src/carp.cc

   1
   2 /*
   3  * $Id: carp.cc,v 1.27 2008/01/14 12:13:49 hno Exp $
   4  *
   5  * DEBUG: section 39    Cache Array Routing Protocol
   6  * AUTHOR: Henrik Nordstrom
   7  * BASED ON: carp.c by Eric Stern and draft-vinod-carp-v1-03.txt
   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 #if USE_CARP
  42
  43 #define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
  44
  45 static int n_carp_peers = 0;
  46 static peer **carp_peers = NULL;
  47 static OBJH carpCachemgr;
  48
  49 static int
  50 peerSortWeight(const void *a, const void *b)
  51 {
  52     const peer *const *p1 = (const peer *const *)a;
  53     const peer *const *p2 = (const peer *const *)b;
  54     return (*p1)->weight - (*p2)->weight;
  55 }
  56
  57 void
  58 carpInit(void)
  59 {
  60     int W = 0;
  61     int K;
  62     int k;
  63     double P_last, X_last, Xn;
  64     peer *p;
  65     peer **P;
  66     char *t;
  67     /* Clean up */
  68
  69     for (k = 0; k < n_carp_peers; k++) {
  70         cbdataReferenceDone(carp_peers[k]);
  71     }
  72
  73     safe_free(carp_peers);
  74     n_carp_peers = 0;
  75
  76     /* initialize cache manager before we have a chance to leave the execution path */
  77     carpRegisterWithCacheManager();
  78
  79     /* find out which peers we have */
  80
  81     for (p = Config.peers; p; p = p->next) {
  82         if (!p->options.carp)
  83             continue;
  84
  85         assert(p->type == PEER_PARENT);
  86
  87         if (p->weight == 0)
  88             continue;
  89
  90         n_carp_peers++;
  91
  92         W += p->weight;
  93     }
  94
  95     if (n_carp_peers == 0)
  96         return;
  97
  98     carp_peers = (peer **)xcalloc(n_carp_peers, sizeof(*carp_peers));
  99
 100     /* Build a list of the found peers and calculate hashes and load factors */
 101     for (P = carp_peers, p = Config.peers; p; p = p->next) {
 102         if (!p->options.carp)
 103             continue;
 104
 105         if (p->weight == 0)
 106             continue;
 107
 108         /* calculate this peers hash */
 109         p->carp.hash = 0;
 110
 111         for (t = p->name; *t != 0; t++)
 112             p->carp.hash += ROTATE_LEFT(p->carp.hash, 19) + (unsigned int) *t;
 113
 114         p->carp.hash += p->carp.hash * 0x62531965;
 115
 116         p->carp.hash = ROTATE_LEFT(p->carp.hash, 21);
 117
 118         /* and load factor */
 119         p->carp.load_factor = ((double) p->weight) / (double) W;
 120
 121         if (floor(p->carp.load_factor * 1000.0) == 0.0)
 122             p->carp.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(carp_peers, n_carp_peers, sizeof(*carp_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_carp_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 = carp_peers[k - 1];
 150         p->carp.load_multiplier = (Kk1 * (p->carp.load_factor - P_last)) / Xn;
 151         p->carp.load_multiplier += pow(X_last, Kk1);
 152         p->carp.load_multiplier = pow(p->carp.load_multiplier, 1.0 / Kk1);
 153         Xn *= p->carp.load_multiplier;
 154         X_last = p->carp.load_multiplier;
 155         P_last = p->carp.load_factor;
 156     }
 157 }
 158
 159 void
 160 carpRegisterWithCacheManager()
 161 {
 162     CacheManager::GetInstance()->
 163         registerAction("carp", "CARP information", carpCachemgr, 0, 1);
 164 }
 165
 166 peer *
 167 carpSelectParent(HttpRequest * request)
 168 {
 169     int k;
 170     const char *c;
 171     peer *p = NULL;
 172     peer *tp;
 173     unsigned int user_hash = 0;
 174     unsigned int combined_hash;
 175     double score;
 176     double high_score = 0;
 177     const char *key = NULL;
 178
 179     if (n_carp_peers == 0)
 180         return NULL;
 181
 182     key = urlCanonical(request);
 183
 184     /* calculate hash key */
 185     debugs(39, 2, "carpSelectParent: Calculating hash for " << key);
 186
 187     for (c = key; *c != 0; c++)
 188         user_hash += ROTATE_LEFT(user_hash, 19) + *c;
 189
 190     /* select peer */
 191     for (k = 0; k < n_carp_peers; k++) {
 192         tp = carp_peers[k];
 193         combined_hash = (user_hash ^ tp->carp.hash);
 194         combined_hash += combined_hash * 0x62531965;
 195         combined_hash = ROTATE_LEFT(combined_hash, 21);
 196         score = combined_hash * tp->carp.load_multiplier;
 197         debugs(39, 3, "carpSelectParent: " << tp->name << " combined_hash " << combined_hash  <<
 198                " score " << std::setprecision(0) << score);
 199
 200         if ((score > high_score) && peerHTTPOkay(tp, request)) {
 201             p = tp;
 202             high_score = score;
 203         }
 204     }
 205
 206     if (p)
 207         debugs(39, 2, "carpSelectParent: selected " << p->name);
 208
 209     return p;
 210 }
 211
 212 static void
 213 carpCachemgr(StoreEntry * sentry)
 214 {
 215     peer *p;
 216     int sumfetches = 0;
 217     storeAppendPrintf(sentry, "%24s %10s %10s %10s %10s\n",
 218                       "Hostname",
 219                       "Hash",
 220                       "Multiplier",
 221                       "Factor",
 222                       "Actual");
 223
 224     for (p = Config.peers; p; p = p->next)
 225         sumfetches += p->stats.fetches;
 226
 227     for (p = Config.peers; p; p = p->next) {
 228         storeAppendPrintf(sentry, "%24s %10x %10f %10f %10f\n",
 229                           p->name, p->carp.hash,
 230                           p->carp.load_multiplier,
 231                           p->carp.load_factor,
 232                           sumfetches ? (double) p->stats.fetches / sumfetches : -1.0);
 233     }
 234 }
 235
 236 #endif