src/carp.cc

   1
   2 /*
   3  * $Id$
   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 "HttpRequest.h"
  39 #include "mgr/Registration.h"
  40 #include "neighbors.h"
  41 #include "protos.h"
  42 #include "Store.h"
  43 #include "URL.h"
  44 #include "URLScheme.h"
  45
  46 #if HAVE_MATH_H
  47 #include <math.h>
  48 #endif
  49
  50 #define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
  51
  52 static int n_carp_peers = 0;
  53 static peer **carp_peers = NULL;
  54 static OBJH carpCachemgr;
  55
  56 static int
  57 peerSortWeight(const void *a, const void *b)
  58 {
  59     const peer *const *p1 = (const peer *const *)a;
  60     const peer *const *p2 = (const peer *const *)b;
  61     return (*p1)->weight - (*p2)->weight;
  62 }
  63
  64 static void
  65 carpRegisterWithCacheManager(void)
  66 {
  67     Mgr::RegisterAction("carp", "CARP information", carpCachemgr, 0, 1);
  68 }
  69
  70 void
  71 carpInit(void)
  72 {
  73     int W = 0;
  74     int K;
  75     int k;
  76     double P_last, X_last, Xn;
  77     peer *p;
  78     peer **P;
  79     char *t;
  80     /* Clean up */
  81
  82     for (k = 0; k < n_carp_peers; ++k) {
  83         cbdataReferenceDone(carp_peers[k]);
  84     }
  85
  86     safe_free(carp_peers);
  87     n_carp_peers = 0;
  88
  89     /* initialize cache manager before we have a chance to leave the execution path */
  90     carpRegisterWithCacheManager();
  91
  92     /* find out which peers we have */
  93
  94     for (p = Config.peers; p; p = p->next) {
  95         if (!p->options.carp)
  96             continue;
  97
  98         assert(p->type == PEER_PARENT);
  99
 100         if (p->weight == 0)
 101             continue;
 102
 103         ++n_carp_peers;
 104
 105         W += p->weight;
 106     }
 107
 108     if (n_carp_peers == 0)
 109         return;
 110
 111     carp_peers = (peer **)xcalloc(n_carp_peers, sizeof(*carp_peers));
 112
 113     /* Build a list of the found peers and calculate hashes and load factors */
 114     for (P = carp_peers, p = Config.peers; p; p = p->next) {
 115         if (!p->options.carp)
 116             continue;
 117
 118         if (p->weight == 0)
 119             continue;
 120
 121         /* calculate this peers hash */
 122         p->carp.hash = 0;
 123
 124         for (t = p->name; *t != 0; ++t)
 125             p->carp.hash += ROTATE_LEFT(p->carp.hash, 19) + (unsigned int) *t;
 126
 127         p->carp.hash += p->carp.hash * 0x62531965;
 128
 129         p->carp.hash = ROTATE_LEFT(p->carp.hash, 21);
 130
 131         /* and load factor */
 132         p->carp.load_factor = ((double) p->weight) / (double) W;
 133
 134         if (floor(p->carp.load_factor * 1000.0) == 0.0)
 135             p->carp.load_factor = 0.0;
 136
 137         /* add it to our list of peers */
 138         *P = cbdataReference(p);
 139         ++P;
 140     }
 141
 142     /* Sort our list on weight */
 143     qsort(carp_peers, n_carp_peers, sizeof(*carp_peers), peerSortWeight);
 144
 145     /* Calculate the load factor multipliers X_k
 146      *
 147      * X_1 = pow ((K*p_1), (1/K))
 148      * X_k = ([K-k+1] * [P_k - P_{k-1}])/(X_1 * X_2 * ... * X_{k-1})
 149      * X_k += pow ((X_{k-1}, {K-k+1})
 150      * X_k = pow (X_k, {1/(K-k+1)})
 151      * simplified to have X_1 part of the loop
 152      */
 153     K = n_carp_peers;
 154
 155     P_last = 0.0;               /* Empty P_0 */
 156
 157     Xn = 1.0;                   /* Empty starting point of X_1 * X_2 * ... * X_{x-1} */
 158
 159     X_last = 0.0;               /* Empty X_0, nullifies the first pow statement */
 160
 161     for (k = 1; k <= K; ++k) {
 162         double Kk1 = (double) (K - k + 1);
 163         p = carp_peers[k - 1];
 164         p->carp.load_multiplier = (Kk1 * (p->carp.load_factor - P_last)) / Xn;
 165         p->carp.load_multiplier += pow(X_last, Kk1);
 166         p->carp.load_multiplier = pow(p->carp.load_multiplier, 1.0 / Kk1);
 167         Xn *= p->carp.load_multiplier;
 168         X_last = p->carp.load_multiplier;
 169         P_last = p->carp.load_factor;
 170     }
 171 }
 172
 173 peer *
 174 carpSelectParent(HttpRequest * request)
 175 {
 176     int k;
 177     peer *p = NULL;
 178     peer *tp;
 179     unsigned int user_hash = 0;
 180     unsigned int combined_hash;
 181     double score;
 182     double high_score = 0;
 183
 184     if (n_carp_peers == 0)
 185         return NULL;
 186
 187     /* calculate hash key */
 188     debugs(39, 2, "carpSelectParent: Calculating hash for " << urlCanonical(request));
 189
 190     /* select peer */
 191     for (k = 0; k < n_carp_peers; ++k) {
 192         String key;
 193         tp = carp_peers[k];
 194         if (tp->options.carp_key.set) {
 195             //this code follows urlCanonical's pattern.
 196             //   corner cases should use the canonical URL
 197             if (tp->options.carp_key.scheme) {
 198                 // temporary, until bug 1961 URL handling is fixed.
 199                 const URLScheme sch = request->protocol;
 200                 key.append(sch.const_str());
 201                 if (key.size()) //if the scheme is not empty
 202                     key.append("://");
 203             }
 204             if (tp->options.carp_key.host) {
 205                 key.append(request->GetHost());
 206             }
 207             if (tp->options.carp_key.port) {
 208                 static char portbuf[7];
 209                 snprintf(portbuf,7,":%d", request->port);
 210                 key.append(portbuf);
 211             }
 212             if (tp->options.carp_key.path) {
 213                 String::size_type pos;
 214                 if ((pos=request->urlpath.find('?'))!=String::npos)
 215                     key.append(request->urlpath.substr(0,pos));
 216                 else
 217                     key.append(request->urlpath);
 218             }
 219             if (tp->options.carp_key.params) {
 220                 String::size_type pos;
 221                 if ((pos=request->urlpath.find('?'))!=String::npos)
 222                     key.append(request->urlpath.substr(pos,request->urlpath.size()));
 223             }
 224         }
 225         // if the url-based key is empty, e.g. because the user is
 226         // asking to balance on the path but the request doesn't supply any,
 227         // then fall back to canonical URL
 228
 229         if (key.size()==0)
 230             key=urlCanonical(request);
 231
 232         for (const char *c = key.rawBuf(), *e=key.rawBuf()+key.size(); c < e; ++c)
 233             user_hash += ROTATE_LEFT(user_hash, 19) + *c;
 234         combined_hash = (user_hash ^ tp->carp.hash);
 235         combined_hash += combined_hash * 0x62531965;
 236         combined_hash = ROTATE_LEFT(combined_hash, 21);
 237         score = combined_hash * tp->carp.load_multiplier;
 238         debugs(39, 3, "carpSelectParent: key=" << key << " name=" << tp->name << " combined_hash=" << combined_hash  <<
 239                " score=" << std::setprecision(0) << score);
 240
 241         if ((score > high_score) && peerHTTPOkay(tp, request)) {
 242             p = tp;
 243             high_score = score;
 244         }
 245     }
 246
 247     if (p)
 248         debugs(39, 2, "carpSelectParent: selected " << p->name);
 249
 250     return p;
 251 }
 252
 253 static void
 254 carpCachemgr(StoreEntry * sentry)
 255 {
 256     peer *p;
 257     int sumfetches = 0;
 258     storeAppendPrintf(sentry, "%24s %10s %10s %10s %10s\n",
 259                       "Hostname",
 260                       "Hash",
 261                       "Multiplier",
 262                       "Factor",
 263                       "Actual");
 264
 265     for (p = Config.peers; p; p = p->next)
 266         sumfetches += p->stats.fetches;
 267
 268     for (p = Config.peers; p; p = p->next) {
 269         storeAppendPrintf(sentry, "%24s %10x %10f %10f %10f\n",
 270                           p->name, p->carp.hash,
 271                           p->carp.load_multiplier,
 272                           p->carp.load_factor,
 273                           sumfetches ? (double) p->stats.fetches / sumfetches : -1.0);
 274     }
 275 }