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
|
/* Copyright 2012 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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 <utility>
#include "mongo/base/disallow_copying.h"
#include "mongo/base/initializer_function.h"
#include "mongo/base/status.h"
#include "mongo/platform/unordered_map.h"
#include "mongo/platform/unordered_set.h"
namespace mongo {
/**
* Representation of a dependency graph of "initialization operations."
*
* Each operation has a unique name, a function object implementing the operation's behavior,
* and a set of prerequisite operations, which may be empty. A legal graph contains no cycles.
*
* Instances of this class are used in two phases. In the first phase, the graph is constructed
* by repeated calls to addInitializer(). In the second phase, a user calls the topSort()
* method to produce an initialization order that respects the dependencies among operations, and
* then uses the getInitializerFunction() to get the behavior function for each operation, in
* turn.
*
* Concurrency Notes: The user is responsible for synchronization. Multiple threads may
* simultaneously call the const functions, getInitializerFunction and topSort, on the same
* instance of InitializerDependencyGraph. However, no thread may call addInitializer while any
* thread is executing those functions or addInitializer on the same instance.
*/
class InitializerDependencyGraph {
MONGO_DISALLOW_COPYING(InitializerDependencyGraph);
public:
InitializerDependencyGraph();
~InitializerDependencyGraph();
/**
* Add a new initializer node, named "name", to the dependency graph, with the given
* behavior, "fn", and the given "prerequisites" (input dependencies) and "dependents"
* (output dependencies).
*
* If "!fn" (fn is NULL in function pointer parlance), returns status with code
* ErrorCodes::badValue. If "name" is a duplicate of a name already present in the graph,
* returns "ErrorCodes::duplicateKey". Otherwise, returns Status::OK() and adds the new node
* to the graph. Note that cycles in the dependency graph are not discovered in this phase.
* Rather, they're discovered by topSort, below.
*/
Status addInitializer(const std::string& name,
const InitializerFunction& fn,
const std::vector<std::string>& prerequisites,
const std::vector<std::string>& dependents);
/**
* Given a dependency operation node named "name", return its behavior function. Returns
* a value that evaluates to "false" in boolean context, otherwise.
*/
InitializerFunction getInitializerFunction(const std::string& name) const;
/**
* Construct a topological sort of the dependency graph, and store that order into
* "sortedNames". Returns Status::OK() on success.
*
* If the graph contains a cycle, returns ErrorCodes::graphContainsCycle, and "sortedNames"
* is an ordered sequence of nodes involved in a cycle. In this case, the first and last
* element of "sortedNames" will be equal.
*
* If any node in the graph names a prerequisite that was never added to the graph via
* addInitializer, this function will return ErrorCodes::badValue.
*
* Any other return value indicates an internal error, and should not occur.
*/
Status topSort(std::vector<std::string>* sortedNames) const;
private:
struct NodeData {
InitializerFunction fn;
unordered_set<std::string> prerequisites;
};
typedef unordered_map<std::string, NodeData> NodeMap;
typedef NodeMap::value_type Node;
/**
* Helper function to recursively top-sort a graph. Used by topSort().
*/
static Status recursiveTopSort(
const NodeMap& nodeMap,
const Node& currentNode,
std::vector<std::string>* inProgressNodeNames,
unordered_set<std::string>* visitedNodeNames,
std::vector<std::string>* sortedNames);
/**
* Map of all named nodes. Nodes named as prerequisites or dependents but not explicitly
* added via addInitializer will either be absent from this map or be present with
* NodeData::fn set to a false-ish value.
*/
NodeMap _nodes;
};
} // namespace mongo
|
