CheckTx

CheckTx is called by the BaseApp when comet receives a transaction from a client, over the p2p network or RPC. The CheckTx method is responsible for validating the transaction and returning an error if the transaction is invalid.

baseapp/abci.go

// CheckTx implements the ABCI interface and executes a tx in CheckTx mode. In
// CheckTx mode, messages are not executed. This means messages are only validated
// and only the AnteHandler is executed. State is persisted to the BaseApp's
// internal CheckTx state if the AnteHandler passes. Otherwise, the ResponseCheckTx
// will contain relevant error information. Regardless of tx execution outcome,
// the ResponseCheckTx will contain relevant gas execution context.
func (app *BaseApp) CheckTx(req *abci.CheckTxRequest) (*abci.CheckTxResponse, error) {
	var mode execMode

	switch {
	case req.Type == abci.CHECK_TX_TYPE_CHECK:
		mode = execModeCheck

	case req.Type == abci.CHECK_TX_TYPE_RECHECK:
		mode = execModeReCheck

	default:
		return nil, fmt.Errorf("unknown RequestCheckTx type: %s", req.Type)
	}

	if app.checkTxHandler == nil {
		gInfo, result, anteEvents, err := app.runTx(mode, req.Tx, nil)
		if err != nil {
			return responseCheckTxWithEvents(err, gInfo.GasWanted, gInfo.GasUsed, anteEvents, app.trace), nil
		}

		return &abci.CheckTxResponse{
			GasWanted: int64(gInfo.GasWanted), // TODO: Should type accept unsigned ints?
			GasUsed:   int64(gInfo.GasUsed),   // TODO: Should type accept unsigned ints?
			Log:       result.Log,
			Data:      result.Data,
			Events:    sdk.MarkEventsToIndex(result.Events, app.indexEvents),
		}, nil
	}

	return app.checkTxHandler(app.runTx, req)
}

// PrepareProposal implements the PrepareProposal ABCI method and returns a
// ResponsePrepareProposal object to the client. The PrepareProposal method is
// responsible for allowing the block proposer to perform application-dependent

See full example on GitHub

CheckTx Handler

CheckTxHandler allows users to extend the logic of CheckTx. CheckTxHandler is called by pasding context and the transaction bytes received through ABCI. It is required that the handler returns deterministic results given the same transaction bytes.

note

we return the raw decoded transaction here to avoid decoding it twice.

type CheckTxHandler func(ctx sdk.Context, tx []byte) (Tx, error)

Setting a custom CheckTxHandler is optional. It can be done from your app.go file:

func NewSimApp(
    logger log.Logger,
    db corestore.KVStoreWithBatch,
    traceStore io.Writer,
    loadLatest bool,
    appOpts servertypes.AppOptions,
    baseAppOptions ...func(*baseapp.BaseApp),
) *SimApp {
  ...
  // Create ChecktxHandler
  checktxHandler := abci.NewCustomCheckTxHandler(...)
  app.SetCheckTxHandler(checktxHandler)
  ...
}