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waiter.go
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waiter.go
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package actor
import (
"context"
"errors"
"fmt"
"strings"
"time"
"github.com/nspcc-dev/neo-go/pkg/core/block"
"github.com/nspcc-dev/neo-go/pkg/core/state"
"github.com/nspcc-dev/neo-go/pkg/neorpc"
"github.com/nspcc-dev/neo-go/pkg/neorpc/result"
"github.com/nspcc-dev/neo-go/pkg/smartcontract/trigger"
"github.com/nspcc-dev/neo-go/pkg/util"
)
// PollingWaiterRetryCount is a threshold for a number of subsequent failed
// attempts to get block count from the RPC server for PollingWaiter. If it fails
// to retrieve block count PollingWaiterRetryCount times in a raw then transaction
// awaiting attempt considered to be failed and an error is returned.
const PollingWaiterRetryCount = 3
var (
// ErrTxNotAccepted is returned when transaction wasn't accepted to the chain
// even after ValidUntilBlock block persist.
ErrTxNotAccepted = errors.New("transaction was not accepted to chain")
// ErrContextDone is returned when Waiter context has been done in the middle
// of transaction awaiting process and no result was received yet.
ErrContextDone = errors.New("waiter context done")
// ErrAwaitingNotSupported is returned from Wait method if Waiter instance
// doesn't support transaction awaiting.
ErrAwaitingNotSupported = errors.New("awaiting not supported")
// ErrMissedEvent is returned when RPCEventWaiter closes receiver channel
// which happens if missed event was received from the RPC server.
ErrMissedEvent = errors.New("some event was missed")
)
type (
// Waiter is an interface providing transaction awaiting functionality to Actor.
Waiter interface {
// Wait allows to wait until transaction will be accepted to the chain. It can be
// used as a wrapper for Send or SignAndSend and accepts transaction hash,
// ValidUntilBlock value and an error. It returns transaction execution result
// or an error if transaction wasn't accepted to the chain. Notice that "already
// exists" err value is not treated as an error by this routine because it
// means that the transactions given might be already accepted or soon going
// to be accepted. Such transaction can be waited for in a usual way, potentially
// with positive result, so that's what will happen.
Wait(h util.Uint256, vub uint32, err error) (*state.AppExecResult, error)
// WaitAny waits until at least one of the specified transactions will be accepted
// to the chain until vub (including). It returns execution result of this
// transaction or an error if none of the transactions was accepted to the chain.
// It uses underlying RPCPollingWaiter or RPCEventWaiter context to interrupt
// awaiting process, but additional ctx can be passed as an argument for the same
// purpose.
WaitAny(ctx context.Context, vub uint32, hashes ...util.Uint256) (*state.AppExecResult, error)
}
// RPCPollingWaiter is an interface that enables transaction awaiting functionality
// for Actor instance based on periodical BlockCount and ApplicationLog polls.
RPCPollingWaiter interface {
// Context should return the RPC client context to be able to gracefully
// shut down all running processes (if so).
Context() context.Context
GetVersion() (*result.Version, error)
GetBlockCount() (uint32, error)
GetApplicationLog(hash util.Uint256, trig *trigger.Type) (*result.ApplicationLog, error)
}
// RPCEventWaiter is an interface that enables improved transaction awaiting functionality
// for Actor instance based on web-socket Block and ApplicationLog notifications. RPCEventWaiter
// contains RPCPollingWaiter under the hood and falls back to polling when subscription-based
// awaiting fails.
RPCEventWaiter interface {
RPCPollingWaiter
ReceiveBlocks(flt *neorpc.BlockFilter, rcvr chan<- *block.Block) (string, error)
ReceiveExecutions(flt *neorpc.ExecutionFilter, rcvr chan<- *state.AppExecResult) (string, error)
Unsubscribe(id string) error
}
)
// NullWaiter is a Waiter stub that doesn't support transaction awaiting functionality.
type NullWaiter struct{}
// PollingWaiter is a polling-based Waiter.
type PollingWaiter struct {
polling RPCPollingWaiter
version *result.Version
}
// EventWaiter is a websocket-based Waiter.
type EventWaiter struct {
ws RPCEventWaiter
polling Waiter
}
// errIsAlreadyExists is a temporary helper until we have #2248 solved. Both C#
// and Go nodes return this string (possibly among other data).
func errIsAlreadyExists(err error) bool {
return strings.Contains(strings.ToLower(err.Error()), "already exists")
}
// newWaiter creates Waiter instance. It can be either websocket-based or
// polling-base, otherwise Waiter stub is returned.
func newWaiter(ra RPCActor, v *result.Version) Waiter {
if eventW, ok := ra.(RPCEventWaiter); ok {
return &EventWaiter{
ws: eventW,
polling: &PollingWaiter{
polling: eventW,
version: v,
},
}
}
if pollW, ok := ra.(RPCPollingWaiter); ok {
return &PollingWaiter{
polling: pollW,
version: v,
}
}
return NewNullWaiter()
}
// NewNullWaiter creates an instance of Waiter stub.
func NewNullWaiter() NullWaiter {
return NullWaiter{}
}
// Wait implements Waiter interface.
func (NullWaiter) Wait(h util.Uint256, vub uint32, err error) (*state.AppExecResult, error) {
return nil, ErrAwaitingNotSupported
}
// WaitAny implements Waiter interface.
func (NullWaiter) WaitAny(ctx context.Context, vub uint32, hashes ...util.Uint256) (*state.AppExecResult, error) {
return nil, ErrAwaitingNotSupported
}
// NewPollingWaiter creates an instance of Waiter supporting poll-based transaction awaiting.
func NewPollingWaiter(waiter RPCPollingWaiter) (*PollingWaiter, error) {
v, err := waiter.GetVersion()
if err != nil {
return nil, err
}
return &PollingWaiter{
polling: waiter,
version: v,
}, nil
}
// Wait implements Waiter interface.
func (w *PollingWaiter) Wait(h util.Uint256, vub uint32, err error) (*state.AppExecResult, error) {
if err != nil && !errIsAlreadyExists(err) {
return nil, err
}
return w.WaitAny(context.TODO(), vub, h)
}
// WaitAny implements Waiter interface.
func (w *PollingWaiter) WaitAny(ctx context.Context, vub uint32, hashes ...util.Uint256) (*state.AppExecResult, error) {
var (
currentHeight uint32
failedAttempt int
pollTime = time.Millisecond * time.Duration(w.version.Protocol.MillisecondsPerBlock) / 2
)
if pollTime == 0 {
pollTime = time.Second
}
timer := time.NewTicker(pollTime)
defer timer.Stop()
for {
select {
case <-timer.C:
blockCount, err := w.polling.GetBlockCount()
if err != nil {
failedAttempt++
if failedAttempt > PollingWaiterRetryCount {
return nil, fmt.Errorf("failed to retrieve block count: %w", err)
}
continue
}
failedAttempt = 0
if blockCount-1 > currentHeight {
currentHeight = blockCount - 1
}
t := trigger.Application
for _, h := range hashes {
res, err := w.polling.GetApplicationLog(h, &t)
if err == nil {
return &state.AppExecResult{
Container: res.Container,
Execution: res.Executions[0],
}, nil
}
}
if currentHeight >= vub {
return nil, ErrTxNotAccepted
}
case <-w.polling.Context().Done():
return nil, fmt.Errorf("%w: %v", ErrContextDone, w.polling.Context().Err()) //nolint:errorlint // errorlint: non-wrapping format verb for fmt.Errorf. Use `%w` to format errors
case <-ctx.Done():
return nil, fmt.Errorf("%w: %v", ErrContextDone, ctx.Err()) //nolint:errorlint // errorlint: non-wrapping format verb for fmt.Errorf. Use `%w` to format errors
}
}
}
// NewEventWaiter creates an instance of Waiter supporting websocket event-based transaction awaiting.
// EventWaiter contains PollingWaiter under the hood and falls back to polling when subscription-based
// awaiting fails.
func NewEventWaiter(waiter RPCEventWaiter) (*EventWaiter, error) {
polling, err := NewPollingWaiter(waiter)
if err != nil {
return nil, err
}
return &EventWaiter{
ws: waiter,
polling: polling,
}, nil
}
// Wait implements Waiter interface.
func (w *EventWaiter) Wait(h util.Uint256, vub uint32, err error) (res *state.AppExecResult, waitErr error) {
if err != nil && !errIsAlreadyExists(err) {
return nil, err
}
return w.WaitAny(context.TODO(), vub, h)
}
// WaitAny implements Waiter interface.
func (w *EventWaiter) WaitAny(ctx context.Context, vub uint32, hashes ...util.Uint256) (res *state.AppExecResult, waitErr error) {
var (
wsWaitErr error
waitersActive int
bRcvr = make(chan *block.Block, 2)
aerRcvr = make(chan *state.AppExecResult, len(hashes))
unsubErrs = make(chan error)
exit = make(chan struct{})
)
// Execution event preceded the block event, thus wait until the VUB-th block to be sure.
since := vub
blocksID, err := w.ws.ReceiveBlocks(&neorpc.BlockFilter{Since: &since}, bRcvr)
if err != nil {
wsWaitErr = fmt.Errorf("failed to subscribe for new blocks: %w", err)
} else {
waitersActive++
go func() {
<-exit
err = w.ws.Unsubscribe(blocksID)
if err != nil {
unsubErrs <- fmt.Errorf("failed to unsubscribe from blocks (id: %s): %w", blocksID, err)
return
}
unsubErrs <- nil
}()
}
if wsWaitErr == nil {
trig := trigger.Application
for _, h := range hashes {
txsID, err := w.ws.ReceiveExecutions(&neorpc.ExecutionFilter{Container: &h}, aerRcvr)
if err != nil {
wsWaitErr = fmt.Errorf("failed to subscribe for execution results: %w", err)
break
}
waitersActive++
go func() {
<-exit
err = w.ws.Unsubscribe(txsID)
if err != nil {
unsubErrs <- fmt.Errorf("failed to unsubscribe from transactions (id: %s): %w", txsID, err)
return
}
unsubErrs <- nil
}()
// There is a potential race between subscription and acceptance, so
// do a polling check once _after_ the subscription.
appLog, err := w.ws.GetApplicationLog(h, &trig)
if err == nil {
res = &state.AppExecResult{
Container: appLog.Container,
Execution: appLog.Executions[0],
}
break // We have the result, no need for other subscriptions.
}
}
}
if wsWaitErr == nil && res == nil {
select {
case _, ok := <-bRcvr:
if !ok {
// We're toast, retry with non-ws client.
bRcvr = nil
aerRcvr = nil
wsWaitErr = ErrMissedEvent
break
}
waitErr = ErrTxNotAccepted
case aer, ok := <-aerRcvr:
if !ok {
// We're toast, retry with non-ws client.
bRcvr = nil
aerRcvr = nil
wsWaitErr = ErrMissedEvent
break
}
res = aer
case <-w.ws.Context().Done():
waitErr = fmt.Errorf("%w: %v", ErrContextDone, w.ws.Context().Err()) //nolint:errorlint // errorlint: non-wrapping format verb for fmt.Errorf. Use `%w` to format errors
case <-ctx.Done():
waitErr = fmt.Errorf("%w: %v", ErrContextDone, ctx.Err()) //nolint:errorlint // errorlint: non-wrapping format verb for fmt.Errorf. Use `%w` to format errors
}
}
close(exit)
if waitersActive > 0 {
// Drain receivers to avoid other notification receivers blocking.
drainLoop:
for {
select {
case _, ok := <-bRcvr:
if !ok { // Missed event means both channels are closed.
bRcvr = nil
aerRcvr = nil
}
case _, ok := <-aerRcvr:
if !ok { // Missed event means both channels are closed.
bRcvr = nil
aerRcvr = nil
}
case unsubErr := <-unsubErrs:
if unsubErr != nil {
errFmt := "unsubscription error: %v"
errArgs := []any{unsubErr}
if waitErr != nil {
errFmt = "%w; " + errFmt
errArgs = append([]any{waitErr}, errArgs...)
}
waitErr = fmt.Errorf(errFmt, errArgs...)
}
waitersActive--
// Wait until all receiver channels finish their work.
if waitersActive == 0 {
break drainLoop
}
}
}
}
if bRcvr != nil {
close(bRcvr)
}
if aerRcvr != nil {
close(aerRcvr)
}
close(unsubErrs)
// Rollback to a poll-based waiter if needed.
if wsWaitErr != nil && waitErr == nil {
res, waitErr = w.polling.WaitAny(ctx, vub, hashes...)
if waitErr != nil {
// Wrap the poll-based error, it's more important.
waitErr = fmt.Errorf("event-based error: %v; poll-based waiter error: %w", wsWaitErr, waitErr) //nolint:errorlint // errorlint: non-wrapping format verb for fmt.Errorf. Use `%w` to format errors
}
}
return
}