, err error) {
+	err = retryOnBusy(ctx, func() error {
+		rows, err = db.DB.QueryContext(ctx, query, args...)
+		err = db.ProcessError(err)
+		return err
+	})
+	return
+}
+
+// QueryRowContext wraps bun.DB.QueryRowContext() with retry-busy timeout.
+func (db *WrappedDB) QueryRowContext(ctx context.Context, query string, args ...any) (row *sql.Row) {
+	_ = retryOnBusy(ctx, func() error {
+		row = db.DB.QueryRowContext(ctx, query, args...)
+		err := db.ProcessError(row.Err())
+		return err
+	})
+	return
+}
+
+// RunInTx is functionally the same as bun.DB.RunInTx() but with retry-busy timeouts.
+func (db *WrappedDB) RunInTx(ctx context.Context, fn func(bun.Tx) error) error {
+	// Attempt to start new transaction.
+	tx, err := db.BeginTx(ctx, nil)
+	if err != nil {
+		return err
+	}
+
+	var done bool
+
+	defer func() {
+		if !done {
+			// Rollback (with retry-backoff).
+			_ = retryOnBusy(ctx, func() error {
+				err := tx.Rollback()
+				return db.errHook(err)
+			})
+		}
+	}()
+
+	// Perform supplied transaction
+	if err := fn(tx); err != nil {
+		return db.errHook(err)
+	}
+
+	// Commit (with retry-backoff).
+	err = retryOnBusy(ctx, func() error {
+		err := tx.Commit()
+		return db.errHook(err)
+	})
+	done = true
+	return err
+}
+
+func (db *WrappedDB) NewValues(model interface{}) *bun.ValuesQuery {
+	return bun.NewValuesQuery(db.DB, model).Conn(db)
+}
+
+func (db *WrappedDB) NewMerge() *bun.MergeQuery {
+	return bun.NewMergeQuery(db.DB).Conn(db)
+}
+
+func (db *WrappedDB) NewSelect() *bun.SelectQuery {
+	return bun.NewSelectQuery(db.DB).Conn(db)
+}
+
+func (db *WrappedDB) NewInsert() *bun.InsertQuery {
+	return bun.NewInsertQuery(db.DB).Conn(db)
+}
+
+func (db *WrappedDB) NewUpdate() *bun.UpdateQuery {
+	return bun.NewUpdateQuery(db.DB).Conn(db)
+}
+
+func (db *WrappedDB) NewDelete() *bun.DeleteQuery {
+	return bun.NewDeleteQuery(db.DB).Conn(db)
+}
+
+func (db *WrappedDB) NewRaw(query string, args ...interface{}) *bun.RawQuery {
+	return bun.NewRawQuery(db.DB, query, args...).Conn(db)
+}
+
+func (db *WrappedDB) NewCreateTable() *bun.CreateTableQuery {
+	return bun.NewCreateTableQuery(db.DB).Conn(db)
+}
+
+func (db *WrappedDB) NewDropTable() *bun.DropTableQuery {
+	return bun.NewDropTableQuery(db.DB).Conn(db)
+}
+
+func (db *WrappedDB) NewCreateIndex() *bun.CreateIndexQuery {
+	return bun.NewCreateIndexQuery(db.DB).Conn(db)
+}
+
+func (db *WrappedDB) NewDropIndex() *bun.DropIndexQuery {
+	return bun.NewDropIndexQuery(db.DB).Conn(db)
+}
+
+func (db *WrappedDB) NewTruncateTable() *bun.TruncateTableQuery {
+	return bun.NewTruncateTableQuery(db.DB).Conn(db)
+}
+
+func (db *WrappedDB) NewAddColumn() *bun.AddColumnQuery {
+	return bun.NewAddColumnQuery(db.DB).Conn(db)
+}
+
+func (db *WrappedDB) NewDropColumn() *bun.DropColumnQuery {
+	return bun.NewDropColumnQuery(db.DB).Conn(db)
+}
+
+// ProcessError processes an error to replace any known values with our own error types,
+// making it easier to catch specific situations (e.g. no rows, already exists, etc)
+func (db *WrappedDB) ProcessError(err error) error {
+	if err == nil {
+		return nil
+	}
+	return db.errHook(err)
+}
+
+// Exists checks the results of a SelectQuery for the existence of the data in question, masking ErrNoEntries errors
+func (db *WrappedDB) Exists(ctx context.Context, query *bun.SelectQuery) (bool, error) {
+	exists, err := query.Exists(ctx)
+	switch err {
+	case nil:
+		return exists, nil
+	case sql.ErrNoRows:
+		return false, nil
+	default:
+		return false, err
+	}
+}
+
+// NotExists is the functional opposite of conn.Exists()
+func (db *WrappedDB) NotExists(ctx context.Context, query *bun.SelectQuery) (bool, error) {
+	exists, err := db.Exists(ctx, query)
+	return !exists, err
+}
+
+// retryOnBusy will retry given function on returned 'errBusy'.
+func retryOnBusy(ctx context.Context, fn func() error) error {
+	var backoff time.Duration
+
+	for i := 0; ; i++ {
+		// Perform func.
+		err := fn()
+
+		if err != errBusy {
+			// May be nil, or may be
+			// some other error, either
+			// way return here.
+			return err
+		}
+
+		// backoff according to a multiplier of 2ms * 2^2n,
+		// up to a maximum possible backoff time of 5 minutes.
+		//
+		// this works out as the following:
+		// 4ms
+		// 16ms
+		// 64ms
+		// 256ms
+		// 1.024s
+		// 4.096s
+		// 16.384s
+		// 1m5.536s
+		// 4m22.144s
+		backoff = 2 * time.Millisecond * (1 << (2*i + 1))
+		if backoff >= 5*time.Minute {
+			break
+		}
+
+		select {
+		// Context cancelled.
+		case <-ctx.Done():
+
+		// Backoff for some time.
+		case <-time.After(backoff):
+		}
+	}
+
+	return gtserror.Newf("%w (waited > %s)", db.ErrBusyTimeout, backoff)
+}