X-Git-Url: https://git.m6w6.name/?a=blobdiff_plain;f=libmemcached%2Fio.cc;h=e246f3ec50d4165eb812e25829bff1b24055c3c1;hb=7fc1ce1d52601c1ba1d8e7ff0035a7243eaf14c3;hp=8b297a7acaed71215d0c9624f632f91c4909bf7f;hpb=387c65c94bec4333da574771fc82a40deabbc3e2;p=awesomized%2Flibmemcached

diff --git a/libmemcached/io.cc b/libmemcached/io.cc
index 8b297a7a..e246f3ec 100644
--- a/libmemcached/io.cc
+++ b/libmemcached/io.cc
@@ -39,6 +39,17 @@
 
 #include <libmemcached/common.h>
 
+#ifdef HAVE_SYS_SOCKET_H
+# include <sys/socket.h>
+#endif
+
+void initialize_binary_request(memcached_instance_st* server, protocol_binary_request_header& header)
+{
+  server->request_id++;
+  header.request.magic= PROTOCOL_BINARY_REQ;
+  header.request.opaque= htons(server->request_id);
+}
+
 enum memc_read_or_write {
   MEM_READ,
   MEM_WRITE
@@ -48,70 +59,68 @@ enum memc_read_or_write {
  * Try to fill the input buffer for a server with as much
  * data as possible.
  *
- * @param ptr the server to pack
+ * @param instance the server to pack
  */
-static bool repack_input_buffer(memcached_server_write_instance_st ptr)
+static bool repack_input_buffer(memcached_instance_st* instance)
 {
-  if (ptr->read_ptr != ptr->read_buffer)
+  if (instance->read_ptr != instance->read_buffer)
   {
     /* Move all of the data to the beginning of the buffer so
      ** that we can fit more data into the buffer...
    */
-    memmove(ptr->read_buffer, ptr->read_ptr, ptr->read_buffer_length);
-    ptr->read_ptr= ptr->read_buffer;
-    ptr->read_data_length= ptr->read_buffer_length;
+    memmove(instance->read_buffer, instance->read_ptr, instance->read_buffer_length);
+    instance->read_ptr= instance->read_buffer;
+    instance->read_data_length= instance->read_buffer_length;
   }
 
   /* There is room in the buffer, try to fill it! */
-  if (ptr->read_buffer_length != MEMCACHED_MAX_BUFFER)
+  if (instance->read_buffer_length != MEMCACHED_MAX_BUFFER)
   {
     do {
       /* Just try a single read to grab what's available */
-      ssize_t nr= recv(ptr->fd,
-                       ptr->read_ptr + ptr->read_data_length,
-                       MEMCACHED_MAX_BUFFER - ptr->read_data_length,
-                       MSG_DONTWAIT);
-
-      switch (nr)
+      ssize_t nr;
+      if ((nr= ::recv(instance->fd,
+                      instance->read_ptr + instance->read_data_length,
+                      MEMCACHED_MAX_BUFFER - instance->read_data_length,
+                      MSG_NOSIGNAL)) <= 0)
       {
-      case SOCKET_ERROR:
+        if (nr == 0)
+        {
+          memcached_set_error(*instance, MEMCACHED_CONNECTION_FAILURE, MEMCACHED_AT);
+        }
+        else
         {
           switch (get_socket_errno())
           {
           case EINTR:
             continue;
 
+#if EWOULDBLOCK != EAGAIN
           case EWOULDBLOCK:
-#ifdef USE_EAGAIN
-          case EAGAIN:
 #endif
-#ifdef TARGET_OS_LINUX
+          case EAGAIN:
+#ifdef __linux
           case ERESTART:
 #endif
             break; // No IO is fine, we can just move on
 
           default:
-            memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
+            memcached_set_errno(*instance, get_socket_errno(), MEMCACHED_AT);
           }
         }
-        break;
 
-      case 0: // Shutdown on the socket has occurred
-        {
-          memcached_set_error(*ptr, MEMCACHED_CONNECTION_FAILURE, MEMCACHED_AT);
-        }
         break;
+      }
+      else // We read data, append to our read buffer
+      {
+        instance->read_data_length+= size_t(nr);
+        instance->read_buffer_length+= size_t(nr);
 
-      default:
-        {
-          ptr->read_data_length+= size_t(nr);
-          ptr->read_buffer_length+= size_t(nr);
-          return true;
-        }
-        break;
+        return true;
       }
-    } while (0);
+    } while (false);
   }
+
   return false;
 }
 
@@ -122,28 +131,28 @@ static bool repack_input_buffer(memcached_server_write_instance_st ptr)
  * when the input buffer is full, so that we _know_ that we have
  * at least _one_ message to process.
  *
- * @param ptr the server to star processing iput messages for
+ * @param instance the server to star processing iput messages for
  * @return true if we processed anything, false otherwise
  */
-static bool process_input_buffer(memcached_server_write_instance_st ptr)
+static bool process_input_buffer(memcached_instance_st* instance)
 {
   /*
    ** We might be able to process some of the response messages if we
    ** have a callback set up
  */
-  if (ptr->root->callbacks != NULL)
+  if (instance->root->callbacks != NULL)
   {
     /*
      * We might have responses... try to read them out and fire
      * callbacks
    */
-    memcached_callback_st cb= *ptr->root->callbacks;
+    memcached_callback_st cb= *instance->root->callbacks;
 
-    memcached_set_processing_input((memcached_st *)ptr->root, true);
+    memcached_set_processing_input((Memcached *)instance->root, true);
 
     char buffer[MEMCACHED_DEFAULT_COMMAND_SIZE];
-    memcached_st *root= (memcached_st *)ptr->root;
-    memcached_return_t error= memcached_response(ptr, buffer, sizeof(buffer), &root->result);
+    Memcached *root= (Memcached *)instance->root;
+    memcached_return_t error= memcached_response(instance, buffer, sizeof(buffer), &root->result);
 
     memcached_set_processing_input(root, false);
 
@@ -151,9 +160,11 @@ static bool process_input_buffer(memcached_server_write_instance_st ptr)
     {
       for (unsigned int x= 0; x < cb.number_of_callback; x++)
       {
-        error= (*cb.callback[x])(ptr->root, &root->result, cb.context);
+        error= (*cb.callback[x])(instance->root, &root->result, cb.context);
         if (error != MEMCACHED_SUCCESS)
+        {
           break;
+        }
       }
 
       /* @todo what should I do with the error message??? */
@@ -165,23 +176,9 @@ static bool process_input_buffer(memcached_server_write_instance_st ptr)
   return false;
 }
 
-static memcached_return_t io_wait(memcached_server_write_instance_st ptr,
-                                  const memc_read_or_write read_or_write)
+static memcached_return_t io_wait(memcached_instance_st* instance,
+                                  const short events)
 {
-  struct pollfd fds;
-  fds.fd= ptr->fd;
-  fds.events= POLLIN;
-
-  if (read_or_write == MEM_WRITE) /* write */
-  {
-    fds.events= POLLOUT;
-    WATCHPOINT_SET(ptr->io_wait_count.write++);
-  }
-  else
-  {
-    WATCHPOINT_SET(ptr->io_wait_count.read++);
-  }
-
   /*
    ** We are going to block on write, but at least on Solaris we might block
    ** on write if we haven't read anything from our input buffer..
@@ -190,85 +187,117 @@ static memcached_return_t io_wait(memcached_server_write_instance_st ptr,
    ** The test is moved down in the purge function to avoid duplication of
    ** the test.
  */
-  if (read_or_write == MEM_WRITE)
+  if (events & POLLOUT)
   {
-    memcached_return_t rc= memcached_purge(ptr);
-    if (rc != MEMCACHED_SUCCESS && rc != MEMCACHED_STORED)
+    if (memcached_purge(instance) == false)
     {
       return MEMCACHED_FAILURE;
     }
   }
 
-  if (ptr->root->poll_timeout == 0) // Mimic 0 causes timeout behavior (not all platforms do this)
+  struct pollfd fds;
+  fds.fd= instance->fd;
+  fds.events= events;
+  fds.revents= 0;
+
+  if (fds.events & POLLOUT) /* write */
+  {
+    instance->io_wait_count.write++;
+  }
+  else
   {
-    return memcached_set_error(*ptr, MEMCACHED_TIMEOUT, MEMCACHED_AT);
+    instance->io_wait_count.read++;
+  }
+
+  if (instance->root->poll_timeout == 0) // Mimic 0 causes timeout behavior (not all platforms do this)
+  {
+    return memcached_set_error(*instance, MEMCACHED_TIMEOUT, MEMCACHED_AT, memcached_literal_param("poll_timeout() was set to zero"));
   }
 
   size_t loop_max= 5;
   while (--loop_max) // While loop is for ERESTART or EINTR
   {
+    int active_fd= poll(&fds, 1, instance->root->poll_timeout);
 
-    int error= poll(&fds, 1, ptr->root->poll_timeout);
-    switch (error)
+    if (active_fd >= 1)
     {
-    case 1: // Success!
-      WATCHPOINT_IF_LABELED_NUMBER(read_or_write && loop_max < 4, "read() times we had to loop, decremented down from 5", loop_max);
-      WATCHPOINT_IF_LABELED_NUMBER(!read_or_write && loop_max < 4, "write() times we had to loop, decremented down from 5", loop_max);
-
-      return MEMCACHED_SUCCESS;
-
-    case 0: // Timeout occured, we let the while() loop do its thing.
-      return memcached_set_error(*ptr, MEMCACHED_TIMEOUT, MEMCACHED_AT);
-
-    default:
-      WATCHPOINT_ERRNO(get_socket_errno());
-      switch (get_socket_errno())
+      assert_msg(active_fd == 1 , "poll() returned an unexpected number of active file descriptors");
+      if (fds.revents & POLLIN or fds.revents & POLLOUT)
       {
-#ifdef TARGET_OS_LINUX
-      case ERESTART:
-#endif
-      case EINTR:
-        break;
-
-      case EFAULT:
-      case ENOMEM:
-        return memcached_set_error(*ptr, MEMCACHED_MEMORY_ALLOCATION_FAILURE, MEMCACHED_AT);
+        return MEMCACHED_SUCCESS;
+      }
 
-      case EINVAL:
-        return memcached_set_error(*ptr, MEMCACHED_MEMORY_ALLOCATION_FAILURE, MEMCACHED_AT, memcached_literal_param("RLIMIT_NOFILE exceeded, or if OSX the timeout value was invalid"));
+      if (fds.revents & POLLHUP)
+      {
+        return memcached_set_error(*instance, MEMCACHED_CONNECTION_FAILURE, MEMCACHED_AT, 
+                                   memcached_literal_param("poll() detected hang up"));
+      }
 
-      default:
-        if (fds.revents & POLLERR)
+      if (fds.revents & POLLERR)
+      {
+        int local_errno= EINVAL;
+        int err;
+        socklen_t len= sizeof (err);
+        if (getsockopt(instance->fd, SOL_SOCKET, SO_ERROR, (char*)&err, &len) == 0)
         {
-          int err;
-          socklen_t len= sizeof (err);
-          if (getsockopt(ptr->fd, SOL_SOCKET, SO_ERROR, &err, &len) == 0)
+          if (err == 0) // treat this as EINTR
           {
-            if (err == 0)
-            {
-              continue;
-            }
-            errno= err;
+            continue;
           }
+          local_errno= err;
         }
-        else
-        {
-          memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
-        }
-        int local_errno= get_socket_errno(); // We cache in case memcached_quit_server() modifies errno
-        memcached_quit_server(ptr, true);
-
-        return memcached_set_errno(*ptr, local_errno, MEMCACHED_AT);
+        memcached_quit_server(instance, true);
+        return memcached_set_errno(*instance, local_errno, MEMCACHED_AT,
+                                   memcached_literal_param("poll() returned POLLHUP"));
       }
+      
+      return memcached_set_error(*instance, MEMCACHED_FAILURE, MEMCACHED_AT, memcached_literal_param("poll() returned a value that was not dealt with"));
+    }
+
+    if (active_fd == 0)
+    {
+      return memcached_set_error(*instance, MEMCACHED_TIMEOUT, MEMCACHED_AT, memcached_literal_param("No active_fd were found"));
     }
+
+    // Only an error should result in this code being called.
+    int local_errno= get_socket_errno(); // We cache in case memcached_quit_server() modifies errno
+    assert_msg(active_fd == -1 , "poll() returned an unexpected value");
+    switch (local_errno)
+    {
+#ifdef __linux
+    case ERESTART:
+#endif
+    case EINTR:
+      continue;
+
+    case EFAULT:
+    case ENOMEM:
+      memcached_set_error(*instance, MEMCACHED_MEMORY_ALLOCATION_FAILURE, MEMCACHED_AT);
+      break;
+
+    case EINVAL:
+      memcached_set_error(*instance, MEMCACHED_MEMORY_ALLOCATION_FAILURE, MEMCACHED_AT, memcached_literal_param("RLIMIT_NOFILE exceeded, or if OSX the timeout value was invalid"));
+      break;
+
+    default:
+      memcached_set_errno(*instance, local_errno, MEMCACHED_AT, memcached_literal_param("poll"));
+    }
+
+    break;
   }
 
-  memcached_quit_server(ptr, true);
+  memcached_quit_server(instance, true);
+
+  if (memcached_has_error(instance))
+  {
+    return memcached_instance_error_return(instance);
+  }
 
-  return memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
+  return memcached_set_error(*instance, MEMCACHED_CONNECTION_FAILURE, MEMCACHED_AT, 
+                             memcached_literal_param("number of attempts to call io_wait() failed"));
 }
 
-static bool io_flush(memcached_server_write_instance_st ptr,
+static bool io_flush(memcached_instance_st* instance,
                      const bool with_flush,
                      memcached_return_t& error)
 {
@@ -278,45 +307,45 @@ static bool io_flush(memcached_server_write_instance_st ptr,
    ** in the purge function to avoid duplicating the logic..
  */
   {
-    memcached_return_t rc;
-    WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
-    rc= memcached_purge(ptr);
+    WATCHPOINT_ASSERT(instance->fd != INVALID_SOCKET);
 
-    if (rc != MEMCACHED_SUCCESS && rc != MEMCACHED_STORED)
+    if (memcached_purge(instance) == false)
     {
       return false;
     }
   }
-  char *local_write_ptr= ptr->write_buffer;
-  size_t write_length= ptr->write_buffer_offset;
+  char *local_write_ptr= instance->write_buffer;
+  size_t write_length= instance->write_buffer_offset;
 
   error= MEMCACHED_SUCCESS;
 
-  WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
+  WATCHPOINT_ASSERT(instance->fd != INVALID_SOCKET);
 
   /* Looking for memory overflows */
 #if defined(DEBUG)
   if (write_length == MEMCACHED_MAX_BUFFER)
-    WATCHPOINT_ASSERT(ptr->write_buffer == local_write_ptr);
-  WATCHPOINT_ASSERT((ptr->write_buffer + MEMCACHED_MAX_BUFFER) >= (local_write_ptr + write_length));
+    WATCHPOINT_ASSERT(instance->write_buffer == local_write_ptr);
+  WATCHPOINT_ASSERT((instance->write_buffer + MEMCACHED_MAX_BUFFER) >= (local_write_ptr + write_length));
 #endif
 
   while (write_length)
   {
-    WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
+    WATCHPOINT_ASSERT(instance->fd != INVALID_SOCKET);
     WATCHPOINT_ASSERT(write_length > 0);
 
-    ssize_t sent_length= 0;
-    WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
+    int flags;
     if (with_flush)
     {
-      sent_length= ::send(ptr->fd, local_write_ptr, write_length, MSG_NOSIGNAL|MSG_DONTWAIT);
+      flags= MSG_NOSIGNAL;
     }
     else
     {
-      sent_length= ::send(ptr->fd, local_write_ptr, write_length, MSG_NOSIGNAL|MSG_DONTWAIT|MSG_MORE);
+      flags= MSG_NOSIGNAL|MSG_MORE;
     }
 
+    ssize_t sent_length= ::send(instance->fd, local_write_ptr, write_length, flags);
+    int local_errno= get_socket_errno(); // We cache in case memcached_quit_server() modifies errno
+
     if (sent_length == SOCKET_ERROR)
     {
 #if 0 // @todo I should look at why we hit this bit of code hard frequently
@@ -327,10 +356,11 @@ static bool io_flush(memcached_server_write_instance_st ptr,
       {
       case ENOBUFS:
         continue;
+
+#if EWOULDBLOCK != EAGAIN
       case EWOULDBLOCK:
-#ifdef USE_EAGAIN
-      case EAGAIN:
 #endif
+      case EAGAIN:
         {
           /*
            * We may be blocked on write because the input buffer
@@ -338,158 +368,178 @@ static bool io_flush(memcached_server_write_instance_st ptr,
            * buffer for more data and retry the write before
            * waiting..
          */
-          if (repack_input_buffer(ptr) or process_input_buffer(ptr))
+          if (repack_input_buffer(instance) or process_input_buffer(instance))
           {
             continue;
           }
 
-          memcached_return_t rc= io_wait(ptr, MEM_WRITE);
+          memcached_return_t rc= io_wait(instance, POLLOUT);
           if (memcached_success(rc))
           {
             continue;
           }
           else if (rc == MEMCACHED_TIMEOUT)
           {
-            error= memcached_set_error(*ptr, MEMCACHED_TIMEOUT, MEMCACHED_AT);
             return false;
           }
 
-          memcached_quit_server(ptr, true);
-          error= memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
+          memcached_quit_server(instance, true);
+          error= memcached_set_errno(*instance, local_errno, MEMCACHED_AT);
           return false;
         }
       case ENOTCONN:
       case EPIPE:
       default:
-        memcached_quit_server(ptr, true);
-        error= memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
-        WATCHPOINT_ASSERT(ptr->fd == INVALID_SOCKET);
+        memcached_quit_server(instance, true);
+        error= memcached_set_errno(*instance, local_errno, MEMCACHED_AT);
+        WATCHPOINT_ASSERT(instance->fd == INVALID_SOCKET);
         return false;
       }
     }
 
-    ptr->io_bytes_sent+= uint32_t(sent_length);
+    instance->io_bytes_sent+= uint32_t(sent_length);
 
     local_write_ptr+= sent_length;
     write_length-= uint32_t(sent_length);
   }
 
   WATCHPOINT_ASSERT(write_length == 0);
-  ptr->write_buffer_offset= 0;
+  instance->write_buffer_offset= 0;
 
   return true;
 }
 
-memcached_return_t memcached_io_wait_for_write(memcached_server_write_instance_st ptr)
+memcached_return_t memcached_io_wait_for_write(memcached_instance_st* instance)
+{
+  return io_wait(instance, POLLOUT);
+}
+
+memcached_return_t memcached_io_wait_for_read(memcached_instance_st* instance)
 {
-  return io_wait(ptr, MEM_WRITE);
+  return io_wait(instance, POLLIN);
 }
 
-memcached_return_t memcached_io_read(memcached_server_write_instance_st ptr,
+static memcached_return_t _io_fill(memcached_instance_st* instance)
+{
+  ssize_t data_read;
+  do
+  {
+    data_read= ::recv(instance->fd, instance->read_buffer, MEMCACHED_MAX_BUFFER, MSG_NOSIGNAL);
+    int local_errno= get_socket_errno(); // We cache in case memcached_quit_server() modifies errno
+
+    if (data_read == SOCKET_ERROR)
+    {
+      switch (get_socket_errno())
+      {
+      case EINTR: // We just retry
+        continue;
+
+      case ETIMEDOUT: // OSX
+#if EWOULDBLOCK != EAGAIN
+      case EWOULDBLOCK:
+#endif
+      case EAGAIN:
+#ifdef __linux
+      case ERESTART:
+#endif
+        {
+          memcached_return_t io_wait_ret;
+          if (memcached_success(io_wait_ret= io_wait(instance, POLLIN)))
+          {
+            continue;
+          }
+
+          return io_wait_ret;
+        }
+
+        /* fall through */
+
+      case ENOTCONN: // Programmer Error
+        WATCHPOINT_ASSERT(0);
+      case ENOTSOCK:
+        WATCHPOINT_ASSERT(0);
+      case EBADF:
+        assert_msg(instance->fd != INVALID_SOCKET, "Programmer error, invalid socket");
+        /* fall through */
+      case EINVAL:
+      case EFAULT:
+      case ECONNREFUSED:
+      default:
+        memcached_quit_server(instance, true);
+        memcached_set_errno(*instance, local_errno, MEMCACHED_AT);
+        break;
+      }
+
+      return memcached_instance_error_return(instance);
+    }
+    else if (data_read == 0)
+    {
+      /*
+        EOF. Any data received so far is incomplete
+        so discard it. This always reads by byte in case of TCP
+        and protocol enforcement happens at memcached_response()
+        looking for '\n'. We do not care for UDB which requests 8 bytes
+        at once. Generally, this means that connection went away. Since
+        for blocking I/O we do not return 0 and for non-blocking case
+        it will return EGAIN if data is not immediatly available.
+      */
+      memcached_quit_server(instance, true);
+      return memcached_set_error(*instance, MEMCACHED_CONNECTION_FAILURE, MEMCACHED_AT, 
+                                 memcached_literal_param("::rec() returned zero, server has disconnected"));
+    }
+    instance->io_wait_count._bytes_read+= data_read;
+  } while (data_read <= 0);
+
+  instance->io_bytes_sent= 0;
+  instance->read_data_length= (size_t) data_read;
+  instance->read_buffer_length= (size_t) data_read;
+  instance->read_ptr= instance->read_buffer;
+
+  return MEMCACHED_SUCCESS;
+}
+
+memcached_return_t memcached_io_read(memcached_instance_st* instance,
                                      void *buffer, size_t length, ssize_t& nread)
 {
-  assert(memcached_is_udp(ptr->root) == false);
-  assert_msg(ptr, "Programmer error, memcached_io_read() recieved an invalid memcached_server_write_instance_st"); // Programmer error
+  assert(memcached_is_udp(instance->root) == false);
+  assert_msg(instance, "Programmer error, memcached_io_read() recieved an invalid Instance"); // Programmer error
   char *buffer_ptr= static_cast<char *>(buffer);
 
-  if (ptr->fd == INVALID_SOCKET)
+  if (instance->fd == INVALID_SOCKET)
   {
 #if 0
-    assert_msg(int(ptr->state) <= int(MEMCACHED_SERVER_STATE_ADDRINFO), "Programmer error, invalid socket state");
+    assert_msg(int(instance->state) <= int(MEMCACHED_SERVER_STATE_ADDRINFO), "Programmer error, invalid socket state");
 #endif
     return MEMCACHED_CONNECTION_FAILURE;
   }
 
   while (length)
   {
-    if (not ptr->read_buffer_length)
+    if (instance->read_buffer_length == 0)
     {
-      ssize_t data_read;
-      do
+      memcached_return_t io_fill_ret;
+      if (memcached_fatal(io_fill_ret= _io_fill(instance)))
       {
-        data_read= ::recv(ptr->fd, ptr->read_buffer, MEMCACHED_MAX_BUFFER, MSG_DONTWAIT);
-        if (data_read == SOCKET_ERROR)
-        {
-          switch (get_socket_errno())
-          {
-          case EINTR: // We just retry
-            continue;
-
-          case ETIMEDOUT: // OSX
-          case EWOULDBLOCK:
-#ifdef USE_EAGAIN
-          case EAGAIN:
-#endif
-#ifdef TARGET_OS_LINUX
-          case ERESTART:
-#endif
-            if (memcached_success(io_wait(ptr, MEM_READ)))
-            {
-              continue;
-            }
-            return MEMCACHED_IN_PROGRESS;
-
-            /* fall through */
-
-          case ENOTCONN: // Programmer Error
-            WATCHPOINT_ASSERT(0);
-          case ENOTSOCK:
-            WATCHPOINT_ASSERT(0);
-          case EBADF:
-            assert_msg(ptr->fd != INVALID_SOCKET, "Programmer error, invalid socket");
-          case EINVAL:
-          case EFAULT:
-          case ECONNREFUSED:
-          default:
-            {
-              memcached_quit_server(ptr, true);
-              nread= -1;
-              return memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
-            }
-          }
-        }
-        else if (data_read == 0)
-        {
-          /*
-            EOF. Any data received so far is incomplete
-            so discard it. This always reads by byte in case of TCP
-            and protocol enforcement happens at memcached_response()
-            looking for '\n'. We do not care for UDB which requests 8 bytes
-            at once. Generally, this means that connection went away. Since
-            for blocking I/O we do not return 0 and for non-blocking case
-            it will return EGAIN if data is not immediatly available.
-          */
-          WATCHPOINT_STRING("We had a zero length recv()");
-          memcached_quit_server(ptr, true);
-          nread= -1;
-          return memcached_set_error(*ptr, MEMCACHED_CONNECTION_FAILURE, MEMCACHED_AT, 
-                                     memcached_literal_param("::rec() returned zero, server has disconnected"));
-        }
-      } while (data_read <= 0);
-
-      ptr->io_bytes_sent = 0;
-      ptr->read_data_length= (size_t) data_read;
-      ptr->read_buffer_length= (size_t) data_read;
-      ptr->read_ptr= ptr->read_buffer;
+        nread= -1;
+        return io_fill_ret;
+      }
     }
 
     if (length > 1)
     {
-      size_t difference;
-
-      difference= (length > ptr->read_buffer_length) ? ptr->read_buffer_length : length;
+      size_t difference= (length > instance->read_buffer_length) ? instance->read_buffer_length : length;
 
-      memcpy(buffer_ptr, ptr->read_ptr, difference);
+      memcpy(buffer_ptr, instance->read_ptr, difference);
       length -= difference;
-      ptr->read_ptr+= difference;
-      ptr->read_buffer_length-= difference;
+      instance->read_ptr+= difference;
+      instance->read_buffer_length-= difference;
       buffer_ptr+= difference;
     }
     else
     {
-      *buffer_ptr= *ptr->read_ptr;
-      ptr->read_ptr++;
-      ptr->read_buffer_length--;
+      *buffer_ptr= *instance->read_ptr;
+      instance->read_ptr++;
+      instance->read_buffer_length--;
       buffer_ptr++;
       break;
     }
@@ -500,14 +550,14 @@ memcached_return_t memcached_io_read(memcached_server_write_instance_st ptr,
   return MEMCACHED_SUCCESS;
 }
 
-memcached_return_t memcached_io_slurp(memcached_server_write_instance_st ptr)
+memcached_return_t memcached_io_slurp(memcached_instance_st* instance)
 {
-  assert_msg(ptr, "Programmer error, invalid memcached_server_write_instance_st");
-  assert(memcached_is_udp(ptr->root) == false);
+  assert_msg(instance, "Programmer error, invalid Instance");
+  assert(memcached_is_udp(instance->root) == false);
 
-  if (ptr->fd == INVALID_SOCKET)
+  if (instance->fd == INVALID_SOCKET)
   {
-    assert_msg(int(ptr->state) <= int(MEMCACHED_SERVER_STATE_ADDRINFO), "Invalid socket state");
+    assert_msg(int(instance->state) <= int(MEMCACHED_SERVER_STATE_ADDRINFO), "Invalid socket state");
     return MEMCACHED_CONNECTION_FAILURE;
   }
 
@@ -515,7 +565,7 @@ memcached_return_t memcached_io_slurp(memcached_server_write_instance_st ptr)
   char buffer[MEMCACHED_MAX_BUFFER];
   do
   {
-    data_read= recv(ptr->fd, ptr->read_buffer, sizeof(buffer), MSG_DONTWAIT);
+    data_read= ::recv(instance->fd, instance->read_buffer, sizeof(buffer), MSG_NOSIGNAL);
     if (data_read == SOCKET_ERROR)
     {
       switch (get_socket_errno())
@@ -524,14 +574,14 @@ memcached_return_t memcached_io_slurp(memcached_server_write_instance_st ptr)
         continue;
 
       case ETIMEDOUT: // OSX
+#if EWOULDBLOCK != EAGAIN
       case EWOULDBLOCK:
-#ifdef USE_EAGAIN
-      case EAGAIN:
 #endif
-#ifdef TARGET_OS_LINUX
+      case EAGAIN:
+#ifdef __linux
       case ERESTART:
 #endif
-        if (memcached_success(io_wait(ptr, MEM_READ)))
+        if (memcached_success(io_wait(instance, POLLIN)))
         {
           continue;
         }
@@ -540,11 +590,12 @@ memcached_return_t memcached_io_slurp(memcached_server_write_instance_st ptr)
         /* fall through */
 
       case ENOTCONN: // Programmer Error
-        WATCHPOINT_ASSERT(0);
+        assert(0);
       case ENOTSOCK:
-        WATCHPOINT_ASSERT(0);
+        assert(0);
       case EBADF:
-        assert_msg(ptr->fd != INVALID_SOCKET, "Invalid socket state");
+        assert_msg(instance->fd != INVALID_SOCKET, "Invalid socket state");
+        /* fall through */
       case EINVAL:
       case EFAULT:
       case ECONNREFUSED:
@@ -557,36 +608,39 @@ memcached_return_t memcached_io_slurp(memcached_server_write_instance_st ptr)
   return MEMCACHED_CONNECTION_FAILURE;
 }
 
-static ssize_t _io_write(memcached_server_write_instance_st ptr,
-                         const void *buffer, size_t length, bool with_flush)
+static bool _io_write(memcached_instance_st* instance,
+                      const void *buffer, size_t length, bool with_flush,
+                      size_t& written)
 {
-  WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
-  assert(memcached_is_udp(ptr->root) == false);
+  assert(instance->fd != INVALID_SOCKET);
+  assert(memcached_is_udp(instance->root) == false);
 
-  size_t original_length= length;
   const char *buffer_ptr= static_cast<const char *>(buffer);
 
+  const size_t original_length= length;
+
   while (length)
   {
     char *write_ptr;
     size_t buffer_end= MEMCACHED_MAX_BUFFER;
-    size_t should_write= buffer_end -ptr->write_buffer_offset;
+    size_t should_write= buffer_end -instance->write_buffer_offset;
     should_write= (should_write < length) ? should_write : length;
 
-    write_ptr= ptr->write_buffer + ptr->write_buffer_offset;
+    write_ptr= instance->write_buffer + instance->write_buffer_offset;
     memcpy(write_ptr, buffer_ptr, should_write);
-    ptr->write_buffer_offset+= should_write;
+    instance->write_buffer_offset+= should_write;
     buffer_ptr+= should_write;
     length-= should_write;
 
-    if (ptr->write_buffer_offset == buffer_end)
+    if (instance->write_buffer_offset == buffer_end)
     {
-      WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
+      WATCHPOINT_ASSERT(instance->fd != INVALID_SOCKET);
 
       memcached_return_t rc;
-      if (io_flush(ptr, with_flush, rc) == false)
+      if (io_flush(instance, with_flush, rc) == false)
       {
-        return -1;
+        written= original_length -length;
+        return false;
       }
     }
   }
@@ -594,102 +648,144 @@ static ssize_t _io_write(memcached_server_write_instance_st ptr,
   if (with_flush)
   {
     memcached_return_t rc;
-    WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
-    if (io_flush(ptr, with_flush, rc) == false)
+    WATCHPOINT_ASSERT(instance->fd != INVALID_SOCKET);
+    if (io_flush(instance, with_flush, rc) == false)
     {
-      return -1;
+      written= original_length -length;
+      return false;
     }
   }
 
-  return (ssize_t) original_length;
+  written= original_length -length;
+
+  return true;
 }
 
-bool memcached_io_write(memcached_server_write_instance_st ptr)
+bool memcached_io_write(memcached_instance_st* instance)
 {
-  return (_io_write(ptr, NULL, 0, true) >= 0);
+  size_t written;
+  return _io_write(instance, NULL, 0, true, written);
 }
 
-ssize_t memcached_io_write(memcached_server_write_instance_st ptr,
+ssize_t memcached_io_write(memcached_instance_st* instance,
                            const void *buffer, const size_t length, const bool with_flush)
 {
-  return _io_write(ptr, buffer, length, with_flush);
+  size_t written;
+
+  if (_io_write(instance, buffer, length, with_flush, written) == false)
+  {
+    return -1;
+  }
+
+  return ssize_t(written);
 }
 
-ssize_t memcached_io_writev(memcached_server_write_instance_st ptr,
-                            libmemcached_io_vector_st vector[],
-                            const size_t number_of, const bool with_flush)
+bool memcached_io_writev(memcached_instance_st* instance,
+                         libmemcached_io_vector_st vector[],
+                         const size_t number_of, const bool with_flush)
 {
+  ssize_t complete_total= 0;
   ssize_t total= 0;
 
   for (size_t x= 0; x < number_of; x++, vector++)
   {
-    ssize_t returnable;
-
+    complete_total+= vector->length;
     if (vector->length)
     {
-      if ((returnable= _io_write(ptr, vector->buffer, vector->length, false)) == -1)
+      size_t written;
+      if ((_io_write(instance, vector->buffer, vector->length, false, written)) == false)
       {
-        return -1;
+        return false;
       }
-      total+= returnable;
+      total+= written;
     }
   }
 
   if (with_flush)
   {
-    if (memcached_io_write(ptr) == false)
+    if (memcached_io_write(instance) == false)
     {
-      return -1;
+      return false;
     }
   }
 
-  return total;
+  return (complete_total == total);
 }
 
-
-void memcached_io_close(memcached_server_write_instance_st ptr)
+void memcached_instance_st::start_close_socket()
 {
-  if (ptr->fd == INVALID_SOCKET)
+  if (fd != INVALID_SOCKET)
   {
-    return;
+    shutdown(fd, SHUT_WR);
+    options.is_shutting_down= true;
   }
+}
 
-  /* in case of death shutdown to avoid blocking at close() */
-  if (shutdown(ptr->fd, SHUT_RDWR) == SOCKET_ERROR && get_socket_errno() != ENOTCONN)
+void memcached_instance_st::reset_socket()
+{
+  if (fd != INVALID_SOCKET)
   {
-    WATCHPOINT_NUMBER(ptr->fd);
-    WATCHPOINT_ERRNO(get_socket_errno());
-    WATCHPOINT_ASSERT(get_socket_errno());
+    (void)closesocket(fd);
+    fd= INVALID_SOCKET;
   }
+}
 
-  if (closesocket(ptr->fd) == SOCKET_ERROR)
+void memcached_instance_st::close_socket()
+{
+  if (fd != INVALID_SOCKET)
   {
-    WATCHPOINT_ERRNO(get_socket_errno());
+    int shutdown_options= SHUT_RD;
+    if (options.is_shutting_down == false)
+    {
+      shutdown_options= SHUT_RDWR;
+    }
+
+    /* in case of death shutdown to avoid blocking at close() */
+    if (shutdown(fd, shutdown_options) == SOCKET_ERROR and get_socket_errno() != ENOTCONN)
+    {
+      WATCHPOINT_NUMBER(fd);
+      WATCHPOINT_ERRNO(get_socket_errno());
+      WATCHPOINT_ASSERT(get_socket_errno());
+    }
+
+    reset_socket();
+    state= MEMCACHED_SERVER_STATE_NEW;
   }
-  ptr->state= MEMCACHED_SERVER_STATE_NEW;
-  ptr->fd= INVALID_SOCKET;
+
+  state= MEMCACHED_SERVER_STATE_NEW;
+  cursor_active_= 0;
+  io_bytes_sent= 0;
+  write_buffer_offset= size_t(root and memcached_is_udp(root) ? UDP_DATAGRAM_HEADER_LENGTH : 0);
+  read_buffer_length= 0;
+  read_ptr= read_buffer;
+  options.is_shutting_down= false;
+  memcached_server_response_reset(this);
+
+  // We reset the version so that if we end up talking to a different server
+  // we don't have stale server version information.
+  major_version= minor_version= micro_version= UINT8_MAX;
 }
 
-memcached_server_write_instance_st memcached_io_get_readable_server(memcached_st *memc)
+memcached_instance_st* memcached_io_get_readable_server(Memcached *memc, memcached_return_t&)
 {
 #define MAX_SERVERS_TO_POLL 100
   struct pollfd fds[MAX_SERVERS_TO_POLL];
-  unsigned int host_index= 0;
+  nfds_t host_index= 0;
 
-  for (uint32_t x= 0; x < memcached_server_count(memc) && host_index < MAX_SERVERS_TO_POLL; ++x)
+  for (uint32_t x= 0; x < memcached_server_count(memc) and host_index < MAX_SERVERS_TO_POLL; ++x)
   {
-    memcached_server_write_instance_st instance= memcached_server_instance_fetch(memc, x);
+    memcached_instance_st* instance= memcached_instance_fetch(memc, x);
 
     if (instance->read_buffer_length > 0) /* I have data in the buffer */
     {
       return instance;
     }
 
-    if (memcached_server_response_count(instance) > 0)
+    if (instance->response_count() > 0)
     {
-      fds[host_index].events = POLLIN;
-      fds[host_index].revents = 0;
-      fds[host_index].fd = instance->fd;
+      fds[host_index].events= POLLIN;
+      fds[host_index].revents= 0;
+      fds[host_index].fd= instance->fd;
       ++host_index;
     }
   }
@@ -699,10 +795,9 @@ memcached_server_write_instance_st memcached_io_get_readable_server(memcached_st
     /* We have 0 or 1 server with pending events.. */
     for (uint32_t x= 0; x< memcached_server_count(memc); ++x)
     {
-      memcached_server_write_instance_st instance=
-        memcached_server_instance_fetch(memc, x);
+      memcached_instance_st* instance= memcached_instance_fetch(memc, x);
 
-      if (memcached_server_response_count(instance) > 0)
+      if (instance->response_count() > 0)
       {
         return instance;
       }
@@ -721,17 +816,18 @@ memcached_server_write_instance_st memcached_io_get_readable_server(memcached_st
     break;
 
   default:
-    for (size_t x= 0; x < host_index; ++x)
+    for (nfds_t x= 0; x < host_index; ++x)
     {
       if (fds[x].revents & POLLIN)
       {
         for (uint32_t y= 0; y < memcached_server_count(memc); ++y)
         {
-          memcached_server_write_instance_st instance=
-            memcached_server_instance_fetch(memc, y);
+          memcached_instance_st* instance= memcached_instance_fetch(memc, y);
 
           if (instance->fd == fds[x].fd)
+          {
             return instance;
+          }
         }
       }
     }
@@ -743,16 +839,16 @@ memcached_server_write_instance_st memcached_io_get_readable_server(memcached_st
 /*
   Eventually we will just kill off the server with the problem.
 */
-void memcached_io_reset(memcached_server_write_instance_st ptr)
+void memcached_io_reset(memcached_instance_st* instance)
 {
-  memcached_quit_server(ptr, true);
+  memcached_quit_server(instance, true);
 }
 
 /**
  * Read a given number of bytes from the server and place it into a specific
  * buffer. Reset the IO channel on this server if an error occurs.
  */
-memcached_return_t memcached_safe_read(memcached_server_write_instance_st ptr,
+memcached_return_t memcached_safe_read(memcached_instance_st* instance,
                                        void *dta,
                                        const size_t size)
 {
@@ -764,7 +860,7 @@ memcached_return_t memcached_safe_read(memcached_server_write_instance_st ptr,
     ssize_t nread;
     memcached_return_t rc;
 
-    while (memcached_continue(rc= memcached_io_read(ptr, data + offset, size - offset, nread))) { };
+    while (memcached_continue(rc= memcached_io_read(instance, data + offset, size - offset, nread))) { };
 
     if (memcached_failed(rc))
     {
@@ -777,7 +873,7 @@ memcached_return_t memcached_safe_read(memcached_server_write_instance_st ptr,
   return MEMCACHED_SUCCESS;
 }
 
-memcached_return_t memcached_io_readline(memcached_server_write_instance_st ptr,
+memcached_return_t memcached_io_readline(memcached_instance_st* instance,
                                          char *buffer_ptr,
                                          size_t size,
                                          size_t& total_nr)
@@ -787,7 +883,7 @@ memcached_return_t memcached_io_readline(memcached_server_write_instance_st ptr,
 
   while (line_complete == false)
   {
-    if (ptr->read_buffer_length == 0)
+    if (instance->read_buffer_length == 0)
     {
       /*
        * We don't have any data in the buffer, so let's fill the read
@@ -795,11 +891,11 @@ memcached_return_t memcached_io_readline(memcached_server_write_instance_st ptr,
        * the logic.
      */
       ssize_t nread;
-      memcached_return_t rc= memcached_io_read(ptr, buffer_ptr, 1, nread);
+      memcached_return_t rc= memcached_io_read(instance, buffer_ptr, 1, nread);
       if (memcached_failed(rc) and rc == MEMCACHED_IN_PROGRESS)
       {
-        memcached_quit_server(ptr, true);
-        return memcached_set_error(*ptr, rc, MEMCACHED_AT);
+        memcached_quit_server(instance, true);
+        return memcached_set_error(*instance, rc, MEMCACHED_AT);
       }
       else if (memcached_failed(rc))
       {
@@ -816,15 +912,15 @@ memcached_return_t memcached_io_readline(memcached_server_write_instance_st ptr,
     }
 
     /* Now let's look in the buffer and copy as we go! */
-    while (ptr->read_buffer_length && total_nr < size && !line_complete)
+    while (instance->read_buffer_length and total_nr < size and line_complete == false)
     {
-      *buffer_ptr = *ptr->read_ptr;
+      *buffer_ptr = *instance->read_ptr;
       if (*buffer_ptr == '\n')
       {
         line_complete = true;
       }
-      --ptr->read_buffer_length;
-      ++ptr->read_ptr;
+      --instance->read_buffer_length;
+      ++instance->read_ptr;
       ++total_nr;
       ++buffer_ptr;
     }