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persist.go
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/
persist.go
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// Copyright (c) 2015 RightScale, Inc. - see LICENSE
// issues:
// - need to rotate() in NewLog? not clear
// - ordering of replay and persist-all in NewLog not clear
package persist
import (
"encoding/gob"
"fmt"
"io"
"sync"
"time"
"gopkg.in/inconshreveable/log15.v2"
)
type pLog struct {
client LogClient // client which we make callbacks
size int // size used to decide when to rotate
sizeLimit int // size limit when to rotate
sizeReplay int // size of the initial replay
objects uint64 // number of objects output, purely for stats
encoder *gob.Encoder
priDest LogDestination // primary dest, where we initially replay from
secDest LogDestination // secondary dest, no replay and OK if "down"
rotating bool // avoid concurrent rotations
errState error
log log15.Logger
sync.Mutex
}
// Return some statistics about the logging
func (pl *pLog) Stats() map[string]float64 {
pl.Lock()
defer pl.Unlock()
stats := make(map[string]float64)
stats["LogSizeReplay"] = float64(pl.sizeReplay)
stats["LogSize"] = float64(pl.size + pl.sizeReplay)
stats["LogSizeLimit"] = float64(pl.sizeLimit)
stats["ObjectOutputRate"] = float64(pl.objects)
stats["ErrorState"] = 0.0
if pl.errState != nil {
stats["ErrorState"] = 1.0
}
return stats
}
// Close the log for test purposes
func (pl *pLog) Close() {
for {
pl.Lock()
if !pl.rotating {
break
}
pl.Unlock()
time.Sleep(1 * time.Millisecond)
}
pl.priDest.Close()
if pl.secDest != nil {
pl.secDest.Close()
}
pl.Unlock()
}
// SetSizeLimit sets the log size limit at which a rotation occurs, the size value is in
// addition to the initial size produced by the initial snapshot, i.e., it doesn't count that
func (pl *pLog) SetSizeLimit(bytes int) { pl.sizeLimit = bytes }
// HealthCheck returns nil if everything is OK and an error if the log is in an error state
func (pl *pLog) HealthCheck() error { return pl.errState }
// hack...
var pLogError bool
// Output a log entry
func (pl *pLog) Output(logEvent interface{}) error {
pl.Lock()
defer pl.Unlock()
//pl.log.Debug("persist.Output", "ev", logEvent)
if pl.errState != nil {
if !pLogError {
pl.log.Crit("Persistence log in error state: " +
pl.errState.Error())
pLogError = true
}
return pl.errState
}
pLogError = false
if pl.encoder == nil {
return fmt.Errorf("uninitialized persistence log (nil encoder)")
}
// perverse stuff: we need to slap the event into an interface{} so gob later allows
// us to decode into an interface{}
pl.objects += 1
var t interface{} = logEvent
err := pl.encoder.Encode(&t)
if err != nil {
pl.errState = err
} else if !pl.rotating && pl.size > pl.sizeLimit {
pl.rotate()
}
return err
}
func (pl *pLog) SetSecondaryDestination(dest LogDestination) error {
pl.Lock()
defer pl.Unlock()
return fmt.Errorf("not implemented yet!")
/*
if pl.secDest != nil {
return fmt.Errorf("secondary destination is already set")
}
pl.secDest = dest
return pl.rotate()
*/
}
// perform a log rotation, must be called while holding the pl.Lock()
func (pl *pLog) rotate() {
if pl.rotating {
return
}
pl.rotating = true
pl.log.Info("Persist: starting rotation")
go pl.finishRotate()
}
func (pl *pLog) finishRotate() {
// tell all log destinations to start a rotation
pl.Lock()
defer pl.Unlock()
pl.size = 0
pl.sizeReplay = 0
err := pl.priDest.StartRotate()
if pl.secDest != nil {
pl.secDest.StartRotate() // TODO: record error
}
if err != nil {
pl.errState = err
return
}
// we need a new encoder 'cause we start a fresh stream
pl.encoder = gob.NewEncoder(pl)
// now create a full snapshot, relinquish the lock while doing that 'cause otherwise
// we end up with deadlocks since PersistAll will end up calling pl.Output()
pl.Unlock()
pl.client.PersistAll(pl)
pl.Lock()
// tell all log destinations that we're done with the rotation
err = pl.priDest.EndRotate()
if pl.secDest != nil {
pl.secDest.EndRotate() // TODO: record error
}
pl.rotating = false
if err != nil {
pl.log.Crit("Finished rotation with error",
"replay_size", pl.sizeReplay, "err", err)
pl.errState = err
} else {
pl.log.Info("Finished rotation", "replay_size", pl.sizeReplay)
}
return
}
// replay a log file
func (pl *pLog) replay() (err error) {
for i, rr := range pl.priDest.ReplayReaders() {
pl.log.Info("Starting replay", "log_num", i+1)
dec := gob.NewDecoder(rr)
// iterate reading one log entry after another until EOF is reached
count := 0
for {
var ev interface{}
err := dec.Decode(&ev)
if err == io.EOF {
break // done replaying
}
if err != nil {
pl.log.Debug("replay decode failed", "err", err, "log_num", i+1,
"count", count)
return fmt.Errorf("replay decode failed in log %d after %d entries: %s",
i+1, count, err.Error())
}
//pl.log.Debug("replay decoded", "ev", ev)
count += 1
err = pl.client.Replay(ev)
if err != nil {
return fmt.Errorf("replay failed on entry %d: %s", count, err.Error())
}
}
rr.Close()
}
pl.log.Debug("Ending replay", "logs", len(pl.priDest.ReplayReaders()))
return nil
}
// Write is called by the gob encoder and needs to write the bytes to all destinations
func (pl *pLog) Write(p []byte) (int, error) {
if pl.errState != nil {
return 0, pl.errState // in error state don't move!
}
// track size for log rotation, initial snapshot doesn't count towards limit
l := len(p)
if !pl.rotating {
pl.size += len(p)
} else {
pl.sizeReplay += len(p)
}
// write to primary destination
n, err := pl.priDest.Write(p)
if n != l || err != nil {
pl.errState = err
return n, err
}
// write to secondary destination
if pl.secDest != nil {
pl.secDest.Write(p) // TODO: record error
}
return n, nil
}
// NewLog reopens an existing log, replays all log entries, and then prepares to append
// to it. The call to NewLog completes once any necessary replay has completed.
func NewLog(priDest LogDestination, client LogClient, logger log15.Logger) (Log, error) {
pl := &pLog{
client: client,
sizeLimit: 1024 * 1024, // 1MB default
priDest: priDest,
log: logger.New("start", time.Now()),
}
pl.encoder = gob.NewEncoder(pl)
pl.log.Debug("Starting replay")
err := pl.replay()
if err != nil {
pl.errState = err
return nil, err
}
pl.log.Info("Replay done")
// now create a full snapshot
pl.log.Debug("Starting snapshot")
pl.rotating = true
pl.client.PersistAll(pl)
pl.rotating = false
pl.log.Info("Snapshot done")
// tell all log destinations that we're done with the rotation
err = pl.priDest.EndRotate()
if pl.secDest != nil {
pl.secDest.EndRotate() // TODO: record error
}
if err != nil {
pl.errState = err
return nil, err
}
return pl, err
}