feat: use postgres

mail/internal/adapters/postgres/mailstore/store.go

@@ -0,0 +1,119 @@
+// Package mailstore implements the PostgreSQL-backed source-of-truth
+// persistence used by Mail Service.
+//
+// The package owns the on-disk shape of the `mail` schema (defined in
+// `galaxy/mail/internal/adapters/postgres/migrations`) and translates the
+// schema-agnostic Store interfaces declared by each `internal/service/*` use
+// case into concrete `database/sql` operations driven by the pgx driver.
+// Atomic composite operations (acceptance, render, attempt commit, resend)
+// execute inside explicit `BEGIN … COMMIT` transactions; the attempt
+// scheduler's claim path uses `SELECT … FOR UPDATE SKIP LOCKED` to coordinate
+// across multiple worker processes.
+//
+// Stage 4 of `PG_PLAN.md` migrates Mail Service away from Redis-backed
+// durable state. The inbound `mail:delivery_commands` Redis Stream and its
+// consumer offset remain on Redis; the store is no longer aware of them.
+package mailstore
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+	"time"
+)
+
+// Config configures one PostgreSQL-backed mail store instance. The store does
+// not own the underlying *sql.DB lifecycle: the caller (typically the service
+// runtime) opens, instruments, migrates, and closes the pool. The store only
+// borrows the pool and bounds individual round trips with OperationTimeout.
+type Config struct {
+	// DB stores the connection pool the store uses for every query.
+	DB *sql.DB
+
+	// OperationTimeout bounds one round trip. The store creates a derived
+	// context for each operation so callers cannot starve the pool with an
+	// unbounded ctx. Multi-statement transactions inherit this bound for the
+	// whole BEGIN … COMMIT span.
+	OperationTimeout time.Duration
+}
+
+// Store persists Mail Service durable state in PostgreSQL and exposes the
+// per-use-case Store interfaces required by acceptance, render, execution,
+// operator listing, and the attempt scheduler.
+type Store struct {
+	db               *sql.DB
+	operationTimeout time.Duration
+}
+
+// New constructs one PostgreSQL-backed mail store from cfg.
+func New(cfg Config) (*Store, error) {
+	if cfg.DB == nil {
+		return nil, errors.New("new postgres mail store: db must not be nil")
+	}
+	if cfg.OperationTimeout <= 0 {
+		return nil, errors.New("new postgres mail store: operation timeout must be positive")
+	}
+	return &Store{
+		db:               cfg.DB,
+		operationTimeout: cfg.OperationTimeout,
+	}, nil
+}
+
+// Close is a no-op for the PostgreSQL-backed store: the connection pool is
+// owned by the caller (the runtime) and closed once the runtime shuts down.
+// The accessor remains so the runtime wiring can treat the store like the
+// previous Redis-backed implementation.
+func (store *Store) Close() error {
+	return nil
+}
+
+// Ping verifies that the configured PostgreSQL backend is reachable. It runs
+// `db.PingContext` under the configured operation timeout.
+func (store *Store) Ping(ctx context.Context) error {
+	operationCtx, cancel, err := withTimeout(ctx, "ping postgres mail store", store.operationTimeout)
+	if err != nil {
+		return err
+	}
+	defer cancel()
+
+	if err := store.db.PingContext(operationCtx); err != nil {
+		return fmt.Errorf("ping postgres mail store: %w", err)
+	}
+	return nil
+}
+
+// withTx runs fn inside a BEGIN … COMMIT transaction bounded by the store's
+// operation timeout. It rolls back on any error or panic and returns whatever
+// fn returned. The transaction uses the default isolation level (`READ
+// COMMITTED`); per-row locking is achieved through `SELECT … FOR UPDATE`
+// issued inside fn.
+func (store *Store) withTx(ctx context.Context, operation string, fn func(ctx context.Context, tx *sql.Tx) error) error {
+	operationCtx, cancel, err := withTimeout(ctx, operation, store.operationTimeout)
+	if err != nil {
+		return err
+	}
+	defer cancel()
+
+	tx, err := store.db.BeginTx(operationCtx, nil)
+	if err != nil {
+		return fmt.Errorf("%s: begin: %w", operation, err)
+	}
+
+	if err := fn(operationCtx, tx); err != nil {
+		_ = tx.Rollback()
+		return err
+	}
+
+	if err := tx.Commit(); err != nil {
+		return fmt.Errorf("%s: commit: %w", operation, err)
+	}
+	return nil
+}
+
+// operationContext bounds one read or write that does not need a transaction
+// envelope (single statement). It mirrors store.withTx for non-transactional
+// callers.
+func (store *Store) operationContext(ctx context.Context, operation string) (context.Context, context.CancelFunc, error) {
+	return withTimeout(ctx, operation, store.operationTimeout)
+}