path: root/ethdb/database.go

package ethdb

import (
    "time"

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

var OpenFileLimit = 64

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

    GetTimer   metrics.Timer // Timer for measuring the database get request counts and latencies
    PutTimer   metrics.Timer // Timer for measuring the database put request counts and latencies
    DelTimer   metrics.Timer // Timer for measuring the database delete request counts and latencies
    MissMeter  metrics.Meter // MEter for measuring the missed database get requests
    ReadMeter  metrics.Meter // Meter for measuring the database get request data usage
    WriteMeter metrics.Meter // Meter for measuring the database put request data usage
}

// 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 curruption 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
    }
    database := &LDBDatabase{
        fn: file,
        db: db,
    }

    return database, 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 {
        start := time.Now()
        defer self.PutTimer.UpdateSince(start)
    }
    // 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 {
        start := time.Now()
        defer self.GetTimer.UpdateSince(start)
    }
    // 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 {
        start := time.Now()
        defer self.DelTimer.UpdateSince(start)
    }
    // 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() {
    if err := self.Flush(); err != nil {
        glog.V(logger.Error).Infof("error: flush '%s': %v\n", self.fn, err)
    }

    self.db.Close()
    glog.V(logger.Error).Infoln("flushed and closed db:", self.fn)
}