-
Notifications
You must be signed in to change notification settings - Fork 487
/
data_reader.go
183 lines (153 loc) · 4.87 KB
/
data_reader.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
package v2
import (
"bytes"
"context"
"fmt"
"io"
tempo_io "github.com/grafana/tempo/pkg/io"
"github.com/grafana/tempo/tempodb/backend"
"github.com/grafana/tempo/tempodb/encoding/common"
"github.com/klauspost/compress/zstd"
)
type dataReader struct {
contextReader backend.ContextReader
pageBuffer []byte
encoding backend.Encoding
pool ReaderPool
compressedReader io.Reader
}
// constDataHeader is a singleton data header. the data header is
// stateless b/c there are no fields. to very minorly reduce allocations all
// data should just use this.
var constDataHeader = &dataHeader{}
// NewDataReader constructs a v2 DataReader that handles paged...reading
func NewDataReader(r backend.ContextReader, encoding backend.Encoding) (common.DataReader, error) {
pool, err := getReaderPool(encoding)
if err != nil {
return nil, err
}
return &dataReader{
encoding: encoding,
contextReader: r,
pool: pool,
}, nil
}
// Read implements common.DataReader
func (r *dataReader) Read(ctx context.Context, records []common.Record, pagesBuffer [][]byte, buffer []byte) ([][]byte, []byte, error) {
if len(records) == 0 {
return nil, buffer, nil
}
start := records[0].Start
length := uint32(0)
for _, record := range records {
length += record.Length
}
if cap(buffer) < int(length) {
buffer = make([]byte, length)
}
buffer = buffer[:length]
_, err := r.contextReader.ReadAt(ctx, buffer, int64(start))
if err != nil {
return nil, nil, err
}
compressedPagesBuffer := make([][]byte, len(records))
cursor := uint32(0)
previousEnd := uint64(0)
for i, record := range records {
end := cursor + record.Length
if end > uint32(len(buffer)) {
return nil, nil, fmt.Errorf("record out of bounds while reading pages: %d, %d, %d, %d", cursor, record.Length, end, len(buffer))
}
if previousEnd != record.Start && previousEnd != 0 {
return nil, nil, fmt.Errorf("non-contiguous pages requested from dataReader: %d, %+v", previousEnd, record)
}
compressedPagesBuffer[i] = buffer[cursor:end]
cursor += record.Length
previousEnd = record.Start + uint64(record.Length)
}
// read and strip page data
compressedPages := make([][]byte, 0, len(compressedPagesBuffer))
for _, v0Page := range compressedPagesBuffer {
page, err := unmarshalPageFromBytes(v0Page, constDataHeader)
if err != nil {
return nil, nil, err
}
compressedPages = append(compressedPages, page.data)
}
// prepare pagesBuffer
if cap(pagesBuffer) < len(compressedPages) {
// extend pagesBuffer
diff := len(compressedPages) - cap(pagesBuffer)
pagesBuffer = append(pagesBuffer[:cap(pagesBuffer)], make([][]byte, diff)...)
} else {
pagesBuffer = pagesBuffer[:len(compressedPages)]
}
// now decompress
for i, page := range compressedPages {
reader, err := r.getCompressedReader(page)
if err != nil {
return nil, nil, err
}
// TODO: leaky abstraction. can a real programmer fix this in the future?
// zstd decoder is ~10-20% faster then the streaming io.Reader interface so prefer that
decoder, ok := reader.(*zstd.Decoder)
if ok {
pagesBuffer[i], err = decoder.DecodeAll(page, pagesBuffer[i][:0])
} else {
pagesBuffer[i], err = tempo_io.ReadAllWithBuffer(reader, len(page), pagesBuffer[i])
}
if err != nil {
return nil, nil, err
}
}
return pagesBuffer, buffer, nil
}
func (r *dataReader) Close() {
if r.compressedReader != nil {
r.pool.PutReader(r.compressedReader)
}
}
// NextPage implements common.DataReader
func (r *dataReader) NextPage(buffer []byte) ([]byte, uint32, error) {
reader, err := r.contextReader.Reader()
if err != nil {
return nil, 0, err
}
page, err := unmarshalPageFromReader(reader, constDataHeader, r.pageBuffer)
if err != nil {
return nil, 0, err
}
r.pageBuffer = page.data
compressedReader, err := r.getCompressedReader(page.data)
if err != nil {
return nil, 0, err
}
// TODO: leaky abstraction. can a real programmer fix this in the future?
// zstd decoder is ~10-20% faster then the streaming io.Reader interface so prefer that
decoder, ok := compressedReader.(*zstd.Decoder)
if ok {
buffer, err = decoder.DecodeAll(page.data, buffer[:0])
} else {
buffer, err = tempo_io.ReadAllWithBuffer(compressedReader, len(page.data), buffer)
}
if err != nil {
return nil, 0, err
}
return buffer, page.totalLength, nil
}
func (r *dataReader) getCompressedReader(page []byte) (io.Reader, error) {
var err error
var reader io.Reader
// we are going to use the stateless zstd decoding functionality. if you pass
// a non-nil reader to .GetReader() and then use .DecodeAll() the process hangs
// for unknown reasons. so don't do that.
if r.encoding != backend.EncZstd {
reader = bytes.NewReader(page)
}
if r.compressedReader == nil {
r.compressedReader, err = r.pool.GetReader(reader)
} else {
r.compressedReader, err = r.pool.ResetReader(reader, r.compressedReader)
}
return r.compressedReader, err
}