src/pconn.cc

   1 /*
   2  * $Id$
   3  *
   4  * DEBUG: section 48    Persistent Connections
   5  * AUTHOR: Duane Wessels
   6  *
   7  * SQUID Web Proxy Cache          http://www.squid-cache.org/
   8  * ----------------------------------------------------------
   9  *
  10  *  Squid is the result of efforts by numerous individuals from
  11  *  the Internet community; see the CONTRIBUTORS file for full
  12  *  details.   Many organizations have provided support for Squid's
  13  *  development; see the SPONSORS file for full details.  Squid is
  14  *  Copyrighted (C) 2001 by the Regents of the University of
  15  *  California; see the COPYRIGHT file for full details.  Squid
  16  *  incorporates software developed and/or copyrighted by other
  17  *  sources; see the CREDITS file for full details.
  18  *
  19  *  This program is free software; you can redistribute it and/or modify
  20  *  it under the terms of the GNU General Public License as published by
  21  *  the Free Software Foundation; either version 2 of the License, or
  22  *  (at your option) any later version.
  23  *
  24  *  This program is distributed in the hope that it will be useful,
  25  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  26  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  27  *  GNU General Public License for more details.
  28  *
  29  *  You should have received a copy of the GNU General Public License
  30  *  along with this program; if not, write to the Free Software
  31  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  32  *
  33  */
  34
  35 #include "squid.h"
  36 #include "CacheManager.h"
  37 #include "Store.h"
  38 #include "comm.h"
  39 #include "pconn.h"
  40 #include "fde.h"
  41
  42 #define PCONN_FDS_SZ    8       /* pconn set size, increase for better memcache hit rate */
  43
  44 static MemAllocator *pconn_fds_pool = NULL;
  45 PconnModule * PconnModule::instance = NULL;
  46 CBDATA_CLASS_INIT(IdleConnList);
  47
  48 /* ========== IdleConnList ============================================ */
  49
  50 IdleConnList::IdleConnList(const char *key, PconnPool *thePool) : parent(thePool)
  51 {
  52     hash.key = xstrdup(key);
  53     nfds_alloc = PCONN_FDS_SZ;
  54     nfds = 0;
  55     fds = (int *)pconn_fds_pool->alloc();
  56 }
  57
  58 IdleConnList::~IdleConnList()
  59 {
  60
  61     parent->unlinkList(this);
  62
  63     if (nfds_alloc == PCONN_FDS_SZ)
  64         pconn_fds_pool->freeOne(fds);
  65     else
  66         xfree(fds);
  67
  68     xfree(hash.key);
  69 }
  70
  71 int
  72 IdleConnList::findFDIndex (int fd)
  73 {
  74     int index;
  75
  76     for (index = nfds - 1; index >= 0; --index) {
  77         if (fds[index] == fd)
  78             return index;
  79     }
  80
  81     return -1;
  82 }
  83
  84 bool
  85 IdleConnList::removeFD(int fd)
  86 {
  87     int index = findFDIndex(fd);
  88     if (index < 0) {
  89         debugs(48, 2, "IdleConnList::removeFD: FD " << fd << " NOT FOUND!");
  90         return false;
  91     }
  92     debugs(48, 3, "IdleConnList::removeFD: found FD " << fd << " at index " << index);
  93
  94     for (; index < nfds - 1; index++)
  95         fds[index] = fds[index + 1];
  96
  97     if (--nfds == 0) {
  98         debugs(48, 3, "IdleConnList::removeFD: deleting " << hashKeyStr(&hash));
  99         delete this;
 100     }
 101     return true;
 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->freeOne(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     if (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     if (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, Ip::Address &client_address)
 182 {
 183     LOCAL_ARRAY(char, buf, SQUIDHOSTNAMELEN * 3 + 10);
 184     char ntoabuf[MAX_IPSTRLEN];
 185
 186     if (domain && !client_address.IsAnyAddr())
 187         snprintf(buf, SQUIDHOSTNAMELEN * 3 + 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 * 3 + 10, "%s:%d/%s", host, (int) port, domain);
 190     else if ((!domain) && !client_address.IsAnyAddr())
 191         snprintf(buf, SQUIDHOSTNAMELEN * 3 + 10, "%s:%d-%s", host, (int) port, client_address.NtoA(ntoabuf,MAX_IPSTRLEN));
 192     else
 193         snprintf(buf, SQUIDHOSTNAMELEN * 3 + 10, "%s:%d", host, (int) port);
 194
 195     debugs(48,6,"PconnPool::key(" << (host?host:"(no host!)") << "," << port << "," << (domain?domain:"(no domain)") << "," << client_address << "is {" << buf << "}" );
 196     return buf;
 197 }
 198
 199 void
 200 PconnPool::dumpHist(StoreEntry * e)
 201 {
 202     int i;
 203     storeAppendPrintf(e,
 204                       "%s persistent connection counts:\n"
 205                       "\n"
 206                       "\treq/\n"
 207                       "\tconn      count\n"
 208                       "\t----  ---------\n",
 209                       descr);
 210
 211     for (i = 0; i < PCONN_HIST_SZ; i++) {
 212         if (hist[i] == 0)
 213             continue;
 214
 215         storeAppendPrintf(e, "\t%4d  %9d\n", i, hist[i]);
 216     }
 217 }
 218
 219 void
 220 PconnPool::dumpHash(StoreEntry *e)
 221 {
 222     int i;
 223     hash_link *walker = NULL;
 224     hash_table *hid = table;
 225     hash_first(hid);
 226
 227     for (i = 0, walker = hid->next; walker; walker = hash_next(hid)) {
 228         storeAppendPrintf(e, "\t item %5d: %s\n", i++, (char *)(walker->key));
 229     }
 230 }
 231
 232 /* ========== PconnPool PUBLIC FUNCTIONS ============================================ */
 233
 234 PconnPool::PconnPool(const char *aDescr) : table(NULL), descr(aDescr)
 235 {
 236     int i;
 237     table = hash_create((HASHCMP *) strcmp, 229, hash_string);
 238
 239     for (i = 0; i < PCONN_HIST_SZ; i++)
 240         hist[i] = 0;
 241
 242     PconnModule::GetInstance()->add(this);
 243 }
 244
 245 PconnPool::~PconnPool()
 246 {
 247     descr = NULL;
 248     hashFreeMemory(table);
 249 }
 250
 251 void
 252 PconnPool::push(int fd, const char *host, u_short port, const char *domain, Ip::Address &client_address)
 253 {
 254     IdleConnList *list;
 255     const char *aKey;
 256     LOCAL_ARRAY(char, desc, FD_DESC_SZ);
 257
 258     if (fdUsageHigh()) {
 259         debugs(48, 3, "PconnPool::push: Not many unused FDs");
 260         comm_close(fd);
 261         return;
 262     } else if (shutting_down) {
 263         comm_close(fd);
 264         debugs(48, 3, "PconnPool::push: Squid is shutting down. Refusing to do anything");
 265         return;
 266     }
 267
 268     aKey = key(host, port, domain, client_address);
 269
 270     list = (IdleConnList *) hash_lookup(table, aKey);
 271
 272     if (list == NULL) {
 273         list = new IdleConnList(aKey, this);
 274         debugs(48, 3, "PconnPool::push: new IdleConnList for {" << hashKeyStr(&list->hash) << "}" );
 275         hash_join(table, &list->hash);
 276     } else {
 277         debugs(48, 3, "PconnPool::push: found IdleConnList for {" << hashKeyStr(&list->hash) << "}" );
 278     }
 279
 280     list->push(fd);
 281
 282     assert(!comm_has_incomplete_write(fd));
 283     snprintf(desc, FD_DESC_SZ, "%s idle connection", host);
 284     fd_note(fd, desc);
 285     debugs(48, 3, "PconnPool::push: pushed FD " << fd << " for " << aKey);
 286 }
 287
 288 /**
 289  * Return a pconn fd for host:port if available and retriable.
 290  * Otherwise, return -1.
 291  *
 292  * We close available persistent connection if the caller transaction is not
 293  * retriable to avoid having a growing number of open connections when many
 294  * transactions create persistent connections but are not retriable.
 295  */
 296 int
 297 PconnPool::pop(const char *host, u_short port, const char *domain, Ip::Address &client_address, bool isRetriable)
 298 {
 299     const char * aKey = key(host, port, domain, client_address);
 300
 301     IdleConnList *list = (IdleConnList *)hash_lookup(table, aKey);
 302     if (list == NULL) {
 303         debugs(48, 3, "PconnPool::pop: lookup for key {" << aKey << "} failed.");
 304         return -1;
 305     } else {
 306         debugs(48, 3, "PconnPool::pop: found " << hashKeyStr(&list->hash) << (isRetriable?"(to use)":"(to kill)") );
 307     }
 308
 309     int fd = list->findUseableFD(); // search from the end. skip pending reads.
 310
 311     if (fd >= 0) {
 312         list->clearHandlers(fd);
 313
 314         /* might delete list */
 315         if (list->removeFD(fd) && !isRetriable) {
 316             comm_close(fd);
 317             return -1;
 318         }
 319     }
 320
 321     return fd;
 322 }
 323
 324 void
 325 PconnPool::unlinkList(IdleConnList *list) const
 326 {
 327     hash_remove_link(table, &list->hash);
 328 }
 329
 330 void
 331 PconnPool::count(int uses)
 332 {
 333     if (uses >= PCONN_HIST_SZ)
 334         uses = PCONN_HIST_SZ - 1;
 335
 336     hist[uses]++;
 337 }
 338
 339 /* ========== PconnModule ============================================ */
 340
 341 /*
 342  * This simple class exists only for the cache manager
 343  */
 344
 345 PconnModule::PconnModule() : pools(NULL), poolCount(0)
 346 {
 347     pools = (PconnPool **) xcalloc(MAX_NUM_PCONN_POOLS, sizeof(*pools));
 348     pconn_fds_pool = memPoolCreate("pconn_fds", PCONN_FDS_SZ * sizeof(int));
 349     debugs(48, 0, "persistent connection module initialized");
 350     registerWithCacheManager();
 351 }
 352
 353 PconnModule *
 354 PconnModule::GetInstance()
 355 {
 356     if (instance == NULL)
 357         instance = new PconnModule;
 358
 359     return instance;
 360 }
 361
 362 void
 363 PconnModule::registerWithCacheManager(void)
 364 {
 365     CacheManager::GetInstance()->
 366     registerAction("pconn",
 367                    "Persistent Connection Utilization Histograms",
 368                    DumpWrapper, 0, 1);
 369 }
 370
 371 void
 372
 373 PconnModule::add
 374 (PconnPool *aPool)
 375 {
 376     assert(poolCount < MAX_NUM_PCONN_POOLS);
 377     *(pools+poolCount) = aPool;
 378     poolCount++;
 379 }
 380
 381 void
 382 PconnModule::dump(StoreEntry *e)
 383 {
 384     int i;
 385
 386     for (i = 0; i < poolCount; i++) {
 387         storeAppendPrintf(e, "\n Pool %d Stats\n", i);
 388         (*(pools+i))->dumpHist(e);
 389         storeAppendPrintf(e, "\n Pool %d Hash Table\n",i);
 390         (*(pools+i))->dumpHash(e);
 391     }
 392 }
 393
 394 void
 395 PconnModule::DumpWrapper(StoreEntry *e)
 396 {
 397     PconnModule::GetInstance()->dump(e);
 398 }