path: root/ethdb/database.go

// Copyright 2014 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 ethdb

import (
    "strconv"
    "strings"
    "sync"
    "time"

    "github.com/ethereum/go-ethereum/compression/rle"
    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
    "github.com/ethereum/go-ethereum/metrics"
    "github.com/syndtr/goleveldb/leveldb"
    "github.com/syndtr/goleveldb/leveldb/errors"
    "github.com/syndtr/goleveldb/leveldb/iterator"
    "github.com/syndtr/goleveldb/leveldb/opt"

    gometrics "github.com/rcrowley/go-metrics"
)

var OpenFileLimit = 64

type LDBDatabase struct {
    fn string      // filename for reporting
    db *leveldb.DB // LevelDB instance

    getTimer       gometrics.Timer // Timer for measuring the database get request counts and latencies
    putTimer       gometrics.Timer // Timer for measuring the database put request counts and latencies
    delTimer       gometrics.Timer // Timer for measuring the database delete request counts and latencies
    missMeter      gometrics.Meter // Meter for measuring the missed database get requests
    readMeter      gometrics.Meter // Meter for measuring the database get request data usage
    writeMeter     gometrics.Meter // Meter for measuring the database put request data usage
    compTimeMeter  gometrics.Meter // Meter for measuring the total time spent in database compaction
    compReadMeter  gometrics.Meter // Meter for measuring the data read during compaction
    compWriteMeter gometrics.Meter // Meter for measuring the data written during compaction

    quitLock sync.Mutex      // Mutex protecting the quit channel access
    quitChan chan chan error // Quit channel to stop the metrics collection before closing the database
}

// NewLDBDatabase returns a LevelDB wrapped object. LDBDatabase does not persist data by
// it self but requires a background poller which syncs every X. `Flush` should be called
// when data needs to be stored and written to disk.
func NewLDBDatabase(file string) (*LDBDatabase, error) {
    // Open the db
    db, err := leveldb.OpenFile(file, &opt.Options{OpenFilesCacheCapacity: OpenFileLimit})
    // check for corruption and attempt to recover
    if _, iscorrupted := err.(*errors.ErrCorrupted); iscorrupted {
        db, err = leveldb.RecoverFile(file, nil)
    }
    // (re) check for errors and abort if opening of the db failed
    if err != nil {
        return nil, err
    }
    return &LDBDatabase{
        fn: file,
        db: db,
    }, nil
}

// Put puts the given key / value to the queue
func (self *LDBDatabase) Put(key []byte, value []byte) error {
    // Measure the database put latency, if requested
    if self.putTimer != nil {
        defer self.putTimer.UpdateSince(time.Now())
    }
    // Generate the data to write to disk, update the meter and write
    dat := rle.Compress(value)

    if self.writeMeter != nil {
        self.writeMeter.Mark(int64(len(dat)))
    }
    return self.db.Put(key, dat, nil)
}

// Get returns the given key if it's present.
func (self *LDBDatabase) Get(key []byte) ([]byte, error) {
    // Measure the database get latency, if requested
    if self.getTimer != nil {
        defer self.getTimer.UpdateSince(time.Now())
    }
    // Retrieve the key and increment the miss counter if not found
    dat, err := self.db.Get(key, nil)
    if err != nil {
        if self.missMeter != nil {
            self.missMeter.Mark(1)
        }
        return nil, err
    }
    // Otherwise update the actually retrieved amount of data
    if self.readMeter != nil {
        self.readMeter.Mark(int64(len(dat)))
    }
    return rle.Decompress(dat)
}

// Delete deletes the key from the queue and database
func (self *LDBDatabase) Delete(key []byte) error {
    // Measure the database delete latency, if requested
    if self.delTimer != nil {
        defer self.delTimer.UpdateSince(time.Now())
    }
    // Execute the actual operation
    return self.db.Delete(key, nil)
}

func (self *LDBDatabase) NewIterator() iterator.Iterator {
    return self.db.NewIterator(nil, nil)
}

// Flush flushes out the queue to leveldb
func (self *LDBDatabase) Flush() error {
    return nil
}

func (self *LDBDatabase) Close() {
    // Stop the metrics collection to avoid internal database races
    self.quitLock.Lock()
    defer self.quitLock.Unlock()

    if self.quitChan != nil {
        errc := make(chan error)
        self.quitChan <- errc
        if err := <-errc; err != nil {
            glog.V(logger.Error).Infof("metrics failure in '%s': %v\n", self.fn, err)
        }
    }
    // Flush and close the database
    if err := self.Flush(); err != nil {
        glog.V(logger.Error).Infof("flushing '%s' failed: %v\n", self.fn, err)
    }
    self.db.Close()
    glog.V(logger.Error).Infoln("flushed and closed db:", self.fn)
}

func (self *LDBDatabase) LDB() *leveldb.DB {
    return self.db
}

// Meter configures the database metrics collectors and
func (self *LDBDatabase) Meter(prefix string) {
    // Initialize all the metrics collector at the requested prefix
    self.getTimer = metrics.NewTimer(prefix + "user/gets")
    self.putTimer = metrics.NewTimer(prefix + "user/puts")
    self.delTimer = metrics.NewTimer(prefix + "user/dels")
    self.missMeter = metrics.NewMeter(prefix + "user/misses")
    self.readMeter = metrics.NewMeter(prefix + "user/reads")
    self.writeMeter = metrics.NewMeter(prefix + "user/writes")
    self.compTimeMeter = metrics.NewMeter(prefix + "compact/time")
    self.compReadMeter = metrics.NewMeter(prefix + "compact/input")
    self.compWriteMeter = metrics.NewMeter(prefix + "compact/output")

    // Create a quit channel for the periodic collector and run it
    self.quitLock.Lock()
    self.quitChan = make(chan chan error)
    self.quitLock.Unlock()

    go self.meter(3 * time.Second)
}

// meter periodically retrieves internal leveldb counters and reports them to
// the metrics subsystem.
//
// This is how a stats table look like (currently):
//   Compactions
//    Level |   Tables   |    Size(MB)   |    Time(sec)  |    Read(MB)   |   Write(MB)
//   -------+------------+---------------+---------------+---------------+---------------
//      0   |          0 |       0.00000 |       1.27969 |       0.00000 |      12.31098
//      1   |         85 |     109.27913 |      28.09293 |     213.92493 |     214.26294
//      2   |        523 |    1000.37159 |       7.26059 |      66.86342 |      66.77884
//      3   |        570 |    1113.18458 |       0.00000 |       0.00000 |       0.00000
func (self *LDBDatabase) meter(refresh time.Duration) {
    // Create the counters to store current and previous values
    counters := make([][]float64, 2)
    for i := 0; i < 2; i++ {
        counters[i] = make([]float64, 3)
    }
    // Iterate ad infinitum and collect the stats
    for i := 1; ; i++ {
        // Retrieve the database stats
        stats, err := self.db.GetProperty("leveldb.stats")
        if err != nil {
            glog.V(logger.Error).Infof("failed to read database stats: %v", err)
            return
        }
        // 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 {
            glog.V(logger.Error).Infof("compaction table not found")
            return
        }
        lines = lines[3:]

        // Iterate over all the table rows, and accumulate the entries
        for j := 0; j < len(counters[i%2]); j++ {
            counters[i%2][j] = 0
        }
        for _, line := range lines {
            parts := strings.Split(line, "|")
            if len(parts) != 6 {
                break
            }
            for idx, counter := range parts[3:] {
                if value, err := strconv.ParseFloat(strings.TrimSpace(counter), 64); err != nil {
                    glog.V(logger.Error).Infof("compaction entry parsing failed: %v", err)
                    return
                } else {
                    counters[i%2][idx] += value
                }
            }
        }
        // Update all the requested meters
        if self.compTimeMeter != nil {
            self.compTimeMeter.Mark(int64((counters[i%2][0] - counters[(i-1)%2][0]) * 1000 * 1000 * 1000))
        }
        if self.compReadMeter != nil {
            self.compReadMeter.Mark(int64((counters[i%2][1] - counters[(i-1)%2][1]) * 1024 * 1024))
        }
        if self.compWriteMeter != nil {
            self.compWriteMeter.Mark(int64((counters[i%2][2] - counters[(i-1)%2][2]) * 1024 * 1024))
        }
        // Sleep a bit, then repeat the stats collection
        select {
        case errc := <-self.quitChan:
            // Quit requesting, stop hammering the database
            errc <- nil
            return

        case <-time.After(refresh):
            // Timeout, gather a new set of stats
        }
    }
}