src/carp.cc

   1
   2 /*
   3  * DEBUG: section 39    Cache Array Routing Protocol
   4  * AUTHOR: Henrik Nordstrom
   5  * BASED ON: carp.c by Eric Stern and draft-vinod-carp-v1-03.txt
   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 #include "URL.h"
  41 #include "URLScheme.h"
  42
  43 #if HAVE_MATH_H
  44 #include <math.h>
  45 #endif
  46
  47 #define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
  48
  49 static int n_carp_peers = 0;
  50 static peer **carp_peers = NULL;
  51 static OBJH carpCachemgr;
  52
  53 static int
  54 peerSortWeight(const void *a, const void *b)
  55 {
  56     const peer *const *p1 = (const peer *const *)a;
  57     const peer *const *p2 = (const peer *const *)b;
  58     return (*p1)->weight - (*p2)->weight;
  59 }
  60
  61 static void
  62 carpRegisterWithCacheManager(void)
  63 {
  64     Mgr::RegisterAction("carp", "CARP information", carpCachemgr, 0, 1);
  65 }
  66
  67 void
  68 carpInit(void)
  69 {
  70     int W = 0;
  71     int K;
  72     int k;
  73     double P_last, X_last, Xn;
  74     peer *p;
  75     peer **P;
  76     char *t;
  77     /* Clean up */
  78
  79     for (k = 0; k < n_carp_peers; ++k) {
  80         cbdataReferenceDone(carp_peers[k]);
  81     }
  82
  83     safe_free(carp_peers);
  84     n_carp_peers = 0;
  85
  86     /* initialize cache manager before we have a chance to leave the execution path */
  87     carpRegisterWithCacheManager();
  88
  89     /* find out which peers we have */
  90
  91     for (p = Config.peers; p; p = p->next) {
  92         if (!p->options.carp)
  93             continue;
  94
  95         assert(p->type == PEER_PARENT);
  96
  97         if (p->weight == 0)
  98             continue;
  99
 100         ++n_carp_peers;
 101
 102         W += p->weight;
 103     }
 104
 105     if (n_carp_peers == 0)
 106         return;
 107
 108     carp_peers = (peer **)xcalloc(n_carp_peers, sizeof(*carp_peers));
 109
 110     /* Build a list of the found peers and calculate hashes and load factors */
 111     for (P = carp_peers, p = Config.peers; p; p = p->next) {
 112         if (!p->options.carp)
 113             continue;
 114
 115         if (p->weight == 0)
 116             continue;
 117
 118         /* calculate this peers hash */
 119         p->carp.hash = 0;
 120
 121         for (t = p->name; *t != 0; ++t)
 122             p->carp.hash += ROTATE_LEFT(p->carp.hash, 19) + (unsigned int) *t;
 123
 124         p->carp.hash += p->carp.hash * 0x62531965;
 125
 126         p->carp.hash = ROTATE_LEFT(p->carp.hash, 21);
 127
 128         /* and load factor */
 129         p->carp.load_factor = ((double) p->weight) / (double) W;
 130
 131         if (floor(p->carp.load_factor * 1000.0) == 0.0)
 132             p->carp.load_factor = 0.0;
 133
 134         /* add it to our list of peers */
 135         *P = cbdataReference(p);
 136         ++P;
 137     }
 138
 139     /* Sort our list on weight */
 140     qsort(carp_peers, n_carp_peers, sizeof(*carp_peers), peerSortWeight);
 141
 142     /* Calculate the load factor multipliers X_k
 143      *
 144      * X_1 = pow ((K*p_1), (1/K))
 145      * X_k = ([K-k+1] * [P_k - P_{k-1}])/(X_1 * X_2 * ... * X_{k-1})
 146      * X_k += pow ((X_{k-1}, {K-k+1})
 147      * X_k = pow (X_k, {1/(K-k+1)})
 148      * simplified to have X_1 part of the loop
 149      */
 150     K = n_carp_peers;
 151
 152     P_last = 0.0;               /* Empty P_0 */
 153
 154     Xn = 1.0;                   /* Empty starting point of X_1 * X_2 * ... * X_{x-1} */
 155
 156     X_last = 0.0;               /* Empty X_0, nullifies the first pow statement */
 157
 158     for (k = 1; k <= K; ++k) {
 159         double Kk1 = (double) (K - k + 1);
 160         p = carp_peers[k - 1];
 161         p->carp.load_multiplier = (Kk1 * (p->carp.load_factor - P_last)) / Xn;
 162         p->carp.load_multiplier += pow(X_last, Kk1);
 163         p->carp.load_multiplier = pow(p->carp.load_multiplier, 1.0 / Kk1);
 164         Xn *= p->carp.load_multiplier;
 165         X_last = p->carp.load_multiplier;
 166         P_last = p->carp.load_factor;
 167     }
 168 }
 169
 170 peer *
 171 carpSelectParent(HttpRequest * request)
 172 {
 173     int k;
 174     peer *p = NULL;
 175     peer *tp;
 176     unsigned int user_hash = 0;
 177     unsigned int combined_hash;
 178     double score;
 179     double high_score = 0;
 180
 181     if (n_carp_peers == 0)
 182         return NULL;
 183
 184     /* calculate hash key */
 185     debugs(39, 2, "carpSelectParent: Calculating hash for " << urlCanonical(request));
 186
 187     /* select peer */
 188     for (k = 0; k < n_carp_peers; ++k) {
 189         String key;
 190         tp = carp_peers[k];
 191         if (tp->options.carp_key.set) {
 192             //this code follows urlCanonical's pattern.
 193             //   corner cases should use the canonical URL
 194             if (tp->options.carp_key.scheme) {
 195                 // temporary, until bug 1961 URL handling is fixed.
 196                 const URLScheme sch = request->protocol;
 197                 key.append(sch.const_str());
 198                 if (key.size()) //if the scheme is not empty
 199                     key.append("://");
 200             }
 201             if (tp->options.carp_key.host) {
 202                 key.append(request->GetHost());
 203             }
 204             if (tp->options.carp_key.port) {
 205                 static char portbuf[7];
 206                 snprintf(portbuf,7,":%d", request->port);
 207                 key.append(portbuf);
 208             }
 209             if (tp->options.carp_key.path) {
 210                 String::size_type pos;
 211                 if ((pos=request->urlpath.find('?'))!=String::npos)
 212                     key.append(request->urlpath.substr(0,pos));
 213                 else
 214                     key.append(request->urlpath);
 215             }
 216             if (tp->options.carp_key.params) {
 217                 String::size_type pos;
 218                 if ((pos=request->urlpath.find('?'))!=String::npos)
 219                     key.append(request->urlpath.substr(pos,request->urlpath.size()));
 220             }
 221         }
 222         // if the url-based key is empty, e.g. because the user is
 223         // asking to balance on the path but the request doesn't supply any,
 224         // then fall back to canonical URL
 225
 226         if (key.size()==0)
 227             key=urlCanonical(request);
 228
 229         for (const char *c = key.rawBuf(), *e=key.rawBuf()+key.size(); c < e; ++c)
 230             user_hash += ROTATE_LEFT(user_hash, 19) + *c;
 231         combined_hash = (user_hash ^ tp->carp.hash);
 232         combined_hash += combined_hash * 0x62531965;
 233         combined_hash = ROTATE_LEFT(combined_hash, 21);
 234         score = combined_hash * tp->carp.load_multiplier;
 235         debugs(39, 3, "carpSelectParent: key=" << key << " name=" << tp->name << " combined_hash=" << combined_hash  <<
 236                " score=" << std::setprecision(0) << score);
 237
 238         if ((score > high_score) && peerHTTPOkay(tp, request)) {
 239             p = tp;
 240             high_score = score;
 241         }
 242     }
 243
 244     if (p)
 245         debugs(39, 2, "carpSelectParent: selected " << p->name);
 246
 247     return p;
 248 }
 249
 250 static void
 251 carpCachemgr(StoreEntry * sentry)
 252 {
 253     peer *p;
 254     int sumfetches = 0;
 255     storeAppendPrintf(sentry, "%24s %10s %10s %10s %10s\n",
 256                       "Hostname",
 257                       "Hash",
 258                       "Multiplier",
 259                       "Factor",
 260                       "Actual");
 261
 262     for (p = Config.peers; p; p = p->next)
 263         sumfetches += p->stats.fetches;
 264
 265     for (p = Config.peers; p; p = p->next) {
 266         storeAppendPrintf(sentry, "%24s %10x %10f %10f %10f\n",
 267                           p->name, p->carp.hash,
 268                           p->carp.load_multiplier,
 269                           p->carp.load_factor,
 270                           sumfetches ? (double) p->stats.fetches / sumfetches : -1.0);
 271     }
 272 }