Method BeginTx

src/bccore/volapi.go:50–130

(ctx context.Context, volh blobcache.Handle, txspec blobcache.TxParams)

}

func (sys *System) BeginTx(ctx context.Context, volh blobcache.Handle, txspec blobcache.TxParams) (*blobcache.Handle, error) {
	logctx.Info(ctx, "begin", zap.String("method", "BeginTx"), zap.Stringer("oid", volh.OID))
	defer logctx.Info(ctx, "done", zap.String("method", "BeginTx"), zap.Stringer("oid", volh.OID))
	if err := txspec.Validate(); err != nil {
		return nil, err
	}
	vol, rights, err := sys.resolveVol(volh)
	if err != nil {
		return nil, err
	}
	if !rights.Has(blobcache.Action_VOLUME_BEGIN_TX) {
		return nil, blobcache.ErrPermission{
			Handle:   volh,
			Rights:   rights,
			Requires: blobcache.Action_VOLUME_BEGIN_TX,
		}
	}
	if txspec.GCBlobs {
		gcBlobRights := blobcache.ActionSet(blobcache.Action_VOLUME_TX_VISIT | blobcache.Action_VOLUME_TX_IS_VISITED)
		if rights&gcBlobRights == 0 {
			return nil, blobcache.ErrPermission{
				Handle:   volh,
				Rights:   rights,
				Requires: gcBlobRights,
			}
		}
	}
	if txspec.Modify {
		mutatingRights := blobcache.ActionSet(blobcache.Action_VOLUME_TX_SAVE |
			blobcache.Action_VOLUME_TX_POST |
			blobcache.Action_VOLUME_TX_DELETE |
			blobcache.Action_VOLUME_TX_COPY_TO |
			blobcache.Action_VOLUME_TX_LINK_FROM |
			blobcache.Action_VOLUME_TX_UNLINK_FROM |
			blobcache.Action_VOLUME_TX_VISIT |
			blobcache.Action_VOLUME_TX_VISIT_LINKS)
		if rights&mutatingRights == 0 {
			return nil, blobcache.ErrPermission{
				Handle:   volh,
				Rights:   rights,
				Requires: mutatingRights,
			}
		}
	}
	tx, err := vol.backend.BeginTx(ctx, txspec)
	if err != nil {
		return nil, err
	}

	txoid := blobcache.RandomOID()
	sys.mu.Lock()
	if sys.txns == nil {
		sys.txns = make(map[blobcache.OID]transaction)
	}
	sys.txns[txoid] = transaction{
		backend: tx,
		volume:  &vol,
	}