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* $Id: carp.cc,v 1.27 2008/01/14 12:13:49 hno Exp $
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* DEBUG: section 39 Peer user hash based selection
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* AUTHOR: Henrik Nordstrom
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* SQUID Web Proxy Cache http://www.squid-cache.org/
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* ----------------------------------------------------------
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* Squid is the result of efforts by numerous individuals from
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* the Internet community; see the CONTRIBUTORS file for full
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* details. Many organizations have provided support for Squid's
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* development; see the SPONSORS file for full details. Squid is
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* Copyrighted (C) 2001 by the Regents of the University of
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* California; see the COPYRIGHT file for full details. Squid
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* incorporates software developed and/or copyrighted by other
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* sources; see the CREDITS file for full details.
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
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#include "CacheManager.h"
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#include "HttpRequest.h"
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#include "AuthUserRequest.h"
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#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
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static int n_userhash_peers = 0;
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static peer **userhash_peers = NULL;
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static OBJH peerUserHashCachemgr;
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peerSortWeight(const void *a, const void *b)
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const peer *const *p1 = (const peer *const *)a;
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const peer *const *p2 = (const peer *const *)b;
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return (*p1)->weight - (*p2)->weight;
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peerUserHashInit(void)
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double P_last, X_last, Xn;
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for (k = 0; k < n_userhash_peers; k++) {
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cbdataReferenceDone(userhash_peers[k]);
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safe_free(userhash_peers);
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/* find out which peers we have */
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for (p = Config.peers; p; p = p->next) {
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if (!p->options.userhash)
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assert(p->type == PEER_PARENT);
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if (n_userhash_peers == 0)
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userhash_peers = (peer **)xcalloc(n_userhash_peers, sizeof(*userhash_peers));
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/* Build a list of the found peers and calculate hashes and load factors */
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for (P = userhash_peers, p = Config.peers; p; p = p->next) {
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if (!p->options.userhash)
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/* calculate this peers hash */
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p->userhash.hash = 0;
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for (t = p->name; *t != 0; t++)
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p->userhash.hash += ROTATE_LEFT(p->userhash.hash, 19) + (unsigned int) *t;
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p->userhash.hash += p->userhash.hash * 0x62531965;
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p->userhash.hash = ROTATE_LEFT(p->userhash.hash, 21);
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/* and load factor */
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p->userhash.load_factor = ((double) p->weight) / (double) W;
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if (floor(p->userhash.load_factor * 1000.0) == 0.0)
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p->userhash.load_factor = 0.0;
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/* add it to our list of peers */
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*P++ = cbdataReference(p);
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/* Sort our list on weight */
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qsort(userhash_peers, n_userhash_peers, sizeof(*userhash_peers), peerSortWeight);
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/* Calculate the load factor multipliers X_k
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* X_1 = pow ((K*p_1), (1/K))
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* X_k = ([K-k+1] * [P_k - P_{k-1}])/(X_1 * X_2 * ... * X_{k-1})
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* X_k += pow ((X_{k-1}, {K-k+1})
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* X_k = pow (X_k, {1/(K-k+1)})
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* simplified to have X_1 part of the loop
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K = n_userhash_peers;
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P_last = 0.0; /* Empty P_0 */
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Xn = 1.0; /* Empty starting point of X_1 * X_2 * ... * X_{x-1} */
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X_last = 0.0; /* Empty X_0, nullifies the first pow statement */
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for (k = 1; k <= K; k++) {
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double Kk1 = (double) (K - k + 1);
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p = userhash_peers[k - 1];
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p->userhash.load_multiplier = (Kk1 * (p->userhash.load_factor - P_last)) / Xn;
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p->userhash.load_multiplier += pow(X_last, Kk1);
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p->userhash.load_multiplier = pow(p->userhash.load_multiplier, 1.0 / Kk1);
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Xn *= p->userhash.load_multiplier;
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X_last = p->userhash.load_multiplier;
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P_last = p->userhash.load_factor;
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peerUserHashRegisterWithCacheManager(CacheManager & manager)
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manager.registerAction("userhash", "peer userhash information", peerUserHashCachemgr, 0, 1);
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peerUserHashSelectParent(HttpRequest * request)
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unsigned int user_hash = 0;
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unsigned int combined_hash;
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double high_score = 0;
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const char *key = NULL;
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if (n_userhash_peers == 0)
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if (request->auth_user_request)
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key = request->auth_user_request->username();
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/* calculate hash key */
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debugs(39, 2, "peerUserHashSelectParent: Calculating hash for " << key);
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for (c = key; *c != 0; c++)
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user_hash += ROTATE_LEFT(user_hash, 19) + *c;
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for (k = 0; k < n_userhash_peers; k++) {
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tp = userhash_peers[k];
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combined_hash = (user_hash ^ tp->userhash.hash);
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combined_hash += combined_hash * 0x62531965;
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combined_hash = ROTATE_LEFT(combined_hash, 21);
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score = combined_hash * tp->userhash.load_multiplier;
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debugs(39, 3, "peerUserHashSelectParent: " << tp->name << " combined_hash " << combined_hash <<
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" score " << std::setprecision(0) << score);
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if ((score > high_score) && peerHTTPOkay(tp, request)) {
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debugs(39, 2, "peerUserHashSelectParent: selected " << p->name);
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peerUserHashCachemgr(StoreEntry * sentry)
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storeAppendPrintf(sentry, "%24s %10s %10s %10s %10s\n",
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for (p = Config.peers; p; p = p->next)
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sumfetches += p->stats.fetches;
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for (p = Config.peers; p; p = p->next) {
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storeAppendPrintf(sentry, "%24s %10x %10f %10f %10f\n",
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p->name, p->userhash.hash,
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p->userhash.load_multiplier,
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p->userhash.load_factor,
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sumfetches ? (double) p->stats.fetches / sumfetches : -1.0);
added
removed
src/peer_userhash.cc
