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59b2d47f | 1 | /* |
b8ae064d | 2 | * Copyright (C) 1996-2023 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 | ||
ff9d9458 FC |
9 | #ifndef SQUID_SRC_STOREFILESYSTEM_H |
10 | #define SQUID_SRC_STOREFILESYSTEM_H | |
59b2d47f | 11 | |
23b79630 | 12 | #include "base/TypeTraits.h" |
2745fea5 | 13 | #include "store/forward.h" |
b181c1df | 14 | #include <vector> |
59b2d47f | 15 | |
946c686b AJ |
16 | /* ****** DOCUMENTATION ***** */ |
17 | ||
4d95a996 | 18 | /** |
f53969cc | 19 | \defgroup FileSystems Storage Filesystems |
26ac0430 | 20 | * |
f439fbd2 | 21 | \section FileSystemsIntroduction Introduction |
4d95a996 AJ |
22 | \par |
23 | * Traditionally, Squid has always used the Unix filesystem (\link UFS UFS\endlink) | |
24 | * to store cache objects on disk. Over the years, the | |
25 | * poor performance of \link UFS UFS\endlink has become very obvious. In most | |
26 | * cases, \link UFS UFS\endlink limits Squid to about 30-50 requests per second. | |
27 | * Our work indicates that the poor performance is mostly | |
28 | * due to the synchronous nature of open() and unlink() | |
29 | * system calls, and perhaps thrashing of inode/buffer caches. | |
26ac0430 | 30 | * |
4d95a996 AJ |
31 | \par |
32 | * We want to try out our own, customized filesystems with Squid. | |
33 | * In order to do that, we need a well-defined interface | |
34 | * for the bits of Squid that access the permanent storage | |
35 | * devices. We also require tighter control of the replacement | |
36 | * policy by each storage module, rather than a single global | |
37 | * replacement policy. | |
26ac0430 | 38 | * |
4d95a996 AJ |
39 | \section BuildStructure Build structure |
40 | \par | |
41 | * The storage types live in \em src/fs/. Each subdirectory corresponds | |
42 | * to the name of the storage type. When a new storage type is implemented | |
a6093a2d | 43 | * configure.ac must be updated to autogenerate a Makefile in |
4d95a996 AJ |
44 | * \em src/fs/foo/ from a Makefile.in file. |
45 | * | |
9837567d AJ |
46 | * TODO: DOCS: add template addition to configure.ac for storage module addition. |
47 | * TODO: DOCS: add template Makefile.am for storage module addition. | |
26ac0430 | 48 | * |
4d95a996 AJ |
49 | \par |
50 | * configure will take a list of storage types through the | |
51 | * --enable-store-io parameter. This parameter takes a list of | |
2b61af8e | 52 | * space separated storage types. For example, |
73656056 | 53 | * --enable-store-io="ufs aufs" . |
26ac0430 | 54 | * |
4d95a996 AJ |
55 | \par |
56 | * Each storage type must create an archive file | |
57 | * in \em src/fs/foo/.a . This file is automatically linked into | |
58 | * squid at compile time. | |
26ac0430 | 59 | * |
4d95a996 AJ |
60 | \par |
61 | * Each storage filesystem must inherit from StoreFileSystem and provide | |
62 | * all virtual function hooks for squid to operate with. | |
26ac0430 | 63 | * |
4d95a996 AJ |
64 | \section OperationOfStorageModules Operation of a Storage Module |
65 | \par | |
66 | * Squid understands the concept of multiple diverse storage directories. | |
67 | * Each storage directory provides a caching object store, with object | |
68 | * storage, retrieval, indexing and replacement. | |
26ac0430 | 69 | * |
4d95a996 AJ |
70 | \par |
71 | * Each open object has associated with it a storeIOState object. The | |
72 | * storeIOState object is used to record the state of the current | |
73 | * object. Each storeIOState can have a storage module specific data | |
74 | * structure containing information private to the storage module. | |
26ac0430 | 75 | * |
4d95a996 AJ |
76 | \par |
77 | * Each SwapDir has the concept of a maximum object size. This is used | |
78 | * as a basic hint to the storage layer in first choosing a suitable | |
79 | * SwapDir. The checkobj function is then called for suitable | |
80 | * candidate SwapDirs to find out whether it wants to store a | |
81 | * given StoreEntry. A maxobjsize of -1 means 'any size'. | |
82 | */ | |
62ee09ca | 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 | */ | |
23b79630 | 90 | class StoreFileSystem: public Interface |
59b2d47f | 91 | { |
92 | ||
93 | public: | |
59b2d47f | 94 | static void FsAdd(StoreFileSystem &); |
5d84beb5 | 95 | static StoreFileSystem *FindByType(const char *type); |
81481ec0 FC |
96 | static std::vector<StoreFileSystem*> const &FileSystems(); |
97 | typedef std::vector<StoreFileSystem*>::iterator iterator; | |
98 | typedef std::vector<StoreFileSystem*>::const_iterator const_iterator; | |
59b2d47f | 99 | |
23b79630 AR |
100 | StoreFileSystem() = default; |
101 | StoreFileSystem(StoreFileSystem &&) = delete; // no copying/moving of any kind | |
59b2d47f | 102 | |
103 | virtual char const *type () const = 0; | |
104 | virtual SwapDir *createSwapDir() = 0; | |
59b2d47f | 105 | |
106 | private: | |
81481ec0 FC |
107 | static std::vector<StoreFileSystem*> &GetFileSystems(); |
108 | static std::vector<StoreFileSystem*> *_FileSystems; | |
59b2d47f | 109 | }; |
110 | ||
4d95a996 | 111 | // TODO: Kill this typedef! |
59b2d47f | 112 | typedef StoreFileSystem storefs_entry_t; |
113 | ||
ff9d9458 | 114 | #endif /* SQUID_SRC_STOREFILESYSTEM_H */ |
f53969cc | 115 |