NeilClack
6fd5ec919c
- Set SQL connection idle limit to 1 to reduce resource usage - Explicitly define AppConfig table name to prevent GORM pluralization issues
114 lines
4.3 KiB
Go
114 lines
4.3 KiB
Go
// Package db provides a database connection and functions for interacting with the database.
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// The DB object should be held and maintained by the application, not by this package.
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// The application should be responsible for connecting to, migrating, and initial population
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// of the database. This package should only provide the schema definitions and helper functions.
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// Schema definitions should clone API response structures as closely as possible.
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package db
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import (
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"fmt"
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"os"
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"time"
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"gorm.io/driver/sqlite"
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"gorm.io/gorm"
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)
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const (
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connectMaxAttempts = 5
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connectRetryDelay = 500 * time.Millisecond
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)
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// Connect opens the SQLite database at dbpath with WAL mode and a hardened
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// lock-recovery strategy suitable for kiosk use where the process may have
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// crashed and left stale lock artefacts behind.
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func Connect(dbpath string) (*gorm.DB, error) {
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// ── Stale lock recovery ───────────────────────────────────────────────
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// SQLite WAL mode leaves a .db-wal and .db-shm alongside the main file.
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// If the previous process crashed, the OS releases file locks but the
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// artefacts remain. SQLite recovers them automatically on the next open,
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// UNLESS an OS-level advisory lock is still held (rare but possible on
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// Linux with certain crash patterns). Removing them before opening is
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// safe: SQLite treats absent WAL/SHM files as a clean slate and will
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// recreate them. We only do this if the main DB file already exists
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// (i.e. this is not a first-run) to avoid masking legitimate errors.
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if _, err := os.Stat(dbpath); err == nil {
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for _, ext := range []string{"-wal", "-shm"} {
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artefact := dbpath + ext
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if _, err := os.Stat(artefact); err == nil {
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if removeErr := os.Remove(artefact); removeErr != nil {
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// Non-fatal: log and continue — SQLite may still recover.
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fmt.Printf("[DB] warning: could not remove stale %s: %v\n", ext, removeErr)
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} else {
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fmt.Printf("[DB] removed stale lock artefact: %s\n", artefact)
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}
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}
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}
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}
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// ── Connection with retry ─────────────────────────────────────────────
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// Even after removing WAL/SHM, the main DB file itself may still be
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// briefly locked if another process is shutting down. Retry with
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// backoff before giving up.
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var (
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db *gorm.DB
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err error
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)
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for attempt := 1; attempt <= connectMaxAttempts; attempt++ {
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db, err = gorm.Open(sqlite.Open(dbpath), &gorm.Config{})
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if err == nil {
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break
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}
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if attempt == connectMaxAttempts {
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return nil, fmt.Errorf("database still locked after %d attempts: %w", connectMaxAttempts, err)
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}
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fmt.Printf("[DB] open attempt %d/%d failed (%v), retrying in %s\n",
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attempt, connectMaxAttempts, err, connectRetryDelay)
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time.Sleep(connectRetryDelay)
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}
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// ── Connection pool ───────────────────────────────────────────────────
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// SQLite does not support concurrent writers. Setting MaxOpenConns(1)
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// forces gorm to serialise all queries through a single connection,
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// preventing "database is locked" errors from competing goroutines
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// within this process. This is the single most important setting for
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// SQLite in a multi-goroutine application.
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sqlDB, err := db.DB()
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if err != nil {
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return nil, fmt.Errorf("could not get underlying sql.DB: %w", err)
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}
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sqlDB.SetMaxOpenConns(1)
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sqlDB.SetMaxIdleConns(1)
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// ── Pragmas ───────────────────────────────────────────────────────────
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pragmas := []string{
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"PRAGMA journal_mode=WAL",
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"PRAGMA synchronous=FULL",
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"PRAGMA foreign_keys=ON",
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// 5 s gives the serialised connection time to finish a long write
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// before returning SQLITE_BUSY to the application layer.
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"PRAGMA busy_timeout=5000",
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}
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for _, pragma := range pragmas {
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if _, err := sqlDB.Exec(pragma); err != nil {
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return nil, fmt.Errorf("failed to set %q: %w", pragma, err)
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}
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}
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return db, nil
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}
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// Migrate the database schema.
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func Migrate(db *gorm.DB) error {
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return db.AutoMigrate(
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&AppConfig{},
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&Log{},
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&Proclamation{},
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&ProclamationCategory{},
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&SolfeggioFrequency{},
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&AudioFile{},
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)
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}
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