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/*
* $Id: carp.c,v 1.21.6.1 2008/01/22 14:36:06 hno Exp $
*
* 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"
#if USE_CARP
#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 = a, *const *p2 = b;
return (*p1)->weight - (*p2)->weight;
}
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++) {
cbdataUnlock(carp_peers[k]);
}
safe_free(carp_peers);
n_carp_peers = 0;
/* 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 = 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++ = p;
cbdataLock(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;
}
cachemgrRegister("carp", "CARP information", carpCachemgr, 0, 1);
}
peer *
carpSelectParent(request_t * request)
{
int k;
const char *c;
peer *p = NULL;
peer *tp;
unsigned int user_hash = 0;
unsigned int combined_hash;
double score;
double high_score = 0;
const char *key = NULL;
if (n_carp_peers == 0)
return NULL;
key = urlCanonical(request);
/* calculate hash key */
debug(39, 2) ("carpSelectParent: Calculating hash for %s\n", key);
for (c = key; *c != 0; c++)
user_hash += ROTATE_LEFT(user_hash, 19) + *c;
/* select peer */
for (k = 0; k < n_carp_peers; k++) {
tp = carp_peers[k];
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;
debug(39, 3) ("carpSelectParent: %s combined_hash %u score %.0f\n",
tp->name, combined_hash, score);
if ((score > high_score) && peerHTTPOkay(tp, request)) {
p = tp;
high_score = score;
}
}
if (p)
debug(39, 2) ("carpSelectParent: selected %s\n", 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);
}
}
#endif
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