path: root/core/rawdb/freezer.go

// Copyright 2018 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 rawdb

import (
    "errors"
    "fmt"
    "math"
    "sync/atomic"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/ethdb"
    "github.com/ethereum/go-ethereum/log"
    "github.com/ethereum/go-ethereum/metrics"
)

// errUnknownTable is returned if the user attempts to read from a table that is
// not tracked by the freezer.
var errUnknownTable = errors.New("unknown table")

const (
    // freezerRecheckInterval is the frequency to check the key-value database for
    // chain progression that might permit new blocks to be frozen into immutable
    // storage.
    freezerRecheckInterval = time.Minute

    // freezerBlockGraduation is the number of confirmations a block must achieve
    // before it becomes elligible for chain freezing. This must exceed any chain
    // reorg depth, since the freezer also deletes all block siblings.
    freezerBlockGraduation = 60000

    // freezerBatchLimit is the maximum number of blocks to freeze in one batch
    // before doing an fsync and deleting it from the key-value store.
    freezerBatchLimit = 30000
)

// freezer is an memory mapped append-only database to store immutable chain data
// into flat files:
//
// - The append only nature ensures that disk writes are minimized.
// - The memory mapping ensures we can max out system memory for caching without
//   reserving it for go-ethereum. This would also reduce the memory requirements
//   of Geth, and thus also GC overhead.
type freezer struct {
    tables map[string]*freezerTable // Data tables for storing everything
    frozen uint64                   // Number of blocks already frozen
}

// newFreezer creates a chain freezer that moves ancient chain data into
// append-only flat file containers.
func newFreezer(datadir string, namespace string) (*freezer, error) {
    // Create the initial freezer object
    var (
        readMeter  = metrics.NewRegisteredMeter(namespace+"ancient/read", nil)
        writeMeter = metrics.NewRegisteredMeter(namespace+"ancient/write", nil)
    )
    // Open all the supported data tables
    freezer := &freezer{
        tables: make(map[string]*freezerTable),
    }
    for _, name := range []string{"hashes", "headers", "bodies", "receipts", "diffs"} {
        table, err := newTable(datadir, name, readMeter, writeMeter)
        if err != nil {
            for _, table := range freezer.tables {
                table.Close()
            }
            return nil, err
        }
        freezer.tables[name] = table
    }
    // Truncate all data tables to the same length
    freezer.frozen = math.MaxUint64
    for _, table := range freezer.tables {
        if freezer.frozen > table.items {
            freezer.frozen = table.items
        }
    }
    for _, table := range freezer.tables {
        if err := table.truncate(freezer.frozen); err != nil {
            for _, table := range freezer.tables {
                table.Close()
            }
            return nil, err
        }
    }
    return freezer, nil
}

// Close terminates the chain freezer, unmapping all the data files.
func (f *freezer) Close() error {
    var errs []error
    for _, table := range f.tables {
        if err := table.Close(); err != nil {
            errs = append(errs, err)
        }
    }
    if errs != nil {
        return fmt.Errorf("%v", errs)
    }
    return nil
}

// sync flushes all data tables to disk.
func (f *freezer) sync() error {
    var errs []error
    for _, table := range f.tables {
        if err := table.Sync(); err != nil {
            errs = append(errs, err)
        }
    }
    if errs != nil {
        return fmt.Errorf("%v", errs)
    }
    return nil
}

// Ancient retrieves an ancient binary blob from the append-only immutable files.
func (f *freezer) Ancient(kind string, number uint64) ([]byte, error) {
    if table := f.tables[kind]; table != nil {
        return table.Retrieve(number)
    }
    return nil, errUnknownTable
}

// freeze is a background thread that periodically checks the blockchain for any
// import progress and moves ancient data from the fast database into the freezer.
//
// This functionality is deliberately broken off from block importing to avoid
// incurring additional data shuffling delays on block propagation.
func (f *freezer) freeze(db ethdb.KeyValueStore) {
    nfdb := &nofreezedb{KeyValueStore: db}

    for {
        // Retrieve the freezing threshold. In theory we're interested only in full
        // blocks post-sync, but that would keep the live database enormous during
        // dast sync. By picking the fast block, we still get to deep freeze all the
        // final immutable data without having to wait for sync to finish.
        hash := ReadHeadFastBlockHash(nfdb)
        if hash == (common.Hash{}) {
            log.Debug("Current fast block hash unavailable") // new chain, empty database
            time.Sleep(freezerRecheckInterval)
            continue
        }
        number := ReadHeaderNumber(nfdb, hash)
        switch {
        case number == nil:
            log.Error("Current fast block number unavailable", "hash", hash)
            time.Sleep(freezerRecheckInterval)
            continue

        case *number < freezerBlockGraduation:
            log.Debug("Current fast block not old enough", "number", *number, "hash", hash, "delay", freezerBlockGraduation)
            time.Sleep(freezerRecheckInterval)
            continue

        case *number-freezerBlockGraduation <= f.frozen:
            log.Debug("Ancient blocks frozen already", "number", *number, "hash", hash, "frozen", f.frozen)
            time.Sleep(freezerRecheckInterval)
            continue
        }
        head := ReadHeader(nfdb, hash, *number)
        if head == nil {
            log.Error("Current fast block unavailable", "number", *number, "hash", hash)
            time.Sleep(freezerRecheckInterval)
            continue
        }
        // Seems we have data ready to be frozen, process in usable batches
        limit := *number - freezerBlockGraduation
        if limit-f.frozen > freezerBatchLimit {
            limit = f.frozen + freezerBatchLimit
        }
        var (
            start    = time.Now()
            first    = f.frozen
            ancients = make([]common.Hash, 0, limit)
        )
        for f.frozen < limit {
            // Retrieves all the components of the canonical block
            hash := ReadCanonicalHash(nfdb, f.frozen)
            if hash == (common.Hash{}) {
                log.Error("Canonical hash missing, can't freeze", "number", f.frozen)
                break
            }
            header := ReadHeaderRLP(nfdb, hash, f.frozen)
            if len(header) == 0 {
                log.Error("Block header missing, can't freeze", "number", f.frozen, "hash", hash)
                break
            }
            body := ReadBodyRLP(nfdb, hash, f.frozen)
            if len(body) == 0 {
                log.Error("Block body missing, can't freeze", "number", f.frozen, "hash", hash)
                break
            }
            receipts := ReadReceiptsRLP(nfdb, hash, f.frozen)
            if len(receipts) == 0 {
                log.Error("Block receipts missing, can't freeze", "number", f.frozen, "hash", hash)
                break
            }
            td := ReadTdRLP(nfdb, hash, f.frozen)
            if len(td) == 0 {
                log.Error("Total difficulty missing, can't freeze", "number", f.frozen, "hash", hash)
                break
            }
            // Inject all the components into the relevant data tables
            if err := f.tables["hashes"].Append(f.frozen, hash[:]); err != nil {
                log.Error("Failed to deep freeze hash", "number", f.frozen, "hash", hash, "err", err)
                break
            }
            if err := f.tables["headers"].Append(f.frozen, header); err != nil {
                log.Error("Failed to deep freeze header", "number", f.frozen, "hash", hash, "err", err)
                break
            }
            if err := f.tables["bodies"].Append(f.frozen, body); err != nil {
                log.Error("Failed to deep freeze body", "number", f.frozen, "hash", hash, "err", err)
                break
            }
            if err := f.tables["receipts"].Append(f.frozen, receipts); err != nil {
                log.Error("Failed to deep freeze receipts", "number", f.frozen, "hash", hash, "err", err)
                break
            }
            if err := f.tables["diffs"].Append(f.frozen, td); err != nil {
                log.Error("Failed to deep freeze difficulty", "number", f.frozen, "hash", hash, "err", err)
                break
            }
            log.Trace("Deep froze ancient block", "number", f.frozen, "hash", hash)
            atomic.AddUint64(&f.frozen, 1) // Only modify atomically
            ancients = append(ancients, hash)
        }
        // Batch of blocks have been frozen, flush them before wiping from leveldb
        if err := f.sync(); err != nil {
            log.Crit("Failed to flush frozen tables", "err", err)
        }
        // Wipe out all data from the active database
        batch := db.NewBatch()
        for number := first; number < f.frozen; number++ {
            for _, hash := range readAllHashes(db, number) {
                if hash == ancients[number-first] {
                    deleteBlockWithoutNumber(batch, hash, number)
                } else {
                    DeleteBlock(batch, hash, number)
                }
            }
        }
        if err := batch.Write(); err != nil {
            log.Crit("Failed to delete frozen items", "err", err)
        }
        // Log something friendly for the user
        context := []interface{}{
            "blocks", f.frozen - first, "elapsed", common.PrettyDuration(time.Since(start)), "number", f.frozen - 1,
        }
        if n := len(ancients); n > 0 {
            context = append(context, []interface{}{"hash", ancients[n-1]}...)
        }
        log.Info("Deep froze chain segment", context...)

        // Avoid database thrashing with tiny writes
        if f.frozen-first < freezerBatchLimit {
            time.Sleep(freezerRecheckInterval)
        }
    }
}