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
|
/**
* 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 <string>
#include <vector>
#include "mongo/base/string_data.h"
#include "mongo/platform/mutex.h"
#include "mongo/util/concurrency/mutex.h"
#include "mongo/util/concurrency/with_lock.h"
namespace mongo::logv2 {
/**
* Variable-capacity circular log of line-oriented messages.
*
* Holds up to RamLog::kMaxLines lines and caps total space to RamLog::kMaxSizeBytes [1]. There is
* no limit on the length of the line. RamLog expects the caller to truncate lines to a reasonable
* length.
*
* RamLogs are stored in a global registry, accessed via RamLog::get() and
* RamLog::getIfExists().
*
* RamLogs and their registry are self-synchronizing. See documentary comments.
* To read a RamLog, instantiate a RamLog::LineIterator, documented below.
*
* Note:
* 1. In the degenerate case of a single log line being above RamLog::kMaxSizeBytes, it may
* keep up to two log lines and exceed the size cap.
*/
class RamLog {
RamLog(const RamLog&) = delete;
RamLog& operator=(const RamLog&) = delete;
public:
class LineIterator;
friend class RamLog::LineIterator;
/**
* Returns a pointer to the ramlog named "name", creating one if it did not already exist.
*
* Synchronizes on the RamLog catalog lock, _namedLock.
*/
static RamLog* get(const std::string& name);
/**
* Returns a pointer to the ramlog named "name", or NULL if no such ramlog exists.
*
* Synchronizes on the RamLog catalog lock, _namedLock.
*/
static RamLog* getIfExists(const std::string& name);
/**
* Writes the names of all existing ramlogs into "names".
*
* Synchronizes on the RamLog catalog lock, _namedLock.
*/
static void getNames(std::vector<std::string>& names);
/**
* Writes "str" as a line into the RamLog. If "str" is longer than the maximum
* line size of the log, it keeps two lines.
*
* Synchronized on the instance's own mutex, _mutex.
*/
void write(const std::string& str);
/**
* Empties out the RamLog.
*/
void clear();
private:
explicit RamLog(StringData name);
~RamLog(); // want this private as we want to leak so we can use them till the very end
StringData getLine(size_t lineNumber, WithLock lock) const;
size_t getLineCount(WithLock) const;
void trimIfNeeded(size_t newStr, WithLock lock);
private:
// Maximum number of lines
static constexpr size_t kMaxLines = 1024;
// Maximum capacity of RamLog of string data
static constexpr size_t kMaxSizeBytes = 1024 * 1024;
// Guards all non-static data.
stdx::mutex _mutex; // NOLINT
// Array of lines
std::array<std::string, kMaxLines> _lines;
// First line of ram log
size_t _firstLinePosition;
// Last line of ram log
size_t _lastLinePosition;
// Total size of bytes written
size_t _totalSizeBytes;
// Name of Ram Log
std::string _name;
// Total lines written since last clear, can be > kMaxLines
size_t _totalLinesWritten;
};
/**
* Iterator over the lines of a RamLog.
*
* Also acts as a means of inspecting other properites of a ramlog consistently.
*
* Instances of LineIterator hold the lock for the underlying RamLog for their whole lifetime,
* and so should not be kept around.
*/
class RamLog::LineIterator {
LineIterator(const LineIterator&) = delete;
LineIterator& operator=(const LineIterator&) = delete;
public:
explicit LineIterator(RamLog* ramlog);
/**
* Returns true if there are more lines available to return by calls to next().
*/
bool more() const {
return _nextLineIndex < _ramlog->getLineCount(_lock);
}
/**
* Returns the next line and advances the iterator.
*/
StringData next() {
return _ramlog->getLine(_nextLineIndex++, _lock); // Postfix increment.
}
/**
* Returns the total number of lines ever written to the ramlog.
*/
size_t getTotalLinesWritten();
private:
const RamLog* _ramlog;
// Holds RamLog's mutex
stdx::lock_guard<stdx::mutex> _lock;
size_t _nextLineIndex;
};
} // namespace mongo::logv2
|
