src/peer_userhash.cc

   1
   2 /*
   3  * DEBUG: section 39    Peer user hash based selection
   4  * AUTHOR: Henrik Nordstrom
   5  * BASED ON: carp.cc
   6  *
   7  * SQUID Web Proxy Cache          http://www.squid-cache.org/
   8  * ----------------------------------------------------------
   9  *
  10  *  Squid is the result of efforts by numerous individuals from
  11  *  the Internet community; see the CONTRIBUTORS file for full
  12  *  details.   Many organizations have provided support for Squid's
  13  *  development; see the SPONSORS file for full details.  Squid is
  14  *  Copyrighted (C) 2001 by the Regents of the University of
  15  *  California; see the COPYRIGHT file for full details.  Squid
  16  *  incorporates software developed and/or copyrighted by other
  17  *  sources; see the CREDITS file for full details.
  18  *
  19  *  This program is free software; you can redistribute it and/or modify
  20  *  it under the terms of the GNU General Public License as published by
  21  *  the Free Software Foundation; either version 2 of the License, or
  22  *  (at your option) any later version.
  23  *
  24  *  This program is distributed in the hope that it will be useful,
  25  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  26  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  27  *  GNU General Public License for more details.
  28  *
  29  *  You should have received a copy of the GNU General Public License
  30  *  along with this program; if not, write to the Free Software
  31  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  32  *
  33  */
  34
  35 #include "squid.h"
  36
  37 #if USE_AUTH
  38
  39 #include "auth/UserRequest.h"
  40 #include "CachePeer.h"
  41 #include "globals.h"
  42 #include "HttpRequest.h"
  43 #include "mgr/Registration.h"
  44 #include "neighbors.h"
  45 #include "SquidConfig.h"
  46 #include "Store.h"
  47
  48 #if HAVE_MATH_H
  49 #include <math.h>
  50 #endif
  51
  52 #define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
  53
  54 static int n_userhash_peers = 0;
  55 static CachePeer **userhash_peers = NULL;
  56 static OBJH peerUserHashCachemgr;
  57 static void peerUserHashRegisterWithCacheManager(void);
  58
  59 static int
  60 peerSortWeight(const void *a, const void *b)
  61 {
  62     const CachePeer *const *p1 = (const CachePeer *const *)a;
  63     const CachePeer *const *p2 = (const CachePeer *const *)b;
  64     return (*p1)->weight - (*p2)->weight;
  65 }
  66
  67 void
  68 peerUserHashInit(void)
  69 {
  70     int W = 0;
  71     int K;
  72     int k;
  73     double P_last, X_last, Xn;
  74     CachePeer *p;
  75     CachePeer **P;
  76     char *t;
  77     /* Clean up */
  78
  79     for (k = 0; k < n_userhash_peers; ++k) {
  80         cbdataReferenceDone(userhash_peers[k]);
  81     }
  82
  83     safe_free(userhash_peers);
  84     n_userhash_peers = 0;
  85     /* find out which peers we have */
  86
  87     peerUserHashRegisterWithCacheManager();
  88
  89     for (p = Config.peers; p; p = p->next) {
  90         if (!p->options.userhash)
  91             continue;
  92
  93         assert(p->type == PEER_PARENT);
  94
  95         if (p->weight == 0)
  96             continue;
  97
  98         ++n_userhash_peers;
  99
 100         W += p->weight;
 101     }
 102
 103     if (n_userhash_peers == 0)
 104         return;
 105
 106     userhash_peers = (CachePeer **)xcalloc(n_userhash_peers, sizeof(*userhash_peers));
 107
 108     /* Build a list of the found peers and calculate hashes and load factors */
 109     for (P = userhash_peers, p = Config.peers; p; p = p->next) {
 110         if (!p->options.userhash)
 111             continue;
 112
 113         if (p->weight == 0)
 114             continue;
 115
 116         /* calculate this peers hash */
 117         p->userhash.hash = 0;
 118
 119         for (t = p->name; *t != 0; ++t)
 120             p->userhash.hash += ROTATE_LEFT(p->userhash.hash, 19) + (unsigned int) *t;
 121
 122         p->userhash.hash += p->userhash.hash * 0x62531965;
 123
 124         p->userhash.hash = ROTATE_LEFT(p->userhash.hash, 21);
 125
 126         /* and load factor */
 127         p->userhash.load_factor = ((double) p->weight) / (double) W;
 128
 129         if (floor(p->userhash.load_factor * 1000.0) == 0.0)
 130             p->userhash.load_factor = 0.0;
 131
 132         /* add it to our list of peers */
 133         *P++ = cbdataReference(p);
 134     }
 135
 136     /* Sort our list on weight */
 137     qsort(userhash_peers, n_userhash_peers, sizeof(*userhash_peers), peerSortWeight);
 138
 139     /* Calculate the load factor multipliers X_k
 140      *
 141      * X_1 = pow ((K*p_1), (1/K))
 142      * X_k = ([K-k+1] * [P_k - P_{k-1}])/(X_1 * X_2 * ... * X_{k-1})
 143      * X_k += pow ((X_{k-1}, {K-k+1})
 144      * X_k = pow (X_k, {1/(K-k+1)})
 145      * simplified to have X_1 part of the loop
 146      */
 147     K = n_userhash_peers;
 148
 149     P_last = 0.0;               /* Empty P_0 */
 150
 151     Xn = 1.0;                   /* Empty starting point of X_1 * X_2 * ... * X_{x-1} */
 152
 153     X_last = 0.0;               /* Empty X_0, nullifies the first pow statement */
 154
 155     for (k = 1; k <= K; ++k) {
 156         double Kk1 = (double) (K - k + 1);
 157         p = userhash_peers[k - 1];
 158         p->userhash.load_multiplier = (Kk1 * (p->userhash.load_factor - P_last)) / Xn;
 159         p->userhash.load_multiplier += pow(X_last, Kk1);
 160         p->userhash.load_multiplier = pow(p->userhash.load_multiplier, 1.0 / Kk1);
 161         Xn *= p->userhash.load_multiplier;
 162         X_last = p->userhash.load_multiplier;
 163         P_last = p->userhash.load_factor;
 164     }
 165 }
 166
 167 static void
 168 peerUserHashRegisterWithCacheManager(void)
 169 {
 170     Mgr::RegisterAction("userhash", "peer userhash information", peerUserHashCachemgr,
 171                         0, 1);
 172 }
 173
 174 CachePeer *
 175 peerUserHashSelectParent(HttpRequest * request)
 176 {
 177     int k;
 178     const char *c;
 179     CachePeer *p = NULL;
 180     CachePeer *tp;
 181     unsigned int user_hash = 0;
 182     unsigned int combined_hash;
 183     double score;
 184     double high_score = 0;
 185     const char *key = NULL;
 186
 187     if (n_userhash_peers == 0)
 188         return NULL;
 189
 190     if (request->auth_user_request != NULL)
 191         key = request->auth_user_request->username();
 192
 193     if (!key)
 194         return NULL;
 195
 196     /* calculate hash key */
 197     debugs(39, 2, "peerUserHashSelectParent: Calculating hash for " << key);
 198
 199     for (c = key; *c != 0; ++c)
 200         user_hash += ROTATE_LEFT(user_hash, 19) + *c;
 201
 202     /* select CachePeer */
 203     for (k = 0; k < n_userhash_peers; ++k) {
 204         tp = userhash_peers[k];
 205         combined_hash = (user_hash ^ tp->userhash.hash);
 206         combined_hash += combined_hash * 0x62531965;
 207         combined_hash = ROTATE_LEFT(combined_hash, 21);
 208         score = combined_hash * tp->userhash.load_multiplier;
 209         debugs(39, 3, "peerUserHashSelectParent: " << tp->name << " combined_hash " << combined_hash  <<
 210                " score " << std::setprecision(0) << score);
 211
 212         if ((score > high_score) && peerHTTPOkay(tp, request)) {
 213             p = tp;
 214             high_score = score;
 215         }
 216     }
 217
 218     if (p)
 219         debugs(39, 2, "peerUserHashSelectParent: selected " << p->name);
 220
 221     return p;
 222 }
 223
 224 static void
 225 peerUserHashCachemgr(StoreEntry * sentry)
 226 {
 227     CachePeer *p;
 228     int sumfetches = 0;
 229     storeAppendPrintf(sentry, "%24s %10s %10s %10s %10s\n",
 230                       "Hostname",
 231                       "Hash",
 232                       "Multiplier",
 233                       "Factor",
 234                       "Actual");
 235
 236     for (p = Config.peers; p; p = p->next)
 237         sumfetches += p->stats.fetches;
 238
 239     for (p = Config.peers; p; p = p->next) {
 240         storeAppendPrintf(sentry, "%24s %10x %10f %10f %10f\n",
 241                           p->name, p->userhash.hash,
 242                           p->userhash.load_multiplier,
 243                           p->userhash.load_factor,
 244                           sumfetches ? (double) p->stats.fetches / sumfetches : -1.0);
 245     }
 246 }
 247
 248 #endif /* USE_AUTH */