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
184
185
186
187
188
189
190
191
|
/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <boost/optional.hpp>
#include <cstddef>
#include <cstdint>
#include <tuple>
#include <vector>
#include "mongo/base/disallow_copying.h"
#include "mongo/base/status_with.h"
#include "mongo/bson/util/builder.h"
#include "mongo/db/ftdc/block_compressor.h"
#include "mongo/db/ftdc/config.h"
#include "mongo/db/jsobj.h"
namespace mongo {
/**
* FTDCCompressor is responsible for taking a set of BSON documents containing metrics, and
* compressing them into a highly compressed buffer. Metrics are defined as BSON number or number
* like type (like dates, and timestamps).
*
* Compression Method
* 1. For each document after the first, it computes the delta between it and the preceding document
* for the number fields
* 2. It stores the deltas into an array of std::int64_t.
* 3. It compressed each std::int64_t using VarInt integer compression. See varint.h.
* 4. Encodes zeros in Run Length Encoded pairs of <Count, Zero>
* 5. ZLIB compresses the final processed array
*
* NOTE: This compression ignores non-number data, and assumes the non-number data is constant
* across all documents in the series of documents.
*/
class FTDCCompressor {
MONGO_DISALLOW_COPYING(FTDCCompressor);
public:
/**
* The FTDCCompressor returns one of these values when a sample is added to indicate whether the
* caller should flush the buffer to disk or not.
*/
enum class CompressorState {
/**
* Needs to flush because the schemas has changed. Caller needs to flush.
*/
kSchemaChanged,
/**
* Quota on the number of samples in a metric chunk has been reached. Caller needs to flush.
*/
kCompressorFull,
};
explicit FTDCCompressor(const FTDCConfig* config) : _config(config) {}
/**
* Add a bson document containing metrics into the compressor.
*
* Returns flag indicating whether the caller should flush the compressor buffer to disk.
* 1. kCompressorFull if the compressor is considered full.
* 2. kSchemaChanged if there was a schema change, and buffer should be flushed.
* 3. kHasSpace if it has room for more metrics in the current buffer.
*
* date is the date at which the sample as started to be captured. It will be saved in the
* compressor if this sample is used as the reference document.N
*/
StatusWith<boost::optional<std::tuple<ConstDataRange, CompressorState, Date_t>>> addSample(
const BSONObj& sample, Date_t date);
/**
* Returns the number of enqueued samples.
*
* The a buffer will decompress to (1 + getCountCount). The extra 1 comes
* from the reference document.
*/
std::size_t getSampleCount() const {
// TODO: This method should probably be renamed, since it currently
// returns the number of deltas, which does not include the sample
// implicitly contained in the reference document.
return _deltaCount;
}
/**
* Has a document been added?
*
* If addSample has been called, then we have at least the reference document, but not
* necessarily any additional metric samples. When the buffer is filled to capacity,
* the reference document is reset.
*/
bool hasDataToFlush() const {
return !_referenceDoc.isEmpty();
}
/**
* Gets buffer of compressed data contained in the FTDCCompressor.
*
* The returned buffer is valid until next call to addSample() or getCompressedSamples() with
* CompressBuffer::kGenerateNewCompressedBuffer.
*/
StatusWith<std::tuple<ConstDataRange, Date_t>> getCompressedSamples();
/**
* Reset the state of the compressor.
*
* Callers can use this to reset the compressor to a clean state instead of recreating it.
*/
void reset();
/**
* Compute the offset into an array for given (sample, metric) pair
*/
static size_t getArrayOffset(std::uint32_t sampleCount,
std::uint32_t sample,
std::uint32_t metric) {
return metric * sampleCount + sample;
}
private:
/**
* Reset the state
*/
void _reset(const BSONObj& referenceDoc, Date_t date);
private:
// Block Compressor
BlockCompressor _compressor;
// Config
const FTDCConfig* const _config;
// Reference schema document
BSONObj _referenceDoc;
// Time at which reference schema document was collected.
// Passed in via addSample and returned with each chunk.
Date_t _referenceDocDate;
// Number of Metrics for the reference document
std::uint32_t _metricsCount{0};
// Number of deltas recorded
std::uint32_t _deltaCount{0};
// Max deltas for the current chunk
std::size_t _maxDeltas{0};
// Array of deltas - M x S
// _deltas[Metrics][Samples]
std::vector<std::uint64_t> _deltas;
// Buffer for metric chunk compressed = uncompressed length + compressed data
BufBuilder _compressedChunkBuffer;
// Buffer for uncompressed metric chunk
BufBuilder _uncompressedChunkBuffer;
// Buffer to hold metrics
std::vector<std::uint64_t> _metrics;
std::vector<std::uint64_t> _prevmetrics;
};
} // namespace mongo
|
