git.m6w6.name Git - awesomized/libmemcached/blob - libmemcached/memcached_io.c

   1 /*
   2   Basic socket buffered IO
   3 */
   4
   5 #include "common.h"
   6 #include "memcached_io.h"
   7 #include <sys/select.h>
   8 #include <poll.h>
   9
  10 typedef enum {
  11   MEM_READ,
  12   MEM_WRITE,
  13 } memc_read_or_write;
  14
  15 static ssize_t io_flush(memcached_server_st *ptr, memcached_return *error);
  16 static void increment_udp_message_id(memcached_server_st *ptr);
  17
  18 static memcached_return io_wait(memcached_server_st *ptr,
  19                                 memc_read_or_write read_or_write)
  20 {
  21   struct pollfd fds[1];
  22   short flags= 0;
  23   int error;
  24
  25   if (read_or_write == MEM_WRITE) /* write */
  26     flags= POLLOUT |  POLLERR;
  27   else
  28     flags= POLLIN | POLLERR;
  29
  30   memset(&fds, 0, sizeof(struct pollfd));
  31   fds[0].fd= ptr->fd;
  32   fds[0].events= flags;
  33
  34   /*
  35   ** We are going to block on write, but at least on Solaris we might block
  36   ** on write if we haven't read anything from our input buffer..
  37   ** Try to purge the input buffer if we don't do any flow control in the
  38   ** application layer (just sending a lot of data etc)
  39   ** The test is moved down in the purge function to avoid duplication of
  40   ** the test.
  41   */
  42   if (read_or_write == MEM_WRITE)
  43   {
  44     memcached_return rc=memcached_purge(ptr);
  45     if (rc != MEMCACHED_SUCCESS && rc != MEMCACHED_STORED)
  46        return MEMCACHED_FAILURE;
  47   }
  48
  49   error= poll(fds, 1, ptr->root->poll_timeout);
  50
  51   if (error == 1)
  52     return MEMCACHED_SUCCESS;
  53   else if (error == 0)
  54   {
  55     return MEMCACHED_TIMEOUT;
  56   }
  57
  58   /* Imposssible for anything other then -1 */
  59   WATCHPOINT_ASSERT(error == -1);
  60   memcached_quit_server(ptr, 1);
  61
  62   return MEMCACHED_FAILURE;
  63
  64 }
  65
  66 #ifdef UNUSED
  67 void memcached_io_preread(memcached_st *ptr)
  68 {
  69   unsigned int x;
  70
  71   return;
  72
  73   for (x= 0; x < ptr->number_of_hosts; x++)
  74   {
  75     if (memcached_server_response_count(ptr, x) &&
  76         ptr->hosts[x].read_data_length < MEMCACHED_MAX_BUFFER )
  77     {
  78       size_t data_read;
  79
  80       data_read= read(ptr->hosts[x].fd,
  81                       ptr->hosts[x].read_ptr + ptr->hosts[x].read_data_length,
  82                       MEMCACHED_MAX_BUFFER - ptr->hosts[x].read_data_length);
  83       if (data_read == -1)
  84         continue;
  85
  86       ptr->hosts[x].read_buffer_length+= data_read;
  87       ptr->hosts[x].read_data_length+= data_read;
  88     }
  89   }
  90 }
  91 #endif
  92
  93 ssize_t memcached_io_read(memcached_server_st *ptr,
  94                           void *buffer, size_t length)
  95 {
  96   char *buffer_ptr;
  97
  98   buffer_ptr= buffer;
  99
 100   while (length)
 101   {
 102     if (!ptr->read_buffer_length)
 103     {
 104       ssize_t data_read;
 105
 106       while (1)
 107       {
 108         data_read= read(ptr->fd,
 109                         ptr->read_buffer,
 110                         MEMCACHED_MAX_BUFFER);
 111         if (data_read > 0)
 112           break;
 113         else if (data_read == -1)
 114         {
 115           ptr->cached_errno= errno;
 116           switch (errno)
 117           {
 118           case EAGAIN:
 119           case EINTR:
 120             if (io_wait(ptr, MEM_READ) == MEMCACHED_SUCCESS)
 121               continue;
 122           /* fall through */
 123
 124           default:
 125             {
 126               memcached_quit_server(ptr, 1);
 127               return -1;
 128             }
 129           }
 130         }
 131         else
 132         {
 133           /*
 134             EOF. Any data received so far is incomplete
 135             so discard it. This always reads by byte in case of TCP
 136             and protocol enforcement happens at memcached_response()
 137             looking for '\n'. We do not care for UDB which requests 8 bytes
 138             at once. Generally, this means that connection went away. Since
 139             for blocking I/O we do not return 0 and for non-blocking case
 140             it will return EGAIN if data is not immediatly available.
 141           */
 142           memcached_quit_server(ptr, 1);
 143           return -1;
 144         }
 145       }
 146
 147       ptr->io_bytes_sent = 0;
 148       ptr->read_data_length= data_read;
 149       ptr->read_buffer_length= data_read;
 150       ptr->read_ptr= ptr->read_buffer;
 151     }
 152
 153     if (length > 1)
 154     {
 155       size_t difference;
 156
 157       difference= (length > ptr->read_buffer_length) ? ptr->read_buffer_length : length;
 158
 159       memcpy(buffer_ptr, ptr->read_ptr, difference);
 160       length -= difference;
 161       ptr->read_ptr+= difference;
 162       ptr->read_buffer_length-= difference;
 163       buffer_ptr+= difference;
 164     }
 165     else
 166     {
 167       *buffer_ptr= *ptr->read_ptr;
 168       ptr->read_ptr++;
 169       ptr->read_buffer_length--;
 170       buffer_ptr++;
 171       break;
 172     }
 173   }
 174
 175   ptr->server_failure_counter= 0;
 176   return (size_t)(buffer_ptr - (char*)buffer);
 177 }
 178
 179 ssize_t memcached_io_write(memcached_server_st *ptr,
 180                            const void *buffer, size_t length, char with_flush)
 181 {
 182   size_t original_length;
 183   const char* buffer_ptr;
 184
 185   WATCHPOINT_ASSERT(ptr->fd != -1);
 186
 187   original_length= length;
 188   buffer_ptr= buffer;
 189
 190   while (length)
 191   {
 192     char *write_ptr;
 193     size_t should_write;
 194     size_t buffer_end;
 195
 196     if (ptr->type == MEMCACHED_CONNECTION_UDP)
 197     {
 198       //UDP does not support partial writes
 199       buffer_end= MAX_UDP_DATAGRAM_LENGTH;
 200       should_write= length;
 201       if (ptr->write_buffer_offset + should_write > buffer_end)
 202         return -1;
 203     }
 204     else
 205     {
 206       buffer_end= MEMCACHED_MAX_BUFFER;
 207       should_write= buffer_end - ptr->write_buffer_offset;
 208       should_write= (should_write < length) ? should_write : length;
 209     }
 210
 211     write_ptr= ptr->write_buffer + ptr->write_buffer_offset;
 212     memcpy(write_ptr, buffer_ptr, should_write);
 213     ptr->write_buffer_offset+= should_write;
 214     buffer_ptr+= should_write;
 215     length-= should_write;
 216
 217     if (ptr->write_buffer_offset == buffer_end && ptr->type != MEMCACHED_CONNECTION_UDP)
 218     {
 219       memcached_return rc;
 220       ssize_t sent_length;
 221
 222       WATCHPOINT_ASSERT(ptr->fd != -1);
 223       sent_length= io_flush(ptr, &rc);
 224       if (sent_length == -1)
 225         return -1;
 226
 227       /* If io_flush calls memcached_purge, sent_length may be 0 */
 228       if (sent_length != 0)
 229         WATCHPOINT_ASSERT(sent_length == buffer_end);
 230     }
 231   }
 232
 233   if (with_flush)
 234   {
 235     memcached_return rc;
 236     WATCHPOINT_ASSERT(ptr->fd != -1);
 237     if (io_flush(ptr, &rc) == -1)
 238       return -1;
 239   }
 240
 241   return original_length;
 242 }
 243
 244 memcached_return memcached_io_close(memcached_server_st *ptr)
 245 {
 246   int r;
 247
 248   if (ptr->fd == -1)
 249     return MEMCACHED_SUCCESS;
 250
 251   /* in case of death shutdown to avoid blocking at close() */
 252   if (1)
 253   {
 254     r= shutdown(ptr->fd, SHUT_RDWR);
 255
 256 #ifdef HAVE_DEBUG
 257     if (r && errno != ENOTCONN)
 258     {
 259       WATCHPOINT_NUMBER(ptr->fd);
 260       WATCHPOINT_ERRNO(errno);
 261       WATCHPOINT_ASSERT(errno);
 262     }
 263 #endif
 264   }
 265
 266   r= close(ptr->fd);
 267 #ifdef HAVE_DEBUG
 268   if (r != 0)
 269     WATCHPOINT_ERRNO(errno);
 270 #endif
 271
 272   return MEMCACHED_SUCCESS;
 273 }
 274
 275 memcached_server_st *memcached_io_get_readable_server(memcached_st *memc)
 276 {
 277 #define MAX_SERVERS_TO_POLL 100
 278   struct pollfd fds[MAX_SERVERS_TO_POLL];
 279   int index= 0;
 280
 281   for (int x= 0; x< memc->number_of_hosts && index < MAX_SERVERS_TO_POLL; ++x)
 282   {
 283     if (memc->hosts[x].read_buffer_length > 0) /* I have data in the buffer */
 284       return &memc->hosts[x];
 285
 286     if (memcached_server_response_count(&memc->hosts[x]) > 0)
 287     {
 288       fds[index].events = POLLIN;
 289       fds[index].revents = 0;
 290       fds[index].fd = memc->hosts[x].fd;
 291       ++index;
 292     }
 293   }
 294
 295   if (index < 2)
 296   {
 297     /* We have 0 or 1 server with pending events.. */
 298     for (int x= 0; x< memc->number_of_hosts; ++x)
 299       if (memcached_server_response_count(&memc->hosts[x]) > 0)
 300         return &memc->hosts[x];
 301
 302     return NULL;
 303   }
 304
 305   int err= poll(fds, index, memc->poll_timeout);
 306   switch (err) {
 307   case -1:
 308     memc->cached_errno = errno;
 309     /* FALLTHROUGH */
 310   case 0:
 311     break;
 312   default:
 313     for (int x= 0; x < index; ++x)
 314       if (fds[x].revents & POLLIN)
 315         for (int y= 0; y < memc->number_of_hosts; ++y)
 316           if (memc->hosts[y].fd == fds[x].fd)
 317             return &memc->hosts[y];
 318   }
 319
 320   return NULL;
 321 }
 322
 323 static ssize_t io_flush(memcached_server_st *ptr,
 324                         memcached_return *error)
 325 {
 326   /*
 327   ** We might want to purge the input buffer if we haven't consumed
 328   ** any output yet... The test for the limits is the purge is inline
 329   ** in the purge function to avoid duplicating the logic..
 330   */
 331   {
 332      memcached_return rc;
 333      WATCHPOINT_ASSERT(ptr->fd != -1);
 334      rc= memcached_purge(ptr);
 335
 336      if (rc != MEMCACHED_SUCCESS && rc != MEMCACHED_STORED)
 337        return -1;
 338   }
 339   ssize_t sent_length;
 340   size_t return_length;
 341   char *local_write_ptr= ptr->write_buffer;
 342   size_t write_length= ptr->write_buffer_offset;
 343
 344   *error= MEMCACHED_SUCCESS;
 345
 346   WATCHPOINT_ASSERT(ptr->fd != -1);
 347
 348   // UDP Sanity check, make sure that we are not sending somthing too big
 349   if (ptr->type == MEMCACHED_CONNECTION_UDP && write_length > MAX_UDP_DATAGRAM_LENGTH)
 350     return -1;
 351
 352   if (ptr->write_buffer_offset == 0 || (ptr->type == MEMCACHED_CONNECTION_UDP
 353           && ptr->write_buffer_offset == UDP_DATAGRAM_HEADER_LENGTH))
 354     return 0;
 355
 356   /* Looking for memory overflows */
 357 #if defined(HAVE_DEBUG)
 358   if (write_length == MEMCACHED_MAX_BUFFER)
 359     WATCHPOINT_ASSERT(ptr->write_buffer == local_write_ptr);
 360   WATCHPOINT_ASSERT((ptr->write_buffer + MEMCACHED_MAX_BUFFER) >= (local_write_ptr + write_length));
 361 #endif
 362
 363   return_length= 0;
 364   while (write_length)
 365   {
 366     WATCHPOINT_ASSERT(ptr->fd != -1);
 367     WATCHPOINT_ASSERT(write_length > 0);
 368     sent_length= 0;
 369     if (ptr->type == MEMCACHED_CONNECTION_UDP)
 370       increment_udp_message_id(ptr);
 371     sent_length= write(ptr->fd, local_write_ptr, write_length);
 372
 373     if (sent_length == -1)
 374     {
 375       ptr->cached_errno= errno;
 376       switch (errno)
 377       {
 378       case ENOBUFS:
 379         continue;
 380       case EAGAIN:
 381       {
 382         memcached_return rc;
 383         rc= io_wait(ptr, MEM_WRITE);
 384
 385         if (rc == MEMCACHED_SUCCESS || rc == MEMCACHED_TIMEOUT)
 386           continue;
 387
 388         memcached_quit_server(ptr, 1);
 389         return -1;
 390       }
 391       default:
 392         memcached_quit_server(ptr, 1);
 393         *error= MEMCACHED_ERRNO;
 394         return -1;
 395       }
 396     }
 397
 398     if (ptr->type == MEMCACHED_CONNECTION_UDP && sent_length != write_length)
 399     {
 400       memcached_quit_server(ptr, 1);
 401       return -1;
 402     }
 403
 404     ptr->io_bytes_sent += sent_length;
 405
 406     local_write_ptr+= sent_length;
 407     write_length-= sent_length;
 408     return_length+= sent_length;
 409   }
 410
 411   WATCHPOINT_ASSERT(write_length == 0);
 412   // Need to study this assert() WATCHPOINT_ASSERT(return_length ==
 413   // ptr->write_buffer_offset);
 414
 415   // if we are a udp server, the begining of the buffer is reserverd for
 416   // the upd frame header
 417   if (ptr->type == MEMCACHED_CONNECTION_UDP)
 418     ptr->write_buffer_offset= UDP_DATAGRAM_HEADER_LENGTH;
 419   else
 420     ptr->write_buffer_offset= 0;
 421
 422   return return_length;
 423 }
 424
 425 /*
 426   Eventually we will just kill off the server with the problem.
 427 */
 428 void memcached_io_reset(memcached_server_st *ptr)
 429 {
 430   memcached_quit_server(ptr, 1);
 431 }
 432
 433 /**
 434  * Read a given number of bytes from the server and place it into a specific
 435  * buffer. Reset the IO channel on this server if an error occurs.
 436  */
 437 memcached_return memcached_safe_read(memcached_server_st *ptr,
 438                                      void *dta,
 439                                      size_t size)
 440 {
 441   size_t offset= 0;
 442   char *data= dta;
 443
 444   while (offset < size)
 445   {
 446     ssize_t nread= memcached_io_read(ptr, data + offset, size - offset);
 447     if (nread <= 0)
 448     {
 449       memcached_io_reset(ptr);
 450       return MEMCACHED_UNKNOWN_READ_FAILURE;
 451     }
 452     offset+= nread;
 453   }
 454
 455   return MEMCACHED_SUCCESS;
 456 }
 457
 458 memcached_return memcached_io_readline(memcached_server_st *ptr,
 459                                        char *buffer_ptr,
 460                                        size_t size)
 461 {
 462   bool line_complete= false;
 463   int total_nr= 0;
 464
 465   while (!line_complete)
 466   {
 467     if (ptr->read_buffer_length == 0)
 468     {
 469       /*
 470        * We don't have any data in the buffer, so let's fill the read
 471        * buffer. Call the standard read function to avoid duplicating
 472        * the logic.
 473        */
 474       if (memcached_io_read(ptr, buffer_ptr, 1) != 1)
 475         return MEMCACHED_UNKNOWN_READ_FAILURE;
 476
 477       if (*buffer_ptr == '\n')
 478         line_complete= true;
 479
 480       ++buffer_ptr;
 481       ++total_nr;
 482     }
 483
 484     /* Now let's look in the buffer and copy as we go! */
 485     while (ptr->read_buffer_length && total_nr < size && !line_complete)
 486     {
 487       *buffer_ptr = *ptr->read_ptr;
 488       if (*buffer_ptr == '\n')
 489         line_complete = true;
 490       --ptr->read_buffer_length;
 491       ++ptr->read_ptr;
 492       ++total_nr;
 493       ++buffer_ptr;
 494     }
 495
 496     if (total_nr == size)
 497       return MEMCACHED_PROTOCOL_ERROR;
 498   }
 499
 500   return MEMCACHED_SUCCESS;
 501 }
 502
 503 /*
 504  * The udp request id consists of two seperate sections
 505  *   1) The thread id
 506  *   2) The message number
 507  * The thread id should only be set when the memcached_st struct is created
 508  * and should not be changed.
 509  *
 510  * The message num is incremented for each new message we send, this function
 511  * extracts the message number from message_id, increments it and then
 512  * writes the new value back into the header
 513  */
 514 static void increment_udp_message_id(memcached_server_st *ptr)
 515 {
 516   struct udp_datagram_header_st *header= (struct udp_datagram_header_st *)ptr->write_buffer;
 517   uint16_t cur_req= get_udp_datagram_request_id(header);
 518   uint16_t msg_num= get_msg_num_from_request_id(cur_req);
 519   uint16_t thread_id= get_thread_id_from_request_id(cur_req);
 520
 521   if (((++msg_num) & UDP_REQUEST_ID_THREAD_MASK) != 0)
 522     msg_num= 0;
 523
 524   header->request_id= htons(thread_id | msg_num);
 525 }
 526
 527 memcached_return memcached_io_init_udp_header(memcached_server_st *ptr, uint16_t thread_id)
 528 {
 529   if (thread_id > UDP_REQUEST_ID_MAX_THREAD_ID)
 530     return MEMCACHED_FAILURE;
 531
 532   struct udp_datagram_header_st *header= (struct udp_datagram_header_st *)ptr->write_buffer;
 533   header->request_id= htons(generate_udp_request_thread_id(thread_id));
 534   header->num_datagrams= htons(1);
 535   header->sequence_number= htons(0);
 536
 537   return MEMCACHED_SUCCESS;
 538 }