feat: persist queued server commands

internal/server/store/command.go

@@ -0,0 +1,142 @@
+package store
+
+import (
+	"context"
+	"crypto/subtle"
+	"database/sql"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/klauspost/compress/zstd"
+	"github.com/rvbox/rvbox/internal/domain"
+)
+
+var (
+	ErrCommandConflict = errors.New("command UUID conflicts with immutable request")
+	ErrClientNotFound  = errors.New("target client does not exist")
+)
+
+// QueueCommandInput is the already-validated immutable command payload. The
+// control boundary validates and serializes the ExecutionSpec before it enters
+// this storage layer; the store owns only durable admission and quota charging.
+type QueueCommandInput struct {
+	IssueUUID       domain.UUID
+	ClientID        string
+	IssueTime       time.Time
+	ReceiptTime     time.Time
+	QueueExpiryTime *time.Time
+	ImmutableSHA256 [32]byte
+	ExecutionSpec   []byte
+}
+
+type QueueCommandResult struct {
+	Duplicate bool
+	Lifecycle uint32
+	Revision  uint64
+}
+
+// QueueCommand atomically persists a queued command before it is visible to a
+// dispatcher. Repeating the same UUID/hash is idempotent; a different hash is
+// a hard conflict and cannot replace a previously admitted command.
+func (store *Store) QueueCommand(ctx context.Context, input QueueCommandInput) (QueueCommandResult, error) {
+	if !validCommandInput(input) {
+		return QueueCommandResult{}, errors.New("invalid queued command")
+	}
+	stored, err := compressCommandSpec(input.ExecutionSpec)
+	if err != nil {
+		return QueueCommandResult{}, err
+	}
+	charge, err := EstimateCharge(ChargeInput{EncodedBytes: uint64(len(stored)), SQLiteRows: 1, IndexEntries: 2})
+	if err != nil {
+		return QueueCommandResult{}, err
+	}
+
+	store.writeMu.Lock()
+	defer store.writeMu.Unlock()
+	database, err := store.openDatabase()
+	if err != nil {
+		return QueueCommandResult{}, err
+	}
+	tx, err := database.BeginTx(ctx, nil)
+	if err != nil {
+		return QueueCommandResult{}, err
+	}
+	defer tx.Rollback()
+
+	var storedHash []byte
+	var lifecycle uint32
+	var revision uint64
+	err = tx.QueryRowContext(ctx, `SELECT immutable_request_sha256, lifecycle, revision FROM commands WHERE issue_uuid = ?`, input.IssueUUID[:]).Scan(&storedHash, &lifecycle, &revision)
+	if err == nil {
+		if len(storedHash) != len(input.ImmutableSHA256) || subtle.ConstantTimeCompare(storedHash, input.ImmutableSHA256[:]) != 1 {
+			return QueueCommandResult{}, ErrCommandConflict
+		}
+		return QueueCommandResult{Duplicate: true, Lifecycle: lifecycle, Revision: revision}, tx.Commit()
+	}
+	if !errors.Is(err, sql.ErrNoRows) {
+		return QueueCommandResult{}, err
+	}
+
+	var clientCharged, serverCharged uint64
+	err = tx.QueryRowContext(ctx, `SELECT clients.charged_bytes, storage_counters.command_charged_bytes
+FROM clients JOIN storage_counters ON storage_counters.singleton = 1 WHERE clients.client_id = ?`, input.ClientID).Scan(&clientCharged, &serverCharged)
+	if errors.Is(err, sql.ErrNoRows) {
+		return QueueCommandResult{}, ErrClientNotFound
+	}
+	if err != nil {
+		return QueueCommandResult{}, err
+	}
+	freeBytes, err := store.freeSpaceProbe.AvailableBytes(store.dataDir)
+	if err != nil {
+		return QueueCommandResult{}, fmt.Errorf("check filesystem capacity: %w", err)
+	}
+	decision, err := CheckReservation(store.quotaLimits, ReservationState{
+		ClientTotalCharged: clientCharged, ServerTotalCharged: serverCharged,
+		CloseoutRemaining: store.quotaLimits.CloseoutReserveBytes, FilesystemFreeBytes: freeBytes,
+	}, ReservationRequest{ChargedBytes: charge, PhysicalBytes: uint64(len(stored))})
+	if err != nil {
+		return QueueCommandResult{}, err
+	}
+	var expiry any
+	if input.QueueExpiryTime != nil {
+		expiry = input.QueueExpiryTime.UTC().UnixNano()
+	}
+	_, err = tx.ExecContext(ctx, `INSERT INTO commands (
+issue_uuid, client_id, issue_time, server_receipt_time, queue_expiry_time,
+lifecycle, revision, retained_compressed_bytes, charged_bytes,
+closeout_remaining_bytes, immutable_request_sha256, execution_spec,
+execution_spec_raw_bytes, execution_spec_stored_bytes, execution_spec_compression
+) VALUES (?, ?, ?, ?, ?, 1, 1, ?, ?, ?, ?, ?, ?, ?, 2)`,
+		input.IssueUUID[:], input.ClientID, input.IssueTime.UTC().UnixNano(), input.ReceiptTime.UTC().UnixNano(), expiry,
+		len(stored), charge, decision.CloseoutRemaining, input.ImmutableSHA256[:], stored, len(input.ExecutionSpec), len(stored))
+	if err != nil {
+		return QueueCommandResult{}, err
+	}
+	if _, err := tx.ExecContext(ctx, `UPDATE clients SET charged_bytes = ? WHERE client_id = ?`, decision.ClientTotalCharged, input.ClientID); err != nil {
+		return QueueCommandResult{}, err
+	}
+	if _, err := tx.ExecContext(ctx, `UPDATE storage_counters SET command_charged_bytes = ? WHERE singleton = 1`, decision.ServerTotalCharged); err != nil {
+		return QueueCommandResult{}, err
+	}
+	if err := tx.Commit(); err != nil {
+		return QueueCommandResult{}, err
+	}
+	return QueueCommandResult{Lifecycle: 1, Revision: 1}, nil
+}
+
+func validCommandInput(input QueueCommandInput) bool {
+	if isZeroUUID([16]byte(input.IssueUUID)) || input.ClientID == "" || len(input.ClientID) > 128 || input.IssueTime.IsZero() || input.ReceiptTime.IsZero() || len(input.ExecutionSpec) == 0 || allZero(input.ImmutableSHA256[:]) {
+		return false
+	}
+	return input.QueueExpiryTime == nil || input.QueueExpiryTime.After(input.IssueTime)
+}
+
+func compressCommandSpec(spec []byte) ([]byte, error) {
+	encoder, err := zstd.NewWriter(nil, zstd.WithEncoderConcurrency(1))
+	if err != nil {
+		return nil, err
+	}
+	defer encoder.Close()
+	return encoder.EncodeAll(spec, nil), nil
+}