1libinnhist(3) InterNetNews Documentation libinnhist(3)
2
6 his - routines for managing INN history
7
9 #include <inn/history.h>
10 struct history;
12 struct token;
13 struct histstats {
15 int hitpos;
16 int hitneg;
17 int misses;
18 int dne;
19 };
20 #define HIS_RDONLY ...
22 #define HIS_RDWR ...
23 #define HIS_CREAT ...
24 #define HIS_ONDISK ...
25 #define HIS_INCORE ...
26 #define HIS_MMAP ...
27 enum {
29 HISCTLG_PATH,
30 HISCTLS_PATH,
31 HISCTLS_SYNCCOUNT,
32 HISCTLS_NPAIRS,
33 HISCTLS_IGNOREOLD,
34 HISCTLS_STATINTERVAL
35 };
36 struct history *HISopen(const char *path, const char *method, int flags);
38 bool HISclose(struct history *history);
40 bool HISsync(struct history *history);
42 void HISsetcache(struct history *history, size_t size);
44 bool HISlookup(struct history *history, const char *key, time_t *arrived, time_t *posted, time_t *expires, TOKEN *token);
46 bool HIScheck(struct history *history, const char *key);
48 bool HISwrite(struct history *history, const char *key, time_t arrived, time_t posted, time_t expires, const TOKEN *token);
50 bool HISremember(struct history *history, const char *key, time_t arrived, time_t posted);
52 bool HISreplace(struct history *history, const char *key, time_t arrived, time_t posted, time_t expires, const TOKEN *token);
54 bool HISexpire(struct history *history, const char *path, const char *reason, bool writing, void *cookie, time_t threshold, bool (*exists)(void *cookie, time_t arrived, time_t posted, time_t expires, const TOKEN *token));
56 bool HISwalk(struct history *history, const char *reason, void *cookie, bool (*callback)(void *cookie, time_t arrived, time_t posted, time_t expires, const TOKEN *token));
58 struct histstats HISstats(struct history *history);
60 const char *HISerror(struct history *history);
62 bool HISctl(struct history *history, int request, void *val);
64
66 These functions provide access to the INN history database. They
67 maintain key/value pairs in an opaque database whilst providing for
68 expiry of outdated information.
69 The history structure is an opaque handle returned from HISopen.
71 The HISopen function opens the history file designated by path using
73 the mode flags using the specified method. flags may be HIS_RDONLY to
74 indicate that read-only access to the history database is desired, or
75 HIS_RDWR for read/write access. History methods are defined at build
76 time; the history method currently available is "hisv6". On success a
77 newly initialised history handle is returned, or NULL on failure.
78 HIS_ONDISK, HIS_INCORE and HIS_MMAP may be logically ORed into flags to
80 provide a hint to the underlying history manager as to how it should
81 handle its data files; HIS_ONDISK indicates that the caller would like
82 as much of the data to be kept on disk (and out of memory), HIS_INCORE
83 indicates that the data files should be kept in main memory where
84 possible and HIS_MMAP that the files should be mmap()ed into the
85 processes address space. HIS_INCORE is typically used where a mass
86 rebuild of the history database is being performed; the underlying
87 history manager may assume that the caller will call HISsync() to sync
88 the data files to disk.
89 The HIS_CREAT flag indicates that the history database should be
91 initialised as new; if any options which affect creation of the
92 database need to be set an anonymous history handle should be created
93 by calling HISopen with path set to NULL, any options set using HISctl,
94 then the database opened by calling HISctl with HISCTLS_PATH.
95 The HISclose function closes the handle history and deallocates any
97 resources associated with it. It returns false on failure or true on
98 success.
99 The HISsync function synchronises any outstanding transactions
101 associated with history to disk.
102 HISsetcache associates a cache used for speeding up HIScheck with
104 history. The cache will occupy approximately size bytes.
105 HISlookup retrieves a token from history based on the passed key
107 (normally the Message-ID). If no entry with an associated token can be
108 found, HISlookup will return false. If a token is found arrived,
109 expires, and posted are filled in with the message arrival, expiry, and
110 posting times respectively (or zero, if the time component is not
111 available), in addition to token being set to the retrieved token and a
112 function return value of true. Any of arrived, expires, posted, or
113 token may be NULL in which case that component is not returned to the
114 caller, without affecting the return value.
115 HIScheck checks the database history for key (normally the Message-ID);
117 if key has previously been set via HISwrite, HIScheck returns true,
118 else false.
119 HISwrite writes a new entry to the database history associated with
121 key. arrived, posted, and expired specify the arrival, posting, and
122 expiry time respectively; posted and expired may be specified as <= 0
123 in which case that component shall be treated as absent in the
124 database. token is associated with the specified key. HISwrite returns
125 true on success, or false on failure. The behaviour when key is not
126 unique with respect to the existing entries in history is unspecified.
127 HISremember writes a new entry to the database history associated with
129 key, merely remembering that this key has been seen, together with its
130 arrival time arrived and also its posting time posted, if known.
131 (Otherwise, its posting time may be specified as <= 0 in case it is
132 absent.) HISremember returns true on success, or false on failure.
133 The behaviour when key is not unique with respect to the existing
134 entries in history is unspecified.
135 HISreplace replaces an existing entry in the database history,
137 associated with key. arrived, posted, expired specify the arrival,
138 posting and expiry time respectively; posted and expired may be
139 specified as <= 0 in which case that component shall be treated as
140 absent in the database. token is associated with the specified key; if
141 NULL then the history database merely remembers that this key has been
142 seen, together with its arrival time. HISreplace returns true on
143 success, or false on failure.
144 HISexpire expires the history database associated with history,
146 creating a new, replacement, database in the same location if path is
147 NULL, or in path if not NULL; if path is not NULL then the replacement
148 of the old history database with the new one is assumed to be performed
149 out of band by the caller. The writing flag is normally passed as
150 true, if you wish to inhibit writing of the new database (and so merely
151 see the callbacks), writing may be set false.
152 If the underlying history mechanism needs to pause the server, the
154 reason string is used as the argument to the `ctlinnd pause' command,
155 and as such the server should be reserved by the caller prior to
156 calling HISexpire; if the caller wishes to inhibit pausing of the
157 server, passing NULL will achieve this. If reason is not NULL, then on
158 successful return from HISexpire the server will be left paused and the
159 caller should unpause it.
160 The history database is scanned and entries with an associated storage
162 token are passed to the discrimination function exists.
163 If exists() returns false it indicates that stored entity associated
165 with token is no longer available (or no longer required), and
166 therefore the associated history entry may be expired once it meets the
167 threshold constraint. If exists() returns true the entry is kept as-is
168 in the newly expired history database.
169 The exists function is passed the arrival, posting and expiry times, in
171 addition to the token associated with the entry. Note that posting
172 and/or expiry may be zero, but that the token will never be NULL (such
173 entries are handled solely via the threshold mechanism). The storage
174 token passed to the discrimination function may be updated if required
175 (for example, as might be needed by a hierarchical storage management
176 implementation).
177 Entries in the database with a posting time less than threshold with no
179 token associated with them are deleted from the database. In case the
180 posting time is unknown, the arrival time is used instead.
181 The parameter cookie is passed to the discrimination function, and may
183 be used for any purpose required by the caller.
184 If the discrimination function attempts to access the underlying
186 database (for read or write) during the callback, the behaviour is
187 unspecified.
188 HISwalk provides an iteration function for the specified history
190 database. For every entry in the history database, callback is
191 invoked, passing the cookie, arrival, posting, and expiry times, in
192 addition to the token associated with the entry. If the callback()
193 returns false the iteration is aborted and HISwalk returns false to the
194 caller.
195 To process the entire database in the presence of a running server,
197 reason may be passed; if this argument is not NULL, it is used as an an
198 argument to the `ctlinnd (reserve|pause|go)' commands. If reason is
199 NULL and the server is running, the behaviour of HISwalk is undefined.
200 If the callback function attempts to access the underlying database
202 during the callback, the behaviour is unspecified.
203 HISstats returns statistics on the history cache mechanism; given a
205 handle history, the return value is a struct histstats detailing:
206 "hitpos"
208 The number of times an item was found directly in the cache and
209 known to exist in the underlying history manager.
210 "hitneg"
212 The number of times an item was found directly in the cache and
213 known not to exist in the underlying history manager.
214 "misses"
216 The number of times an item was not found directly in the cache,
217 but on retrieval from the underlying history manager was found to
218 exist.
219 "dne"
221 The number of times an item was not found directly in the cache,
222 but on retrieval from the underlying history manager was found not
223 to exist.
224 Note that the history cache is only checked by HIScheck and only
226 affected by HIScheck, HISwrite, HISremember and HISreplace. Following a
227 call to HISstats the history statistics associated with history are
228 cleared.
229 HISerror returns a string describing the most recent error associated
231 with history; the format and content of these strings is history
232 manager dependent. Note that on setting an error, the history API will
233 call the warn function from libinn(3).
234 HISctl provides a control interface to the underlying history manager.
236 The request argument determines the type of the request and the meaning
237 of the val argument. The values for request are:
238 "HISCTLG_PATH" (const char **)
240 Get the base file path which the history handle represents. val
241 should be a pointer to a location of type const char *. The result
242 must not later be passed to free(3).
243 "HISCTLS_PATH" (const char *)
245 Set the base file path which this history handle should use;
246 typically this is used after an anonymous handle has been created
247 using HISopen(NULL, ...). val should be a value of type const char
248 * and will be copied before being stored internally.
249 "HISCTLS_SYNCCOUNT" (size_t *)
251 Set an upper bound on how many history operations may be pending in
252 core before being synced to permanent storage; 0 indicates
253 unlimited. val should be a pointer to a value of type size_t and
254 will not be modified by the call.
255 "HISCTLS_NPAIRS" (size_t *)
257 Set a hint to the to the underlying history manager as to how many
258 entries there are expected to be in the history database; 0
259 indicates that an automatic or default sizing should be made. val
260 should be a pointer to a value of type size_t and will not be
261 modified by the call.
262 "HISCTLS_IGNOREOLD" (bool *)
264 Instruct the underlying history manager to ignore existing database
265 when creating new ones; typically this option may be set to true if
266 the administrator believes that the existing history database is
267 corrupt and that ignoring it may help. val should be a pointer to
268 a value of type bool and will not be modified by the call.
269 "HISCTLS_STATINTERVAL" (time_t *)
271 For the history v6 and tagged hash managers, set the interval, in
272 seconds, between stat(2)s of the history files checking for
273 replaced files (as happens during expire); this option is typically
274 used by nnrpd(8) like applications. val should be a pointer to a
275 value of type time_t and will not be modified by the call.
276
278 Written by Alex Kiernan <alexk@demon.net> for InterNetNews 2.4.0.
279INN 2.7.0 2022-07-10 libinnhist(3)