path: root/swarm/shed/db.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 shed provides a simple abstraction components to compose
// more complex operations on storage data organized in fields and indexes.
//
// Only type which holds logical information about swarm storage chunks data
// and metadata is Item. This part is not generalized mostly for
// performance reasons.
package shed

import (
    "errors"
    "fmt"
    "strconv"
    "strings"
    "time"

    "github.com/ethereum/go-ethereum/metrics"
    "github.com/ethereum/go-ethereum/swarm/log"
    "github.com/syndtr/goleveldb/leveldb"
    "github.com/syndtr/goleveldb/leveldb/iterator"
    "github.com/syndtr/goleveldb/leveldb/opt"
)

const (
    openFileLimit              = 128 // The limit for LevelDB OpenFilesCacheCapacity.
    writePauseWarningThrottler = 1 * time.Minute
)

// DB provides abstractions over LevelDB in order to
// implement complex structures using fields and ordered indexes.
// It provides a schema functionality to store fields and indexes
// information about naming and types.
type DB struct {
    ldb *leveldb.DB

    compTimeMeter    metrics.Meter // Meter for measuring the total time spent in database compaction
    compReadMeter    metrics.Meter // Meter for measuring the data read during compaction
    compWriteMeter   metrics.Meter // Meter for measuring the data written during compaction
    writeDelayNMeter metrics.Meter // Meter for measuring the write delay number due to database compaction
    writeDelayMeter  metrics.Meter // Meter for measuring the write delay duration due to database compaction
    diskReadMeter    metrics.Meter // Meter for measuring the effective amount of data read
    diskWriteMeter   metrics.Meter // Meter for measuring the effective amount of data written

    quitChan chan chan error // Quit channel to stop the metrics collection before closing the database
}

// NewDB constructs a new DB and validates the schema
// if it exists in database on the given path.
// metricsPrefix is used for metrics collection for the given DB.
func NewDB(path string, metricsPrefix string) (db *DB, err error) {
    ldb, err := leveldb.OpenFile(path, &opt.Options{
        OpenFilesCacheCapacity: openFileLimit,
    })
    if err != nil {
        return nil, err
    }
    db = &DB{
        ldb: ldb,
    }

    if _, err = db.getSchema(); err != nil {
        if err == leveldb.ErrNotFound {
            // save schema with initialized default fields
            if err = db.putSchema(schema{
                Fields:  make(map[string]fieldSpec),
                Indexes: make(map[byte]indexSpec),
            }); err != nil {
                return nil, err
            }
        } else {
            return nil, err
        }
    }

    // Configure meters for DB
    db.configure(metricsPrefix)

    // Create a quit channel for the periodic metrics collector and run it
    db.quitChan = make(chan chan error)

    go db.meter(10 * time.Second)

    return db, nil
}

// Put wraps LevelDB Put method to increment metrics counter.
func (db *DB) Put(key []byte, value []byte) (err error) {
    err = db.ldb.Put(key, value, nil)
    if err != nil {
        metrics.GetOrRegisterCounter("DB.putFail", nil).Inc(1)
        return err
    }
    metrics.GetOrRegisterCounter("DB.put", nil).Inc(1)
    return nil
}

// Get wraps LevelDB Get method to increment metrics counter.
func (db *DB) Get(key []byte) (value []byte, err error) {
    value, err = db.ldb.Get(key, nil)
    if err != nil {
        if err == leveldb.ErrNotFound {
            metrics.GetOrRegisterCounter("DB.getNotFound", nil).Inc(1)
        } else {
            metrics.GetOrRegisterCounter("DB.getFail", nil).Inc(1)
        }
        return nil, err
    }
    metrics.GetOrRegisterCounter("DB.get", nil).Inc(1)
    return value, nil
}

// Delete wraps LevelDB Delete method to increment metrics counter.
func (db *DB) Delete(key []byte) (err error) {
    err = db.ldb.Delete(key, nil)
    if err != nil {
        metrics.GetOrRegisterCounter("DB.deleteFail", nil).Inc(1)
        return err
    }
    metrics.GetOrRegisterCounter("DB.delete", nil).Inc(1)
    return nil
}

// NewIterator wraps LevelDB NewIterator method to increment metrics counter.
func (db *DB) NewIterator() iterator.Iterator {
    metrics.GetOrRegisterCounter("DB.newiterator", nil).Inc(1)

    return db.ldb.NewIterator(nil, nil)
}

// WriteBatch wraps LevelDB Write method to increment metrics counter.
func (db *DB) WriteBatch(batch *leveldb.Batch) (err error) {
    err = db.ldb.Write(batch, nil)
    if err != nil {
        metrics.GetOrRegisterCounter("DB.writebatchFail", nil).Inc(1)
        return err
    }
    metrics.GetOrRegisterCounter("DB.writebatch", nil).Inc(1)
    return nil
}

// Close closes LevelDB database.
func (db *DB) Close() (err error) {
    close(db.quitChan)
    return db.ldb.Close()
}

// Configure configures the database metrics collectors
func (db *DB) configure(prefix string) {
    // Initialize all the metrics collector at the requested prefix
    db.compTimeMeter = metrics.NewRegisteredMeter(prefix+"compact/time", nil)
    db.compReadMeter = metrics.NewRegisteredMeter(prefix+"compact/input", nil)
    db.compWriteMeter = metrics.NewRegisteredMeter(prefix+"compact/output", nil)
    db.diskReadMeter = metrics.NewRegisteredMeter(prefix+"disk/read", nil)
    db.diskWriteMeter = metrics.NewRegisteredMeter(prefix+"disk/write", nil)
    db.writeDelayMeter = metrics.NewRegisteredMeter(prefix+"compact/writedelay/duration", nil)
    db.writeDelayNMeter = metrics.NewRegisteredMeter(prefix+"compact/writedelay/counter", nil)
}

func (db *DB) meter(refresh time.Duration) {
    // Create the counters to store current and previous compaction values
    compactions := make([][]float64, 2)
    for i := 0; i < 2; i++ {
        compactions[i] = make([]float64, 3)
    }
    // Create storage for iostats.
    var iostats [2]float64

    // Create storage and warning log tracer for write delay.
    var (
        delaystats      [2]int64
        lastWritePaused time.Time
    )

    var (
        errc chan error
        merr error
    )

    // Iterate ad infinitum and collect the stats
    for i := 1; errc == nil && merr == nil; i++ {
        // Retrieve the database stats
        stats, err := db.ldb.GetProperty("leveldb.stats")
        if err != nil {
            log.Error("Failed to read database stats", "err", err)
            merr = err
            continue
        }
        // Find the compaction table, skip the header
        lines := strings.Split(stats, "\n")
        for len(lines) > 0 && strings.TrimSpace(lines[0]) != "Compactions" {
            lines = lines[1:]
        }
        if len(lines) <= 3 {
            log.Error("Compaction table not found")
            merr = errors.New("compaction table not found")
            continue
        }
        lines = lines[3:]

        // Iterate over all the table rows, and accumulate the entries
        for j := 0; j < len(compactions[i%2]); j++ {
            compactions[i%2][j] = 0
        }
        for _, line := range lines {
            parts := strings.Split(line, "|")
            if len(parts) != 6 {
                break
            }
            for idx, counter := range parts[3:] {
                value, err := strconv.ParseFloat(strings.TrimSpace(counter), 64)
                if err != nil {
                    log.Error("Compaction entry parsing failed", "err", err)
                    merr = err
                    continue
                }
                compactions[i%2][idx] += value
            }
        }
        // Update all the requested meters
        if db.compTimeMeter != nil {
            db.compTimeMeter.Mark(int64((compactions[i%2][0] - compactions[(i-1)%2][0]) * 1000 * 1000 * 1000))
        }
        if db.compReadMeter != nil {
            db.compReadMeter.Mark(int64((compactions[i%2][1] - compactions[(i-1)%2][1]) * 1024 * 1024))
        }
        if db.compWriteMeter != nil {
            db.compWriteMeter.Mark(int64((compactions[i%2][2] - compactions[(i-1)%2][2]) * 1024 * 1024))
        }

        // Retrieve the write delay statistic
        writedelay, err := db.ldb.GetProperty("leveldb.writedelay")
        if err != nil {
            log.Error("Failed to read database write delay statistic", "err", err)
            merr = err
            continue
        }
        var (
            delayN        int64
            delayDuration string
            duration      time.Duration
            paused        bool
        )
        if n, err := fmt.Sscanf(writedelay, "DelayN:%d Delay:%s Paused:%t", &delayN, &delayDuration, &paused); n != 3 || err != nil {
            log.Error("Write delay statistic not found")
            merr = err
            continue
        }
        duration, err = time.ParseDuration(delayDuration)
        if err != nil {
            log.Error("Failed to parse delay duration", "err", err)
            merr = err
            continue
        }
        if db.writeDelayNMeter != nil {
            db.writeDelayNMeter.Mark(delayN - delaystats[0])
        }
        if db.writeDelayMeter != nil {
            db.writeDelayMeter.Mark(duration.Nanoseconds() - delaystats[1])
        }
        // If a warning that db is performing compaction has been displayed, any subsequent
        // warnings will be withheld for one minute not to overwhelm the user.
        if paused && delayN-delaystats[0] == 0 && duration.Nanoseconds()-delaystats[1] == 0 &&
            time.Now().After(lastWritePaused.Add(writePauseWarningThrottler)) {
            log.Warn("Database compacting, degraded performance")
            lastWritePaused = time.Now()
        }
        delaystats[0], delaystats[1] = delayN, duration.Nanoseconds()

        // Retrieve the database iostats.
        ioStats, err := db.ldb.GetProperty("leveldb.iostats")
        if err != nil {
            log.Error("Failed to read database iostats", "err", err)
            merr = err
            continue
        }
        var nRead, nWrite float64
        parts := strings.Split(ioStats, " ")
        if len(parts) < 2 {
            log.Error("Bad syntax of ioStats", "ioStats", ioStats)
            merr = fmt.Errorf("bad syntax of ioStats %s", ioStats)
            continue
        }
        if n, err := fmt.Sscanf(parts[0], "Read(MB):%f", &nRead); n != 1 || err != nil {
            log.Error("Bad syntax of read entry", "entry", parts[0])
            merr = err
            continue
        }
        if n, err := fmt.Sscanf(parts[1], "Write(MB):%f", &nWrite); n != 1 || err != nil {
            log.Error("Bad syntax of write entry", "entry", parts[1])
            merr = err
            continue
        }
        if db.diskReadMeter != nil {
            db.diskReadMeter.Mark(int64((nRead - iostats[0]) * 1024 * 1024))
        }
        if db.diskWriteMeter != nil {
            db.diskWriteMeter.Mark(int64((nWrite - iostats[1]) * 1024 * 1024))
        }
        iostats[0], iostats[1] = nRead, nWrite

        // Sleep a bit, then repeat the stats collection
        select {
        case errc = <-db.quitChan:
            // Quit requesting, stop hammering the database
        case <-time.After(refresh):
            // Timeout, gather a new set of stats
        }
    }

    if errc == nil {
        errc = <-db.quitChan
    }
    errc <- merr
}