2 * SQUID Web Proxy Cache http://www.squid-cache.org/
3 * ----------------------------------------------------------
5 * Squid is the result of efforts by numerous individuals from
6 * the Internet community; see the CONTRIBUTORS file for full
7 * details. Many organizations have provided support for Squid's
8 * development; see the SPONSORS file for full details. Squid is
9 * Copyrighted (C) 2001 by the Regents of the University of
10 * California; see the COPYRIGHT file for full details. Squid
11 * incorporates software developed and/or copyrighted by other
12 * sources; see the CREDITS file for full details.
14 * This program is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU General Public License as published by
16 * the Free Software Foundation; either version 2 of the License, or
17 * (at your option) any later version.
19 * This program is distributed in the hope that it will be useful,
20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 * GNU General Public License for more details.
24 * You should have received a copy of the GNU General Public License
25 * along with this program; if not, write to the Free Software
26 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
28 * Copyright (c) 2003, Robert Collins <robertc@squid-cache.org>
31 #ifndef SQUID_STOREFILESYSTEM_H
32 #define SQUID_STOREFILESYSTEM_H
34 #include "base/Vector.h"
36 /* ****** DOCUMENTATION ***** */
39 \defgroup FileSystems Storage Filesystems
41 \section Introduction Introduction
43 * Traditionally, Squid has always used the Unix filesystem (\link UFS UFS\endlink)
44 * to store cache objects on disk. Over the years, the
45 * poor performance of \link UFS UFS\endlink has become very obvious. In most
46 * cases, \link UFS UFS\endlink limits Squid to about 30-50 requests per second.
47 * Our work indicates that the poor performance is mostly
48 * due to the synchronous nature of open() and unlink()
49 * system calls, and perhaps thrashing of inode/buffer caches.
52 * We want to try out our own, customized filesystems with Squid.
53 * In order to do that, we need a well-defined interface
54 * for the bits of Squid that access the permanent storage
55 * devices. We also require tighter control of the replacement
56 * policy by each storage module, rather than a single global
59 \section BuildStructure Build structure
61 * The storage types live in \em src/fs/. Each subdirectory corresponds
62 * to the name of the storage type. When a new storage type is implemented
63 * configure.ac must be updated to autogenerate a Makefile in
64 * \em src/fs/foo/ from a Makefile.in file.
66 \todo DOCS: add template addition to configure.ac for storage module addition.
67 \todo DOCS: add template Makefile.am for storage module addition.
70 * configure will take a list of storage types through the
71 * --enable-store-io parameter. This parameter takes a list of
72 * space seperated storage types. For example,
73 * --enable-store-io="ufs coss" .
76 * Each storage type must create an archive file
77 * in \em src/fs/foo/.a . This file is automatically linked into
78 * squid at compile time.
81 * Each storage filesystem must inherit from StoreFileSystem and provide
82 * all virtual function hooks for squid to operate with.
84 \section OperationOfStorageModules Operation of a Storage Module
86 * Squid understands the concept of multiple diverse storage directories.
87 * Each storage directory provides a caching object store, with object
88 * storage, retrieval, indexing and replacement.
91 * Each open object has associated with it a storeIOState object. The
92 * storeIOState object is used to record the state of the current
93 * object. Each storeIOState can have a storage module specific data
94 * structure containing information private to the storage module.
97 * Each SwapDir has the concept of a maximum object size. This is used
98 * as a basic hint to the storage layer in first choosing a suitable
99 * SwapDir. The checkobj function is then called for suitable
100 * candidate SwapDirs to find out whether it wants to store a
101 * given StoreEntry. A maxobjsize of -1 means 'any size'.
109 * The core API for storage modules this class provides all the hooks
110 * squid uses to interact with a filesystem IO module.
112 class StoreFileSystem
116 static void SetupAllFs();
117 static void FsAdd(StoreFileSystem
&);
118 static void FreeAllFs();
119 static Vector
<StoreFileSystem
*> const &FileSystems();
120 typedef Vector
<StoreFileSystem
*>::iterator iterator
;
121 typedef Vector
<StoreFileSystem
*>::const_iterator const_iterator
;
122 StoreFileSystem() : initialised(false) {}
124 virtual ~StoreFileSystem() {}
126 virtual char const *type () const = 0;
127 virtual SwapDir
*createSwapDir() = 0;
128 virtual void done() = 0;
129 virtual void setup() = 0;
131 StoreFileSystem(StoreFileSystem
const &);
132 StoreFileSystem
&operator=(StoreFileSystem
const&);
136 virtual void registerWithCacheManager(void);
139 static Vector
<StoreFileSystem
*> &GetFileSystems();
140 static Vector
<StoreFileSystem
*> *_FileSystems
;
141 static void RegisterAllFsWithCacheManager(void);
144 // TODO: Kill this typedef!
145 typedef StoreFileSystem storefs_entry_t
;
147 #endif /* SQUID_STOREFILESYSTEM_H */