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"
    "os"
    "path/filepath"
    "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"
    "github.com/ethereum/go-ethereum/params"
    "github.com/prometheus/tsdb/fileutil"
)

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

    // errOutOrderInsertion is returned if the user attempts to inject out-of-order
    // binary blobs into the freezer.
    errOutOrderInsertion = errors.New("the append operation is out-order")

    // errSymlinkDatadir is returned if the ancient directory specified by user
    // is a symbolic link.
    errSymlinkDatadir = errors.New("symbolic link datadir is not supported")
)

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

    // 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 {
    // WARNING: The `frozen` field is accessed atomically. On 32 bit platforms, only
    // 64-bit aligned fields can be atomic. The struct is guaranteed to be so aligned,
    // so take advantage of that (https://golang.org/pkg/sync/atomic/#pkg-note-BUG).
    frozen uint64 // Number of blocks already frozen

    tables       map[string]*freezerTable // Data tables for storing everything
    instanceLock fileutil.Releaser        // File-system lock to prevent double opens
}

// 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)
        sizeCounter = metrics.NewRegisteredCounter(namespace+"ancient/size", nil)
    )
    // Ensure the datadir is not a symbolic link if it exists.
    if info, err := os.Lstat(datadir); !os.IsNotExist(err) {
        if info.Mode()&os.ModeSymlink != 0 {
            log.Warn("Symbolic link ancient database is not supported", "path", datadir)
            return nil, errSymlinkDatadir
        }
    }
    // Leveldb uses LOCK as the filelock filename. To prevent the
    // name collision, we use FLOCK as the lock name.
    lock, _, err := fileutil.Flock(filepath.Join(datadir, "FLOCK"))
    if err != nil {
        return nil, err
    }
    // Open all the supported data tables
    freezer := &freezer{
        tables:       make(map[string]*freezerTable),
        instanceLock: lock,
    }
    for name, disableSnappy := range freezerNoSnappy {
        table, err := newTable(datadir, name, readMeter, writeMeter, sizeCounter, disableSnappy)
        if err != nil {
            for _, table := range freezer.tables {
                table.Close()
            }
            lock.Release()
            return nil, err
        }
        freezer.tables[name] = table
    }
    if err := freezer.repair(); err != nil {
        for _, table := range freezer.tables {
            table.Close()
        }
        lock.Release()
        return nil, err
    }
    log.Info("Opened ancient database", "database", datadir)
    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 err := f.instanceLock.Release(); err != nil {
        errs = append(errs, err)
    }
    if errs != nil {
        return fmt.Errorf("%v", errs)
    }
    return nil
}

// HasAncient returns an indicator whether the specified ancient data exists
// in the freezer.
func (f *freezer) HasAncient(kind string, number uint64) (bool, error) {
    if table := f.tables[kind]; table != nil {
        return table.has(number), nil
    }
    return false, 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
}

// Ancients returns the length of the frozen items.
func (f *freezer) Ancients() (uint64, error) {
    return atomic.LoadUint64(&f.frozen), nil
}

// AncientSize returns the ancient size of the specified category.
func (f *freezer) AncientSize(kind string) (uint64, error) {
    if table := f.tables[kind]; table != nil {
        return table.size()
    }
    return 0, errUnknownTable
}

// AppendAncient injects all binary blobs belong to block at the end of the
// append-only immutable table files.
//
// Notably, this function is lock free but kind of thread-safe. All out-of-order
// injection will be rejected. But if two injections with same number happen at
// the same time, we can get into the trouble.
func (f *freezer) AppendAncient(number uint64, hash, header, body, receipts, td []byte) (err error) {
    // Ensure the binary blobs we are appending is continuous with freezer.
    if atomic.LoadUint64(&f.frozen) != number {
        return errOutOrderInsertion
    }
    // Rollback all inserted data if any insertion below failed to ensure
    // the tables won't out of sync.
    defer func() {
        if err != nil {
            rerr := f.repair()
            if rerr != nil {
                log.Crit("Failed to repair freezer", "err", rerr)
            }
            log.Info("Append ancient failed", "number", number, "err", err)
        }
    }()
    // Inject all the components into the relevant data tables
    if err := f.tables[freezerHashTable].Append(f.frozen, hash[:]); err != nil {
        log.Error("Failed to append ancient hash", "number", f.frozen, "hash", hash, "err", err)
        return err
    }
    if err := f.tables[freezerHeaderTable].Append(f.frozen, header); err != nil {
        log.Error("Failed to append ancient header", "number", f.frozen, "hash", hash, "err", err)
        return err
    }
    if err := f.tables[freezerBodiesTable].Append(f.frozen, body); err != nil {
        log.Error("Failed to append ancient body", "number", f.frozen, "hash", hash, "err", err)
        return err
    }
    if err := f.tables[freezerReceiptTable].Append(f.frozen, receipts); err != nil {
        log.Error("Failed to append ancient receipts", "number", f.frozen, "hash", hash, "err", err)
        return err
    }
    if err := f.tables[freezerDifficultyTable].Append(f.frozen, td); err != nil {
        log.Error("Failed to append ancient difficulty", "number", f.frozen, "hash", hash, "err", err)
        return err
    }
    atomic.AddUint64(&f.frozen, 1) // Only modify atomically
    return nil
}

// Truncate discards any recent data above the provided threshold number.
func (f *freezer) TruncateAncients(items uint64) error {
    if atomic.LoadUint64(&f.frozen) <= items {
        return nil
    }
    for _, table := range f.tables {
        if err := table.truncate(items); err != nil {
            return err
        }
    }
    atomic.StoreUint64(&f.frozen, items)
    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
}

// 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.
        hash := ReadHeadBlockHash(nfdb)
        if hash == (common.Hash{}) {
            log.Debug("Current full block hash unavailable") // new chain, empty database
            time.Sleep(freezerRecheckInterval)
            continue
        }
        number := ReadHeaderNumber(nfdb, hash)
        switch {
        case number == nil:
            log.Error("Current full block number unavailable", "hash", hash)
            time.Sleep(freezerRecheckInterval)
            continue

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

        case *number-params.ImmutabilityThreshold <= 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 full block unavailable", "number", *number, "hash", hash)
            time.Sleep(freezerRecheckInterval)
            continue
        }
        // Seems we have data ready to be frozen, process in usable batches
        limit := *number - params.ImmutabilityThreshold
        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
            }
            log.Trace("Deep froze ancient block", "number", f.frozen, "hash", hash)
            // Inject all the components into the relevant data tables
            if err := f.AppendAncient(f.frozen, hash[:], header, body, receipts, td); err != nil {
                break
            }
            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 i := 0; i < len(ancients); i++ {
            // Always keep the genesis block in active database
            if first+uint64(i) != 0 {
                DeleteBlockWithoutNumber(batch, ancients[i], first+uint64(i))
                DeleteCanonicalHash(batch, first+uint64(i))
            }
        }
        if err := batch.Write(); err != nil {
            log.Crit("Failed to delete frozen canonical blocks", "err", err)
        }
        batch.Reset()
        // Wipe out side chain also.
        for number := first; number < f.frozen; number++ {
            // Always keep the genesis block in active database
            if number != 0 {
                for _, hash := range ReadAllHashes(db, number) {
                    DeleteBlock(batch, hash, number)
                }
            }
        }
        if err := batch.Write(); err != nil {
            log.Crit("Failed to delete frozen side blocks", "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)
        }
    }
}

// repair truncates all data tables to the same length.
func (f *freezer) repair() error {
    min := uint64(math.MaxUint64)
    for _, table := range f.tables {
        items := atomic.LoadUint64(&table.items)
        if min > items {
            min = items
        }
    }
    for _, table := range f.tables {
        if err := table.truncate(min); err != nil {
            return err
        }
    }
    atomic.StoreUint64(&f.frozen, min)
    return nil
}