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message-handler.go
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message-handler.go
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// Copyright 2023 Versity Software
// This file is licensed under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
package s3select
import (
"bufio"
"context"
"encoding/binary"
"encoding/xml"
"fmt"
"hash/crc32"
"sync"
"sync/atomic"
"time"
)
// Protocol definition for messages can be found here:
// https://docs.aws.amazon.com/AmazonS3/latest/API/RESTSelectObjectAppendix.html
var (
// From ptotocol def:
// Enum indicating the header value type.
// For Amazon S3 Select, this is always 7.
headerValueType = byte(7)
)
func intToTwoBytes(i int) []byte {
return []byte{byte(i >> 8), byte(i)}
}
func generateHeader(messages ...string) []byte {
var header []byte
for i, message := range messages {
if i%2 == 1 {
header = append(header, headerValueType)
header = append(header, intToTwoBytes(len(message))...)
} else {
header = append(header, byte(len(message)))
}
header = append(header, message...)
}
return header
}
func generateOctetHeader(message string) []byte {
return generateHeader(
":message-type",
"event",
":content-type",
"application/octet-stream",
":event-type",
message)
}
func generateTextHeader(message string) []byte {
return generateHeader(
":message-type",
"event",
":content-type",
"text/xml",
":event-type",
message)
}
func generateNoContentHeader(message string) []byte {
return generateHeader(
":message-type",
"event",
":event-type",
message)
}
const (
// 4 bytes total byte len +
// 4 bytes headers bytes len +
// 4 bytes prelude CRC
preludeLen = 12
// CRC is uint32
msgCrcLen = 4
)
var (
recordsHeader = generateOctetHeader("Records")
continuationHeader = generateNoContentHeader("Cont")
continuationMessage = genMessage(continuationHeader, []byte{})
progressHeader = generateTextHeader("Progress")
statsHeader = generateTextHeader("Stats")
endHeader = generateNoContentHeader("End")
endMessage = genMessage(endHeader, []byte{})
)
func uintToBytes(n uint32) []byte {
b := make([]byte, 4)
binary.BigEndian.PutUint32(b, n)
return b
}
func generatePrelude(msgLen int, headerLen int) []byte {
prelude := make([]byte, 0, preludeLen)
// 4 bytes total byte len
prelude = append(prelude, uintToBytes(uint32(msgLen+headerLen+preludeLen+msgCrcLen))...)
// 4 bytes headers bytes len
prelude = append(prelude, uintToBytes(uint32(headerLen))...)
// 4 bytes prelude CRC
prelude = append(prelude, uintToBytes(crc32.ChecksumIEEE(prelude))...)
return prelude
}
const (
maxHeaderSize = 1024 * 1024
)
func genMessage(header, payload []byte) []byte {
var msg []byte
// below is always true since the size is validated
// in the send record
if len(header) <= maxHeaderSize && len(payload) <= maxMessageSize {
msglen := preludeLen + len(header) + len(payload) + msgCrcLen
msg = make([]byte, 0, msglen)
}
msg = append(msg, generatePrelude(len(payload), len(header))...)
msg = append(msg, header...)
msg = append(msg, payload...)
msg = append(msg, uintToBytes(crc32.ChecksumIEEE(msg))...)
return msg
}
func genRecordsMessage(payload []byte) []byte {
return genMessage(recordsHeader, payload)
}
type progress struct {
XMLName xml.Name `xml:"Progress"`
BytesScanned int64 `xml:"BytesScanned"`
BytesProcessed int64 `xml:"BytesProcessed"`
BytesReturned int64 `xml:"BytesReturned"`
}
func genProgressMessage(bytesScanned, bytesProcessed, bytesReturned int64) []byte {
progress := progress{
BytesScanned: bytesScanned,
BytesProcessed: bytesProcessed,
BytesReturned: bytesReturned,
}
xmlData, _ := xml.MarshalIndent(progress, "", " ")
payload := []byte(xml.Header + string(xmlData))
return genMessage(progressHeader, payload)
}
type stats struct {
XMLName xml.Name `xml:"Stats"`
BytesScanned int64 `xml:"BytesScanned"`
BytesProcessed int64 `xml:"BytesProcessed"`
BytesReturned int64 `xml:"BytesReturned"`
}
func genStatsMessage(bytesScanned, bytesProcessed, bytesReturned int64) []byte {
stats := stats{
BytesScanned: bytesScanned,
BytesProcessed: bytesProcessed,
BytesReturned: bytesReturned,
}
xmlData, _ := xml.MarshalIndent(stats, "", " ")
payload := []byte(xml.Header + string(xmlData))
return genMessage(statsHeader, payload)
}
func genErrorMessage(errorCode, errorMessage string) []byte {
return genMessage(generateHeader(
":error-code",
errorCode,
":error-message",
errorMessage,
":message-type",
"error",
), []byte{})
}
// GetProgress is a callback function that periodically retrieves the current
// values for the following if not nil. This is used to send Progress
// messages back to client.
// BytesScanned => Number of bytes that have been processed before being uncompressed (if the file is compressed).
// BytesProcessed => Number of bytes that have been processed after being uncompressed (if the file is compressed).
type GetProgress func() (bytesScanned int64, bytesProcessed int64)
type MessageHandler struct {
sync.Mutex
ctx context.Context
cancel context.CancelFunc
writer *bufio.Writer
data chan []byte
getProgress GetProgress
stopCh chan bool
resetCh chan bool
bytesReturned int64
}
// NewMessageHandler creates a new MessageHandler instance and starts the event streaming
func NewMessageHandler(ctx context.Context, w *bufio.Writer, getProgressFunc GetProgress) *MessageHandler {
ctx, cancel := context.WithCancel(ctx)
mh := &MessageHandler{
ctx: ctx,
cancel: cancel,
writer: w,
data: make(chan []byte),
getProgress: getProgressFunc,
resetCh: make(chan bool),
stopCh: make(chan bool),
}
go mh.sendBackgroundMessages(mh.resetCh, mh.stopCh)
return mh
}
func (mh *MessageHandler) write(data []byte) error {
mh.Lock()
defer mh.Unlock()
mh.stopCh <- true
defer func() { mh.resetCh <- true }()
_, err := mh.writer.Write(data)
if err != nil {
return err
}
return mh.writer.Flush()
}
const (
continuationInterval = time.Second
progressInterval = time.Minute
)
func (mh *MessageHandler) sendBackgroundMessages(resetCh, stopCh <-chan bool) {
continuationTicker := time.NewTicker(continuationInterval)
defer continuationTicker.Stop()
var progressTicker *time.Ticker
var progressTickerChan <-chan time.Time
if mh.getProgress != nil {
progressTicker = time.NewTicker(progressInterval)
progressTickerChan = progressTicker.C
defer progressTicker.Stop()
}
Loop:
for {
select {
case <-mh.ctx.Done():
break Loop
case <-continuationTicker.C:
err := mh.write(continuationMessage)
if err != nil {
mh.cancel()
break Loop
}
case <-resetCh:
continuationTicker.Reset(continuationInterval)
case <-stopCh:
continuationTicker.Stop()
case <-progressTickerChan:
var bytesScanned, bytesProcessed int64
if mh.getProgress != nil {
bytesScanned, bytesProcessed = mh.getProgress()
}
bytesReturned := atomic.LoadInt64(&mh.bytesReturned)
err := mh.write(genProgressMessage(bytesScanned, bytesProcessed, bytesReturned))
if err != nil {
mh.cancel()
break Loop
}
}
}
}
// SendRecord sends a single Records message
func (mh *MessageHandler) SendRecord(payload []byte) error {
if mh.ctx.Err() != nil {
return mh.ctx.Err()
}
if len(payload) > maxMessageSize {
return fmt.Errorf("record max size exceeded")
}
err := mh.write(genRecordsMessage(payload))
if err != nil {
return err
}
atomic.AddInt64(&mh.bytesReturned, int64(len(payload)))
return nil
}
// Finish terminates message stream with Stats and End message
// generates stats and end message using function args based on:
// BytesScanned => Number of bytes that have been processed before being uncompressed (if the file is compressed).
// BytesProcessed => Number of bytes that have been processed after being uncompressed (if the file is compressed).
func (mh *MessageHandler) Finish(bytesScanned, bytesProcessed int64) error {
if mh.ctx.Err() != nil {
return mh.ctx.Err()
}
bytesReturned := atomic.LoadInt64(&mh.bytesReturned)
err := mh.write(genStatsMessage(bytesScanned, bytesProcessed, bytesReturned))
if err != nil {
return err
}
err = mh.write(endMessage)
if err != nil {
return err
}
mh.cancel()
return nil
}
// FinishWithError terminates event stream with error
func (mh *MessageHandler) FinishWithError(errorCode, errorMessage string) error {
if mh.ctx.Err() != nil {
return mh.ctx.Err()
}
err := mh.write(genErrorMessage(errorCode, errorMessage))
if err != nil {
return err
}
mh.cancel()
return nil
}