use tsMemory to determine whether read from disk or memory

remove lastFlushTime

weed/util/log_buffer/log_buffer.go

@@ -29,7 +29,6 @@ type LogBuffer struct {
 	pos           int
 	startTime     time.Time
 	stopTime      time.Time
-	lastFlushTime time.Time
 	sizeBuf       []byte
 	flushInterval time.Duration
 	flushFn       func(startTime, stopTime time.Time, buf []byte)
@@ -133,8 +132,6 @@ func (m *LogBuffer) loopFlush() {
 			// glog.V(4).Infof("%s flush [%v, %v] size %d", m.name, d.startTime, d.stopTime, len(d.data.Bytes()))
 			m.flushFn(d.startTime, d.stopTime, d.data.Bytes())
 			d.releaseMemory()
-			// local logbuffer is different from aggregate logbuffer here
-			m.lastFlushTime = d.stopTime
 		}
 	}
 }
@@ -165,9 +162,6 @@ func (m *LogBuffer) copyToFlush() *dataToFlush {
 				data:      copiedBytes(m.buf[:m.pos]),
 			}
 			// glog.V(4).Infof("%s flushing [0,%d) with %d entries [%v, %v]", m.name, m.pos, len(m.idx), m.startTime, m.stopTime)
-		} else {
-			// glog.V(4).Infof("%s removed from memory [0,%d) with %d entries [%v, %v]", m.name, m.pos, len(m.idx), m.startTime, m.stopTime)
-			m.lastFlushTime = m.stopTime
 		}
 		m.buf = m.prevBuffers.SealBuffer(m.startTime, m.stopTime, m.buf, m.pos)
 		m.startTime = time.Unix(0, 0)
@@ -188,20 +182,31 @@ func (m *LogBuffer) ReadFromBuffer(lastReadTime time.Time) (bufferCopy *bytes.Bu
 	m.RLock()
 	defer m.RUnlock()
 
-	if !m.lastFlushTime.IsZero() && m.lastFlushTime.After(lastReadTime) {
-		if time.Now().Sub(m.lastFlushTime) < m.flushInterval*2 {
-			diff := m.lastFlushTime.Sub(lastReadTime)
-			glog.V(4).Infof("lastFlush:%v lastRead:%v diff:%v", m.lastFlushTime, lastReadTime, diff)
-			return nil, ResumeFromDiskError
+	// Read from disk and memory
+	//	1. read from disk, last time is = td
+	//	2. in memory, the earliest time = tm
+	//	if tm <= td, case 2.1
+	//		read from memory
+	//	if tm is empty, case 2.2
+	//		read from memory
+	//	if td < tm, case 2.3
+	//		read from disk again
+	var tsMemory time.Time
+	if !m.startTime.IsZero() {
+		tsMemory = m.startTime
+	}
+	for _, prevBuf := range m.prevBuffers.buffers {
+		if !prevBuf.startTime.IsZero() && prevBuf.startTime.Before(tsMemory) {
+			tsMemory = prevBuf.startTime
 		}
 	}
+	if tsMemory.IsZero() { // case 2.2
+		return nil, nil
+	} else if lastReadTime.Before(tsMemory) { // case 2.3
+		return nil, ResumeFromDiskError
+	}
 
-	/*
-		fmt.Printf("read buffer %p: %v last stop time: [%v,%v], pos %d, entries:%d, prevBufs:%d\n", m, lastReadTime, m.startTime, m.stopTime, m.pos, len(m.idx), len(m.prevBuffers.buffers))
-		for i, prevBuf := range m.prevBuffers.buffers {
-			fmt.Printf("  prev %d : %s\n", i, prevBuf.String())
-		}
-	*/
+	// the following is case 2.1
 
 	if lastReadTime.Equal(m.stopTime) {
 		return nil, nil