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bufferedwriter.go
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bufferedwriter.go
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package bufferedwriter
import (
"bufio"
"fmt"
"io"
"sync"
"github.com/VictoriaMetrics/VictoriaMetrics/lib/netutil"
)
// Get returns buffered writer for the given w.
//
// The writer must be returned to the pool after use by calling Put().
func Get(w io.Writer) *Writer {
v := writerPool.Get()
if v == nil {
v = &Writer{
// By default net/http.Server uses 4KB buffers, which are flushed to client with chunked responses.
// These buffers may result in visible overhead for responses exceeding a few megabytes.
// So allocate 64Kb buffers.
bw: bufio.NewWriterSize(w, 64*1024),
}
}
bw := v.(*Writer)
bw.bw.Reset(w)
return bw
}
// Put returns back bw to the pool.
//
// bw cannot be used after returning to the pool.
func Put(bw *Writer) {
bw.reset()
writerPool.Put(bw)
}
var writerPool sync.Pool
// Writer is buffered writer, which may be used in order to reduce overhead
// when sending moderately big responses to http server.
//
// Writer methods can be called from concurrently running goroutines.
// The writer remembers the first occurred error, which can be inspected with Error method.
type Writer struct {
lock sync.Mutex
bw *bufio.Writer
err error
}
func (bw *Writer) reset() {
bw.bw.Reset(nil)
bw.err = nil
}
// Write writes p to bw.
func (bw *Writer) Write(p []byte) (int, error) {
if len(p) == 0 {
return 0, nil
}
bw.lock.Lock()
defer bw.lock.Unlock()
if bw.err != nil {
return 0, bw.err
}
n, err := bw.bw.Write(p)
if err != nil && !netutil.IsTrivialNetworkError(err) {
bw.err = fmt.Errorf("cannot send %d bytes to client: %w", len(p), err)
}
return n, bw.err
}
// Flush flushes bw to the underlying writer.
func (bw *Writer) Flush() error {
bw.lock.Lock()
defer bw.lock.Unlock()
if bw.err != nil {
return bw.err
}
if err := bw.bw.Flush(); err != nil && !netutil.IsTrivialNetworkError(err) {
bw.err = fmt.Errorf("cannot flush data to client: %w", err)
}
return bw.err
}
// Error returns the first occurred error in bw.
func (bw *Writer) Error() error {
bw.lock.Lock()
defer bw.lock.Unlock()
return bw.err
}