4 * SQUID Web Proxy Cache http://www.squid-cache.org/
5 * ----------------------------------------------------------
7 * Squid is the result of efforts by numerous individuals from
8 * the Internet community; see the CONTRIBUTORS file for full
9 * details. Many organizations have provided support for Squid's
10 * development; see the SPONSORS file for full details. Squid is
11 * Copyrighted (C) 2001 by the Regents of the University of
12 * California; see the COPYRIGHT file for full details. Squid
13 * incorporates software developed and/or copyrighted by other
14 * sources; see the CREDITS file for full details.
16 * This program is free software; you can redistribute it and/or modify
17 * it under the terms of the GNU General Public License as published by
18 * the Free Software Foundation; either version 2 of the License, or
19 * (at your option) any later version.
21 * This program is distributed in the hope that it will be useful,
22 * but WITHOUT ANY WARRANTY; without even the implied warranty of
23 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
24 * GNU General Public License for more details.
26 * You should have received a copy of the GNU General Public License
27 * along with this program; if not, write to the Free Software
28 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
30 * Copyright (c) 2003, Robert Collins <robertc@squid-cache.org>
33 #ifndef SQUID_STOREFILESYSTEM_H
34 #define SQUID_STOREFILESYSTEM_H
39 /* ****** DOCUMENTATION ***** */
42 \defgroup FileSystems Storage Filesystems
44 \section Introduction Introduction
46 * Traditionally, Squid has always used the Unix filesystem (\link UFS UFS\endlink)
47 * to store cache objects on disk. Over the years, the
48 * poor performance of \link UFS UFS\endlink has become very obvious. In most
49 * cases, \link UFS UFS\endlink limits Squid to about 30-50 requests per second.
50 * Our work indicates that the poor performance is mostly
51 * due to the synchronous nature of open() and unlink()
52 * system calls, and perhaps thrashing of inode/buffer caches.
55 * We want to try out our own, customized filesystems with Squid.
56 * In order to do that, we need a well-defined interface
57 * for the bits of Squid that access the permanent storage
58 * devices. We also require tighter control of the replacement
59 * policy by each storage module, rather than a single global
62 \section BuildStructure Build structure
64 * The storage types live in \em src/fs/. Each subdirectory corresponds
65 * to the name of the storage type. When a new storage type is implemented
66 * configure.in must be updated to autogenerate a Makefile in
67 * \em src/fs/foo/ from a Makefile.in file.
69 \todo DOCS: add template addition to configure.in for storage module addition.
70 \todo DOCS: add template Makefile.am for storage module addition.
73 * configure will take a list of storage types through the
74 * --enable-store-io parameter. This parameter takes a list of
75 * space seperated storage types. For example,
76 * --enable-store-io="ufs coss" .
79 * Each storage type must create an archive file
80 * in \em src/fs/foo/.a . This file is automatically linked into
81 * squid at compile time.
84 * Each storage filesystem must inherit from StoreFileSystem and provide
85 * all virtual function hooks for squid to operate with.
87 \section OperationOfStorageModules Operation of a Storage Module
89 * Squid understands the concept of multiple diverse storage directories.
90 * Each storage directory provides a caching object store, with object
91 * storage, retrieval, indexing and replacement.
94 * Each open object has associated with it a storeIOState object. The
95 * storeIOState object is used to record the state of the current
96 * object. Each storeIOState can have a storage module specific data
97 * structure containing information private to the storage module.
100 * Each SwapDir has the concept of a maximum object size. This is used
101 * as a basic hint to the storage layer in first choosing a suitable
102 * SwapDir. The checkobj function is then called for suitable
103 * candidate SwapDirs to find out whether it wants to store a
104 * given StoreEntry. A maxobjsize of -1 means 'any size'.
112 * The core API for storage modules this class provides all the hooks
113 * squid uses to interact with a filesystem IO module.
115 class StoreFileSystem
119 static void SetupAllFs();
120 static void FsAdd(StoreFileSystem
&);
121 static void FreeAllFs();
122 static Vector
<StoreFileSystem
*> const &FileSystems();
123 typedef Vector
<StoreFileSystem
*>::iterator iterator
;
124 typedef Vector
<StoreFileSystem
*>::const_iterator const_iterator
;
125 StoreFileSystem() : initialised(false) {}
127 virtual ~StoreFileSystem() {}
129 virtual char const *type () const = 0;
130 virtual SwapDir
*createSwapDir() = 0;
131 virtual void done() = 0;
132 virtual void setup() = 0;
134 StoreFileSystem(StoreFileSystem
const &);
135 StoreFileSystem
&operator=(StoreFileSystem
const&);
139 virtual void registerWithCacheManager(void);
142 static Vector
<StoreFileSystem
*> &GetFileSystems();
143 static Vector
<StoreFileSystem
*> *_FileSystems
;
144 static void RegisterAllFsWithCacheManager(void);
147 // TODO: Kill this typedef!
148 typedef StoreFileSystem storefs_entry_t
;
151 #endif /* SQUID_STOREFILESYSTEM_H */