git.m6w6.name Git - awesomized/libmemcached/blob - libmemcached/get.cc

   1 /*  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
   2  *
   3  *  Libmemcached library
   4  *
   5  *  Copyright (C) 2011 Data Differential, http://datadifferential.com/
   6  *  Copyright (C) 2006-2009 Brian Aker All rights reserved.
   7  *
   8  *  Redistribution and use in source and binary forms, with or without
   9  *  modification, are permitted provided that the following conditions are
  10  *  met:
  11  *
  12  *      * Redistributions of source code must retain the above copyright
  13  *  notice, this list of conditions and the following disclaimer.
  14  *
  15  *      * Redistributions in binary form must reproduce the above
  16  *  copyright notice, this list of conditions and the following disclaimer
  17  *  in the documentation and/or other materials provided with the
  18  *  distribution.
  19  *
  20  *      * The names of its contributors may not be used to endorse or
  21  *  promote products derived from this software without specific prior
  22  *  written permission.
  23  *
  24  *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  25  *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  26  *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  27  *  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  28  *  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  29  *  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  30  *  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  31  *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  32  *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  33  *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  34  *  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  35  *
  36  */
  37
  38 #include <libmemcached/common.h>
  39
  40 /*
  41   What happens if no servers exist?
  42 */
  43 char *memcached_get(memcached_st *ptr, const char *key,
  44                     size_t key_length,
  45                     size_t *value_length,
  46                     uint32_t *flags,
  47                     memcached_return_t *error)
  48 {
  49   return memcached_get_by_key(ptr, NULL, 0, key, key_length, value_length,
  50                               flags, error);
  51 }
  52
  53 static memcached_return_t memcached_mget_by_key_real(memcached_st *ptr,
  54                                                      const char *group_key,
  55                                                      size_t group_key_length,
  56                                                      const char * const *keys,
  57                                                      const size_t *key_length,
  58                                                      size_t number_of_keys,
  59                                                      bool mget_mode);
  60
  61 char *memcached_get_by_key(memcached_st *ptr,
  62                            const char *group_key,
  63                            size_t group_key_length,
  64                            const char *key, size_t key_length,
  65                            size_t *value_length,
  66                            uint32_t *flags,
  67                            memcached_return_t *error)
  68 {
  69   memcached_return_t unused;
  70   if (error == NULL)
  71   {
  72     error= &unused;
  73   }
  74
  75   uint64_t query_id= 0;
  76   if (ptr)
  77   {
  78     query_id= ptr->query_id;
  79   }
  80
  81   /* Request the key */
  82   *error= memcached_mget_by_key_real(ptr, group_key, group_key_length,
  83                                      (const char * const *)&key, &key_length,
  84                                      1, false);
  85   if (ptr)
  86   {
  87     assert_msg(ptr->query_id == query_id +1, "Programmer error, the query_id was not incremented.");
  88   }
  89
  90   if (memcached_failed(*error))
  91   {
  92     if (ptr)
  93     {
  94       if (memcached_has_current_error(*ptr)) // Find the most accurate error
  95       {
  96         *error= memcached_last_error(ptr);
  97       }
  98     }
  99
 100     if (value_length)
 101     {
 102       *value_length= 0;
 103     }
 104
 105     return NULL;
 106   }
 107
 108   char *value= memcached_fetch(ptr, NULL, NULL,
 109                                value_length, flags, error);
 110   assert_msg(ptr->query_id == query_id +1, "Programmer error, the query_id was not incremented.");
 111
 112   /* This is for historical reasons */
 113   if (*error == MEMCACHED_END)
 114     *error= MEMCACHED_NOTFOUND;
 115
 116   if (value == NULL)
 117   {
 118     if (ptr->get_key_failure && *error == MEMCACHED_NOTFOUND)
 119     {
 120       memcached_result_reset(&ptr->result);
 121       memcached_return_t rc= ptr->get_key_failure(ptr, key, key_length, &ptr->result);
 122
 123       /* On all failure drop to returning NULL */
 124       if (rc == MEMCACHED_SUCCESS || rc == MEMCACHED_BUFFERED)
 125       {
 126         if (rc == MEMCACHED_BUFFERED)
 127         {
 128           uint64_t latch; /* We use latch to track the state of the original socket */
 129           latch= memcached_behavior_get(ptr, MEMCACHED_BEHAVIOR_BUFFER_REQUESTS);
 130           if (latch == 0)
 131             memcached_behavior_set(ptr, MEMCACHED_BEHAVIOR_BUFFER_REQUESTS, 1);
 132
 133           rc= memcached_set(ptr, key, key_length,
 134                             (memcached_result_value(&ptr->result)),
 135                             (memcached_result_length(&ptr->result)),
 136                             0,
 137                             (memcached_result_flags(&ptr->result)));
 138
 139           if (rc == MEMCACHED_BUFFERED && latch == 0)
 140           {
 141             memcached_behavior_set(ptr, MEMCACHED_BEHAVIOR_BUFFER_REQUESTS, 0);
 142           }
 143         }
 144         else
 145         {
 146           rc= memcached_set(ptr, key, key_length,
 147                             (memcached_result_value(&ptr->result)),
 148                             (memcached_result_length(&ptr->result)),
 149                             0,
 150                             (memcached_result_flags(&ptr->result)));
 151         }
 152
 153         if (rc == MEMCACHED_SUCCESS || rc == MEMCACHED_BUFFERED)
 154         {
 155           *error= rc;
 156           *value_length= memcached_result_length(&ptr->result);
 157           *flags= memcached_result_flags(&ptr->result);
 158           return memcached_string_take_value(&ptr->result.value);
 159         }
 160       }
 161     }
 162     assert_msg(ptr->query_id == query_id +1, "Programmer error, the query_id was not incremented.");
 163
 164     return NULL;
 165   }
 166
 167   size_t dummy_length;
 168   uint32_t dummy_flags;
 169   memcached_return_t dummy_error;
 170
 171   char *dummy_value= memcached_fetch(ptr, NULL, NULL,
 172                                      &dummy_length, &dummy_flags,
 173                                      &dummy_error);
 174   assert_msg(dummy_value == 0, "memcached_fetch() returned additional values beyond the single get it expected");
 175   assert_msg(dummy_length == 0, "memcached_fetch() returned additional values beyond the single get it expected");
 176   assert_msg(ptr->query_id == query_id +1, "Programmer error, the query_id was not incremented.");
 177
 178   return value;
 179 }
 180
 181 memcached_return_t memcached_mget(memcached_st *ptr,
 182                                   const char * const *keys,
 183                                   const size_t *key_length,
 184                                   size_t number_of_keys)
 185 {
 186   return memcached_mget_by_key(ptr, NULL, 0, keys, key_length, number_of_keys);
 187 }
 188
 189 static memcached_return_t binary_mget_by_key(memcached_st *ptr,
 190                                              uint32_t master_server_key,
 191                                              bool is_group_key_set,
 192                                              const char * const *keys,
 193                                              const size_t *key_length,
 194                                              size_t number_of_keys,
 195                                              bool mget_mode);
 196
 197 static memcached_return_t memcached_mget_by_key_real(memcached_st *ptr,
 198                                                      const char *group_key,
 199                                                      size_t group_key_length,
 200                                                      const char * const *keys,
 201                                                      const size_t *key_length,
 202                                                      size_t number_of_keys,
 203                                                      bool mget_mode)
 204 {
 205   bool failures_occured_in_sending= false;
 206   const char *get_command= "get ";
 207   uint8_t get_command_length= 4;
 208   unsigned int master_server_key= (unsigned int)-1; /* 0 is a valid server id! */
 209
 210   memcached_return_t rc;
 211   if (memcached_failed(rc= initialize_query(ptr, true)))
 212   {
 213     return rc;
 214   }
 215
 216   if (memcached_is_udp(ptr))
 217   {
 218     return memcached_set_error(*ptr, MEMCACHED_NOT_SUPPORTED, MEMCACHED_AT);
 219   }
 220
 221   LIBMEMCACHED_MEMCACHED_MGET_START();
 222
 223   if (number_of_keys == 0)
 224   {
 225     return memcached_set_error(*ptr, MEMCACHED_NOTFOUND, MEMCACHED_AT, memcached_literal_param("number_of_keys was zero"));
 226   }
 227
 228   if (memcached_failed(memcached_key_test(*ptr, keys, key_length, number_of_keys)))
 229   {
 230     return memcached_set_error(*ptr, MEMCACHED_BAD_KEY_PROVIDED, MEMCACHED_AT, memcached_literal_param("A bad key value was provided"));
 231   }
 232
 233   bool is_group_key_set= false;
 234   if (group_key and group_key_length)
 235   {
 236     if (memcached_failed(memcached_key_test(*ptr, (const char * const *)&group_key, &group_key_length, 1)))
 237     {
 238       return memcached_set_error(*ptr, MEMCACHED_BAD_KEY_PROVIDED, MEMCACHED_AT, memcached_literal_param("A bad group key was provided."));
 239     }
 240
 241     master_server_key= memcached_generate_hash_with_redistribution(ptr, group_key, group_key_length);
 242     is_group_key_set= true;
 243   }
 244
 245   /*
 246     Here is where we pay for the non-block API. We need to remove any data sitting
 247     in the queue before we start our get.
 248
 249     It might be optimum to bounce the connection if count > some number.
 250   */
 251   for (uint32_t x= 0; x < memcached_server_count(ptr); x++)
 252   {
 253     memcached_server_write_instance_st instance=
 254       memcached_server_instance_fetch(ptr, x);
 255
 256     if (memcached_server_response_count(instance))
 257     {
 258       char buffer[MEMCACHED_DEFAULT_COMMAND_SIZE];
 259
 260       if (ptr->flags.no_block)
 261       {
 262         memcached_io_write(instance);
 263       }
 264
 265       while(memcached_server_response_count(instance))
 266       {
 267         (void)memcached_response(instance, buffer, MEMCACHED_DEFAULT_COMMAND_SIZE, &ptr->result);
 268       }
 269     }
 270   }
 271
 272   if (ptr->flags.binary_protocol)
 273   {
 274     return binary_mget_by_key(ptr, master_server_key, is_group_key_set, keys,
 275                               key_length, number_of_keys, mget_mode);
 276   }
 277
 278   if (ptr->flags.support_cas)
 279   {
 280     get_command= "gets ";
 281     get_command_length= 5;
 282   }
 283
 284   /*
 285     If a server fails we warn about errors and start all over with sending keys
 286     to the server.
 287   */
 288   WATCHPOINT_ASSERT(rc == MEMCACHED_SUCCESS);
 289   size_t hosts_connected= 0;
 290   for (uint32_t x= 0; x < number_of_keys; x++)
 291   {
 292     memcached_server_write_instance_st instance;
 293     uint32_t server_key;
 294
 295     if (is_group_key_set)
 296     {
 297       server_key= master_server_key;
 298     }
 299     else
 300     {
 301       server_key= memcached_generate_hash_with_redistribution(ptr, keys[x], key_length[x]);
 302     }
 303
 304     instance= memcached_server_instance_fetch(ptr, server_key);
 305
 306     libmemcached_io_vector_st vector[]=
 307     {
 308       { get_command, get_command_length },
 309       { memcached_array_string(ptr->_namespace), memcached_array_size(ptr->_namespace) },
 310       { keys[x], key_length[x] },
 311       { memcached_literal_param(" ") }
 312     };
 313
 314
 315     if (memcached_server_response_count(instance) == 0)
 316     {
 317       rc= memcached_connect(instance);
 318
 319       if (memcached_failed(rc))
 320       {
 321         memcached_set_error(*instance, rc, MEMCACHED_AT);
 322         continue;
 323       }
 324       hosts_connected++;
 325
 326       if ((memcached_io_writev(instance, vector, 4, false)) == -1)
 327       {
 328         failures_occured_in_sending= true;
 329         continue;
 330       }
 331       WATCHPOINT_ASSERT(instance->cursor_active == 0);
 332       memcached_server_response_increment(instance);
 333       WATCHPOINT_ASSERT(instance->cursor_active == 1);
 334     }
 335     else
 336     {
 337       if ((memcached_io_writev(instance, (vector + 1), 3, false)) == -1)
 338       {
 339         memcached_server_response_reset(instance);
 340         failures_occured_in_sending= true;
 341         continue;
 342       }
 343     }
 344   }
 345
 346   if (hosts_connected == 0)
 347   {
 348     LIBMEMCACHED_MEMCACHED_MGET_END();
 349
 350     if (memcached_failed(rc))
 351     {
 352       return rc;
 353     }
 354
 355     return memcached_set_error(*ptr, MEMCACHED_NO_SERVERS, MEMCACHED_AT);
 356   }
 357
 358
 359   /*
 360     Should we muddle on if some servers are dead?
 361   */
 362   bool success_happened= false;
 363   for (uint32_t x= 0; x < memcached_server_count(ptr); x++)
 364   {
 365     memcached_server_write_instance_st instance=
 366       memcached_server_instance_fetch(ptr, x);
 367
 368     if (memcached_server_response_count(instance))
 369     {
 370       /* We need to do something about non-connnected hosts in the future */
 371       if ((memcached_io_write(instance, "\r\n", 2, true)) == -1)
 372       {
 373         failures_occured_in_sending= true;
 374       }
 375       else
 376       {
 377         success_happened= true;
 378       }
 379     }
 380   }
 381
 382   LIBMEMCACHED_MEMCACHED_MGET_END();
 383
 384   if (failures_occured_in_sending && success_happened)
 385   {
 386     return MEMCACHED_SOME_ERRORS;
 387   }
 388
 389   if (success_happened)
 390     return MEMCACHED_SUCCESS;
 391
 392   return MEMCACHED_FAILURE; // Complete failure occurred
 393 }
 394
 395 memcached_return_t memcached_mget_by_key(memcached_st *ptr,
 396                                          const char *group_key,
 397                                          size_t group_key_length,
 398                                          const char * const *keys,
 399                                          const size_t *key_length,
 400                                          size_t number_of_keys)
 401 {
 402   return memcached_mget_by_key_real(ptr, group_key, group_key_length, keys,
 403                                     key_length, number_of_keys, true);
 404 }
 405
 406 memcached_return_t memcached_mget_execute(memcached_st *ptr,
 407                                           const char * const *keys,
 408                                           const size_t *key_length,
 409                                           size_t number_of_keys,
 410                                           memcached_execute_fn *callback,
 411                                           void *context,
 412                                           unsigned int number_of_callbacks)
 413 {
 414   return memcached_mget_execute_by_key(ptr, NULL, 0, keys, key_length,
 415                                        number_of_keys, callback,
 416                                        context, number_of_callbacks);
 417 }
 418
 419 memcached_return_t memcached_mget_execute_by_key(memcached_st *ptr,
 420                                                  const char *group_key,
 421                                                  size_t group_key_length,
 422                                                  const char * const *keys,
 423                                                  const size_t *key_length,
 424                                                  size_t number_of_keys,
 425                                                  memcached_execute_fn *callback,
 426                                                  void *context,
 427                                                  unsigned int number_of_callbacks)
 428 {
 429   memcached_return_t rc;
 430   if (memcached_failed(rc= initialize_query(ptr, false)))
 431   {
 432     return rc;
 433   }
 434
 435   if (memcached_is_udp(ptr))
 436   {
 437     return memcached_set_error(*ptr, MEMCACHED_NOT_SUPPORTED, MEMCACHED_AT);
 438   }
 439
 440   if (memcached_is_binary(ptr) == false)
 441   {
 442     return MEMCACHED_NOT_SUPPORTED;
 443   }
 444
 445   memcached_callback_st *original_callbacks= ptr->callbacks;
 446   memcached_callback_st cb= {
 447     callback,
 448     context,
 449     number_of_callbacks
 450   };
 451
 452   ptr->callbacks= &cb;
 453   rc= memcached_mget_by_key(ptr, group_key, group_key_length, keys,
 454                             key_length, number_of_keys);
 455   ptr->callbacks= original_callbacks;
 456   return rc;
 457 }
 458
 459 static memcached_return_t simple_binary_mget(memcached_st *ptr,
 460                                              uint32_t master_server_key,
 461                                              bool is_group_key_set,
 462                                              const char * const *keys,
 463                                              const size_t *key_length,
 464                                              size_t number_of_keys, bool mget_mode)
 465 {
 466   memcached_return_t rc= MEMCACHED_NOTFOUND;
 467
 468   bool flush= (number_of_keys == 1);
 469
 470   /*
 471     If a server fails we warn about errors and start all over with sending keys
 472     to the server.
 473   */
 474   for (uint32_t x= 0; x < number_of_keys; ++x)
 475   {
 476     uint32_t server_key;
 477
 478     if (is_group_key_set)
 479     {
 480       server_key= master_server_key;
 481     }
 482     else
 483     {
 484       server_key= memcached_generate_hash_with_redistribution(ptr, keys[x], key_length[x]);
 485     }
 486
 487     memcached_server_write_instance_st instance= memcached_server_instance_fetch(ptr, server_key);
 488
 489     if (memcached_server_response_count(instance) == 0)
 490     {
 491       rc= memcached_connect(instance);
 492       if (memcached_failed(rc))
 493       {
 494         continue;
 495       }
 496     }
 497
 498     protocol_binary_request_getk request= { }; //= {.bytes= {0}};
 499     request.message.header.request.magic= PROTOCOL_BINARY_REQ;
 500     if (mget_mode)
 501       request.message.header.request.opcode= PROTOCOL_BINARY_CMD_GETKQ;
 502     else
 503       request.message.header.request.opcode= PROTOCOL_BINARY_CMD_GETK;
 504
 505     memcached_return_t vk;
 506     vk= memcached_validate_key_length(key_length[x],
 507                                       ptr->flags.binary_protocol);
 508     unlikely (vk != MEMCACHED_SUCCESS)
 509     {
 510       if (x > 0)
 511       {
 512         memcached_io_reset(instance);
 513       }
 514
 515       return vk;
 516     }
 517
 518     request.message.header.request.keylen= htons((uint16_t)(key_length[x] + memcached_array_size(ptr->_namespace)));
 519     request.message.header.request.datatype= PROTOCOL_BINARY_RAW_BYTES;
 520     request.message.header.request.bodylen= htonl((uint32_t)( key_length[x] + memcached_array_size(ptr->_namespace)));
 521
 522     libmemcached_io_vector_st vector[]=
 523     {
 524       { request.bytes, sizeof(request.bytes) },
 525       { memcached_array_string(ptr->_namespace), memcached_array_size(ptr->_namespace) },
 526       { keys[x], key_length[x] }
 527     };
 528
 529     if (memcached_io_writev(instance, vector, 3, flush) == -1)
 530     {
 531       memcached_server_response_reset(instance);
 532       rc= MEMCACHED_SOME_ERRORS;
 533       continue;
 534     }
 535
 536     /* We just want one pending response per server */
 537     memcached_server_response_reset(instance);
 538     memcached_server_response_increment(instance);
 539     if ((x > 0 && x == ptr->io_key_prefetch) && memcached_flush_buffers(ptr) != MEMCACHED_SUCCESS)
 540     {
 541       rc= MEMCACHED_SOME_ERRORS;
 542     }
 543   }
 544
 545   if (mget_mode)
 546   {
 547     /*
 548       Send a noop command to flush the buffers
 549     */
 550     protocol_binary_request_noop request= {}; //= {.bytes= {0}};
 551     request.message.header.request.magic= PROTOCOL_BINARY_REQ;
 552     request.message.header.request.opcode= PROTOCOL_BINARY_CMD_NOOP;
 553     request.message.header.request.datatype= PROTOCOL_BINARY_RAW_BYTES;
 554
 555     for (uint32_t x= 0; x < memcached_server_count(ptr); ++x)
 556     {
 557       memcached_server_write_instance_st instance= memcached_server_instance_fetch(ptr, x);
 558
 559       if (memcached_server_response_count(instance))
 560       {
 561         if (memcached_io_write(instance) == false)
 562         {
 563           memcached_server_response_reset(instance);
 564           memcached_io_reset(instance);
 565           rc= MEMCACHED_SOME_ERRORS;
 566         }
 567
 568         if (memcached_io_write(instance, request.bytes,
 569                                sizeof(request.bytes), true) == -1)
 570         {
 571           memcached_server_response_reset(instance);
 572           memcached_io_reset(instance);
 573           rc= MEMCACHED_SOME_ERRORS;
 574         }
 575       }
 576     }
 577   }
 578
 579
 580   return rc;
 581 }
 582
 583 static memcached_return_t replication_binary_mget(memcached_st *ptr,
 584                                                   uint32_t* hash,
 585                                                   bool* dead_servers,
 586                                                   const char *const *keys,
 587                                                   const size_t *key_length,
 588                                                   size_t number_of_keys)
 589 {
 590   memcached_return_t rc= MEMCACHED_NOTFOUND;
 591   uint32_t start= 0;
 592   uint64_t randomize_read= memcached_behavior_get(ptr, MEMCACHED_BEHAVIOR_RANDOMIZE_REPLICA_READ);
 593
 594   if (randomize_read)
 595     start= (uint32_t)random() % (uint32_t)(ptr->number_of_replicas + 1);
 596
 597   /* Loop for each replica */
 598   for (uint32_t replica= 0; replica <= ptr->number_of_replicas; ++replica)
 599   {
 600     bool success= true;
 601
 602     for (uint32_t x= 0; x < number_of_keys; ++x)
 603     {
 604       if (hash[x] == memcached_server_count(ptr))
 605         continue; /* Already successfully sent */
 606
 607       uint32_t server= hash[x] + replica;
 608
 609       /* In case of randomized reads */
 610       if (randomize_read && ((server + start) <= (hash[x] + ptr->number_of_replicas)))
 611         server += start;
 612
 613       while (server >= memcached_server_count(ptr))
 614       {
 615         server -= memcached_server_count(ptr);
 616       }
 617
 618       if (dead_servers[server])
 619       {
 620         continue;
 621       }
 622
 623       memcached_server_write_instance_st instance= memcached_server_instance_fetch(ptr, server);
 624
 625       if (memcached_server_response_count(instance) == 0)
 626       {
 627         rc= memcached_connect(instance);
 628
 629         if (memcached_failed(rc))
 630         {
 631           memcached_io_reset(instance);
 632           dead_servers[server]= true;
 633           success= false;
 634           continue;
 635         }
 636       }
 637
 638       protocol_binary_request_getk request= {};
 639       request.message.header.request.magic= PROTOCOL_BINARY_REQ;
 640       request.message.header.request.opcode= PROTOCOL_BINARY_CMD_GETK;
 641       request.message.header.request.keylen= htons((uint16_t)(key_length[x] + memcached_array_size(ptr->_namespace)));
 642       request.message.header.request.datatype= PROTOCOL_BINARY_RAW_BYTES;
 643       request.message.header.request.bodylen= htonl((uint32_t)(key_length[x] + memcached_array_size(ptr->_namespace)));
 644
 645       /*
 646        * We need to disable buffering to actually know that the request was
 647        * successfully sent to the server (so that we should expect a result
 648        * back). It would be nice to do this in buffered mode, but then it
 649        * would be complex to handle all error situations if we got to send
 650        * some of the messages, and then we failed on writing out some others
 651        * and we used the callback interface from memcached_mget_execute so
 652        * that we might have processed some of the responses etc. For now,
 653        * just make sure we work _correctly_
 654      */
 655       libmemcached_io_vector_st vector[]=
 656       {
 657         { request.bytes, sizeof(request.bytes) },
 658         { memcached_array_string(ptr->_namespace), memcached_array_size(ptr->_namespace) },
 659         { keys[x], key_length[x] }
 660       };
 661
 662       if (memcached_io_writev(instance, vector, 3, true) == -1)
 663       {
 664         memcached_io_reset(instance);
 665         dead_servers[server]= true;
 666         success= false;
 667         continue;
 668       }
 669
 670       memcached_server_response_increment(instance);
 671       hash[x]= memcached_server_count(ptr);
 672     }
 673
 674     if (success)
 675     {
 676       break;
 677     }
 678   }
 679
 680   return rc;
 681 }
 682
 683 static memcached_return_t binary_mget_by_key(memcached_st *ptr,
 684                                              uint32_t master_server_key,
 685                                              bool is_group_key_set,
 686                                              const char * const *keys,
 687                                              const size_t *key_length,
 688                                              size_t number_of_keys,
 689                                              bool mget_mode)
 690 {
 691   if (ptr->number_of_replicas == 0)
 692   {
 693     return simple_binary_mget(ptr, master_server_key, is_group_key_set,
 694                               keys, key_length, number_of_keys, mget_mode);
 695   }
 696
 697   uint32_t* hash= libmemcached_xvalloc(ptr, number_of_keys, uint32_t);
 698   bool* dead_servers= libmemcached_xcalloc(ptr, memcached_server_count(ptr), bool);
 699
 700   if (hash == NULL || dead_servers == NULL)
 701   {
 702     libmemcached_free(ptr, hash);
 703     libmemcached_free(ptr, dead_servers);
 704     return MEMCACHED_MEMORY_ALLOCATION_FAILURE;
 705   }
 706
 707   if (is_group_key_set)
 708   {
 709     for (size_t x= 0; x < number_of_keys; x++)
 710     {
 711       hash[x]= master_server_key;
 712     }
 713   }
 714   else
 715   {
 716     for (size_t x= 0; x < number_of_keys; x++)
 717     {
 718       hash[x]= memcached_generate_hash_with_redistribution(ptr, keys[x], key_length[x]);
 719     }
 720   }
 721
 722   memcached_return_t rc= replication_binary_mget(ptr, hash, dead_servers, keys,
 723                                                  key_length, number_of_keys);
 724
 725   WATCHPOINT_IFERROR(rc);
 726   libmemcached_free(ptr, hash);
 727   libmemcached_free(ptr, dead_servers);
 728
 729   return MEMCACHED_SUCCESS;
 730 }