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protocol.go
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protocol.go
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package logstash
import (
"bytes"
"compress/zlib"
"encoding/binary"
"encoding/json"
"errors"
"fmt"
"io"
"net"
"time"
"github.com/elastic/beats/libbeat/common"
"github.com/elastic/beats/libbeat/logp"
)
type protocol struct {
conn net.Conn
timeout time.Duration
compressLevel int
// the beat name
beat []byte
eventsBuffer *bytes.Buffer
}
var (
// ErrProtocolError is returned if an protocol error was detected in the
// conversation with lumberjack server.
ErrProtocolError = errors.New("lumberjack protocol error")
errAllEventsEncoding = errors.New("failed to encode all events")
)
var (
codeVersion byte = '2'
codeWindowSize = []byte{codeVersion, 'W'}
codeJSONDataFrame = []byte{codeVersion, 'J'}
codeCompressed = []byte{codeVersion, 'C'}
)
func newClientProcol(
conn net.Conn,
timeout time.Duration,
compressLevel int,
beat string,
) (*protocol, error) {
// validate by creating and discarding zlib writer with configured level
if compressLevel > 0 {
tmp := bytes.NewBuffer(nil)
w, err := zlib.NewWriterLevel(tmp, compressLevel)
if err != nil {
return nil, err
}
w.Close()
}
encodedBeat, err := json.Marshal(beat)
if err != nil {
return nil, err
}
return &protocol{
conn: conn,
timeout: timeout,
compressLevel: compressLevel,
eventsBuffer: bytes.NewBuffer(nil),
beat: encodedBeat,
}, nil
}
func (p *protocol) Close() error {
return p.conn.Close()
}
func (p *protocol) sendEvents(events []common.MapStr) ([]common.MapStr, error) {
conn := p.conn
if len(events) == 0 {
return nil, nil
}
debug("send events")
// serialize all raw events into output buffer, removing all events encoding failed for
outEvents, err := p.serializeEvents(events)
count := uint32(len(outEvents))
if count == 0 {
// encoding of all events failed. Let's stop here and report all events
// as exported so no one tries to send/encode the same events once again
// The compress/encode function already prints critical per failed encoding
// failure.
debug("no events serializable")
return nil, errAllEventsEncoding
}
// send window size:
debug("send window size")
if err := p.sendWindowSize(count); err != nil {
return nil, err
}
if p.compressLevel > 0 {
err = p.sendCompressed(p.eventsBuffer.Bytes())
} else {
debug("write events")
_, err = conn.Write(p.eventsBuffer.Bytes())
}
if err != nil {
return nil, err
}
debug("did send %v events", count)
return outEvents, nil
}
func (p *protocol) recvACK() (uint32, error) {
conn := p.conn
if err := conn.SetReadDeadline(time.Now().Add(p.timeout)); err != nil {
return 0, err
}
response := make([]byte, 6)
ackbytes := 0
for ackbytes < 6 {
n, err := conn.Read(response[ackbytes:])
if err != nil {
debug("read ack sequence failed with: %v", err)
return 0, err
}
ackbytes += n
}
isACK := response[0] == codeVersion && response[1] == 'A'
if !isACK {
return 0, ErrProtocolError
}
seq := binary.BigEndian.Uint32(response[2:])
return seq, nil
}
// wait for ACK (accept partial ACK to reset timeout)
// reset timeout timer for every ACK received.
func (p *protocol) awaitACK(count uint32) (uint32, error) {
debug("await ack")
var ackSeq uint32
var err error
// read until all acks
for ackSeq < count {
ackSeq, err = p.recvACK()
if err != nil {
debug("receive ack failed with: %v", err)
return ackSeq, err
}
}
if ackSeq > count {
return count, fmt.Errorf(
"invalid sequence number received (seq=%v, expected=%v)", ackSeq, count)
}
return ackSeq, nil
}
func (p *protocol) sendWindowSize(window uint32) error {
conn := p.conn
if err := conn.SetWriteDeadline(time.Now().Add(p.timeout)); err != nil {
return err
}
if _, err := conn.Write(codeWindowSize); err != nil {
return err
}
return writeUint32(conn, window)
}
func (p *protocol) sendCompressed(payload []byte) error {
debug("send compressed")
conn := p.conn
if err := conn.SetWriteDeadline(time.Now().Add(p.timeout)); err != nil {
return err
}
debug("write compressed header")
if _, err := conn.Write(codeCompressed); err != nil {
return err
}
if err := writeUint32(conn, uint32(len(payload))); err != nil {
return err
}
debug("send payload")
for len(payload) > 0 {
n, err := conn.Write(payload)
payload = payload[n:]
if err != nil {
return err
}
}
return nil
}
func (p *protocol) serializeEvents(events []common.MapStr) ([]common.MapStr, error) {
p.eventsBuffer.Reset()
if p.compressLevel > 0 {
w, _ := zlib.NewWriterLevel(p.eventsBuffer, p.compressLevel)
outEvents, err := p.doSerializeEvents(w, events)
if err != nil {
return nil, err
}
if err := w.Close(); err != nil {
debug("Finalizing zlib compression failed with: %s", err)
return nil, err
}
return outEvents, nil
}
return p.doSerializeEvents(p.eventsBuffer, events)
}
func (p *protocol) doSerializeEvents(out io.Writer, events []common.MapStr) ([]common.MapStr, error) {
var sequence uint32
okEvents := events
for _, event := range events {
sequence++
err := p.serializeDataFrame(out, event, sequence)
if err != nil {
logp.Critical("failed to encode event: %v", err)
sequence--
goto failedLoop
}
}
return okEvents, nil
failedLoop:
// on serialization error continue serializing remaining events and collect
// serializable events only
okEvents = events[:sequence]
restEvents := events[sequence+1:]
for _, event := range restEvents {
sequence++
err := p.serializeDataFrame(out, event, sequence)
if err != nil {
logp.Critical("failed to encode event: %v", err)
sequence--
continue
}
okEvents = append(okEvents, event)
}
return okEvents, nil
}
func (p *protocol) serializeDataFrame(
out io.Writer,
event common.MapStr,
seq uint32,
) error {
// Write JSON Data Frame:
// version: uint8 = '2'
// code: uint8 = 'J'
// seq: uint32
// payloadLen (bytes): uint32
// payload: JSON document
jsonEvent, err := serializeEvent(event, p.beat)
if err != nil {
debug("Fail to json encode event (%v): %#v", err, event)
return err
}
if _, err := out.Write(codeJSONDataFrame); err != nil { // version + code
return err
}
if err := writeUint32(out, seq); err != nil {
return err
}
if err := writeUint32(out, uint32(len(jsonEvent))); err != nil {
return err
}
if _, err := out.Write(jsonEvent); err != nil {
return err
}
return nil
}
func serializeEvent(event common.MapStr, beat []byte) ([]byte, error) {
buf := bytes.NewBuffer(nil)
buf.WriteRune('{')
if _, hasMeta := event["@metadata"]; !hasMeta {
typ := event["type"].(string)
buf.WriteString(`"@metadata":{"type":`)
tmp, err := json.Marshal(typ)
if err != nil {
return nil, err
}
buf.Write(tmp)
buf.WriteString(`,"beat":`)
buf.Write(beat)
buf.WriteString(`},`)
}
for k, v := range event {
// append key
tmp, err := json.Marshal(k)
if err != nil {
return nil, err
}
buf.Write(tmp)
buf.WriteRune(':')
// append value
tmp, err = json.Marshal(v)
if err != nil {
return nil, err
}
buf.Write(tmp)
buf.WriteRune(',')
}
b := buf.Bytes()
b[len(b)-1] = '}'
return b, nil
}
func writeUint32(out io.Writer, v uint32) error {
return binary.Write(out, binary.BigEndian, v)
}