src/peer_sourcehash.cc

   1
   2 /*
   3  * $Id: carp.cc,v 1.27 2008/01/14 12:13:49 hno Exp $
   4  *
   5  * DEBUG: section 39    Peer source 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
  41 #define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
  42
  43 static int n_carp_peers = 0;
  44 static peer **carp_peers = NULL;
  45 static OBJH carpCachemgr;
  46
  47 static int
  48 peerSortWeight(const void *a, const void *b)
  49 {
  50     const peer *const *p1 = (const peer *const *)a;
  51     const peer *const *p2 = (const peer *const *)b;
  52     return (*p1)->weight - (*p2)->weight;
  53 }
  54
  55 void
  56 carpInit(void)
  57 {
  58     int W = 0;
  59     int K;
  60     int k;
  61     double P_last, X_last, Xn;
  62     peer *p;
  63     peer **P;
  64     char *t;
  65     /* Clean up */
  66
  67     for (k = 0; k < n_carp_peers; k++) {
  68         cbdataReferenceDone(carp_peers[k]);
  69     }
  70
  71     safe_free(carp_peers);
  72     n_carp_peers = 0;
  73     /* find out which peers we have */
  74
  75     for (p = Config.peers; p; p = p->next) {
  76         if (!p->options.carp)
  77             continue;
  78
  79         assert(p->type == PEER_PARENT);
  80
  81         if (p->weight == 0)
  82             continue;
  83
  84         n_carp_peers++;
  85
  86         W += p->weight;
  87     }
  88
  89     if (n_carp_peers == 0)
  90         return;
  91
  92     carp_peers = (peer **)xcalloc(n_carp_peers, sizeof(*carp_peers));
  93
  94     /* Build a list of the found peers and calculate hashes and load factors */
  95     for (P = carp_peers, p = Config.peers; p; p = p->next) {
  96         if (!p->options.carp)
  97             continue;
  98
  99         if (p->weight == 0)
 100             continue;
 101
 102         /* calculate this peers hash */
 103         p->carp.hash = 0;
 104
 105         for (t = p->name; *t != 0; t++)
 106             p->carp.hash += ROTATE_LEFT(p->carp.hash, 19) + (unsigned int) *t;
 107
 108         p->carp.hash += p->carp.hash * 0x62531965;
 109
 110         p->carp.hash = ROTATE_LEFT(p->carp.hash, 21);
 111
 112         /* and load factor */
 113         p->carp.load_factor = ((double) p->weight) / (double) W;
 114
 115         if (floor(p->carp.load_factor * 1000.0) == 0.0)
 116             p->carp.load_factor = 0.0;
 117
 118         /* add it to our list of peers */
 119         *P++ = cbdataReference(p);
 120     }
 121
 122     /* Sort our list on weight */
 123     qsort(carp_peers, n_carp_peers, sizeof(*carp_peers), peerSortWeight);
 124
 125     /* Calculate the load factor multipliers X_k
 126      *
 127      * X_1 = pow ((K*p_1), (1/K))
 128      * X_k = ([K-k+1] * [P_k - P_{k-1}])/(X_1 * X_2 * ... * X_{k-1})
 129      * X_k += pow ((X_{k-1}, {K-k+1})
 130      * X_k = pow (X_k, {1/(K-k+1)})
 131      * simplified to have X_1 part of the loop
 132      */
 133     K = n_carp_peers;
 134
 135     P_last = 0.0;               /* Empty P_0 */
 136
 137     Xn = 1.0;                   /* Empty starting point of X_1 * X_2 * ... * X_{x-1} */
 138
 139     X_last = 0.0;               /* Empty X_0, nullifies the first pow statement */
 140
 141     for (k = 1; k <= K; k++) {
 142         double Kk1 = (double) (K - k + 1);
 143         p = carp_peers[k - 1];
 144         p->carp.load_multiplier = (Kk1 * (p->carp.load_factor - P_last)) / Xn;
 145         p->carp.load_multiplier += pow(X_last, Kk1);
 146         p->carp.load_multiplier = pow(p->carp.load_multiplier, 1.0 / Kk1);
 147         Xn *= p->carp.load_multiplier;
 148         X_last = p->carp.load_multiplier;
 149         P_last = p->carp.load_factor;
 150     }
 151 }
 152
 153 void
 154 carpRegisterWithCacheManager(CacheManager & manager)
 155 {
 156     manager.registerAction("carp", "CARP information", carpCachemgr, 0, 1);
 157 }
 158
 159 peer *
 160 carpSelectParent(HttpRequest * request)
 161 {
 162     int k;
 163     const char *c;
 164     peer *p = NULL;
 165     peer *tp;
 166     unsigned int user_hash = 0;
 167     unsigned int combined_hash;
 168     double score;
 169     double high_score = 0;
 170     const char *key = NULL;
 171     char ntoabuf[MAX_IPSTRLEN];
 172
 173     if (n_carp_peers == 0)
 174         return NULL;
 175
 176     key = request->client_addr.NtoA(ntoabuf, sizeof(ntoabuf));
 177
 178     /* calculate hash key */
 179     debugs(39, 2, "carpSelectParent: Calculating hash for " << key);
 180
 181     for (c = key; *c != 0; c++)
 182         user_hash += ROTATE_LEFT(user_hash, 19) + *c;
 183
 184     /* select peer */
 185     for (k = 0; k < n_carp_peers; k++) {
 186         tp = carp_peers[k];
 187         combined_hash = (user_hash ^ tp->carp.hash);
 188         combined_hash += combined_hash * 0x62531965;
 189         combined_hash = ROTATE_LEFT(combined_hash, 21);
 190         score = combined_hash * tp->carp.load_multiplier;
 191         debugs(39, 3, "carpSelectParent: " << tp->name << " combined_hash " << combined_hash  <<
 192                " score " << std::setprecision(0) << score);
 193
 194         if ((score > high_score) && peerHTTPOkay(tp, request)) {
 195             p = tp;
 196             high_score = score;
 197         }
 198     }
 199
 200     if (p)
 201         debugs(39, 2, "carpSelectParent: selected " << p->name);
 202
 203     return p;
 204 }
 205
 206 static void
 207 carpCachemgr(StoreEntry * sentry)
 208 {
 209     peer *p;
 210     int sumfetches = 0;
 211     storeAppendPrintf(sentry, "%24s %10s %10s %10s %10s\n",
 212                       "Hostname",
 213                       "Hash",
 214                       "Multiplier",
 215                       "Factor",
 216                       "Actual");
 217
 218     for (p = Config.peers; p; p = p->next)
 219         sumfetches += p->stats.fetches;
 220
 221     for (p = Config.peers; p; p = p->next) {
 222         storeAppendPrintf(sentry, "%24s %10x %10f %10f %10f\n",
 223                           p->name, p->carp.hash,
 224                           p->carp.load_multiplier,
 225                           p->carp.load_factor,
 226                           sumfetches ? (double) p->stats.fetches / sumfetches : -1.0);
 227     }
 228 }