3
* $Id: carp.cc,v 1.27 2008/01/14 12:13:49 hno Exp $
5
* DEBUG: section 39 Peer source hash based selection
6
* AUTHOR: Henrik Nordstrom
9
* SQUID Web Proxy Cache http://www.squid-cache.org/
10
* ----------------------------------------------------------
12
* Squid is the result of efforts by numerous individuals from
13
* the Internet community; see the CONTRIBUTORS file for full
14
* details. Many organizations have provided support for Squid's
15
* development; see the SPONSORS file for full details. Squid is
16
* Copyrighted (C) 2001 by the Regents of the University of
17
* California; see the COPYRIGHT file for full details. Squid
18
* incorporates software developed and/or copyrighted by other
19
* sources; see the CREDITS file for full details.
21
* This program is free software; you can redistribute it and/or modify
22
* it under the terms of the GNU General Public License as published by
23
* the Free Software Foundation; either version 2 of the License, or
24
* (at your option) any later version.
26
* This program is distributed in the hope that it will be useful,
27
* but WITHOUT ANY WARRANTY; without even the implied warranty of
28
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
29
* GNU General Public License for more details.
31
* You should have received a copy of the GNU General Public License
32
* along with this program; if not, write to the Free Software
33
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
38
#include "CacheManager.h"
40
#include "HttpRequest.h"
42
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
44
static int n_sourcehash_peers = 0;
45
static peer **sourcehash_peers = NULL;
46
static OBJH peerSourceHashCachemgr;
49
peerSortWeight(const void *a, const void *b)
51
const peer *const *p1 = (const peer *const *)a;
52
const peer *const *p2 = (const peer *const *)b;
53
return (*p1)->weight - (*p2)->weight;
57
peerSourceHashInit(void)
62
double P_last, X_last, Xn;
68
for (k = 0; k < n_sourcehash_peers; k++) {
69
cbdataReferenceDone(sourcehash_peers[k]);
72
safe_free(sourcehash_peers);
73
n_sourcehash_peers = 0;
74
/* find out which peers we have */
76
for (p = Config.peers; p; p = p->next) {
77
if (!p->options.sourcehash)
80
assert(p->type == PEER_PARENT);
90
if (n_sourcehash_peers == 0)
93
sourcehash_peers = (peer **)xcalloc(n_sourcehash_peers, sizeof(*sourcehash_peers));
95
/* Build a list of the found peers and calculate hashes and load factors */
96
for (P = sourcehash_peers, p = Config.peers; p; p = p->next) {
97
if (!p->options.sourcehash)
103
/* calculate this peers hash */
104
p->sourcehash.hash = 0;
106
for (t = p->name; *t != 0; t++)
107
p->sourcehash.hash += ROTATE_LEFT(p->sourcehash.hash, 19) + (unsigned int) *t;
109
p->sourcehash.hash += p->sourcehash.hash * 0x62531965;
111
p->sourcehash.hash = ROTATE_LEFT(p->sourcehash.hash, 21);
113
/* and load factor */
114
p->sourcehash.load_factor = ((double) p->weight) / (double) W;
116
if (floor(p->sourcehash.load_factor * 1000.0) == 0.0)
117
p->sourcehash.load_factor = 0.0;
119
/* add it to our list of peers */
120
*P++ = cbdataReference(p);
123
/* Sort our list on weight */
124
qsort(sourcehash_peers, n_sourcehash_peers, sizeof(*sourcehash_peers), peerSortWeight);
126
/* Calculate the load factor multipliers X_k
128
* X_1 = pow ((K*p_1), (1/K))
129
* X_k = ([K-k+1] * [P_k - P_{k-1}])/(X_1 * X_2 * ... * X_{k-1})
130
* X_k += pow ((X_{k-1}, {K-k+1})
131
* X_k = pow (X_k, {1/(K-k+1)})
132
* simplified to have X_1 part of the loop
134
K = n_sourcehash_peers;
136
P_last = 0.0; /* Empty P_0 */
138
Xn = 1.0; /* Empty starting point of X_1 * X_2 * ... * X_{x-1} */
140
X_last = 0.0; /* Empty X_0, nullifies the first pow statement */
142
for (k = 1; k <= K; k++) {
143
double Kk1 = (double) (K - k + 1);
144
p = sourcehash_peers[k - 1];
145
p->sourcehash.load_multiplier = (Kk1 * (p->sourcehash.load_factor - P_last)) / Xn;
146
p->sourcehash.load_multiplier += pow(X_last, Kk1);
147
p->sourcehash.load_multiplier = pow(p->sourcehash.load_multiplier, 1.0 / Kk1);
148
Xn *= p->sourcehash.load_multiplier;
149
X_last = p->sourcehash.load_multiplier;
150
P_last = p->sourcehash.load_factor;
155
peerSourceHashRegisterWithCacheManager(CacheManager & manager)
157
manager.registerAction("sourcehash", "peer sourcehash information", peerSourceHashCachemgr, 0, 1);
161
peerSourceHashSelectParent(HttpRequest * request)
167
unsigned int user_hash = 0;
168
unsigned int combined_hash;
170
double high_score = 0;
171
const char *key = NULL;
173
if (n_sourcehash_peers == 0)
176
key = inet_ntoa(request->client_addr);
178
/* calculate hash key */
179
debugs(39, 2, "peerSourceHashSelectParent: Calculating hash for " << key);
181
for (c = key; *c != 0; c++)
182
user_hash += ROTATE_LEFT(user_hash, 19) + *c;
185
for (k = 0; k < n_sourcehash_peers; k++) {
186
tp = sourcehash_peers[k];
187
combined_hash = (user_hash ^ tp->sourcehash.hash);
188
combined_hash += combined_hash * 0x62531965;
189
combined_hash = ROTATE_LEFT(combined_hash, 21);
190
score = combined_hash * tp->sourcehash.load_multiplier;
191
debugs(39, 3, "peerSourceHashSelectParent: " << tp->name << " combined_hash " << combined_hash <<
192
" score " << std::setprecision(0) << score);
194
if ((score > high_score) && peerHTTPOkay(tp, request)) {
201
debugs(39, 2, "peerSourceHashSelectParent: selected " << p->name);
207
peerSourceHashCachemgr(StoreEntry * sentry)
211
storeAppendPrintf(sentry, "%24s %10s %10s %10s %10s\n",
218
for (p = Config.peers; p; p = p->next)
219
sumfetches += p->stats.fetches;
221
for (p = Config.peers; p; p = p->next) {
222
storeAppendPrintf(sentry, "%24s %10x %10f %10f %10f\n",
223
p->name, p->sourcehash.hash,
224
p->sourcehash.load_multiplier,
225
p->sourcehash.load_factor,
226
sumfetches ? (double) p->stats.fetches / sumfetches : -1.0);
added
removed
src/peer_sourcehash.cc
