xref: /titanic_41/usr/src/lib/libslp/clib/slp_da_cache.c (revision 7c478bd95313f5f23a4c958a745db2134aa03244)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License, Version 1.0 only
6  * (the "License").  You may not use this file except in compliance
7  * with the License.
8  *
9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10  * or http://www.opensolaris.org/os/licensing.
11  * See the License for the specific language governing permissions
12  * and limitations under the License.
13  *
14  * When distributing Covered Code, include this CDDL HEADER in each
15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16  * If applicable, add the following below this CDDL HEADER, with the
17  * fields enclosed by brackets "[]" replaced with your own identifying
18  * information: Portions Copyright [yyyy] [name of copyright owner]
19  *
20  * CDDL HEADER END
21  */
22 /*
23  * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 #pragma ident	"%Z%%M%	%I%	%E% SMI"
28 
29 /*
30  * This module contains a cache used to optimized scope and DA
31  * discovery. Entries live for a short duration only (about 10 seconds),
32  * although their lifetime can be advanced somewhat by frequent use.
33  * The intent is that the canonical source for DAs will always be slpd,
34  * so the short lifetime of cache entries is designed to force clients
35  * to consult slpd frequently so as to pick up the latest DA state
36  * quickly.
37  *
38  * The cache is managed by a thread which monitors calls into the cache.
39  * If the cache has been unused for a certain amount of time, the thread
40  * frees the cache and exits.
41  *
42  * The cache is keyed on the queries sent to slpd to access slpd's DA
43  * table. Associated with each query is a reply (in the format of an
44  * on-the-wire SLP SRVRPLY message).
45  * The cache is accessed by the following two functions:
46  *
47  * slp_find_das_cached:		searches the cache
48  * slp_put_das_cached:		adds a reply to the cache
49  *
50  * All parameters added to the cache are copied in first, and all results
51  * read from the cache are copied out, so all memory must be freed by
52  * the caller.
53  */
54 
55 #include <stdio.h>
56 #include <stdlib.h>
57 #include <thread.h>
58 #include <synch.h>
59 #include <syslog.h>
60 #include <string.h>
61 #include <sys/types.h>
62 #include <time.h>
63 #include <errno.h>
64 #include <slp-internal.h>
65 
66 /* These constants control the behaviour of the cache */
67 #define	MAX_LIFETIME	25	/* max lifetime, in seconds */
68 #define	ADVANCE_PER_USE	5	/* seconds lifetime is extended on each use */
69 #define	INIT_LIFETIME	10	/* cache entries start with this lifetime */
70 
71 /* Management thread components */
72 #define	IDLE_TIMEOUT	30	/* thread will exit after this idle time */
73 static int cache_thr_running;
74 static mutex_t start_lock = DEFAULTMUTEX;
75 static int cache_called;
76 static cond_t cache_called_cond;
77 static mutex_t cache_called_lock = DEFAULTMUTEX;
78 static SLPError start_cache_thr();
79 static void cache_thr();
80 
81 /* The cache and cache synchronization */
82 static void *da_cache;
83 static mutex_t cache_lock = DEFAULTMUTEX;
84 struct cache_entry {
85 	const char *query;
86 	const char *reply;
87 	unsigned int reply_len;
88 	time_t max_life;
89 	time_t expires;
90 };
91 typedef struct cache_entry cache_entry_t;
92 
93 /* cache management and searching */
94 static int compare_entries(const void *, const void *);
95 static void free_cache_entry(void *, VISIT);
96 
97 /*
98  * Searches the cache for the reply to 'query'. Returns the reply if
99  * found, otherwise NULL.
100  * The caller must free the result.
101  */
slp_find_das_cached(const char * query)102 char *slp_find_das_cached(const char *query) {
103 	cache_entry_t ce[1], **ans;
104 	char *reply = NULL;
105 	time_t now;
106 
107 	if (!cache_thr_running) {
108 		if (start_cache_thr() != SLP_OK) {
109 			return (NULL);
110 		}
111 	}
112 
113 	(void) mutex_lock(&cache_lock);
114 	ce->query = query;
115 
116 	ans = slp_tfind(ce, &da_cache, compare_entries);
117 	if (ans) {
118 		now = time(NULL);
119 		if ((*ans)->expires < now || (*ans)->max_life < now) {
120 			goto done;
121 		}
122 
123 		/* copy out the reply */
124 		if (!(reply = malloc((*ans)->reply_len))) {
125 			slp_err(LOG_CRIT, 0, "slp_find_das_cached",
126 						"out of memory");
127 			goto done;
128 		}
129 		(void) memcpy(reply, (*ans)->reply, (*ans)->reply_len);
130 		(*ans)->expires += ADVANCE_PER_USE;
131 	}
132 
133 	/* notify cache thread of call */
134 	(void) mutex_lock(&cache_called_lock);
135 	cache_called = 1;
136 	(void) cond_signal(&cache_called_cond);
137 	(void) mutex_unlock(&cache_called_lock);
138 
139 done:
140 	(void) mutex_unlock(&cache_lock);
141 	return (reply);
142 }
143 
144 /*
145  * Adds 'reply' to the cache under the index 'query'. Both parameters
146  * are copied in first, so the caller may free them after the call.
147  * 'len' is the length of 'reply' in bytes.
148  */
slp_put_das_cached(const char * query,const char * reply,unsigned int len)149 void slp_put_das_cached(const char *query, const char *reply,
150 			unsigned int len) {
151 	cache_entry_t *ce, **ce2;
152 	time_t now;
153 
154 	if (!cache_thr_running) {
155 		if (start_cache_thr() != SLP_OK) {
156 			return;
157 		}
158 	}
159 
160 	/* create the cache entry for this reply */
161 	if (!(ce = malloc(sizeof (*ce)))) {
162 		slp_err(LOG_CRIT, 0, "slp_put_das_cached", "out of memory");
163 		return;
164 	}
165 
166 	if (!(ce->query = strdup(query))) {
167 		free(ce);
168 		slp_err(LOG_CRIT, 0, "slp_put_das_cached", "out of memory");
169 		return;
170 	}
171 
172 	if (!(ce->reply = malloc(len))) {
173 		free((void *) (ce->query));
174 		free(ce);
175 		slp_err(LOG_CRIT, 0, "slp_put_das_cached", "out of memory");
176 		return;
177 	}
178 	(void) memcpy((void *) (ce->reply), reply, len);
179 	ce->reply_len = len;
180 	now = time(NULL);
181 	ce->max_life = now + MAX_LIFETIME;
182 	ce->expires = now + INIT_LIFETIME;
183 
184 	/* write to the cache */
185 	(void) mutex_lock(&cache_lock);
186 	ce2 = slp_tsearch((void *) ce, &da_cache, compare_entries);
187 	if (ce != *ce2) {
188 		/* overwrite existing entry */
189 		free((void *) ((*ce2)->query));
190 		free((void *) ((*ce2)->reply));
191 		free(*ce2);
192 		*ce2 = ce;
193 	}
194 
195 	(void) mutex_unlock(&cache_lock);
196 }
197 
compare_entries(const void * x1,const void * x2)198 static int compare_entries(const void *x1, const void *x2) {
199 	cache_entry_t *e1 = (cache_entry_t *)x1;
200 	cache_entry_t *e2 = (cache_entry_t *)x2;
201 
202 	return (strcasecmp(e1->query, e2->query));
203 }
204 
free_cache_entry(void * node,VISIT order)205 static void free_cache_entry(void *node, VISIT order) {
206 	if (order == endorder || order == leaf) {
207 		cache_entry_t *ce = *(cache_entry_t **)node;
208 
209 		free((void *) (ce->query));
210 		free((void *) (ce->reply));
211 		free(ce);
212 		free(node);
213 	}
214 }
215 
start_cache_thr()216 static SLPError start_cache_thr() {
217 	int terr;
218 	SLPError err = SLP_OK;
219 
220 	(void) mutex_lock(&start_lock);
221 
222 	if (cache_thr_running) {
223 		goto start_done;
224 	}
225 
226 	(void) cond_init(&cache_called_cond, 0, NULL);
227 
228 	if ((terr = thr_create(
229 		0, NULL, (void *(*)(void *)) cache_thr,
230 		NULL, 0, NULL)) != 0) {
231 		slp_err(LOG_CRIT, 0, "start_cache_thr",
232 			"could not start thread: %s", strerror(terr));
233 		err = SLP_INTERNAL_SYSTEM_ERROR;
234 		goto start_done;
235 	}
236 	cache_thr_running = 1;
237 
238 start_done:
239 	(void) mutex_unlock(&start_lock);
240 	return (err);
241 }
242 
cache_thr()243 static void cache_thr() {
244 	timestruc_t timeout;
245 	timeout.tv_nsec = 0;
246 
247 	(void) mutex_lock(&cache_called_lock);
248 	cache_called = 0;
249 
250 	while (cache_called == 0) {
251 		int err;
252 
253 		timeout.tv_sec = IDLE_TIMEOUT;
254 		err = cond_reltimedwait(&cache_called_cond,
255 					&cache_called_lock, &timeout);
256 
257 		if (err == ETIME) {
258 			(void) mutex_lock(&cache_lock);
259 			/* free cache */
260 			if (da_cache) {
261 				slp_twalk(da_cache,
262 			(void (*)(void *, VISIT, int, void *))free_cache_entry,
263 						0, NULL);
264 			}
265 			da_cache = NULL;
266 			(void) mutex_unlock(&cache_lock);
267 			cache_thr_running = 0;
268 			(void) mutex_unlock(&cache_called_lock);
269 			thr_exit(NULL);
270 		} else {
271 			cache_called = 0;
272 		}
273 	}
274 }
275