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             {
 121               memcached_return rc;
 122
 123               rc= io_wait(ptr, MEM_READ);
 124
 125               if (rc == MEMCACHED_SUCCESS)
 126                 continue;
 127             }
 128           /* fall trough */
 129           default:
 130             {
 131               memcached_quit_server(ptr, 1);
 132               return -1;
 133             }
 134           }
 135         }
 136         else
 137         {
 138           /*
 139             EOF. Any data received so far is incomplete
 140             so discard it. This always reads by byte in case of TCP
 141             and protocol enforcement happens at memcached_response()
 142             looking for '\n'. We do not care for UDB which requests 8 bytes
 143             at once. Generally, this means that connection went away. Since
 144             for blocking I/O we do not return 0 and for non-blocking case
 145             it will return EGAIN if data is not immediatly available.
 146           */
 147           memcached_quit_server(ptr, 1);
 148           return -1;
 149         }
 150       }
 151
 152       ptr->io_bytes_sent = 0;
 153       ptr->read_data_length= data_read;
 154       ptr->read_buffer_length= data_read;
 155       ptr->read_ptr= ptr->read_buffer;
 156     }
 157
 158     if (length > 1)
 159     {
 160       size_t difference;
 161
 162       difference= (length > ptr->read_buffer_length) ? ptr->read_buffer_length : length;
 163
 164       memcpy(buffer_ptr, ptr->read_ptr, difference);
 165       length -= difference;
 166       ptr->read_ptr+= difference;
 167       ptr->read_buffer_length-= difference;
 168       buffer_ptr+= difference;
 169     }
 170     else
 171     {
 172       *buffer_ptr= *ptr->read_ptr;
 173       ptr->read_ptr++;
 174       ptr->read_buffer_length--;
 175       buffer_ptr++;
 176       break;
 177     }
 178   }
 179
 180   return (size_t)(buffer_ptr - (char*)buffer);
 181 }
 182
 183 ssize_t memcached_io_write(memcached_server_st *ptr,
 184                            const void *buffer, size_t length, char with_flush)
 185 {
 186   size_t original_length;
 187   const char* buffer_ptr;
 188
 189   WATCHPOINT_ASSERT(ptr->fd != -1);
 190
 191   original_length= length;
 192   buffer_ptr= buffer;
 193
 194   while (length)
 195   {
 196     char *write_ptr;
 197     size_t should_write;
 198     size_t buffer_end;
 199
 200     if (ptr->type == MEMCACHED_CONNECTION_UDP)
 201     {
 202       //UDP does not support partial writes
 203       buffer_end= MAX_UDP_DATAGRAM_LENGTH;
 204       should_write= length;
 205       if (ptr->write_buffer_offset + should_write > buffer_end)
 206         return -1;
 207     }
 208     else
 209     {
 210       buffer_end= MEMCACHED_MAX_BUFFER;
 211       should_write= buffer_end - ptr->write_buffer_offset;
 212       should_write= (should_write < length) ? should_write : length;
 213     }
 214
 215     write_ptr= ptr->write_buffer + ptr->write_buffer_offset;
 216     memcpy(write_ptr, buffer_ptr, should_write);
 217     ptr->write_buffer_offset+= should_write;
 218     buffer_ptr+= should_write;
 219     length-= should_write;
 220
 221     if (ptr->write_buffer_offset == buffer_end && ptr->type != MEMCACHED_CONNECTION_UDP)
 222     {
 223       memcached_return rc;
 224       ssize_t sent_length;
 225
 226       WATCHPOINT_ASSERT(ptr->fd != -1);
 227       sent_length= io_flush(ptr, &rc);
 228       if (sent_length == -1)
 229         return -1;
 230
 231       /* If io_flush calls memcached_purge, sent_length may be 0 */
 232       if (sent_length != 0)
 233         WATCHPOINT_ASSERT(sent_length == buffer_end);
 234     }
 235   }
 236
 237   if (with_flush)
 238   {
 239     memcached_return rc;
 240     WATCHPOINT_ASSERT(ptr->fd != -1);
 241     if (io_flush(ptr, &rc) == -1)
 242       return -1;
 243   }
 244
 245   return original_length;
 246 }
 247
 248 memcached_return memcached_io_close(memcached_server_st *ptr)
 249 {
 250   int r;
 251
 252   if (ptr->fd == -1)
 253     return MEMCACHED_SUCCESS;
 254
 255   /* in case of death shutdown to avoid blocking at close() */
 256   if (1)
 257   {
 258     r= shutdown(ptr->fd, SHUT_RDWR);
 259
 260 #ifdef HAVE_DEBUG
 261     if (r && errno != ENOTCONN)
 262     {
 263       WATCHPOINT_NUMBER(ptr->fd);
 264       WATCHPOINT_ERRNO(errno);
 265       WATCHPOINT_ASSERT(errno);
 266     }
 267 #endif
 268   }
 269
 270   r= close(ptr->fd);
 271 #ifdef HAVE_DEBUG
 272   if (r != 0)
 273     WATCHPOINT_ERRNO(errno);
 274 #endif
 275
 276   return MEMCACHED_SUCCESS;
 277 }
 278
 279 static ssize_t io_flush(memcached_server_st *ptr,
 280                         memcached_return *error)
 281 {
 282   /*
 283   ** We might want to purge the input buffer if we haven't consumed
 284   ** any output yet... The test for the limits is the purge is inline
 285   ** in the purge function to avoid duplicating the logic..
 286   */
 287   {
 288      memcached_return rc;
 289      WATCHPOINT_ASSERT(ptr->fd != -1);
 290      rc= memcached_purge(ptr);
 291
 292      if (rc != MEMCACHED_SUCCESS && rc != MEMCACHED_STORED)
 293        return -1;
 294   }
 295   ssize_t sent_length;
 296   size_t return_length;
 297   char *local_write_ptr= ptr->write_buffer;
 298   size_t write_length= ptr->write_buffer_offset;
 299
 300   *error= MEMCACHED_SUCCESS;
 301
 302   WATCHPOINT_ASSERT(ptr->fd != -1);
 303
 304   // UDP Sanity check, make sure that we are not sending somthing too big
 305   if (ptr->type == MEMCACHED_CONNECTION_UDP && write_length > MAX_UDP_DATAGRAM_LENGTH)
 306     return -1;
 307
 308   if (ptr->write_buffer_offset == 0 || (ptr->type == MEMCACHED_CONNECTION_UDP
 309           && ptr->write_buffer_offset == UDP_DATAGRAM_HEADER_LENGTH))
 310     return 0;
 311
 312   /* Looking for memory overflows */
 313 #if defined(HAVE_DEBUG)
 314   if (write_length == MEMCACHED_MAX_BUFFER)
 315     WATCHPOINT_ASSERT(ptr->write_buffer == local_write_ptr);
 316   WATCHPOINT_ASSERT((ptr->write_buffer + MEMCACHED_MAX_BUFFER) >= (local_write_ptr + write_length));
 317 #endif
 318
 319   return_length= 0;
 320   while (write_length)
 321   {
 322     WATCHPOINT_ASSERT(ptr->fd != -1);
 323     WATCHPOINT_ASSERT(write_length > 0);
 324     sent_length= 0;
 325     if (ptr->type == MEMCACHED_CONNECTION_UDP)
 326       increment_udp_message_id(ptr);
 327     sent_length= write(ptr->fd, local_write_ptr, write_length);
 328
 329     if (sent_length == -1)
 330     {
 331       ptr->cached_errno= errno;
 332       switch (errno)
 333       {
 334       case ENOBUFS:
 335         continue;
 336       case EAGAIN:
 337       {
 338         memcached_return rc;
 339         rc= io_wait(ptr, MEM_WRITE);
 340
 341         if (rc == MEMCACHED_SUCCESS || rc == MEMCACHED_TIMEOUT)
 342           continue;
 343
 344         memcached_quit_server(ptr, 1);
 345         return -1;
 346       }
 347       default:
 348         memcached_quit_server(ptr, 1);
 349         *error= MEMCACHED_ERRNO;
 350         return -1;
 351       }
 352     }
 353
 354     if (ptr->type == MEMCACHED_CONNECTION_UDP && sent_length != write_length)
 355     {
 356       memcached_quit_server(ptr, 1);
 357       return -1;
 358     }
 359
 360     ptr->io_bytes_sent += sent_length;
 361
 362     local_write_ptr+= sent_length;
 363     write_length-= sent_length;
 364     return_length+= sent_length;
 365   }
 366
 367   WATCHPOINT_ASSERT(write_length == 0);
 368   // Need to study this assert() WATCHPOINT_ASSERT(return_length ==
 369   // ptr->write_buffer_offset);
 370
 371   // if we are a udp server, the begining of the buffer is reserverd for
 372   // the upd frame header
 373   if (ptr->type == MEMCACHED_CONNECTION_UDP)
 374     ptr->write_buffer_offset= UDP_DATAGRAM_HEADER_LENGTH;
 375   else
 376     ptr->write_buffer_offset= 0;
 377
 378   return return_length;
 379 }
 380
 381 /*
 382   Eventually we will just kill off the server with the problem.
 383 */
 384 void memcached_io_reset(memcached_server_st *ptr)
 385 {
 386   memcached_quit_server(ptr, 1);
 387 }
 388
 389 /**
 390  * Read a given number of bytes from the server and place it into a specific
 391  * buffer. Reset the IO channel on this server if an error occurs.
 392  */
 393 memcached_return memcached_safe_read(memcached_server_st *ptr,
 394                                      void *dta,
 395                                      size_t size)
 396 {
 397   size_t offset= 0;
 398   char *data= dta;
 399
 400   while (offset < size)
 401   {
 402     ssize_t nread= memcached_io_read(ptr, data + offset, size - offset);
 403     if (nread <= 0)
 404     {
 405       memcached_io_reset(ptr);
 406       return MEMCACHED_UNKNOWN_READ_FAILURE;
 407     }
 408     offset+= nread;
 409   }
 410
 411   return MEMCACHED_SUCCESS;
 412 }
 413
 414 memcached_return memcached_io_readline(memcached_server_st *ptr,
 415                                        char *buffer_ptr,
 416                                        size_t size)
 417 {
 418   bool line_complete= false;
 419   int total_nr= 0;
 420
 421   while (!line_complete)
 422   {
 423     if (ptr->read_buffer_length == 0)
 424     {
 425       /*
 426        * We don't have any data in the buffer, so let's fill the read
 427        * buffer. Call the standard read function to avoid duplicating
 428        * the logic.
 429        */
 430       if (memcached_io_read(ptr, buffer_ptr, 1) != 1)
 431         return MEMCACHED_UNKNOWN_READ_FAILURE;
 432
 433       if (*buffer_ptr == '\n')
 434         line_complete= true;
 435
 436       ++buffer_ptr;
 437       ++total_nr;
 438     }
 439
 440     /* Now let's look in the buffer and copy as we go! */
 441     while (ptr->read_buffer_length && total_nr < size && !line_complete)
 442     {
 443       *buffer_ptr = *ptr->read_ptr;
 444       if (*buffer_ptr == '\n')
 445         line_complete = true;
 446       --ptr->read_buffer_length;
 447       ++ptr->read_ptr;
 448       ++total_nr;
 449       ++buffer_ptr;
 450     }
 451
 452     if (total_nr == size)
 453       return MEMCACHED_PROTOCOL_ERROR;
 454   }
 455
 456   return MEMCACHED_SUCCESS;
 457 }
 458
 459 /*
 460  * The udp request id consists of two seperate sections
 461  *   1) The thread id
 462  *   2) The message number
 463  * The thread id should only be set when the memcached_st struct is created
 464  * and should not be changed.
 465  *
 466  * The message num is incremented for each new message we send, this function
 467  * extracts the message number from message_id, increments it and then
 468  * writes the new value back into the header
 469  */
 470 static void increment_udp_message_id(memcached_server_st *ptr)
 471 {
 472   struct udp_datagram_header_st *header= (struct udp_datagram_header_st *)ptr->write_buffer;
 473   uint16_t cur_req= get_udp_datagram_request_id(header);
 474   uint16_t msg_num= get_msg_num_from_request_id(cur_req);
 475   uint16_t thread_id= get_thread_id_from_request_id(cur_req);
 476
 477   if (((++msg_num) & UDP_REQUEST_ID_THREAD_MASK) != 0)
 478     msg_num= 0;
 479
 480   header->request_id= htons(thread_id | msg_num);
 481 }
 482
 483 memcached_return memcached_io_init_udp_header(memcached_server_st *ptr, uint16_t thread_id)
 484 {
 485   if (thread_id > UDP_REQUEST_ID_MAX_THREAD_ID)
 486     return MEMCACHED_FAILURE;
 487
 488   struct udp_datagram_header_st *header= (struct udp_datagram_header_st *)ptr->write_buffer;
 489   header->request_id= htons(generate_udp_request_thread_id(thread_id));
 490   header->num_datagrams= htons(1);
 491   header->sequence_number= htons(0);
 492
 493   return MEMCACHED_SUCCESS;
 494 }