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streamiteratorhandlerfile.go
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/
streamiteratorhandlerfile.go
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package jsonfileprovider
import (
"bufio"
"errors"
"io"
"os"
"github.com/nbigot/ministream/types"
"github.com/goccy/go-json"
"go.uber.org/zap"
)
const EOLChar = '\n'
type StreamIteratorHandlerFile struct {
// implements IStreamIteratorHandler interface
streamUUID types.StreamUUID
itUUID types.StreamIteratorUUID
initialized bool
file *os.File
filename string
FileOffset int64
bytesRead int64
nextRecordIdRead types.MessageId
index *StreamIndexFile
reader *bufio.Reader
logger *zap.Logger
}
func (h *StreamIteratorHandlerFile) Open() error {
// open the json data file
if h.filename == "" {
return errors.New("empty stream filename")
}
if h.file != nil {
h.file.Close()
}
var err error
h.file, err = os.Open(h.filename)
if err != nil {
return err
}
return nil
}
func (h *StreamIteratorHandlerFile) Close() error {
if h.file != nil {
h.file.Close()
h.file = nil
}
if h.index != nil {
h.index.Close()
h.index = nil
}
return nil
}
func (h *StreamIteratorHandlerFile) Seek(request *types.StreamIteratorRequest) error {
var (
err error
nextRecordIdToRead types.MessageId
)
if h.initialized {
_, err = h.file.Seek(h.FileOffset, io.SeekStart)
return err
}
switch request.IteratorType {
case "FIRST_MESSAGE":
nextRecordIdToRead, h.FileOffset, err = h.index.GetOffsetFirstMessage()
case "LAST_MESSAGE":
nextRecordIdToRead, h.FileOffset, err = h.index.GetOffsetLastMessage()
case "AFTER_LAST_MESSAGE":
nextRecordIdToRead, h.FileOffset, err = h.index.GetOffsetAfterLastMessage()
case "AT_MESSAGE_ID":
nextRecordIdToRead, h.FileOffset, err = h.index.GetOffsetAtMessageId(request.MessageId)
case "AFTER_MESSAGE_ID":
nextRecordIdToRead, h.FileOffset, err = h.index.GetOffsetAfterMessageId(request.MessageId)
case "AT_TIMESTAMP":
nextRecordIdToRead, h.FileOffset, err = h.index.GetOffsetAtTimestamp(&request.Timestamp)
default:
h.FileOffset = 0
nextRecordIdToRead = 0
err = errors.New("invalid iterator type")
}
if err == nil {
if _, err = h.file.Seek(h.FileOffset, io.SeekStart); err != nil {
return err
}
h.initialized = true
h.reader = bufio.NewReaderSize(h.file, 1024*1024)
h.reader.Reset(h.file)
h.nextRecordIdRead = nextRecordIdToRead
}
return err
}
func (h *StreamIteratorHandlerFile) SaveSeek() error {
var err error
h.FileOffset, err = h.file.Seek(0, io.SeekCurrent)
return err
}
func (h *StreamIteratorHandlerFile) GetNextRecord() (types.MessageId, interface{}, bool, bool, error) {
line, errRead := h.reader.ReadString(EOLChar)
if errRead != nil {
// err is often io.EOF (end of file reached)
// err may also raise when EOL char was not found
errSeek := h.SaveSeek()
if errSeek != nil {
// result is: (no record, no record found, cannot continue, error)
return 0, nil, false, false, errSeek
}
if errRead == io.EOF {
// result is: (no record, no record found, cannot continue, no error)
return 0, nil, false, false, nil
} else {
h.logger.Error(
"cannot read record line",
zap.String("topic", "streamiterator"),
zap.String("method", "GetNextRecord"),
zap.String("stream.uuid", h.streamUUID.String()),
zap.String("it.uuid", h.itUUID.String()),
zap.String("line", line),
zap.Error(errRead),
)
// result is: (no record, no record found (or cannot read it), cannot continue, error)
return 0, nil, true, false, errRead
}
}
h.bytesRead += int64(len(line))
lastRecordIdRead := h.nextRecordIdRead
h.nextRecordIdRead++
var message interface{}
if errUnmarshal := json.Unmarshal([]byte(line), &message); errUnmarshal != nil {
h.logger.Error(
"json format error",
zap.String("topic", "streamiterator"),
zap.String("method", "GetNextRecord"),
zap.String("stream.uuid", h.streamUUID.String()),
zap.String("it.uuid", h.itUUID.String()),
zap.String("line", line),
zap.Error(errUnmarshal),
)
// result is: (no record, record found, may continue, error)
return lastRecordIdRead, nil, true, true, errUnmarshal
}
// result is: (valid record, record found, may continue, no error)
return lastRecordIdRead, message, true, true, nil
}
func NewStreamIteratorHandlerFile(streamUUID types.StreamUUID, iteratorUUID types.StreamIteratorUUID, filename string, idx *StreamIndexFile, logger *zap.Logger) *StreamIteratorHandlerFile {
return &StreamIteratorHandlerFile{
streamUUID: streamUUID,
itUUID: iteratorUUID,
initialized: false,
file: nil,
filename: filename,
FileOffset: 0,
bytesRead: 0,
nextRecordIdRead: 0,
index: idx,
reader: nil,
logger: logger,
}
}