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