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