ethclient: add HTTP fallback for subscriptions

pull/27541/head
Felix Lange 1 year ago
parent 699243f8ae
commit e7f2c8feb8
  1. 12
      ethclient/ethclient.go
  2. 150
      ethclient/httpsub.go

@ -329,9 +329,9 @@ func (ec *Client) SyncProgress(ctx context.Context) (*ethereum.SyncProgress, err
func (ec *Client) SubscribeNewHead(ctx context.Context, ch chan<- *types.Header) (ethereum.Subscription, error) { func (ec *Client) SubscribeNewHead(ctx context.Context, ch chan<- *types.Header) (ethereum.Subscription, error) {
sub, err := ec.c.EthSubscribe(ctx, ch, "newHeads") sub, err := ec.c.EthSubscribe(ctx, ch, "newHeads")
if err != nil { if err != nil {
// Defensively prefer returning nil interface explicitly on error-path, instead if errors.Is(err, rpc.ErrNotificationsUnsupported) {
// of letting default golang behavior wrap it with non-nil interface that stores return ec.subscribeNewHeadPolling(ctx, ch)
// nil concrete type value. }
return nil, err return nil, err
} }
return sub, nil return sub, nil
@ -405,9 +405,9 @@ func (ec *Client) SubscribeFilterLogs(ctx context.Context, q ethereum.FilterQuer
} }
sub, err := ec.c.EthSubscribe(ctx, ch, "logs", arg) sub, err := ec.c.EthSubscribe(ctx, ch, "logs", arg)
if err != nil { if err != nil {
// Defensively prefer returning nil interface explicitly on error-path, instead if errors.Is(err, rpc.ErrNotificationsUnsupported) {
// of letting default golang behavior wrap it with non-nil interface that stores return ec.subscribeFilterLogsPolling(ctx, q, ch)
// nil concrete type value. }
return nil, err return nil, err
} }
return sub, nil return sub, nil

@ -0,0 +1,150 @@
// Copyright 2023 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package ethclient
import (
"context"
"sync"
"time"
"github.com/ethereum/go-ethereum"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/event"
"github.com/ethereum/go-ethereum/rpc"
)
// subscribeNewHeadPolling creates a block filter and polls it.
// This is the fallback for SubscribeNewHead on HTTP connections.
func (ec *Client) subscribeNewHeadPolling(ctx context.Context, ch chan<- *types.Header) (event.Subscription, error) {
var id string
err := ec.c.CallContext(ctx, &id, "eth_newBlockFilter")
if err != nil {
return nil, err
}
sub := newFilterSub(ec.c, id, ch)
return sub, nil
}
// subscribeFilterLogs subscribes to a log filter.
// This is the fallback for SubscribeFilterLogs on HTTP connections.
func (ec *Client) subscribeFilterLogsPolling(ctx context.Context, q ethereum.FilterQuery, ch chan<- types.Log) (ethereum.Subscription, error) {
arg, err := toFilterArg(q)
if err != nil {
return nil, err
}
var id string
err = ec.c.CallContext(ctx, &id, "eth_newFilter", arg)
if err != nil {
return nil, err
}
sub := newFilterSub(ec.c, id, ch)
return sub, nil
}
// filterSub implements event.Subscription with the polling filter API.
type filterSub[Result any] struct {
// The channel to send the results to
resultc chan<- Result
errc chan error
closed chan struct{}
unsubOnce sync.Once
id string
client *rpc.Client
}
func newFilterSub[Result any](client *rpc.Client, id string, resultc chan<- Result) *filterSub[Result] {
sub := &filterSub[Result]{
resultc: resultc,
errc: make(chan error, 1),
closed: make(chan struct{}),
client: client,
}
go sub.poll()
return sub
}
// Unsubscribe cancels the event subscription.
func (s *filterSub[Result]) Unsubscribe() {
s.closeWithError(nil)
}
// Err returns the subscription error channel.
func (s *filterSub[Result]) Err() <-chan error {
return s.errc
}
func (s *filterSub[Result]) poll() {
var timer = time.NewTicker(10 * time.Second)
for {
err := s.getChanges()
if err != nil {
s.closeWithError(err)
return
}
// Wait for next time.
select {
case <-timer.C:
case <-s.closed:
return
}
}
}
func (s *filterSub[Result]) closeWithError(err error) {
s.unsubOnce.Do(func() {
close(s.closed)
unsubErr := s.uninstallFilter()
if unsubErr != nil && err == nil {
err = unsubErr
}
if err != nil {
select {
case s.errc <- err:
default:
}
}
close(s.errc)
})
}
// getChanges calls eth_getFilterChanges and delivers the results.
func (s *filterSub[Result]) getChanges() error {
ctx, done := context.WithTimeout(context.Background(), 10*time.Second)
defer done()
var results []Result
err := s.client.CallContext(ctx, &results, "eth_getFilterChanges", s.id)
if err != nil {
return err
}
for _, result := range results {
select {
case s.resultc <- result:
case <-s.closed:
return nil
}
}
return nil
}
// uninstallFilter removes the filter on the server side.
func (s *filterSub[Result]) uninstallFilter() error {
ctx, done := context.WithTimeout(context.Background(), 10*time.Second)
defer done()
return s.client.CallContext(ctx, nil, "eth_uninstallFilter", s.id)
}
Loading…
Cancel
Save