func handleReqAppend(r io.Reader, w io.Writer, pool *topicPool) error {
dec := proto.NewDecoder(r)
cid := dec.DecodeUint32()
topic := dec.DecodeShortBytes()
msgs := make([][]byte, dec.DecodeArrayLen())
if err := dec.Err(); err != nil {
_ = writeErrResp(w, cid, "cannot decode request")
return errwrap.Err(err, "cannot decode")
}
if len(topic) == 0 {
_ = writeErrResp(w, cid, "topic name not given")
return nil
}
if len(msgs) == 0 {
return writeErrResp(w, cid, "no messages")
}
var mrd proto.MsgReader
for i := range msgs {
b, err := mrd.ReadBytes(r)
if err != nil {
_ = writeErrResp(w, cid, "cannot read message")
return errwrap.Err(err, "cannot read message")
}
msgs[i] = b
}
s, err := pool.Topic(string(topic))
if err != nil {
_ = writeErrResp(w, cid, "topic not available")
return errwrap.Err(err, "cannot decode")
}
index, err := s.Append(msgs)
if err != nil {
_ = writeErrResp(w, cid, "cannot store messages")
return errwrap.Err(err, "storage error: cannot append")
}
var b bytes.Buffer
enc := proto.NewEncoder(&b)
enc.EncodeUint8(proto.AppendResp)
enc.EncodeUint32(cid)
enc.EncodeUint64(index)
if err := enc.Err(); err != nil {
_ = writeErrResp(w, cid, "cannot encode response")
return errwrap.Err(err, "cannot encode response")
}
if _, err := b.WriteTo(w); err != nil {
_ = writeErrResp(w, cid, "cannot write response")
return errwrap.Err(err, "cannot write response")
}
return nil
}
func main() {
log.SetOutput(os.Stdout)
log.SetFlags(0)
addr := flag.String("addr", "localhost:12345", "Server address")
flag.Parse()
if a := len(flag.Args()); a < 3 || a > 4 {
fmt.Fprintf(os.Stderr, `
Usage:
%s <topic> <offset> <limit> [<timeout>]
`, os.Args[0])
os.Exit(2)
}
topic := flag.Args()[0]
offset, err := strconv.ParseInt(flag.Args()[1], 10, 64)
if err != nil {
log.Fatalf("invalid offset value: %s", err)
}
limit, err := strconv.ParseInt(flag.Args()[2], 10, 64)
if err != nil {
log.Fatalf("invalid limit value: %s", err)
}
if limit < 1 {
log.Fatal("limit must be greater than 0")
}
var timeout int64
if len(flag.Args()) == 4 {
timeout, err = strconv.ParseInt(flag.Args()[3], 10, 64)
if err != nil {
log.Fatalf("invalid timeout value: %s", err)
}
}
cid := uint32(time.Now().Unix())
var b bytes.Buffer
enc := proto.NewEncoder(&b)
enc.EncodeUint8(proto.SliceReq)
enc.EncodeUint32(cid)
enc.EncodeShortBytes([]byte(topic))
enc.EncodeUint64(uint64(offset))
enc.EncodeUint16(uint16(limit))
enc.EncodeUint16(uint16(timeout))
c, err := net.Dial("tcp", *addr)
if err != nil {
log.Fatalf("cannot connect to server: %s", err)
}
defer c.Close()
if _, err := b.WriteTo(c); err != nil {
log.Fatalf("cannot send request: %s", err)
}
dec := proto.NewDecoder(c)
switch kind := dec.DecodeUint8(); kind {
case proto.SliceResp:
case proto.ErrResp:
if rcid := dec.DecodeUint32(); rcid != cid {
log.Printf("correlation ID missmatch, want %d, got %d", cid, rcid)
}
log.Fatalf("error response: %q", dec.DecodeBytes())
default:
log.Fatalf("unknown response kind: %d", kind)
}
if rcid := dec.DecodeUint32(); rcid != cid {
log.Printf("correlation ID missmatch, want %d, got %d", cid, rcid)
}
msgcnt := dec.DecodeArrayLen()
var rw proto.MsgReader
for i := 0; i < int(msgcnt); i++ {
b, err := rw.ReadBytes(c)
if err != nil {
log.Fatalf("cannot read message: %s", err)
}
dec := proto.NewDecoder(bytes.NewBuffer(b))
show("[f%d k%d t%d #%d]",
dec.DecodeUint8(), dec.DecodeUint16(), dec.DecodeUint64(),
dec.DecodeUint64())
show("%q", dec.DecodeShortBytes())
show("%s", dec.DecodeBytes())
show("")
}
}
// Slicing with offset == number of messages will block for max timeout before
// returning response. If during wait time any new message was written to
// topic, it will be returned. Otherwise if timeout was reached and no new
// messages was published, timeout error is returned.
// Slicing with offset > number of messages instantly returns out of bound
// error.
func (s *store) Slice(offset, limit uint64, timeout time.Duration) ([][]byte, error) {
if limit == 0 {
return nil, nil
}
s.mu.RLock()
amount := s.index.Count()
s.mu.RUnlock()
// TODO use notification instead of busy looping
deadline := time.After(timeout)
waitMessages:
for {
switch {
case offset == amount:
select {
case <-deadline:
return nil, errors.New("no new messages")
case <-time.After(10 * time.Millisecond):
s.mu.RLock()
amount = s.index.Count()
s.mu.RUnlock()
}
case offset > amount:
return nil, errors.New("out of bound")
default:
break waitMessages
}
}
s.mu.RLock()
defer s.mu.RUnlock()
if offset+limit > amount {
limit = amount - offset
}
if pos, err := s.index.Offset(offset); err != nil {
return nil, errwrap.Err(err, "cannot read index")
} else {
if _, err := s.log.Seek(pos, os.SEEK_SET); err != nil {
return nil, errwrap.Err(err, "cannot seek")
}
}
res := make([][]byte, 0, limit)
var rd proto.MsgReader
for i := 0; i < int(limit); i++ {
b, err := rd.ReadBytes(s.log)
switch err {
case nil:
case proto.ErrNotEnoughData, io.EOF:
return res, nil
default:
return res, err
}
res = append(res, b)
}
return res, nil
}