path: root/dex/bloombits.go

// Copyright 2017 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 dex

import (
    "context"
    "time"

    "github.com/dexon-foundation/dexon/common"
    "github.com/dexon-foundation/dexon/common/bitutil"
    "github.com/dexon-foundation/dexon/core"
    "github.com/dexon-foundation/dexon/core/bloombits"
    "github.com/dexon-foundation/dexon/core/rawdb"
    "github.com/dexon-foundation/dexon/core/types"
    "github.com/dexon-foundation/dexon/ethdb"
)

const (
    // bloomServiceThreads is the number of goroutines used globally by an Ethereum
    // instance to service bloombits lookups for all running filters.
    bloomServiceThreads = 16

    // bloomFilterThreads is the number of goroutines used locally per filter to
    // multiplex requests onto the global servicing goroutines.
    bloomFilterThreads = 3

    // bloomRetrievalBatch is the maximum number of bloom bit retrievals to service
    // in a single batch.
    bloomRetrievalBatch = 16

    // bloomRetrievalWait is the maximum time to wait for enough bloom bit requests
    // to accumulate request an entire batch (avoiding hysteresis).
    bloomRetrievalWait = time.Duration(0)
)

// startBloomHandlers starts a batch of goroutines to accept bloom bit database
// retrievals from possibly a range of filters and serving the data to satisfy.
func (dex *Dexon) startBloomHandlers(sectionSize uint64) {
    for i := 0; i < bloomServiceThreads; i++ {
        go func() {
            for {
                select {
                case <-dex.shutdownChan:
                    return

                case request := <-dex.bloomRequests:
                    task := <-request
                    task.Bitsets = make([][]byte, len(task.Sections))
                    for i, section := range task.Sections {
                        head := rawdb.ReadCanonicalHash(dex.chainDb, (section+1)*sectionSize-1)
                        if compVector, err := rawdb.ReadBloomBits(dex.chainDb, task.Bit, section, head); err == nil {
                            if blob, err := bitutil.DecompressBytes(compVector, int(sectionSize/8)); err == nil {
                                task.Bitsets[i] = blob
                            } else {
                                task.Error = err
                            }
                        } else {
                            task.Error = err
                        }
                    }
                    request <- task
                }
            }
        }()
    }
}

const (
    // bloomThrottling is the time to wait between processing two consecutive index
    // sections. It's useful during chain upgrades to prevent disk overload.
    bloomThrottling = 100 * time.Millisecond
)

// BloomIndexer implements a core.ChainIndexer, building up a rotated bloom bits index
// for the Ethereum header bloom filters, permitting blazing fast filtering.
type BloomIndexer struct {
    size    uint64               // section size to generate bloombits for
    db      ethdb.Database       // database instance to write index data and metadata into
    gen     *bloombits.Generator // generator to rotate the bloom bits crating the bloom index
    section uint64               // Section is the section number being processed currently
    head    common.Hash          // Head is the hash of the last header processed
}

// NewBloomIndexer returns a chain indexer that generates bloom bits data for the
// canonical chain for fast logs filtering.
func NewBloomIndexer(db ethdb.Database, size, confirms uint64) *core.ChainIndexer {
    backend := &BloomIndexer{
        db:   db,
        size: size,
    }
    table := ethdb.NewTable(db, string(rawdb.BloomBitsIndexPrefix))

    return core.NewChainIndexer(db, table, backend, size, confirms, bloomThrottling, "bloombits")
}

// Reset implements core.ChainIndexerBackend, starting a new bloombits index
// section.
func (b *BloomIndexer) Reset(ctx context.Context, section uint64, lastSectionHead common.Hash) error {
    gen, err := bloombits.NewGenerator(uint(b.size))
    b.gen, b.section, b.head = gen, section, common.Hash{}
    return err
}

// Process implements core.ChainIndexerBackend, adding a new header's bloom into
// the index.
func (b *BloomIndexer) Process(ctx context.Context, header *types.Header) error {
    b.gen.AddBloom(uint(header.Number.Uint64()-b.section*b.size), header.Bloom)
    b.head = header.Hash()
    return nil
}

// Commit implements core.ChainIndexerBackend, finalizing the bloom section and
// writing it out into the database.
func (b *BloomIndexer) Commit() error {
    batch := b.db.NewBatch()
    for i := 0; i < types.BloomBitLength; i++ {
        bits, err := b.gen.Bitset(uint(i))
        if err != nil {
            return err
        }
        rawdb.WriteBloomBits(batch, uint(i), b.section, b.head, bitutil.CompressBytes(bits))
    }
    return batch.Write()
}