peer_sourcehash.cc
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1 /*
2  * Copyright (C) 1996-2017 The Squid Software Foundation and contributors
3  *
4  * Squid software is distributed under GPLv2+ license and includes
5  * contributions from numerous individuals and organizations.
6  * Please see the COPYING and CONTRIBUTORS files for details.
7  */
8 
9 /* DEBUG: section 39 Peer source hash based selection */
10 
11 #include "squid.h"
12 #include "CachePeer.h"
13 #include "HttpRequest.h"
14 #include "mgr/Registration.h"
15 #include "neighbors.h"
16 #include "SquidConfig.h"
17 #include "Store.h"
18 
19 #include <cmath>
20 
21 #define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
22 
23 static int n_sourcehash_peers = 0;
24 static CachePeer **sourcehash_peers = NULL;
27 
28 static int
29 peerSortWeight(const void *a, const void *b)
30 {
31  const CachePeer *const *p1 = (const CachePeer *const *)a;
32  const CachePeer *const *p2 = (const CachePeer *const *)b;
33  return (*p1)->weight - (*p2)->weight;
34 }
35 
36 void
38 {
39  int W = 0;
40  int K;
41  int k;
42  double P_last, X_last, Xn;
43  CachePeer *p;
44  CachePeer **P;
45  char *t;
46  /* Clean up */
47 
48  for (k = 0; k < n_sourcehash_peers; ++k) {
49  cbdataReferenceDone(sourcehash_peers[k]);
50  }
51 
52  safe_free(sourcehash_peers);
53  n_sourcehash_peers = 0;
54  /* find out which peers we have */
55 
56  for (p = Config.peers; p; p = p->next) {
57  if (!p->options.sourcehash)
58  continue;
59 
60  assert(p->type == PEER_PARENT);
61 
62  if (p->weight == 0)
63  continue;
64 
66 
67  W += p->weight;
68  }
69 
71 
72  if (n_sourcehash_peers == 0)
73  return;
74 
75  sourcehash_peers = (CachePeer **)xcalloc(n_sourcehash_peers, sizeof(*sourcehash_peers));
76 
77  /* Build a list of the found peers and calculate hashes and load factors */
78  for (P = sourcehash_peers, p = Config.peers; p; p = p->next) {
79  if (!p->options.sourcehash)
80  continue;
81 
82  if (p->weight == 0)
83  continue;
84 
85  /* calculate this peers hash */
86  p->sourcehash.hash = 0;
87 
88  for (t = p->name; *t != 0; ++t)
89  p->sourcehash.hash += ROTATE_LEFT(p->sourcehash.hash, 19) + (unsigned int) *t;
90 
91  p->sourcehash.hash += p->sourcehash.hash * 0x62531965;
92 
93  p->sourcehash.hash = ROTATE_LEFT(p->sourcehash.hash, 21);
94 
95  /* and load factor */
96  p->sourcehash.load_factor = ((double) p->weight) / (double) W;
97 
98  if (floor(p->sourcehash.load_factor * 1000.0) == 0.0)
99  p->sourcehash.load_factor = 0.0;
100 
101  /* add it to our list of peers */
102  *P++ = cbdataReference(p);
103  }
104 
105  /* Sort our list on weight */
106  qsort(sourcehash_peers, n_sourcehash_peers, sizeof(*sourcehash_peers), peerSortWeight);
107 
108  /* Calculate the load factor multipliers X_k
109  *
110  * X_1 = pow ((K*p_1), (1/K))
111  * X_k = ([K-k+1] * [P_k - P_{k-1}])/(X_1 * X_2 * ... * X_{k-1})
112  * X_k += pow ((X_{k-1}, {K-k+1})
113  * X_k = pow (X_k, {1/(K-k+1)})
114  * simplified to have X_1 part of the loop
115  */
116  K = n_sourcehash_peers;
117 
118  P_last = 0.0; /* Empty P_0 */
119 
120  Xn = 1.0; /* Empty starting point of X_1 * X_2 * ... * X_{x-1} */
121 
122  X_last = 0.0; /* Empty X_0, nullifies the first pow statement */
123 
124  for (k = 1; k <= K; ++k) {
125  double Kk1 = (double) (K - k + 1);
126  p = sourcehash_peers[k - 1];
127  p->sourcehash.load_multiplier = (Kk1 * (p->sourcehash.load_factor - P_last)) / Xn;
128  p->sourcehash.load_multiplier += pow(X_last, Kk1);
129  p->sourcehash.load_multiplier = pow(p->sourcehash.load_multiplier, 1.0 / Kk1);
130  Xn *= p->sourcehash.load_multiplier;
131  X_last = p->sourcehash.load_multiplier;
132  P_last = p->sourcehash.load_factor;
133  }
134 }
135 
136 static void
138 {
139  Mgr::RegisterAction("sourcehash", "peer sourcehash information",
140  peerSourceHashCachemgr, 0, 1);
141 }
142 
143 CachePeer *
145 {
146  int k;
147  const char *c;
148  CachePeer *p = NULL;
149  CachePeer *tp;
150  unsigned int user_hash = 0;
151  unsigned int combined_hash;
152  double score;
153  double high_score = 0;
154  const char *key = NULL;
155  char ntoabuf[MAX_IPSTRLEN];
156 
157  if (n_sourcehash_peers == 0)
158  return NULL;
159 
160  key = request->client_addr.toStr(ntoabuf, sizeof(ntoabuf));
161 
162  /* calculate hash key */
163  debugs(39, 2, "peerSourceHashSelectParent: Calculating hash for " << key);
164 
165  for (c = key; *c != 0; ++c)
166  user_hash += ROTATE_LEFT(user_hash, 19) + *c;
167 
168  /* select CachePeer */
169  for (k = 0; k < n_sourcehash_peers; ++k) {
170  tp = sourcehash_peers[k];
171  combined_hash = (user_hash ^ tp->sourcehash.hash);
172  combined_hash += combined_hash * 0x62531965;
173  combined_hash = ROTATE_LEFT(combined_hash, 21);
174  score = combined_hash * tp->sourcehash.load_multiplier;
175  debugs(39, 3, "peerSourceHashSelectParent: " << tp->name << " combined_hash " << combined_hash <<
176  " score " << std::setprecision(0) << score);
177 
178  if ((score > high_score) && peerHTTPOkay(tp, request)) {
179  p = tp;
180  high_score = score;
181  }
182  }
183 
184  if (p)
185  debugs(39, 2, "peerSourceHashSelectParent: selected " << p->name);
186 
187  return p;
188 }
189 
190 static void
192 {
193  CachePeer *p;
194  int sumfetches = 0;
195  storeAppendPrintf(sentry, "%24s %10s %10s %10s %10s\n",
196  "Hostname",
197  "Hash",
198  "Multiplier",
199  "Factor",
200  "Actual");
201 
202  for (p = Config.peers; p; p = p->next)
203  sumfetches += p->stats.fetches;
204 
205  for (p = Config.peers; p; p = p->next) {
206  storeAppendPrintf(sentry, "%24s %10x %10f %10f %10f\n",
207  p->name, p->sourcehash.hash,
208  p->sourcehash.load_multiplier,
209  p->sourcehash.load_factor,
210  sumfetches ? (double) p->stats.fetches / sumfetches : -1.0);
211  }
212 }
213 
#define assert(EX)
Definition: assert.h:17
int peerHTTPOkay(const CachePeer *p, HttpRequest *request)
Definition: neighbors.cc:248
#define cbdataReferenceDone(var)
Definition: cbdata.h:350
CachePeer * next
Definition: CachePeer.h:154
#define xcalloc
Definition: membanger.c:57
CachePeer * peers
Definition: SquidConfig.h:243
struct _request * request(char *urlin)
Definition: tcp-banger2.c:291
struct CachePeer::@29 stats
#define safe_free(x)
Definition: xalloc.h:73
char * name
Definition: CachePeer.h:40
char * p
Definition: membanger.c:43
void OBJH(StoreEntry *)
Definition: forward.h:44
static OBJH peerSourceHashCachemgr
bool sourcehash
Definition: CachePeer.h:117
#define ROTATE_LEFT(x, n)
static int peerSortWeight(const void *a, const void *b)
#define debugs(SECTION, LEVEL, CONTENT)
Definition: Debug.h:123
#define cbdataReference(var)
Definition: cbdata.h:341
void RegisterAction(char const *action, char const *desc, OBJH *handler, int pw_req_flag, int atomic)
Definition: Registration.cc:16
Ip::Address client_addr
Definition: HttpRequest.h:137
peer_t type
Definition: CachePeer.h:42
int fetches
Definition: CachePeer.h:49
void peerSourceHashInit(void)
bool SIGHDLR int STUB void int
Definition: stub_tools.cc:68
CachePeer * peerSourceHashSelectParent(HttpRequest *request)
int weight
Definition: CachePeer.h:126
struct CachePeer::@31 options
void const cache_key * key
int a
Definition: membanger.c:50
#define MAX_IPSTRLEN
Length of buffer that needs to be allocated to old a null-terminated IP-string.
Definition: forward.h:23
char * toStr(char *buf, const unsigned int blen, int force=AF_UNSPEC) const
Definition: Address.cc:810
static void peerSourceHashRegisterWithCacheManager(void)
void storeAppendPrintf(StoreEntry *e, const char *fmt,...)
Definition: store.cc:904
static int n_sourcehash_peers
class SquidConfig Config
Definition: SquidConfig.cc:12
#define NULL
Definition: types.h:166

 

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