path: root/eth/filters/filter_system.go

// Copyright 2015 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 filters implements an ethereum filtering system for block,
// transactions and log events.
package filters

import (
	"context"
	"errors"
	"fmt"
	"sync"
	"time"

	"github.com/ava-labs/coreth/core"
	"github.com/ava-labs/coreth/core/rawdb"
	"github.com/ava-labs/coreth/core/types"
	"github.com/ava-labs/coreth/rpc"
	ethereum "github.com/ava-labs/go-ethereum"
	"github.com/ava-labs/go-ethereum/common"
	"github.com/ava-labs/go-ethereum/event"
	"github.com/ava-labs/go-ethereum/log"
)

// Type determines the kind of filter and is used to put the filter in to
// the correct bucket when added.
type Type byte

const (
	// UnknownSubscription indicates an unknown subscription type
	UnknownSubscription Type = iota
	// LogsSubscription queries for new or removed (chain reorg) logs
	LogsSubscription
	// PendingLogsSubscription queries for logs in pending blocks
	PendingLogsSubscription
	// MinedAndPendingLogsSubscription queries for logs in mined and pending blocks.
	MinedAndPendingLogsSubscription
	// PendingTransactionsSubscription queries tx hashes for pending
	// transactions entering the pending state
	PendingTransactionsSubscription
	// BlocksSubscription queries hashes for blocks that are imported
	BlocksSubscription
	// LastSubscription keeps track of the last index
	LastIndexSubscription
)

const (

	// txChanSize is the size of channel listening to NewTxsEvent.
	// The number is referenced from the size of tx pool.
	txChanSize = 4096
	// rmLogsChanSize is the size of channel listening to RemovedLogsEvent.
	rmLogsChanSize = 10
	// logsChanSize is the size of channel listening to LogsEvent.
	logsChanSize = 10
	// chainEvChanSize is the size of channel listening to ChainEvent.
	chainEvChanSize = 10
)

var (
	ErrInvalidSubscriptionID = errors.New("invalid id")
)

type subscription struct {
	id        rpc.ID
	typ       Type
	created   time.Time
	logsCrit  ethereum.FilterQuery
	logs      chan []*types.Log
	hashes    chan []common.Hash
	headers   chan *types.Header
	installed chan struct{} // closed when the filter is installed
	err       chan error    // closed when the filter is uninstalled
}

// EventSystem creates subscriptions, processes events and broadcasts them to the
// subscription which match the subscription criteria.
type EventSystem struct {
	mux       *event.TypeMux
	backend   Backend
	lightMode bool
	lastHead  *types.Header

	// Subscriptions
	txsSub        event.Subscription         // Subscription for new transaction event
	logsSub       event.Subscription         // Subscription for new log event
	rmLogsSub     event.Subscription         // Subscription for removed log event
	chainSub      event.Subscription         // Subscription for new chain event
	pendingLogSub *event.TypeMuxSubscription // Subscription for pending log event

	// Channels
	install   chan *subscription         // install filter for event notification
	uninstall chan *subscription         // remove filter for event notification
	txsCh     chan core.NewTxsEvent      // Channel to receive new transactions event
	logsCh    chan []*types.Log          // Channel to receive new log event
	rmLogsCh  chan core.RemovedLogsEvent // Channel to receive removed log event
	chainCh   chan core.ChainEvent       // Channel to receive new chain event
}

// NewEventSystem creates a new manager that listens for event on the given mux,
// parses and filters them. It uses the all map to retrieve filter changes. The
// work loop holds its own index that is used to forward events to filters.
//
// The returned manager has a loop that needs to be stopped with the Stop function
// or by stopping the given mux.
func NewEventSystem(mux *event.TypeMux, backend Backend, lightMode bool) *EventSystem {
	m := &EventSystem{
		mux:       mux,
		backend:   backend,
		lightMode: lightMode,
		install:   make(chan *subscription),
		uninstall: make(chan *subscription),
		txsCh:     make(chan core.NewTxsEvent, txChanSize),
		logsCh:    make(chan []*types.Log, logsChanSize),
		rmLogsCh:  make(chan core.RemovedLogsEvent, rmLogsChanSize),
		chainCh:   make(chan core.ChainEvent, chainEvChanSize),
	}

	// Subscribe events
	m.txsSub = m.backend.SubscribeNewTxsEvent(m.txsCh)
	m.logsSub = m.backend.SubscribeLogsEvent(m.logsCh)
	m.rmLogsSub = m.backend.SubscribeRemovedLogsEvent(m.rmLogsCh)
	m.chainSub = m.backend.SubscribeChainEvent(m.chainCh)
	// TODO(rjl493456442): use feed to subscribe pending log event
	m.pendingLogSub = m.mux.Subscribe(core.PendingLogsEvent{})

	// Make sure none of the subscriptions are empty
	if m.txsSub == nil || m.logsSub == nil || m.rmLogsSub == nil || m.chainSub == nil ||
		m.pendingLogSub.Closed() {
		log.Crit("Subscribe for event system failed")
	}

	go m.eventLoop()
	return m
}

// Subscription is created when the client registers itself for a particular event.
type Subscription struct {
	ID        rpc.ID
	f         *subscription
	es        *EventSystem
	unsubOnce sync.Once
}

// Err returns a channel that is closed when unsubscribed.
func (sub *Subscription) Err() <-chan error {
	return sub.f.err
}

// Unsubscribe uninstalls the subscription from the event broadcast loop.
func (sub *Subscription) Unsubscribe() {
	sub.unsubOnce.Do(func() {
	uninstallLoop:
		for {
			// write uninstall request and consume logs/hashes. This prevents
			// the eventLoop broadcast method to deadlock when writing to the
			// filter event channel while the subscription loop is waiting for
			// this method to return (and thus not reading these events).
			select {
			case sub.es.uninstall <- sub.f:
				break uninstallLoop
			case <-sub.f.logs:
			case <-sub.f.hashes:
			case <-sub.f.headers:
			}
		}

		// wait for filter to be uninstalled in work loop before returning
		// this ensures that the manager won't use the event channel which
		// will probably be closed by the client asap after this method returns.
		<-sub.Err()
	})
}

// subscribe installs the subscription in the event broadcast loop.
func (es *EventSystem) subscribe(sub *subscription) *Subscription {
	es.install <- sub
	<-sub.installed
	return &Subscription{ID: sub.id, f: sub, es: es}
}

// SubscribeLogs creates a subscription that will write all logs matching the
// given criteria to the given logs channel. Default value for the from and to
// block is "latest". If the fromBlock > toBlock an error is returned.
func (es *EventSystem) SubscribeLogs(crit ethereum.FilterQuery, logs chan []*types