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// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package logtail
import (
"bytes"
"errors"
"fmt"
"sync"
)
type Buffer interface {
// TryReadLine tries to read a log line from the ring buffer.
// If no line is available it returns a nil slice.
// If the ring buffer is closed it returns io.EOF.
//
// The returned slice may point to data that will be overwritten
// by a subsequent call to TryReadLine.
TryReadLine() ([]byte, error)
// Write writes a log line into the ring buffer.
Write([]byte) (int, error)
}
func NewMemoryBuffer(numEntries int) Buffer {
return &memBuffer{
pending: make(chan qentry, numEntries),
}
}
type memBuffer struct {
next []byte
pending chan qentry
dropMu sync.Mutex
dropCount int
}
func (m *memBuffer) TryReadLine() ([]byte, error) {
if m.next != nil {
msg := m.next
m.next = nil
return msg, nil
}
select {
case ent := <-m.pending:
if ent.dropCount > 0 {
m.next = ent.msg
buf := new(bytes.Buffer)
fmt.Fprintf(buf, "----------- %d logs dropped ----------", ent.dropCount)
return buf.Bytes(), nil
}
return ent.msg, nil
default:
return nil, nil
}
}
func (m *memBuffer) Write(b []byte) (int, error) {
m.dropMu.Lock()
defer m.dropMu.Unlock()
ent := qentry{
msg: b,
dropCount: m.dropCount,
}
select {
case m.pending <- ent:
m.dropCount = 0
return len(b), nil
default:
m.dropCount++
return 0, errBufferFull
}
}
type qentry struct {
msg []byte
dropCount int
}
var errBufferFull = errors.New("logtail: buffer full")
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