/src/carp.cc
C++ | 267 lines | 164 code | 45 blank | 58 comment | 36 complexity | d7777374d1d9597115213a41a68730cc MD5 | raw file
- /*
- * $Id$
- *
- * DEBUG: section 39 Cache Array Routing Protocol
- * AUTHOR: Henrik Nordstrom
- * BASED ON: carp.c by Eric Stern and draft-vinod-carp-v1-03.txt
- *
- * SQUID Web Proxy Cache http://www.squid-cache.org/
- * ----------------------------------------------------------
- *
- * Squid is the result of efforts by numerous individuals from
- * the Internet community; see the CONTRIBUTORS file for full
- * details. Many organizations have provided support for Squid's
- * development; see the SPONSORS file for full details. Squid is
- * Copyrighted (C) 2001 by the Regents of the University of
- * California; see the COPYRIGHT file for full details. Squid
- * incorporates software developed and/or copyrighted by other
- * sources; see the CREDITS file for full details.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
- *
- */
- #include "squid.h"
- #include "HttpRequest.h"
- #include "mgr/Registration.h"
- #include "Store.h"
- #include "URLScheme.h"
- #define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
- static int n_carp_peers = 0;
- static peer **carp_peers = NULL;
- static OBJH carpCachemgr;
- static int
- peerSortWeight(const void *a, const void *b)
- {
- const peer *const *p1 = (const peer *const *)a;
- const peer *const *p2 = (const peer *const *)b;
- return (*p1)->weight - (*p2)->weight;
- }
- static void
- carpRegisterWithCacheManager(void)
- {
- Mgr::RegisterAction("carp", "CARP information", carpCachemgr, 0, 1);
- }
- void
- carpInit(void)
- {
- int W = 0;
- int K;
- int k;
- double P_last, X_last, Xn;
- peer *p;
- peer **P;
- char *t;
- /* Clean up */
- for (k = 0; k < n_carp_peers; k++) {
- cbdataReferenceDone(carp_peers[k]);
- }
- safe_free(carp_peers);
- n_carp_peers = 0;
- /* initialize cache manager before we have a chance to leave the execution path */
- carpRegisterWithCacheManager();
- /* find out which peers we have */
- for (p = Config.peers; p; p = p->next) {
- if (!p->options.carp)
- continue;
- assert(p->type == PEER_PARENT);
- if (p->weight == 0)
- continue;
- n_carp_peers++;
- W += p->weight;
- }
- if (n_carp_peers == 0)
- return;
- carp_peers = (peer **)xcalloc(n_carp_peers, sizeof(*carp_peers));
- /* Build a list of the found peers and calculate hashes and load factors */
- for (P = carp_peers, p = Config.peers; p; p = p->next) {
- if (!p->options.carp)
- continue;
- if (p->weight == 0)
- continue;
- /* calculate this peers hash */
- p->carp.hash = 0;
- for (t = p->name; *t != 0; t++)
- p->carp.hash += ROTATE_LEFT(p->carp.hash, 19) + (unsigned int) *t;
- p->carp.hash += p->carp.hash * 0x62531965;
- p->carp.hash = ROTATE_LEFT(p->carp.hash, 21);
- /* and load factor */
- p->carp.load_factor = ((double) p->weight) / (double) W;
- if (floor(p->carp.load_factor * 1000.0) == 0.0)
- p->carp.load_factor = 0.0;
- /* add it to our list of peers */
- *P++ = cbdataReference(p);
- }
- /* Sort our list on weight */
- qsort(carp_peers, n_carp_peers, sizeof(*carp_peers), peerSortWeight);
- /* Calculate the load factor multipliers X_k
- *
- * X_1 = pow ((K*p_1), (1/K))
- * X_k = ([K-k+1] * [P_k - P_{k-1}])/(X_1 * X_2 * ... * X_{k-1})
- * X_k += pow ((X_{k-1}, {K-k+1})
- * X_k = pow (X_k, {1/(K-k+1)})
- * simplified to have X_1 part of the loop
- */
- K = n_carp_peers;
- P_last = 0.0; /* Empty P_0 */
- Xn = 1.0; /* Empty starting point of X_1 * X_2 * ... * X_{x-1} */
- X_last = 0.0; /* Empty X_0, nullifies the first pow statement */
- for (k = 1; k <= K; k++) {
- double Kk1 = (double) (K - k + 1);
- p = carp_peers[k - 1];
- p->carp.load_multiplier = (Kk1 * (p->carp.load_factor - P_last)) / Xn;
- p->carp.load_multiplier += pow(X_last, Kk1);
- p->carp.load_multiplier = pow(p->carp.load_multiplier, 1.0 / Kk1);
- Xn *= p->carp.load_multiplier;
- X_last = p->carp.load_multiplier;
- P_last = p->carp.load_factor;
- }
- }
- peer *
- carpSelectParent(HttpRequest * request)
- {
- int k;
- peer *p = NULL;
- peer *tp;
- unsigned int user_hash = 0;
- unsigned int combined_hash;
- double score;
- double high_score = 0;
- if (n_carp_peers == 0)
- return NULL;
- /* calculate hash key */
- debugs(39, 2, "carpSelectParent: Calculating hash for " << urlCanonical(request));
- /* select peer */
- for (k = 0; k < n_carp_peers; k++) {
- String key;
- tp = carp_peers[k];
- if (tp->options.carp_key.set) {
- //this code follows urlCanonical's pattern.
- // corner cases should use the canonical URL
- if (tp->options.carp_key.scheme) {
- // temporary, until bug 1961 URL handling is fixed.
- const URLScheme sch = request->protocol;
- key.append(sch.const_str());
- if (key.size()) //if the scheme is not empty
- key.append("://");
- }
- if (tp->options.carp_key.host) {
- key.append(request->GetHost());
- }
- if (tp->options.carp_key.port) {
- static char portbuf[7];
- snprintf(portbuf,7,":%d", request->port);
- key.append(portbuf);
- }
- if (tp->options.carp_key.path) {
- String::size_type pos;
- if ((pos=request->urlpath.find('?'))!=String::npos)
- key.append(request->urlpath.substr(0,pos));
- else
- key.append(request->urlpath);
- }
- if (tp->options.carp_key.params) {
- String::size_type pos;
- if ((pos=request->urlpath.find('?'))!=String::npos)
- key.append(request->urlpath.substr(pos,request->urlpath.size()));
- }
- }
- // if the url-based key is empty, e.g. because the user is
- // asking to balance on the path but the request doesn't supply any,
- // then fall back to canonical URL
- if (key.size()==0)
- key=urlCanonical(request);
- for (const char *c = key.rawBuf(), *e=key.rawBuf()+key.size(); c < e; c++)
- user_hash += ROTATE_LEFT(user_hash, 19) + *c;
- combined_hash = (user_hash ^ tp->carp.hash);
- combined_hash += combined_hash * 0x62531965;
- combined_hash = ROTATE_LEFT(combined_hash, 21);
- score = combined_hash * tp->carp.load_multiplier;
- debugs(39, 3, "carpSelectParent: key=" << key << " name=" << tp->name << " combined_hash=" << combined_hash <<
- " score=" << std::setprecision(0) << score);
- if ((score > high_score) && peerHTTPOkay(tp, request)) {
- p = tp;
- high_score = score;
- }
- }
- if (p)
- debugs(39, 2, "carpSelectParent: selected " << p->name);
- return p;
- }
- static void
- carpCachemgr(StoreEntry * sentry)
- {
- peer *p;
- int sumfetches = 0;
- storeAppendPrintf(sentry, "%24s %10s %10s %10s %10s\n",
- "Hostname",
- "Hash",
- "Multiplier",
- "Factor",
- "Actual");
- for (p = Config.peers; p; p = p->next)
- sumfetches += p->stats.fetches;
- for (p = Config.peers; p; p = p->next) {
- storeAppendPrintf(sentry, "%24s %10x %10f %10f %10f\n",
- p->name, p->carp.hash,
- p->carp.load_multiplier,
- p->carp.load_factor,
- sumfetches ? (double) p->stats.fetches / sumfetches : -1.0);
- }
- }