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
|
// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
/*
* Ceph - scalable distributed file system
*
* Copyright (C) 2013 Inktank Storage, Inc.
*
* This is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 2.1, as published by the Free Software
* Foundation. See file COPYING.
*
*/
#ifndef MAPCACHER_H
#define MAPCACHER_H
#include "include/Context.h"
#include "common/sharedptr_registry.hpp"
namespace MapCacher {
/**
* Abstraction for ordering key updates
*/
template<typename K, typename V>
class Transaction {
public:
/// Std::set keys according to map
virtual void set_keys(
const std::map<K, V> &keys ///< [in] keys/values to std::set
) = 0;
/// Remove keys
virtual void remove_keys(
const std::set<K> &to_remove ///< [in] keys to remove
) = 0;
/// Add context to fire when data is readable
virtual void add_callback(
Context *c ///< [in] Context to fire on readable
) = 0;
virtual ~Transaction() {}
};
/**
* Abstraction for fetching keys
*/
template<typename K, typename V>
class StoreDriver {
public:
/// Returns requested key values
virtual int get_keys(
const std::set<K> &keys, ///< [in] keys requested
std::map<K, V> *got ///< [out] values for keys obtained
) = 0; ///< @return error value
/// Returns next key
virtual int get_next(
const K &key, ///< [in] key after which to get next
std::pair<K, V> *next ///< [out] first key after key
) = 0; ///< @return 0 on success, -ENOENT if there is no next
virtual ~StoreDriver() {}
};
/**
* Uses SharedPtrRegistry to cache objects of in progress writes
* allowing the user to read/write a consistent view of the map
* without flushing writes.
*/
template<typename K, typename V>
class MapCacher {
private:
StoreDriver<K, V> *driver;
SharedPtrRegistry<K, boost::optional<V> > in_progress;
typedef typename SharedPtrRegistry<K, boost::optional<V> >::VPtr VPtr;
typedef ContainerContext<std::set<VPtr> > TransHolder;
public:
MapCacher(StoreDriver<K, V> *driver) : driver(driver) {}
/// Fetch first key/value std::pair after specified key
int get_next(
K key, ///< [in] key after which to get next
std::pair<K, V> *next ///< [out] next key
) {
while (true) {
std::pair<K, boost::optional<V> > cached;
std::pair<K, V> store;
bool got_cached = in_progress.get_next(key, &cached);
bool got_store = false;
int r = driver->get_next(key, &store);
if (r < 0 && r != -ENOENT) {
return r;
} else if (r == 0) {
got_store = true;
}
if (!got_cached && !got_store) {
return -ENOENT;
} else if (
got_cached &&
(!got_store || store.first >= cached.first)) {
if (cached.second) {
if (next)
*next = make_pair(cached.first, cached.second.get());
return 0;
} else {
key = cached.first;
continue; // value was cached as removed, recurse
}
} else {
if (next)
*next = store;
return 0;
}
}
ceph_abort(); // not reachable
return -EINVAL;
} ///< @return error value, 0 on success, -ENOENT if no more entries
/// Adds operation setting keys to Transaction
void set_keys(
const std::map<K, V> &keys, ///< [in] keys/values to std::set
Transaction<K, V> *t ///< [out] transaction to use
) {
std::set<VPtr> vptrs;
for (auto i = keys.begin(); i != keys.end(); ++i) {
VPtr ip = in_progress.lookup_or_create(i->first, i->second);
*ip = i->second;
vptrs.insert(ip);
}
t->set_keys(keys);
t->add_callback(new TransHolder(vptrs));
}
/// Adds operation removing keys to Transaction
void remove_keys(
const std::set<K> &keys, ///< [in]
Transaction<K, V> *t ///< [out] transaction to use
) {
std::set<VPtr> vptrs;
for (auto i = keys.begin(); i != keys.end(); ++i) {
boost::optional<V> empty;
VPtr ip = in_progress.lookup_or_create(*i, empty);
*ip = empty;
vptrs.insert(ip);
}
t->remove_keys(keys);
t->add_callback(new TransHolder(vptrs));
}
/// Gets keys, uses cached values for unstable keys
int get_keys(
const std::set<K> &keys_to_get, ///< [in] std::set of keys to fetch
std::map<K, V> *got ///< [out] keys gotten
) {
std::set<K> to_get;
std::map<K, V> _got;
for (auto i = keys_to_get.begin();
i != keys_to_get.end();
++i) {
VPtr val = in_progress.lookup(*i);
if (val) {
if (*val)
got->insert(make_pair(*i, val->get()));
//else: value cached is empty, key doesn't exist
} else {
to_get.insert(*i);
}
}
int r = driver->get_keys(to_get, &_got);
if (r < 0)
return r;
for (auto i = _got.begin(); i != _got.end(); ++i) {
got->insert(*i);
}
return 0;
} ///< @return error value, 0 on success
};
} // namespace
#endif
|
