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