src/peer_sourcehash.cc

   1
   2 /*
   3  * DEBUG: section 39    Peer source 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 #include "CachePeer.h"
  37 #include "HttpRequest.h"
  38 #include "mgr/Registration.h"
  39 #include "neighbors.h"
  40 #include "SquidConfig.h"
  41 #include "Store.h"
  42
  43 #if HAVE_MATH_H
  44 #include <math.h>
  45 #endif
  46
  47 #define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
  48
  49 static int n_sourcehash_peers = 0;
  50 static CachePeer **sourcehash_peers = NULL;
  51 static OBJH peerSourceHashCachemgr;
  52 static void peerSourceHashRegisterWithCacheManager(void);
  53
  54 static int
  55 peerSortWeight(const void *a, const void *b)
  56 {
  57     const CachePeer *const *p1 = (const CachePeer *const *)a;
  58     const CachePeer *const *p2 = (const CachePeer *const *)b;
  59     return (*p1)->weight - (*p2)->weight;
  60 }
  61
  62 void
  63 peerSourceHashInit(void)
  64 {
  65     int W = 0;
  66     int K;
  67     int k;
  68     double P_last, X_last, Xn;
  69     CachePeer *p;
  70     CachePeer **P;
  71     char *t;
  72     /* Clean up */
  73
  74     for (k = 0; k < n_sourcehash_peers; ++k) {
  75         cbdataReferenceDone(sourcehash_peers[k]);
  76     }
  77
  78     safe_free(sourcehash_peers);
  79     n_sourcehash_peers = 0;
  80     /* find out which peers we have */
  81
  82     for (p = Config.peers; p; p = p->next) {
  83         if (!p->options.sourcehash)
  84             continue;
  85
  86         assert(p->type == PEER_PARENT);
  87
  88         if (p->weight == 0)
  89             continue;
  90
  91         ++n_sourcehash_peers;
  92
  93         W += p->weight;
  94     }
  95
  96     peerSourceHashRegisterWithCacheManager();
  97
  98     if (n_sourcehash_peers == 0)
  99         return;
 100
 101     sourcehash_peers = (CachePeer **)xcalloc(n_sourcehash_peers, sizeof(*sourcehash_peers));
 102
 103     /* Build a list of the found peers and calculate hashes and load factors */
 104     for (P = sourcehash_peers, p = Config.peers; p; p = p->next) {
 105         if (!p->options.sourcehash)
 106             continue;
 107
 108         if (p->weight == 0)
 109             continue;
 110
 111         /* calculate this peers hash */
 112         p->sourcehash.hash = 0;
 113
 114         for (t = p->name; *t != 0; ++t)
 115             p->sourcehash.hash += ROTATE_LEFT(p->sourcehash.hash, 19) + (unsigned int) *t;
 116
 117         p->sourcehash.hash += p->sourcehash.hash * 0x62531965;
 118
 119         p->sourcehash.hash = ROTATE_LEFT(p->sourcehash.hash, 21);
 120
 121         /* and load factor */
 122         p->sourcehash.load_factor = ((double) p->weight) / (double) W;
 123
 124         if (floor(p->sourcehash.load_factor * 1000.0) == 0.0)
 125             p->sourcehash.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(sourcehash_peers, n_sourcehash_peers, sizeof(*sourcehash_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_sourcehash_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 = sourcehash_peers[k - 1];
 153         p->sourcehash.load_multiplier = (Kk1 * (p->sourcehash.load_factor - P_last)) / Xn;
 154         p->sourcehash.load_multiplier += pow(X_last, Kk1);
 155         p->sourcehash.load_multiplier = pow(p->sourcehash.load_multiplier, 1.0 / Kk1);
 156         Xn *= p->sourcehash.load_multiplier;
 157         X_last = p->sourcehash.load_multiplier;
 158         P_last = p->sourcehash.load_factor;
 159     }
 160 }
 161
 162 static void
 163 peerSourceHashRegisterWithCacheManager(void)
 164 {
 165     Mgr::RegisterAction("sourcehash", "peer sourcehash information",
 166                         peerSourceHashCachemgr, 0, 1);
 167 }
 168
 169 CachePeer *
 170 peerSourceHashSelectParent(HttpRequest * request)
 171 {
 172     int k;
 173     const char *c;
 174     CachePeer *p = NULL;
 175     CachePeer *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     char ntoabuf[MAX_IPSTRLEN];
 182
 183     if (n_sourcehash_peers == 0)
 184         return NULL;
 185
 186     key = request->client_addr.NtoA(ntoabuf, sizeof(ntoabuf));
 187
 188     /* calculate hash key */
 189     debugs(39, 2, "peerSourceHashSelectParent: Calculating hash for " << key);
 190
 191     for (c = key; *c != 0; ++c)
 192         user_hash += ROTATE_LEFT(user_hash, 19) + *c;
 193
 194     /* select CachePeer */
 195     for (k = 0; k < n_sourcehash_peers; ++k) {
 196         tp = sourcehash_peers[k];
 197         combined_hash = (user_hash ^ tp->sourcehash.hash);
 198         combined_hash += combined_hash * 0x62531965;
 199         combined_hash = ROTATE_LEFT(combined_hash, 21);
 200         score = combined_hash * tp->sourcehash.load_multiplier;
 201         debugs(39, 3, "peerSourceHashSelectParent: " << tp->name << " combined_hash " << combined_hash  <<
 202                " score " << std::setprecision(0) << score);
 203
 204         if ((score > high_score) && peerHTTPOkay(tp, request)) {
 205             p = tp;
 206             high_score = score;
 207         }
 208     }
 209
 210     if (p)
 211         debugs(39, 2, "peerSourceHashSelectParent: selected " << p->name);
 212
 213     return p;
 214 }
 215
 216 static void
 217 peerSourceHashCachemgr(StoreEntry * sentry)
 218 {
 219     CachePeer *p;
 220     int sumfetches = 0;
 221     storeAppendPrintf(sentry, "%24s %10s %10s %10s %10s\n",
 222                       "Hostname",
 223                       "Hash",
 224                       "Multiplier",
 225                       "Factor",
 226                       "Actual");
 227
 228     for (p = Config.peers; p; p = p->next)
 229         sumfetches += p->stats.fetches;
 230
 231     for (p = Config.peers; p; p = p->next) {
 232         storeAppendPrintf(sentry, "%24s %10x %10f %10f %10f\n",
 233                           p->name, p->sourcehash.hash,
 234                           p->sourcehash.load_multiplier,
 235                           p->sourcehash.load_factor,
 236                           sumfetches ? (double) p->stats.fetches / sumfetches : -1.0);
 237     }
 238 }