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59b2d47f | 1 | /* |
bbc27441 | 2 | * Copyright (C) 1996-2014 The Squid Software Foundation and contributors |
59b2d47f | 3 | * |
bbc27441 AJ |
4 | * Squid software is distributed under GPLv2+ license and includes |
5 | * contributions from numerous individuals and organizations. | |
6 | * Please see the COPYING and CONTRIBUTORS files for details. | |
59b2d47f | 7 | */ |
8 | ||
9 | #ifndef SQUID_STOREFILESYSTEM_H | |
10 | #define SQUID_STOREFILESYSTEM_H | |
11 | ||
b181c1df | 12 | #include <vector> |
59b2d47f | 13 | |
946c686b AJ |
14 | /* ****** DOCUMENTATION ***** */ |
15 | ||
4d95a996 AJ |
16 | /** |
17 | \defgroup FileSystems Storage Filesystems | |
26ac0430 | 18 | * |
4d95a996 AJ |
19 | \section Introduction Introduction |
20 | \par | |
21 | * Traditionally, Squid has always used the Unix filesystem (\link UFS UFS\endlink) | |
22 | * to store cache objects on disk. Over the years, the | |
23 | * poor performance of \link UFS UFS\endlink has become very obvious. In most | |
24 | * cases, \link UFS UFS\endlink limits Squid to about 30-50 requests per second. | |
25 | * Our work indicates that the poor performance is mostly | |
26 | * due to the synchronous nature of open() and unlink() | |
27 | * system calls, and perhaps thrashing of inode/buffer caches. | |
26ac0430 | 28 | * |
4d95a996 AJ |
29 | \par |
30 | * We want to try out our own, customized filesystems with Squid. | |
31 | * In order to do that, we need a well-defined interface | |
32 | * for the bits of Squid that access the permanent storage | |
33 | * devices. We also require tighter control of the replacement | |
34 | * policy by each storage module, rather than a single global | |
35 | * replacement policy. | |
26ac0430 | 36 | * |
4d95a996 AJ |
37 | \section BuildStructure Build structure |
38 | \par | |
39 | * The storage types live in \em src/fs/. Each subdirectory corresponds | |
40 | * to the name of the storage type. When a new storage type is implemented | |
a6093a2d | 41 | * configure.ac must be updated to autogenerate a Makefile in |
4d95a996 AJ |
42 | * \em src/fs/foo/ from a Makefile.in file. |
43 | * | |
a6093a2d | 44 | \todo DOCS: add template addition to configure.ac for storage module addition. |
4d95a996 | 45 | \todo DOCS: add template Makefile.am for storage module addition. |
26ac0430 | 46 | * |
4d95a996 AJ |
47 | \par |
48 | * configure will take a list of storage types through the | |
49 | * --enable-store-io parameter. This parameter takes a list of | |
50 | * space seperated storage types. For example, | |
73656056 | 51 | * --enable-store-io="ufs aufs" . |
26ac0430 | 52 | * |
4d95a996 AJ |
53 | \par |
54 | * Each storage type must create an archive file | |
55 | * in \em src/fs/foo/.a . This file is automatically linked into | |
56 | * squid at compile time. | |
26ac0430 | 57 | * |
4d95a996 AJ |
58 | \par |
59 | * Each storage filesystem must inherit from StoreFileSystem and provide | |
60 | * all virtual function hooks for squid to operate with. | |
26ac0430 | 61 | * |
4d95a996 AJ |
62 | \section OperationOfStorageModules Operation of a Storage Module |
63 | \par | |
64 | * Squid understands the concept of multiple diverse storage directories. | |
65 | * Each storage directory provides a caching object store, with object | |
66 | * storage, retrieval, indexing and replacement. | |
26ac0430 | 67 | * |
4d95a996 AJ |
68 | \par |
69 | * Each open object has associated with it a storeIOState object. The | |
70 | * storeIOState object is used to record the state of the current | |
71 | * object. Each storeIOState can have a storage module specific data | |
72 | * structure containing information private to the storage module. | |
26ac0430 | 73 | * |
4d95a996 AJ |
74 | \par |
75 | * Each SwapDir has the concept of a maximum object size. This is used | |
76 | * as a basic hint to the storage layer in first choosing a suitable | |
77 | * SwapDir. The checkobj function is then called for suitable | |
78 | * candidate SwapDirs to find out whether it wants to store a | |
79 | * given StoreEntry. A maxobjsize of -1 means 'any size'. | |
80 | */ | |
62ee09ca | 81 | |
e1f7507e AJ |
82 | class SwapDir; |
83 | ||
4d95a996 AJ |
84 | /** |
85 | \ingroup FileSystems | |
86 | * | |
87 | * The core API for storage modules this class provides all the hooks | |
88 | * squid uses to interact with a filesystem IO module. | |
89 | */ | |
59b2d47f | 90 | class StoreFileSystem |
91 | { | |
92 | ||
93 | public: | |
94 | static void SetupAllFs(); | |
95 | static void FsAdd(StoreFileSystem &); | |
96 | static void FreeAllFs(); | |
81481ec0 FC |
97 | static std::vector<StoreFileSystem*> const &FileSystems(); |
98 | typedef std::vector<StoreFileSystem*>::iterator iterator; | |
99 | typedef std::vector<StoreFileSystem*>::const_iterator const_iterator; | |
e1f7507e | 100 | StoreFileSystem() : initialised(false) {} |
59b2d47f | 101 | |
26ac0430 | 102 | virtual ~StoreFileSystem() {} |
59b2d47f | 103 | |
104 | virtual char const *type () const = 0; | |
105 | virtual SwapDir *createSwapDir() = 0; | |
106 | virtual void done() = 0; | |
107 | virtual void setup() = 0; | |
108 | // Not implemented | |
109 | StoreFileSystem(StoreFileSystem const &); | |
110 | StoreFileSystem &operator=(StoreFileSystem const&); | |
111 | ||
112 | protected: | |
113 | bool initialised; | |
6b7d87bb | 114 | virtual void registerWithCacheManager(void); |
59b2d47f | 115 | |
116 | private: | |
81481ec0 FC |
117 | static std::vector<StoreFileSystem*> &GetFileSystems(); |
118 | static std::vector<StoreFileSystem*> *_FileSystems; | |
6b7d87bb | 119 | static void RegisterAllFsWithCacheManager(void); |
59b2d47f | 120 | }; |
121 | ||
4d95a996 | 122 | // TODO: Kill this typedef! |
59b2d47f | 123 | typedef StoreFileSystem storefs_entry_t; |
124 | ||
59b2d47f | 125 | #endif /* SQUID_STOREFILESYSTEM_H */ |