src/carp.cc

   1
   2 /*
   3  * $Id: carp.cc,v 1.20 2002/10/13 20:34:59 robertc 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 "Store.h"
  39
  40 #if USE_CARP
  41
  42 #define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
  43
  44 static int n_carp_peers = 0;
  45 static peer **carp_peers = NULL;
  46 static OBJH carpCachemgr;
  47
  48 static int
  49 peerSortWeight(const void *a, const void *b)
  50 {
  51     const peer *const *p1 = a, *const *p2 = 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     for (k = 0; k < n_carp_peers; k++) {
  67         cbdataReferenceDone(carp_peers[k]);
  68     }
  69     safe_free(carp_peers);
  70     n_carp_peers = 0;
  71     /* find out which peers we have */
  72     for (p = Config.peers; p; p = p->next) {
  73         if (!p->options.carp)
  74             continue;
  75         assert(p->type == PEER_PARENT);
  76         if (p->weight == 0)
  77             continue;
  78         n_carp_peers++;
  79         W += p->weight;
  80     }
  81     if (n_carp_peers == 0)
  82         return;
  83     carp_peers = xcalloc(n_carp_peers, sizeof(*carp_peers));
  84     /* Build a list of the found peers and calculate hashes and load factors */
  85     for (P = carp_peers, p = Config.peers; p; p = p->next) {
  86         if (!p->options.carp)
  87             continue;
  88         if (p->weight == 0)
  89             continue;
  90         /* calculate this peers hash */
  91         p->carp.hash = 0;
  92         for (t = p->host; *t != 0; t++)
  93             p->carp.hash += ROTATE_LEFT(p->carp.hash, 19) + (unsigned int) *t;
  94         p->carp.hash += p->carp.hash * 0x62531965;
  95         p->carp.hash = ROTATE_LEFT(p->carp.hash, 21);
  96         /* and load factor */
  97         p->carp.load_factor = ((double) p->weight) / (double) W;
  98         if (floor(p->carp.load_factor * 1000.0) == 0.0)
  99             p->carp.load_factor = 0.0;
 100         /* add it to our list of peers */
 101         *P++ = cbdataReference(p);
 102     }
 103     /* Sort our list on weight */
 104     qsort(carp_peers, n_carp_peers, sizeof(*carp_peers), peerSortWeight);
 105     /* Calculate the load factor multipliers X_k
 106      *
 107      * X_1 = pow ((K*p_1), (1/K))
 108      * X_k = ([K-k+1] * [P_k - P_{k-1}])/(X_1 * X_2 * ... * X_{k-1})
 109      * X_k += pow ((X_{k-1}, {K-k+1})
 110      * X_k = pow (X_k, {1/(K-k+1)})
 111      * simplified to have X_1 part of the loop
 112      */
 113     K = n_carp_peers;
 114     P_last = 0.0;               /* Empty P_0 */
 115     Xn = 1.0;                   /* Empty starting point of X_1 * X_2 * ... * X_{x-1} */
 116     X_last = 0.0;               /* Empty X_0, nullifies the first pow statement */
 117     for (k = 1; k <= K; k++) {
 118         double Kk1 = (double) (K - k + 1);
 119         p = carp_peers[k - 1];
 120         p->carp.load_multiplier = (Kk1 * (p->carp.load_factor - P_last)) / Xn;
 121         p->carp.load_multiplier += pow(X_last, Kk1);
 122         p->carp.load_multiplier = pow(p->carp.load_multiplier, 1.0 / Kk1);
 123         Xn *= p->carp.load_multiplier;
 124         X_last = p->carp.load_multiplier;
 125         P_last = p->carp.load_factor;
 126     }
 127     cachemgrRegister("carp", "CARP information", carpCachemgr, 0, 1);
 128 }
 129
 130 peer *
 131 carpSelectParent(request_t * request)
 132 {
 133     int k;
 134     const char *c;
 135     peer *p = NULL;
 136     peer *tp;
 137     unsigned int user_hash = 0;
 138     unsigned int combined_hash;
 139     double score;
 140     double high_score = 0;
 141     const char *key = NULL;
 142
 143     if (n_carp_peers == 0)
 144         return NULL;
 145
 146     key = urlCanonical(request);
 147
 148     /* calculate hash key */
 149     debug(39, 2) ("carpSelectParent: Calculating hash for %s\n", key);
 150     for (c = key; *c != 0; c++)
 151         user_hash += ROTATE_LEFT(user_hash, 19) + *c;
 152     /* select peer */
 153     for (k = 0; k < n_carp_peers; k++) {
 154         tp = carp_peers[k];
 155         combined_hash = (user_hash ^ tp->carp.hash);
 156         combined_hash += combined_hash * 0x62531965;
 157         combined_hash = ROTATE_LEFT(combined_hash, 21);
 158         score = combined_hash * tp->carp.load_multiplier;
 159         debug(39, 3) ("carpSelectParent: %s combined_hash %u score %.0f\n",
 160             tp->host, combined_hash, score);
 161         if ((score > high_score) && peerHTTPOkay(tp, request)) {
 162             p = tp;
 163             high_score = score;
 164         }
 165     }
 166     if (p)
 167         debug(39, 2) ("carpSelectParent: selected %s\n", p->host);
 168     return p;
 169 }
 170
 171 static void
 172 carpCachemgr(StoreEntry * sentry)
 173 {
 174     peer *p;
 175     int sumfetches = 0;
 176     storeAppendPrintf(sentry, "%24s %10s %10s %10s %10s\n",
 177         "Hostname",
 178         "Hash",
 179         "Multiplier",
 180         "Factor",
 181         "Actual");
 182     for (p = Config.peers; p; p = p->next)
 183         sumfetches += p->stats.fetches;
 184     for (p = Config.peers; p; p = p->next) {
 185         storeAppendPrintf(sentry, "%24s %10x %10f %10f %10f\n",
 186             p->host, p->carp.hash,
 187             p->carp.load_multiplier,
 188             p->carp.load_factor,
 189             sumfetches ? (double) p->stats.fetches / sumfetches : -1.0);
 190     }
 191 }
 192
 193 #endif