src/pconn.cc

   1
   2 /*
   3  * $Id: pconn.cc,v 1.55 2007/12/27 01:03:13 hno Exp $
   4  *
   5  * DEBUG: section 48    Persistent Connections
   6  * AUTHOR: Duane Wessels
   7  *
   8  * SQUID Web Proxy Cache          http://www.squid-cache.org/
   9  * ----------------------------------------------------------
  10  *
  11  *  Squid is the result of efforts by numerous individuals from
  12  *  the Internet community; see the CONTRIBUTORS file for full
  13  *  details.   Many organizations have provided support for Squid's
  14  *  development; see the SPONSORS file for full details.  Squid is
  15  *  Copyrighted (C) 2001 by the Regents of the University of
  16  *  California; see the COPYRIGHT file for full details.  Squid
  17  *  incorporates software developed and/or copyrighted by other
  18  *  sources; see the CREDITS file for full details.
  19  *
  20  *  This program is free software; you can redistribute it and/or modify
  21  *  it under the terms of the GNU General Public License as published by
  22  *  the Free Software Foundation; either version 2 of the License, or
  23  *  (at your option) any later version.
  24  *
  25  *  This program is distributed in the hope that it will be useful,
  26  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  27  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  28  *  GNU General Public License for more details.
  29  *
  30  *  You should have received a copy of the GNU General Public License
  31  *  along with this program; if not, write to the Free Software
  32  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  33  *
  34  */
  35
  36 #include "squid.h"
  37 #include "CacheManager.h"
  38 #include "Store.h"
  39 #include "comm.h"
  40 #include "pconn.h"
  41 #include "fde.h"
  42
  43 #define PCONN_FDS_SZ    8       /* pconn set size, increase for better memcache hit rate */
  44
  45 static MemAllocator *pconn_fds_pool = NULL;
  46 PconnModule * PconnModule::instance = NULL;
  47 CBDATA_CLASS_INIT(IdleConnList);
  48
  49 /* ========== IdleConnList ============================================ */
  50
  51 IdleConnList::IdleConnList(const char *key, PconnPool *thePool) : parent(thePool)
  52 {
  53     hash.key = xstrdup(key);
  54     nfds_alloc = PCONN_FDS_SZ;
  55     nfds = 0;
  56     fds = (int *)pconn_fds_pool->alloc();
  57 }
  58
  59 IdleConnList::~IdleConnList()
  60 {
  61
  62     parent->unlinkList(this);
  63
  64     if (nfds_alloc == PCONN_FDS_SZ)
  65         pconn_fds_pool->free(fds);
  66     else
  67         xfree(fds);
  68
  69     xfree(hash.key);
  70 }
  71
  72 int
  73 IdleConnList::findFDIndex (int fd)
  74 {
  75     int index;
  76
  77     for (index = nfds - 1; index >= 0; --index) {
  78         if (fds[index] == fd)
  79             return index;
  80     }
  81
  82     return -1;
  83 }
  84
  85 void
  86 IdleConnList::removeFD(int fd)
  87 {
  88     int index = findFDIndex(fd);
  89     if (index < 0) {
  90         debugs(48, 0, "IdleConnList::removeFD: FD " << fd << " NOT FOUND!");
  91         return;
  92     }
  93     debugs(48, 3, "IdleConnList::removeFD: found FD " << fd << " at index " << index);
  94
  95     for (; index < nfds - 1; index++)
  96         fds[index] = fds[index + 1];
  97
  98     if (--nfds == 0) {
  99         debugs(48, 3, "IdleConnList::removeFD: deleting " << hashKeyStr(&hash));
 100         delete this;
 101     }
 102 }
 103
 104 void
 105 IdleConnList::clearHandlers(int fd)
 106 {
 107     comm_read_cancel(fd, IdleConnList::read, this);
 108     commSetTimeout(fd, -1, NULL, NULL);
 109 }
 110
 111 void
 112 IdleConnList::push(int fd)
 113 {
 114     if (nfds == nfds_alloc) {
 115         debugs(48, 3, "IdleConnList::push: growing FD array");
 116         nfds_alloc <<= 1;
 117         int *old = fds;
 118         fds = (int *)xmalloc(nfds_alloc * sizeof(int));
 119         xmemcpy(fds, old, nfds * sizeof(int));
 120
 121         if (nfds == PCONN_FDS_SZ)
 122             pconn_fds_pool->free(old);
 123         else
 124             xfree(old);
 125     }
 126
 127     fds[nfds++] = fd;
 128     comm_read(fd, fakeReadBuf, sizeof(fakeReadBuf), IdleConnList::read, this);
 129     commSetTimeout(fd, Config.Timeout.pconn, IdleConnList::timeout, this);
 130 }
 131
 132 /*
 133  * XXX this routine isn't terribly efficient - if there's a pending
 134  * read event (which signifies the fd will close in the next IO loop!)
 135  * we ignore the FD and move onto the next one. This means, as an example,
 136  * if we have a lot of FDs open to a very popular server and we get a bunch
 137  * of requests JUST as they timeout (say, it shuts down) we'll be wasting
 138  * quite a bit of CPU. Just keep it in mind.
 139  */
 140 int
 141 IdleConnList::findUseableFD()
 142 {
 143     assert(nfds);
 144
 145     for (int i=nfds-1; i>=0; i--) {
 146         if (!comm_has_pending_read_callback(fds[i])) {
 147             return fds[i];
 148         }
 149     }
 150
 151     return -1;
 152 }
 153
 154 void
 155 IdleConnList::read(int fd, char *buf, size_t len, comm_err_t flag, int xerrno, void *data)
 156 {
 157     debugs(48, 3, "IdleConnList::read: " << len << " bytes from FD " << fd);
 158
 159     if (flag == COMM_ERR_CLOSING) {
 160         /* Bail out early on COMM_ERR_CLOSING - close handlers will tidy up for us */
 161         return;
 162     }
 163
 164     IdleConnList *list = (IdleConnList *) data;
 165     list->removeFD(fd); /* might delete list */
 166     comm_close(fd);
 167 }
 168
 169 void
 170 IdleConnList::timeout(int fd, void *data)
 171 {
 172     debugs(48, 3, "IdleConnList::timeout: FD " << fd);
 173     IdleConnList *list = (IdleConnList *) data;
 174     list->removeFD(fd); /* might delete list */
 175     comm_close(fd);
 176 }
 177
 178 /* ========== PconnPool PRIVATE FUNCTIONS ============================================ */
 179
 180 const char *
 181 PconnPool::key(const char *host, u_short port, const char *domain, IPAddress &client_address)
 182 {
 183     LOCAL_ARRAY(char, buf, SQUIDHOSTNAMELEN * 2 + 10);
 184     char ntoabuf[MAX_IPSTRLEN];
 185
 186     if (domain && !client_address.IsAnyAddr())
 187         snprintf(buf, SQUIDHOSTNAMELEN * 2 + 10, "%s:%d-%s/%s", host, (int) port, client_address.NtoA(ntoabuf,MAX_IPSTRLEN), domain);
 188     else if (domain && client_address.IsAnyAddr())
 189         snprintf(buf, SQUIDHOSTNAMELEN * 2 + 10, "%s:%d/%s", host, (int) port, domain);
 190     else if ((!domain) && !client_address.IsAnyAddr())
 191         snprintf(buf, SQUIDHOSTNAMELEN * 2 + 10, "%s:%d-%s", host, (int) port, client_address.NtoA(ntoabuf,MAX_IPSTRLEN));
 192     else
 193         snprintf(buf, SQUIDHOSTNAMELEN * 2 + 10, "%s:%d", host, (int) port);
 194
 195     return buf;
 196 }
 197
 198 void
 199 PconnPool::dumpHist(StoreEntry * e)
 200 {
 201     int i;
 202     storeAppendPrintf(e,
 203                       "%s persistent connection counts:\n"
 204                       "\n"
 205                       "\treq/\n"
 206                       "\tconn      count\n"
 207                       "\t----  ---------\n",
 208                       descr);
 209
 210     for (i = 0; i < PCONN_HIST_SZ; i++) {
 211         if (hist[i] == 0)
 212             continue;
 213
 214         storeAppendPrintf(e, "\t%4d  %9d\n", i, hist[i]);
 215     }
 216 }
 217
 218 /* ========== PconnPool PUBLIC FUNCTIONS ============================================ */
 219
 220 PconnPool::PconnPool(const char *aDescr) : table(NULL), descr(aDescr)
 221 {
 222     int i;
 223     table = hash_create((HASHCMP *) strcmp, 229, hash_string);
 224
 225     for (i = 0; i < PCONN_HIST_SZ; i++)
 226         hist[i] = 0;
 227
 228     PconnModule::GetInstance()->add
 229     (this);
 230 }
 231
 232 void
 233 PconnPool::push(int fd, const char *host, u_short port, const char *domain, IPAddress &client_address)
 234 {
 235
 236     IdleConnList *list;
 237     const char *aKey;
 238     LOCAL_ARRAY(char, desc, FD_DESC_SZ);
 239
 240     if (fdUsageHigh()) {
 241         debugs(48, 3, "PconnPool::push: Not many unused FDs");
 242         comm_close(fd);
 243         return;
 244     } else if (shutting_down) {
 245         comm_close(fd);
 246         return;
 247     }
 248
 249     aKey = key(host, port, domain, client_address);
 250
 251     list = (IdleConnList *) hash_lookup(table, aKey);
 252
 253     if (list == NULL) {
 254         list = new IdleConnList(aKey, this);
 255         debugs(48, 3, "pconnNew: adding " << hashKeyStr(&list->hash));
 256         hash_join(table, &list->hash);
 257     }
 258
 259     list->push(fd);
 260
 261     assert(!comm_has_incomplete_write(fd));
 262     snprintf(desc, FD_DESC_SZ, "%s idle connection", host);
 263     fd_note(fd, desc);
 264     debugs(48, 3, "PconnPool::push: pushed FD " << fd << " for " << aKey);
 265 }
 266
 267 /*
 268  * Return a pconn fd for host:port if available and retriable.
 269  * Otherwise, return -1.
 270  *
 271  * We close available persistent connection if the caller transaction is not
 272  * retriable to avoid having a growing number of open connections when many
 273  * transactions create persistent connections but are not retriable.
 274  */
 275 int
 276
 277 PconnPool::pop(const char *host, u_short port, const char *domain, IPAddress &client_address, bool isRetriable)
 278 {
 279     IdleConnList *list;
 280     const char * aKey = key(host, port, domain, client_address);
 281     list = (IdleConnList *)hash_lookup(table, aKey);
 282
 283     if (list == NULL)
 284         return -1;
 285
 286     int fd = list->findUseableFD(); // search from the end. skip pending reads.
 287
 288     if (fd >= 0) {
 289         list->clearHandlers(fd);
 290         list->removeFD(fd);     /* might delete list */
 291
 292         if (!isRetriable) {
 293             comm_close(fd);
 294             return -1;
 295         }
 296     }
 297
 298     return fd;
 299 }
 300
 301 void
 302 PconnPool::unlinkList(IdleConnList *list) const
 303 {
 304     hash_remove_link(table, &list->hash);
 305 }
 306
 307 void
 308 PconnPool::count(int uses)
 309 {
 310     if (uses >= PCONN_HIST_SZ)
 311         uses = PCONN_HIST_SZ - 1;
 312
 313     hist[uses]++;
 314 }
 315
 316 /* ========== PconnModule ============================================ */
 317
 318 /*
 319  * This simple class exists only for the cache manager
 320  */
 321
 322 PconnModule::PconnModule() : pools(NULL), poolCount(0)
 323 {
 324     pools = (PconnPool **) xcalloc(MAX_NUM_PCONN_POOLS, sizeof(*pools));
 325     pconn_fds_pool = memPoolCreate("pconn_fds", PCONN_FDS_SZ * sizeof(int));
 326     debugs(48, 0, "persistent connection module initialized");
 327     registerWithCacheManager();
 328 }
 329
 330 PconnModule *
 331 PconnModule::GetInstance()
 332 {
 333     if (instance == NULL)
 334         instance = new PconnModule;
 335
 336     return instance;
 337 }
 338
 339 void
 340 PconnModule::registerWithCacheManager(void)
 341 {
 342     CacheManager::GetInstance()->
 343     registerAction("pconn",
 344                    "Persistent Connection Utilization Histograms",
 345                    DumpWrapper, 0, 1);
 346 }
 347
 348 void
 349
 350 PconnModule::add
 351 (PconnPool *aPool)
 352 {
 353     assert(poolCount < MAX_NUM_PCONN_POOLS);
 354     *(pools+poolCount) = aPool;
 355     poolCount++;
 356 }
 357
 358 void
 359 PconnModule::dump(StoreEntry *e)
 360 {
 361     int i;
 362
 363     for (i = 0; i < poolCount; i++) {
 364         (*(pools+i))->dumpHist(e);
 365     }
 366 }
 367
 368 void
 369 PconnModule::DumpWrapper(StoreEntry *e)
 370 {
 371     PconnModule::GetInstance()->dump(e);
 372 }