Method doRunGC

value.go:1688–1822

(lf *logFile, discardRatio float64, tr trace.Trace)

}

func (vlog *valueLog) doRunGC(lf *logFile, discardRatio float64, tr trace.Trace) (err error) {
	// Update stats before exiting
	defer func() {
		if err == nil {
			vlog.lfDiscardStats.Lock()
			delete(vlog.lfDiscardStats.m, lf.fid)
			vlog.lfDiscardStats.Unlock()
		}
	}()

	type reason struct {
		total   float64
		discard float64
		count   int
	}

	fi, err := lf.fd.Stat()
	if err != nil {
		tr.LazyPrintf("Error while finding file size: %v", err)
		tr.SetError()
		return err
	}

	// Set up the sampling window sizes.
	sizeWindow := float64(fi.Size()) * 0.1                          // 10% of the file as window.
	sizeWindowM := sizeWindow / (1 << 20)                           // in MBs.
	countWindow := int(float64(vlog.opt.ValueLogMaxEntries) * 0.01) // 1% of num entries.
	tr.LazyPrintf("Size window: %5.2f. Count window: %d.", sizeWindow, countWindow)

	// Pick a random start point for the log.
	skipFirstM := float64(rand.Int63n(fi.Size())) // Pick a random starting location.
	skipFirstM -= sizeWindow                      // Avoid hitting EOF by moving back by window.
	skipFirstM /= float64(mi)                     // Convert to MBs.
	tr.LazyPrintf("Skip first %5.2f MB of file of size: %d MB", skipFirstM, fi.Size()/mi)
	var skipped float64

	var r reason
	start := time.Now()
	y.AssertTrue(vlog.db != nil)
	s := new(y.Slice)
	var numIterations int
	_, err = vlog.iterate(lf, 0, func(e Entry, vp valuePointer) error {
		numIterations++
		esz := float64(vp.Len) / (1 << 20) // in MBs.
		if skipped < skipFirstM {
			skipped += esz
			return nil
		}

		// Sample until we reach the window sizes or exceed 10 seconds.
		if r.count > countWindow {
			tr.LazyPrintf("Stopping sampling after %d entries.", countWindow)
			return errStop
		}
		if r.total > sizeWindowM {
			tr.LazyPrintf("Stopping sampling after reaching window size.")
			return errStop
		}