src/peer_userhash.cc

   1
   2 /*
   3  * $Id$
   4  *
   5  * DEBUG: section 39    Peer user hash based selection
   6  * AUTHOR: Henrik Nordstrom
   7  * BASED ON: carp.cc
   8  *
   9  * SQUID Web Proxy Cache          http://www.squid-cache.org/
  10  * ----------------------------------------------------------
  11  *
  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.
  20  *
  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.
  25  *
  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.
  30  *
  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.
  34  *
  35  */
  36
  37 #include "squid-old.h"
  38
  39 #if USE_AUTH
  40
  41 #include "mgr/Registration.h"
  42 #include "Store.h"
  43 #include "HttpRequest.h"
  44 #include "auth/UserRequest.h"
  45
  46 #define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
  47
  48 static int n_userhash_peers = 0;
  49 static peer **userhash_peers = NULL;
  50 static OBJH peerUserHashCachemgr;
  51 static void peerUserHashRegisterWithCacheManager(void);
  52
  53 static int
  54 peerSortWeight(const void *a, const void *b)
  55 {
  56     const peer *const *p1 = (const peer *const *)a;
  57     const peer *const *p2 = (const peer *const *)b;
  58     return (*p1)->weight - (*p2)->weight;
  59 }
  60
  61 void
  62 peerUserHashInit(void)
  63 {
  64     int W = 0;
  65     int K;
  66     int k;
  67     double P_last, X_last, Xn;
  68     peer *p;
  69     peer **P;
  70     char *t;
  71     /* Clean up */
  72
  73     for (k = 0; k < n_userhash_peers; ++k) {
  74         cbdataReferenceDone(userhash_peers[k]);
  75     }
  76
  77     safe_free(userhash_peers);
  78     n_userhash_peers = 0;
  79     /* find out which peers we have */
  80
  81
  82     peerUserHashRegisterWithCacheManager();
  83
  84     for (p = Config.peers; p; p = p->next) {
  85         if (!p->options.userhash)
  86             continue;
  87
  88         assert(p->type == PEER_PARENT);
  89
  90         if (p->weight == 0)
  91             continue;
  92
  93         ++n_userhash_peers;
  94
  95         W += p->weight;
  96     }
  97
  98     if (n_userhash_peers == 0)
  99         return;
 100
 101     userhash_peers = (peer **)xcalloc(n_userhash_peers, sizeof(*userhash_peers));
 102
 103     /* Build a list of the found peers and calculate hashes and load factors */
 104     for (P = userhash_peers, p = Config.peers; p; p = p->next) {
 105         if (!p->options.userhash)
 106             continue;
 107
 108         if (p->weight == 0)
 109             continue;
 110
 111         /* calculate this peers hash */
 112         p->userhash.hash = 0;
 113
 114         for (t = p->name; *t != 0; ++t)
 115             p->userhash.hash += ROTATE_LEFT(p->userhash.hash, 19) + (unsigned int) *t;
 116
 117         p->userhash.hash += p->userhash.hash * 0x62531965;
 118
 119         p->userhash.hash = ROTATE_LEFT(p->userhash.hash, 21);
 120
 121         /* and load factor */
 122         p->userhash.load_factor = ((double) p->weight) / (double) W;
 123
 124         if (floor(p->userhash.load_factor * 1000.0) == 0.0)
 125             p->userhash.load_factor = 0.0;
 126
 127         /* add it to our list of peers */
 128         *P++ = cbdataReference(p);
 129     }
 130
 131     /* Sort our list on weight */
 132     qsort(userhash_peers, n_userhash_peers, sizeof(*userhash_peers), peerSortWeight);
 133
 134     /* Calculate the load factor multipliers X_k
 135      *
 136      * X_1 = pow ((K*p_1), (1/K))
 137      * X_k = ([K-k+1] * [P_k - P_{k-1}])/(X_1 * X_2 * ... * X_{k-1})
 138      * X_k += pow ((X_{k-1}, {K-k+1})
 139      * X_k = pow (X_k, {1/(K-k+1)})
 140      * simplified to have X_1 part of the loop
 141      */
 142     K = n_userhash_peers;
 143
 144     P_last = 0.0;               /* Empty P_0 */
 145
 146     Xn = 1.0;                   /* Empty starting point of X_1 * X_2 * ... * X_{x-1} */
 147
 148     X_last = 0.0;               /* Empty X_0, nullifies the first pow statement */
 149
 150     for (k = 1; k <= K; ++k) {
 151         double Kk1 = (double) (K - k + 1);
 152         p = userhash_peers[k - 1];
 153         p->userhash.load_multiplier = (Kk1 * (p->userhash.load_factor - P_last)) / Xn;
 154         p->userhash.load_multiplier += pow(X_last, Kk1);
 155         p->userhash.load_multiplier = pow(p->userhash.load_multiplier, 1.0 / Kk1);
 156         Xn *= p->userhash.load_multiplier;
 157         X_last = p->userhash.load_multiplier;
 158         P_last = p->userhash.load_factor;
 159     }
 160 }
 161
 162 static void
 163 peerUserHashRegisterWithCacheManager(void)
 164 {
 165     Mgr::RegisterAction("userhash", "peer userhash information", peerUserHashCachemgr,
 166                         0, 1);
 167 }
 168
 169 peer *
 170 peerUserHashSelectParent(HttpRequest * request)
 171 {
 172     int k;
 173     const char *c;
 174     peer *p = NULL;
 175     peer *tp;
 176     unsigned int user_hash = 0;
 177     unsigned int combined_hash;
 178     double score;
 179     double high_score = 0;
 180     const char *key = NULL;
 181
 182     if (n_userhash_peers == 0)
 183         return NULL;
 184
 185     if (request->auth_user_request != NULL)
 186         key = request->auth_user_request->username();
 187
 188     if (!key)
 189         return NULL;
 190
 191     /* calculate hash key */
 192     debugs(39, 2, "peerUserHashSelectParent: Calculating hash for " << key);
 193
 194     for (c = key; *c != 0; ++c)
 195         user_hash += ROTATE_LEFT(user_hash, 19) + *c;
 196
 197     /* select peer */
 198     for (k = 0; k < n_userhash_peers; ++k) {
 199         tp = userhash_peers[k];
 200         combined_hash = (user_hash ^ tp->userhash.hash);
 201         combined_hash += combined_hash * 0x62531965;
 202         combined_hash = ROTATE_LEFT(combined_hash, 21);
 203         score = combined_hash * tp->userhash.load_multiplier;
 204         debugs(39, 3, "peerUserHashSelectParent: " << tp->name << " combined_hash " << combined_hash  <<
 205                " score " << std::setprecision(0) << score);
 206
 207         if ((score > high_score) && peerHTTPOkay(tp, request)) {
 208             p = tp;
 209             high_score = score;
 210         }
 211     }
 212
 213     if (p)
 214         debugs(39, 2, "peerUserHashSelectParent: selected " << p->name);
 215
 216     return p;
 217 }
 218
 219 static void
 220 peerUserHashCachemgr(StoreEntry * sentry)
 221 {
 222     peer *p;
 223     int sumfetches = 0;
 224     storeAppendPrintf(sentry, "%24s %10s %10s %10s %10s\n",
 225                       "Hostname",
 226                       "Hash",
 227                       "Multiplier",
 228                       "Factor",
 229                       "Actual");
 230
 231     for (p = Config.peers; p; p = p->next)
 232         sumfetches += p->stats.fetches;
 233
 234     for (p = Config.peers; p; p = p->next) {
 235         storeAppendPrintf(sentry, "%24s %10x %10f %10f %10f\n",
 236                           p->name, p->userhash.hash,
 237                           p->userhash.load_multiplier,
 238                           p->userhash.load_factor,
 239                           sumfetches ? (double) p->stats.fetches / sumfetches : -1.0);
 240     }
 241 }
 242
 243 #endif /* USE_AUTH */